West Nile Virus
GMO Safety
Healthy Human Gut
page 10
page 18
page 20
Vol. 58, No. 4, Fall 2015
Living with both bad and beneficial
Microbes
Microbes: Good, Bad and Overall Fascinating
Claudia Husseneder
They go by many names – germs, bugs, microbes and microorganisms. The tiny organisms,
which are usually invisible to the naked eye, include bacteria and archaea (both single-cell
organisms that lack cell nuclei), protists (single cell algae, slime molds and protozoa that contain
nuclei) and fungi. Viruses are considered “organisms at the edge of life” because they do not fit
the classical definition of life. Viruses possess genetic material and reproduce; however, they do
so by hijacking the metabolism of a host cell. Nevertheless, they are important plant and animal
disease agents, and the viruses infecting bacteria (bacteriophages) are increasingly touted as
tools for manipulating bacteria communities without the use of antibiotics. Therefore, viruses
deserve their place among the microbes featured in this issue of Louisiana Agriculture.
Microbes are labelled with many superlatives. They are the tiniest and simplest organisms, yet
the oldest life form on this planet. If the Earth were 24 hours old, microbes would have appeared
at 5 a.m., dinosaurs at 10 p.m. and humans just seconds before midnight. Microbes had sole
dominion over the Earth for about 3 billion years, and they are now found almost everywhere.
They have successfully conquered every habitat from 7 miles deep in the ocean to 40 miles
high in the atmosphere and from hot geysers to the Antarctic ice. Microbes are survivalists.
They thrive in the vacuum of outer space and live through nuclear blasts; a few are resistant to
almost every known antibiotic. They are Earth’s most abundant organisms. For every human on
this planet, there are 10 million trillion microbes. The human gut alone contains 10 times more
bacteria than cells in the human body.
Most people regard microbes as something negative to recoil from. However, less than 5
percent of microbes cause disease, and most play vital roles in many processes of life. Simply
put, humans cannot live without microbes, not only because they are everywhere, but also
because they are beneficial.
The LSU AgCenter is engaged in microbial research and diagnostics to combat disease,
increase agriculture productivity and improve the health of our citizens and our environment.
Because pathogenic microbes might pose a risk of infection, strict safeguards are in place for
microbial research and application. Two committees oversee these activities. The Inter-Institutional
Biological and Recombinant DNA Safety Committee follows federal guidelines for review and
approval of all teaching, diagnostic, research and extension activities that involve potentially
hazardous biological materials. The Institutional Review Board reviews research with human
subjects to ensure their protection.
Pathogenic viruses, bacteria, protozoa and fungi are the cause of many infectious diseases of
humans, animals and plants. This Louisiana Agriculture focus issue features articles on the impact
and fight against microbial diseases that infect Louisiana’s crops and livestock and sometimes its
citizens. The issue includes diagnostics and treatment of emerging plant diseases, fish disease,
and disease threatening cattle and deer as well as detection and prevention of food-borne
diseases. Special attention has been given to insects that are vectors for transmitting microbial
diseases in plants, animals and humans. Fortunately, microorganisms also provide innovative
and safe solutions for pest control. Microbes can be used as Trojan horses to deliver insecticidal
and antimicrobial peptides. Proteins derived from bacteria – such as the Bacillus thuringiensis
(Bt) toxin – are frequently used in crop protection and mosquito larvicide.
Despite the fear that microbial pathogens instill in us, it is important to keep in mind that most
microbes play beneficial roles and that life without them is impossible. Microbes are responsible
for nutrient cycling in the ecosystem; they are decomposers and fixate nitrogen from the air
to make it available for plants. Microbes support fertile soil conditions and create compost.
Microbial fermentation is used in food and beverage production – baking bread, making pickles
and brewing beer, for example. Oxidative capabilities of microbes are harnessed for treatment
of sewage and for oil spill cleanup. Microbes are the workhorses in energy production, turning
agricultural and urban waste into biogas and biofuel; they are used in biochemical production,
making organic acids and bioactive molecules like enzymes and vitamins. Microbes are genetic
tools and expression systems to mass produce proteins. Last, but not least, almost all plants and
animals, including humans, rely on microbial symbionts that live in tight association with their hosts
to aid them in fending off disease, supplementing nutrition and facilitating energy metabolism.
Microbes have a powerful story to tell. Let’s put these tiny organisms under the microscope
(pun intended) and examine their contributions to our world as the good, the bad and the
overall fascinating.
Claudia Husseneder is a professor in the Department of Entomology and the lead scientist
for this issue of Louisiana Agriculture.
2
Louisiana Agriculture, Fall 2015
EDITORIAL BOARD: John S. Russin, Chairman
Linda Foster Benedict
Michael Blazier
Rick Bogren
Melissa Cater
Glen T. Gentry
Kurt M. Guidry
Dustin Harrell
Claudia Husseneder
Kathy Kramer
Megan La Peyre
EDITOR: Linda Foster Benedict
ASSOCIATE EDITOR: Rick Bogren
DESIGNER: Kathy Kramer
CONTRIBUTORS: Tobie Blanchard, Elma
Sue McCallum, Olivia McClure and Johnny
Morgan
WEB DESIGN: Ronda Clark and Kathy
Kramer
Louisiana Agriculture is published quarterly
by the Louisiana Agricultural Experiment
Station. Subscriptions are free. You may also
subscribe to a Web version of the magazine,
which is available at www.LSUAgCenter.
com. Please go to the “Louisiana Agriculture
Magazine” site if you would like to receive
an email notification when a new issue
is online. If you would like to download
the magazine to your e-reader, go to the
magazine’s website, choose the correct
format, and follow the directions on your
mobile device. For more information or to
subscribe, please contact:
Linda Foster Benedict, Editor
Louisiana Agriculture
115 Knapp Hall
110 LSU Union Square
Baton Rouge, LA 70803
(225) 578-2263
[email protected]
www.LSUAgCenter.com
William B. Richardson, LSU Vice President for Agriculture
Louisiana State University Agricultural Center
Louisiana Agricultural Experiment Station
Louisiana Cooperative Extension Service
LSU College of Agriculture
The LSU AgCenter and LSU provide equal opportunities
in programs and employment..
The mention of a pesticide or use of a trade name for any
product is intended only as a report of research and does
not constitute an endorsement or recommendation by the
Louisiana Agricultural Experiment Station, nor does it imply
that a mentioned product is superior to other products of a
similar nature not mentioned. Uses of pesticides discussed
here have not necessarily been approved by governmental
regulatory agencies. Information on approved uses normally
appears on the manufacturer’s label.
Vol. 58, No. 4, Fall 2015
Published Since 1957
2
Microbes: Good, Bad and Overall Fascinating
4
6
8
AgCenter News
College of Ag News
Termite Gut Microbes: Tools and Targets for Control
Claudia Husseneder
Claudia Husseneder, Chinmay V. Tikhe, Lane Foil and Chris Gissendanner
10 Mosquitoes and West Nile Virus
Kristen Healy, Emily Boothe and Nicholas DeLisi
12 Norovirus and Oysters in Louisiana
Naim Montazeri, Morgan Maite and Marlene Janes
14 Studying Rice-Microbe-Insect Interactions to Increase Rice Production
Lina Bernaola and Michael Stout
16 On-farm Food Safety Research Helps Louisiana Growers
Comply with New Law
Achyut Adhikari
18 Bt technology: A Major Advancement in Insect Pest Control
David Kerns
19 Internal Regulations and Safeguards for Biological Materials
Kenneth R. Bondioli
19 Protection for Human Subjects
Michael J. Keenan
20 Resistant Starch Fermentation and Human Health
Michael J. Keenan
21 Scientist Helps Ensure Safety for LSU AgCenter Food Incubator Products
Olivia McClure
22 Plant Pathogens Threaten the Louisiana Plant World
Lawrence E. Datnoff
24 Linking Soil Microbes and Ecosystem Functions
Lisa Fultz
25 Use of Microbes As Expression Systems
Ted Gauthier
26 Plant Diagnostic Center Serves Louisiana
Raj Singh
27 Rose Disease Found for First Time in Louisiana
Johnny Morgan
28 Studies on the Transmission of Insect-borne Viruses That Cause
Hemorrhagic Disease in Deer, Cattle
Lane Foil, Michael Becker, Willie Andrew Forbes, Glen T. Gentry, James M. LaCour,
Stephanie R. Ringler and Jonathan L. Roberts
30 Use of Microbes in Oil Spill Cleanup
Andy Nyman
31 Ruminants and Their Rumen Microbes
Guillermo Scaglia
31 Using Microbes to Fight Disease in Catfish
Ron Thune
32 Pending FDA Rules Could Increase Demand for AgCenter-Developed
Cattle Vaccine
Rick Bogren
33 Prevent Foodborne Illness at Home
Wenqing Xu
34 AgCenter Scientists at the Forefront of Brucellosis Eradication
Sue D. Hagius and Philip H. Elzer
35 Using Microorganisms in the Manufacture of Dairy Foods
Kayanush J. Aryana and Luis Vargas
ON THE COVER: Photo illustrations of microbes were provided by Ying Xiao, research
associate in the Department of Biological Sciences, and courtesy of the LSU Socolofsky
Microscopy Center, Shared Instrumentation Facility, Institute for Advanced Materials.
Louisiana Agriculture, Fall 2015
3
AgCenter News
22 awarded Master Cattleman status
Graduates of the Louisiana Master Cattleman program were recognized on Oct. 8 during a field day at the Dean Lee Research and Extension Center in
Alexandria. LSU AgCenter regional beef coordinator Vince Deshotel said 59 people have graduated in the past two years from the program in the LSU AgCenter
Central Region. The program involves 10 sessions covering a wide range of material for beef production. From left, kneeling, Glen Rideau, Joe Doucet,
Chris Douget, Tom Ardoin, AgCenter Central Regional Director Boyd Padgett, Scott Aymond, Danny Miller, Dwayne Landreneau; standing, Deshotel, Randy
Beauboeuf, interim director of the AgCenter School of Animal Sciences Christine Navarre, Carol Bliss, Klaire Fontenot, Wesley Coffman, Russell Miller, Terry
Latiolais, David Morris, Terry Ardoin and Robert Duncan. Not shown are Michael Fontenot, Shane Freeman, Tara Freeman, Ted Freeman and Jay Guidry. Photo by
Bruce Schultz
Facility renamed H. Rouse
Caffey Rice Research Station
Family, friends and former co-workers gathered Nov. 4 for the renaming of the LSU AgCenter Rice Research Station for the late H. Rouse
Caffey in recognition of his dedication to the rice
industry and Louisiana agriculture.
Several facilities could have been chosen to
honor Caffey’s name because of his work with
numerous agricultural research facilities, said Bill
Richardson, LSU vice president for agriculture
and dean of the College of Agriculture, who succeeded Caffey as LSU AgCenter chancellor. “The
Rice Research Station was nearest and dearest to
his heart,” he said.
Farmer Jackie Loewer, chairman of the Louisiana Rice Research Board, said without the station, the rice industry would not exist in Louisiana today. “Without Rouse Caffey, it wouldn’t be
the station it is today.”
Caffey, who died in 2012, retired from the LSU
AgCenter in 1997 after serving 13 years as chancellor. He also was chancellor of LSU of Alexandria, vice chancellor of the LSU AgCenter, associate director of the LSU Agricultural Experiment
Station. He was director of the Rice Experiment
Station from 1962 until 1970 and was rice research project leader in Mississippi. Bruce Schultz
4
Louisiana Agriculture, Fall 2015
New plants hot topic at Hammond field day
More than 335 people attended the Landscape Horticulture Field Day and the Southeast Louisiana
Nursery Association Trade Show on Oct. 8 at the Hammond Research Station. LSU AgCenter horticulturist
Yan Chen, at right, discusses different varieties of caladiums. Photo by Johnny Morgan
Scientists try to slow spread
of emerald ash borer
Efforts are underway in north Louisiana
to slow the spread of an invasive species that
threatens to destroy native ash trees. The trees
play an important part in bottomland ecosystems and also have an economic value to the
timber industry.
“The emerald ash borer was detected for
the first time in northern Louisiana in February
2015,” said LSU AgCenter entomologist Rodrigo Diaz. “It is a beetle native to China that has
decimated ash trees in the northeastern United States within the past 15 years and has been
spreading and moving south.”
Diaz said the emerald ash borer kills ash
trees by digging tunnels below the bark, cutting the flow of sap throughout the tree. In six
to seven years the tree will die, he said.
According to Wood Johnson, an entomologist with the U.S. Forest Service, emerald ash
borer adults have been collected in Claiborne,
Bossier and Webster parishes. It has only been
found in trees within Webster Parish.
The LSU
AgCenter, the U.S.
Forest Service, the
Louisiana Department
of Agriculture and
Forestry, and the
Animal and the Plant
Health Inspection
Service have
collaborated to get a
biocontrol effort off
the ground in north
Louisiana.
LSU AgCenter entomologist Rodrigo Diaz releases a sample of parasitoid wasps
To help slow the
onto an infected ash tree in Shongaloo, Louisiana. Photo by Brandy Orlando
spread of the borer,
comes from research conducted primarily in
the entomologists are releasing three species
northern climates. By monitoring the borer and
of wasps, with each targeting different growth
the parasitoid wasps in north Louisiana, the enstages of the borer.
tomologists hope to learn more about both the
“We obtained a release permit for the parborers and the wasps in the South.
asitoids from the USDA to use as a tool to manBrandy Orlando
age the emerald ash borer,” Diaz said.
Much of the information on the insect
Sugarcane byproducts
used in skin, bone tissue
engineering
New multipurpose building opens at 4-H camp
Louisiana sugar producers may one day
have a new market for their crops.
LSU AgCenter researchers at the Audubon
Sugar Institute are continuing a tissue engineering study that began as a study by former graduate student Akanksha Kanitkar. The study involves making skin and bone tissue scaffolds
from aconitic acid, cinnamic acid and glycerol –
all byproducts of sugarcane processing.
According to Giovanna Aita, an associate
professor who directed Kanitkar’s work, the
study involves creating nontoxic, biodegradable polyesters from molasses and bagasse.
“This would be not only profitable for the
sugarcane industry as a means of value addition by the use of its byproducts, but it also unfolds a path for generating novel biomaterials
for tissue engineering applications,” Aita said.
Scaffolds are structures made from the
polyesters that scientists use to create new
tissues.
“We are studying the polyesters for their
mechanical properties and porosity, as well as
their ability to support stem cell growth,” Aita
said.
Scaffolds made from these polyesters degrade at a rate that is favorable for new skin
growth. This knowledge could be used for creating skin tissue to use in wound repair. A. Denise Attaway
After years of wishing, planning and fundraising, the new $1.2 million multipurpose pavilion at the LSU AgCenter Grant Walker 4-H Educational Center became reality on Oct. 30 with a
dedication and ribbon cutting.
The building is named after Ellis S. Martin,
father of Jonathan Martin, chief executive officer of RoyOMartin. The RoyOMartin company
provided much of the funding for the project.
The 10,000-square-foot facility provides indoor space for 4-H campers to gather and line
up for lunch during inclement weather as well
as be available for other activities.
The project got off the ground after former
state Sen. Randy Ewing took charge of fundraising from private sources. Ewing said 137 contributors stepped up to offer funding and inkind services. Bruce Schultz
Jonathan Martin, chief executive officer of
RoyOMartin, cuts the ribbon to the Ellis S. Martin
Multipurpose Pavilion at the LSU AgCenter
Grant Walker 4-H Educational Center during the
dedication ceremony Oct. 30. Left to right are
Louisiana 4-H Foundation board chairman Charles
Dill; Martin; former state Sen. Randy Ewing, and
Patrick Tuck, 4-H Foundation executive director.
Photo by Bruce Schultz
The multipurpose pavilion provides 10,000 square feet of space. Panorama photo by Bruce Schultz
Louisiana Agriculture, Fall 2015
5
College of Ag News
Students hope to improve agriculture in their home countries
LSU AgCenter International Programs is
helping seven international graduate students
earn their doctorates so they can return home
with hopes of sparking much-needed change
in farming practices and policies.
The students, who have worked as university lecturers and government employees, are
part of the Borlaug Higher Education for Agricultural Research and Development (BHEARD)
program. It is funded by the U.S. Agency for International Development (USAID) and managed by Michigan State University.
“It is an honor for the LSU AgCenter to have
been selected as the host training institution
for the BHEARD scholars,” said David Picha, director of AgCenter International Programs.
The students will complete coursework on
LSU’s campus and then return to their home
countries to do a research project under their
faculty adviser’s supervision. LSU will grant
their degrees.
“BHEARD has given me an opportunity to
be exposed to a high-level environment, build
my skills and research,” said Chunala Njombwa,
a former livestock researcher at the Lunyangwa Agricultural Research Station in Malawi. “By
coming here, we will build partnerships. Now
I know these guys who want to come up with
projects that will help small-scale farmers in
our countries.”
Though the students are from five countries and work in different fields of expertise,
they point to similar issues hindering agriculture in the developing world. Food security is
a common theme. But unlike Americans may
assume, it is more a problem of quality than
quantity.
“As much as you want to make food affordable and accessible, safety and quality are
equally important things,” said Bennett Dzandu, a former University of Ghana teaching assistant studying food science at LSU. “The issue
is that in Africa and many places, it is rather the
opposite way. Quantity and cheapness is at the
expense of quality and safety of the ones consuming the food.” Olivia McClure
LSU AgCenter International Programs is helping seven students pursue doctorates at LSU. Front row from
left, Murshida Khan, of Bangladesh, and Fausta Marie Dutuze, of Rwanda. Back row from left, Chunala
Njombwa, of Malawi; Bennett Dzandu, of Ghana; Fydess Khundi, of Malawi; Emmanuel Kyereh, of Ghana;
and Susan Karimiha, AgCenter International Programs coordinator. Another student, Sarah Kagoya, of
Uganda, is not pictured. Photo by Olivia McClure
Slovakian student promotes
study abroad
Natália Antošová, an LSU graduate student
from Slovakia, is working with LSU AgCenter
International Programs to help promote study
abroad opportunities for LSU students. Photo by
Tobie Blanchard
Natália Antošová, a College of Agriculture
graduate student in agricultural economics
from Slovakia, wants to help LSU students have
a similar experience to the one she is having.
The college has partnered with the Slovak
University of Agriculture (SUA) in Nitra, Slovakia, for student and faculty exchanges and research collaboration. Faculty at SUA recommended Antošová for the exchange program.
This is her first time in the U.S.
“School is demanding. Studies are deeper
and move at a quick pace,” Antošová said.
Being away from home and family commitments allows her to focus on school more, Antošová said. But that doesn’t mean she spends
all of her time studying. In her short time at
LSU, she has found ways to become involved
in campus life, including taking part in the LSU
homecoming parade with the LSU International Student Association.
As part of the exchange, Antošová is working for the LSU AgCenter International Programs department as an international relations
student adviser.
“I bring information to students about opportunities to travel and study abroad and organize events, and promote study abroad in
every way,” she said. Tobie Blanchard
Salassi new head of ag economics department
The LSU AgCenter and LSU College of Agriculture have
named Michael Salassi head of the Department of Agricultural Economics and Agribusiness. Salassi has served
on the faculty of the department for 21 years and is the
J. Nelson Fairbanks Endowed Professor for Agricultural
Economics.
He replaces Gail Cramer, who retired in July.
Salassi received bachelor’s and master’s degrees from
LSU and a doctorate from Mississippi State University. He
worked for the U.S. Department of Agriculture’s Economic
Research Service in Washington, D.C., for nine years before
returning to LSU as an associate professor in 1994. He became a full professor in 2002.
Salassi also served as the assistant director of the Louisiana Agricultural Experiment Station, the AgCenter’s research division. His main focus during his career has been
production economics and farm management. Tobie Blanchard
Michael Salassi
6
Louisiana Agriculture, Fall 2015
Nine students receive research grants
Casey Kenny, a freshman in the LSU College of Agriculture, is a recipient of the prestigious Penelope
W. and E. Roe Stamps IV Leadership Scholarship.
Kenny plans to use some of the scholarship money
to fund research on feline viruses. Photo by Tobie
Blanchard
Stamps scholarship goes to
ag student
Casey Kenny considers cats her first love.
The freshman in the LSU College of Agriculture
wants to work with small animals, exotics and
wildlife as a veterinarian. While in college she
plans to search for a cure for feline leukemia
and feline immunodeficiency virus.
Kenny is one of five LSU freshmen to receive
the prestigious Penelope W. and E. Roe Stamps
IV Leadership Scholarship. With the scholarship
comes full cost of attendance for four years,
with up to $14,000 for enrichment opportunities, such as research.
Kenny plans to use the money to finance
her research on feline viruses.
“I’ve seen these viruses, and they are terrible,” Kenny said. “I hate that so many cats are
suffering from these diseases, which may have
cures that have not been explored.”
During high school, Kenny began shadowing a veterinarian in her hometown of Montgomery, New York. Later, she was hired to work
in the clinic. She said feral cats would come into
the clinic with feline leukemia and feline immunodeficiency virus. With no cure, they would
just have to treat the symptoms of the virus.
She said the viruses are easily spread among
cats.
Kenny’s grades and scores could have taken
her anywhere, but she said she was looking for
a big state school. She visited LSU and was invited to apply for the Stamps scholarship. Earning the award made her decision easy.
“I really love LSU. Life is totally different
here,” she said. Tobie Blanchard
Every day for six weeks, Ariel Bergeron went
to the LSU AgCenter poultry research facility to
feed and water quail. Bergeron, a senior majoring in animal sciences, is studying nutrition requirements of quail less than six weeks old.
The LSU College of Agriculture gave grants
to Bergeron and eight other undergraduate students to pursue research in their fields of study.
Bergeron and her faculty adviser, Theresia Lavergne, a poultry specialist, chose to look
at this subject because not much research has
been done on nutrition requirements of quail in
the past 30 years.
“Bobwhite quail are a popular gamebird in
Louisiana, but they are having trouble surviving
in the wild,” Bergeron said. “More people will be
raising quail, so we want to know what the optimal diet is.”
Research projects help prepare students like
Bergeron for graduate school and careers that
involve research, Lavergne said.
Other College of Agriculture research grants
went to the following students:
Ryan Ardoin is studying consumer perception
and purchase intent of low-sodium mayonnaise
products with Witoon Prinyawiwatkul, a food
sciences professor.
Katie Bowes is looking at the effects of salinity in survival, growth and biomass of the aquatic plant Ruppa maritima with Megan Lapeyre, an
adjunct professor in the School of Renewable
Natural Resources.
Brittany Craft is examining the effects of participating in a culinary skill-building program on
high school students’ willingness to consume
fruits, vegetables and whole-grain foods with
Georgianna Tuuri, an associate professor in the
School of Nutrition and Food Sciences.
Haley Hutchins plans to characterize the diversity of the fungi Colletotrichum associated with
Louisiana plants with Vinson Doyle, assistant
professor in the Department of Plant Pathology
and Crop Physiology.
Samantha Lanjewar wants to determine if seven specific genes, used to test various performance levels of cattle, can be successfully amplified in a type of cell called a fibroblast. She is
working with Kenneth Bondioli, professor in the
School of Animal Sciences.
Scarlett Swindler is working with food scientist
Marlene Janes to look for rapid and reliable detection methods of the human norovirus in marine waters.
Carly Thaxton aims to assess dietary intake of
pregnant women, while also looking at fatty
acid levels by analyzing the mother’s red blood
cells, with Carol Lammi-Keefe, a professor in the
School of Nutrition and Food Sciences.
Colleen Walsh is conducting research on an invasive species, Daphnia lumholtz, commonly
known as water fleas, with William Kelso, a professor in the School of Renewable Natural Resources. Tobie Blanchard
‘Cocktails and Cuisine’ raises $20,000 for scholarships
More than 130 people attended the LSU College of Agriculture’s 2nd annual Cocktails and Cuisine
Benefiting Scholarships, which was Oct. 16 at LaHouse on LSU’s campus. Attendees included (from left
to right) Paula and Harold Lambert, and Gene and Sheila Reagan. The evening featured a silent auction,
a jazz trio, and food from tenants of the LSU AgCenter Food Incubator. The event raised more than
$20,000 for scholarships. Sponsors included ZEN-NOH Grain, ConAgra Foods/Lamb Weston, Horizon Ag
LLC, Gowan Company, Bracy’s Nursery LLC, Louisiana Agricultural Consultants Association, East Iberville
Industry Neighbor Companies, Louisiana Agribusiness Council, and Louisiana Association of Conservation
Districts. Photo by Tobie Blanchard
Louisiana Agriculture, Fall 2015
7
Termite Gut Microbes
Tools and Targets for Control
Claudia Husseneder, Chinmay V. Tikhe, Lane Foil and Chris Gissendanner
T
ermite colonies are often called “superorganisms” for several reasons. First of
all, termites are social insects that live
in large and densely populated colonies with
specialized castes, including workers, soldiers
and reproductives. These castes all perform
different tasks. The superorganism concept
then extends into the microbial world of the
termite gut, which is sometimes referred to as
the world’s smallest and most efficient bioreactor. Termites live exclusively on plant dry
matter, such as wood, which lacks essential
nutrients and is difficult to digest. Therefore,
termites rely on microbial symbionts to aid in
digestion and energy production in the gut of
their workers, which are responsible for foraging, digesting the food and feeding other
members of the colony via regurgitation and
anal excretion of fluids.
In subterranean termites, such as the
Formosan subterranean termite, which is
found in Louisiana and the Southeastern
United States, the hind gut of workers is specialized to harbor microbes from the three
categories, or domains, of life – archaea, bacteria and eukaryota.
Archaea were originally classified as bacteria but were recently put into a domain of
their own because of unique properties that
make them different from both bacteria and
eukaryota. Most archaea in the termite gut
are methane producers, making termites the
second largest source of atmospheric methane
on the planet after the ruminants.
Research at the LSU AgCenter has identified more than 200 different bacteria species
residing in the gut of Formosan subterranean
termites, some of them unique and specific to
termites. The bacteria community supports
important functions in regard to nutrition
and energy production. For example, bacteria
produce and recycle nitrogen as a source for
protein synthesis. They synthesize vitamins
and reduce hydrogen to create energy-producing byproducts that the termites can use.
The bacteria scavenge oxygen in the termite gut to provide the anaerobic environment
required by the protists, which are eukaryota
organisms. The three species of protists in the
gut of Formosan subterranean termites are
the most valuable players when it comes to
digestion of wood. Without these protists in
their guts, termites starve to death (Figure 1).
This need for termites to have obligatory microbial symbionts in their guts gave
researchers at the LSU AgCenter and the
University of Louisiana at Monroe a new idea
for controlling termites. The researchers use
bacteria and protists as tools and targets, rather
than chemical insecticides, to kill termites.
Because the diverse bacteria community in
the termite gut is of vital importance to the
health of the termite colony, bacteria make
a good target for aiming at termite control.
Bacteriophages, also called phages, are viruses
that kill bacteria. Phages are highly host-specific and do not infect cells of plants, animals
or humans. Thus, using a phage cocktail to
disrupt the bacteria community in the termite gut might be a feasible option for termite management, either as a stand-alone or
in conjunction with chemical insecticides.
Because nothing was known about bacteriophages and their roles in the termite gut,
researchers from the LSU AgCenter and the
University of Louisiana at Monroe started to
isolate and describe phages from the gut of
Formosan subterranean workers (Figure 2). To
date, the full genome of three phages has been
sequenced. The host specificity of those phages
Pseudotrichonympha
Holomastigotoides
ranges from narrow, in which they infect only
a single species of bacteria, to fairly broad, in
which they infect several closely related species. The phages include lytic phages that infect
and kill their host bacterium immediately and
temperate phages that can integrate into the
bacteria genome and stay dormant for a while
until they go into the lytic phase. More phages
are currently being tested for their efficacy
against termite gut bacteria. Experiments are
underway to provide proof of concept that
natural phages can disrupt the termites’ bacterial community and, thus, weaken or even
kill a termite colony. In addition, researchers
are planning to engineer phages to produce
targeted antimicrobial peptides.
AgCenter researchers already have provided proof of concept that genetically engineered microbes can serve as Trojan horses to
express and spread gene products in the gut
of Formosan subterranean termites without
risking detection and elimination by the termites’ natural defenses. Enterobacter cloacae, a
bacterium common in the gut of many organisms, was isolated from Formosan termites and
engineered to express green fluorescent protein, a marker that could be easily traced visually by its bright green fluorescence. Workers
readily ingested the engineered bacteria, and
the bacteria survived for six weeks and longer
in their guts. Workers also transferred the
bacteria to other workers and soldiers, which
helps to spread the gene product throughout
a termite colony.
The next step involved the search for a
targeted toxin that specifically kills the cellulose-digesting protists in the termite gut.
Researchers at the AgCenter already had
experiences with lytic peptides as antimicrobial agents. Lytic peptides are a natural part
Spirotrichonympha
Figure 1. The three species of cellulose-digesting protists in the gut of Formosan subterranean termite workers. Loss of these protists leads to the death of the
termite colony by starvation.
8
Louisiana Agriculture, Fall 2015
to alter the microbial community in the gut.
In the case of termites, such microbiome engineering has the ultimate goal of pest control.
Similar approaches can be used in the future
to strategically increase beneficial microbes
and reduce pathogens in the gut of organisms,
including humans.
Figure 2. Electron microscope images of two novel bacteriophages isolated from the gut
of Formosan termites.
of the immune system and kill protists and
bacteria but have no negative effect on cells of
plants or animals including humans. Research
showed that minute concentrations of the lytic
peptide Hecate kill all protists in the gut of
Formosan termite workers when injected into
the hindgut by way of a tiny enema (Figure
3). Unfortunately, feeding termites with lytic
peptides was not an option because the peptides were broken down in the digestive tract
and lost their lytic function. Delivery by a
genetically engineered microbial Trojan horse
was promising not only to spread the toxin,
but also protect it from digestion.
To make the lytic peptide more specific to
the target protists and protect nontarget organisms from the lytic peptide action, a ligand was
designed that binds the lytic peptide to protists but not to other cells. Freeze-dried yeast
(Kluyveromyces lactis), which was engineered
to express lytic peptide coupled to the ligand,
was incorporated into cellulose bait discs and
fed to Formosan termites in the laboratory.
Workers readily ingested the yeast and spread
it to their colony mates (Figure 4). The yeast
expressed and secreted ligand-lytic peptide
into the termite gut. The ligand bound to the
cellulose-digesting protists in the gut, and the
lytic peptide killed them. All three species of
protists in the gut of Formosan termites were
killed within three weeks of first ingestion of
the yeast, and termite lab colonies died within
two weeks after. The comparatively slow-acting system is necessary to guarantee spread of
the Trojan horse and its payload throughout
the entire colony. Current research is testing
termite-specific gut bacteria and bacteriophages, instead of ubiquitous yeast, as Trojan
horses to deliver protist-killing ligand-lytic
peptides into termite colonies to increase
environmental safety.
Research into the termite gut model shows
that microbes (genetically engineered Trojan
horses or natural bacteriophages) can be used
Claudia Husseneder is a professor, and Lane
Foil is Pennington Regents Chair for Wildlife
Research in the Department of Entomology.
Chinmay Tikhe is a Ph.D. student in
Husseneder’s lab. Chris Gissendanner is
an associate professor at the University of
Louisiana at Monroe School of Pharmacy.
Figure 3. Injection of peptide solution via an
enema into a termite worker immobilized in a
pipette tip.
Figure 4. Yeast expressing ligand-lytic peptide as Trojan horse for termite control.
Louisiana Agriculture, Fall 2015
9
Mosquitoes and West Nile Virus
Biology, behavior and insecticide susceptibility of
Culex quinquefasciatus, the primary vector in Louisiana
Kristen Healy, Emily Boothe and Nicholas DeLisi
W
est Nile virus is considered the
most widespread arbovirus
(viruses transmitted by insects
and related arthropods) in the world. The
virus is transmitted to humans and animals
by the bite of an infected mosquito. About
80 percent of the humans that become
infected do not develop symptoms, whereas
20 percent develop flu-like symptoms. Less
than 1 percent develop more serious neurological complications, such as encephalitis,
a disease that causes swelling of the brain.
Although it first appeared in the
United States in 1999, West Nile virus
still remains an important infectious disease. According to the Centers for Disease
Control and Prevention (CDC), West Nile
virus has contributed to more than 41,762
cases of illness and 1,765 deaths in the
United States since 1999. In Louisiana alone,
there have been 1,575 cases reported to the
CDC between 1999 and 2014. While there
is the potential for year-round activity,
most West Nile virus cases occur between
July and October. Therefore, personal protection from mosquitoes is crucial every
summer and fall.
Figure 1. A collection of mosquitoes being
sorted by species. In Louisiana, mosquito control
programs will sort mosquitoes and then submit
them for testing for West Nile virus. Photo by
Kristen Healy
10
Louisiana Agriculture, Fall 2015
There are more than 3,000 species of
mosquitoes in the world, and only a few
are potential vectors for West Nile virus.
The Southern house mosquito (Culex quinquefasciatus) is the most important vector
for West Nile virus in Louisiana because it
cycles the virus in birds and can occasionally transmit the virus to humans. Because
of its importance in the cycle of West Nile
virus in Louisiana, the Southern house
mosquito is the main target for mosquito
control districts in Louisiana. Mosquito
districts across Louisiana will collect
samples of mosquitoes, identify them by
species, and then submit them for West
Nile virus testing (Figure 1). In response
to West Nile virus activity in mosquitoes,
control programs will employ different
methodologies to control mosquitoes that
can transmit the virus. To determine the
effect of control on virus activity and mosquito populations, LSU AgCenter scientists
are developing new tools to assess control
efficacy in the state. This includes developing new trap designs to collect host-seeking
house mosquitoes, understanding the biology of important vector mosquito species
(Figure 2), and evaluating pesticide susceptibility in the state for products designed for
larval control and adult mosquito control.
The gold standard for collecting house
mosquitoes in the United States is the
gravid trap (Figure 3). This trap functions
by collecting mosquitoes ready to lay eggs in
water (gravid females). While gravid traps
have historically collected large number of
house mosquitoes, this type of surveillance
represents the population of gravid females
within an area rather than the host-seeking population that poses the greatest risk
to humans and West Nile virus infection.
The host-seeking mosquitoes are seeking
a blood meal.
Figure 2. Nicholas DeLisi, a graduate student,
determines the temperature and pH of a
container habitat being used by mosquito larvae.
Photo by Kristen Healy
Figure 3. A gravid trap collects mosquitoes that
are looking for a place to lay eggs. Mosquitoes
locate the trap by the “stinky water,” which is
attractive to egg-laying mosquitoes. Photo by
Kristen Healy
One of the main factors that has contributed to the success of West Nile virus
in the United States is that mosquitoes cycle
the virus in bird populations. Birds that do
not become ill or die from the infection and
that have high levels of virus aid in the cycle
of the virus. In addition, mosquito species
that are suitable vectors contribute to the
complexity of this virus in Louisiana.
Southern house mosquito
To find a better trap for host-seeking
mosquitoes, LSU AgCenter scientists are
conducting studies within three parishes
in Louisiana – St. Tammany, Tangipahoa
and East Baton Rouge – to evaluate different
trap designs. This has included a longitudinal study to compare traps throughout
the entire season to make comparisons
of gravid and host-seeking populations.
AgCenter researchers are discovering that
standard mosquito traps can be simply
modified to collect more host-seeking
mosquitoes by removing the lightbulb and
baiting them with dry ice. Although the
data are still being evaluated, this would
be a useful discovery for mosquito control
districts wishing to evaluate host-seeking
house mosquito populations to evaluate
different levels of risk for West Nile virus.
Mosquito control as a tool to
prevent disease transmission
The best defense against transmission
of West Nile virus comes in the form of
mosquito control. Since the early 1900s,
mosquito control has been built around
the concept of integrated mosquito management. This system involves using
multiple control strategies, such as larval
control with mosquito-specific bacteria,
reducing standing water, monitoring of
mosquito populations, evaluating mosquitoes and birds for viruses, and adult
mosquito control using pesticides. Most
people are not aware of the many components of integrated mosquito management
that go on in Louisiana because they are
most familiar with spray trucks. Because
mosquito control does such a good job at
reducing mosquitoes, most people do not
realize how deleterious mosquitoes can be
to human and animal populations. Before
modern mosquito control, tens of thousands of individuals in Louisiana lost their
lives to yellow fever and malaria, which are
both caused by mosquito-borne pathogens.
Thankfully, Louisiana has many parishwide mosquito control districts conducting
integrated mosquito management. A loss
of mosquito control programs could result
in dramatic increases in both nuisance and
vector mosquito species.
One of the goals of LSU AgCenter
research is to help mosquito programs
ensure that their control methodology is
effective. Fortunately, mosquito control
programs have a selection of products that
they can use to control mosquitoes. By
evaluating if a product is effective, they
can determine if they need to switch to a
product with a different mode of action.
The efficacy of a product can easily be
evaluated in the lab by conducting bottle
bioassays for adult mosquitoes (Figure 4) or
cup bioassays for the larvae (Figure 5). In
these types of tests, scientists place mosquitoes in vials with known concentrations of
pesticides and determine the percent dying
or time to death. If there is variation from
standard susceptible populations, the scientists then evaluate the potential causes
by doing more in-depth studies.
Kristen Healy is an assistant professor; Emily Boothe is a research associate; and Nicholas
DeLisi is a graduate assistant, all in the Department of Entomology
Figure 5. Researchers evaluate the efficacy of
different mosquito control products that target
the immature mosquitoes, which are called larvae.
Photo by Kristen Healy
Dead adult mosquitoes. Photo by Emily Boothe
Figure 4. Emily Boothe, a research associate, conducts bottle bioassays to evaluate the efficacy of
pesticides in adult mosquito populations. Photo by Kristen Healy
Louisiana Agriculture, Fall 2015
11
Norovirus and Oysters in Louisiana
Naim Montazeri, Morgan Maite and Marlene Janes
A
t some point in your life you have
become ill with what is referred to
as stomach flu. Stomach flu is caused
by norovirus and is the foremost common
cause of gastrointestinal tract infections in
humans, resulting in nausea, vomiting, diarrhea and low-grade fever. As a result, norovirus and many other similar viruses, such as
enterovirus and hepatitis A virus, that cause
intestinal disease are called enteric viruses.
Infected individuals can shed millions of
viruses in their feces or vomit. Annually, 15
million people get sick in the United States
with norovirus; therefore, it can be found in
large amounts in human sewage.
You may be exposed to the viruses
through contaminated surfaces or foods.
Ingesting the pathogen by touching contaminated hands to the mouth or eating
contaminated food can make you sick, and
that’s how norovirus is spread. To the best
of our knowledge, these viruses do not
grow in foods; they are merely transmitted
to food, where they linger for an extended
period of time.
A sick food handler can transfer the virus
to your food. Fresh produce grown using
sewage-contaminated irrigation water can
harbor enteric viruses. Filter-feeding molluscan shellfish such as oysters exposed to
sewage-contaminated waters can actively
concentrate viruses. If the oyster is consumed raw, the virus can be transmitted
to humans and cause illness. These viruses
enter source waterways through the direct or
indirect discharge of treated and untreated
human and animal waste into surface waters.
Sewage is one of the major contamination sources for norovirus and other enteric
pathogens. Regulatory agencies are using
some bacteria and viruses of natural microbial flora of human and warm-blooded
animal guts – such as fecal coliforms,
Escherichia coli, enterococci and coliphages
– to assess the level of fecal pollution in
environmental waters or food. Currently,
the Louisiana Department of Health and
Hospitals Molluscan Shellfish Program uses
microbial indicators of fecal contamination
as the determining factor in closing mollus-
Naim Montazeri and the first haul of oysters for the day. Photo by Liu Da
12
Louisiana Agriculture, Fall 2015
can shellfish harvesting areas due to virus
contamination. Furthermore, several outbreaks of norovirus have been traced to consumption of oysters obtained from Louisiana
sites. On April 28 and 29, 2012, 14 people
became ill with norovirus after consuming
oysters at a restaurant in New Orleans. The
oysters were traced back to an oyster harvesting area off the Louisiana coast. As a result,
LDHH closed the harvesting area. In January
2013, LDHH closed another area due to suspected norovirus contamination of oysters.
Samples of harvesting water or oysters are
not directly tested for the presence of viral
contamination during suspected outbreaks.
These outbreaks further highlight the limited data on virus occurrence in Louisiana
harvest water and oysters.
AgCenter scientists investigated the
occurrence of norovirus and microbial indicators of fecal contamination in the Eastern
oysters (Crassostrea virginica) and water
from commercial harvesting areas along
the Louisiana Gulf Coast from January to
November 2013. The sampling locations
were among the most active commercial
oyster-harvesting areas and remained open
during the sampling period.
Microbial fecal indicators were detected
but at levels too low to be of public health
concern. Even with low levels of fecal contamination in the open areas were oysters
and harvesting water were collected, norovirus was detected in only one oyster sample.
In general, the level of microbial indicators
was too low to draw a conclusion of their
effectiveness in predicting the pathogens.
However, norovirus can be present even
when water and oysters are considered bacteriologically safe. Although this study showed
low concentrations of noroviruses in oysters,
whether this can be a health concern needs
to be further investigated because little is
known regarding the risks associated with
the concentration of norovirus in oysters.
An outbreak of norovirus occurred
January 2013 in Cameron Parish, Louisiana.
The individuals who had become ill had
eaten oysters collected from the Louisiana
Gulf Coast. A stool specimen from an
Microbial Load log CFU/100 mL or log PFU/100 mL
7
Enterococci
E. coli
6
Fecal coliforms
5
Male-specific coliphages
4
3
2
1
0
Influent
Effluent
Marlene Janes, standing in center, and Naim Montazeri, left, harvest oysters from the Gulf of Mexico for
sampling. Also in the boat are Jody Donewar, the captain, and Jen Shields. Photo by Liu Da
infected individual associated with the
outbreak and the suspected oysters were
analyzed. The norovirus strain in the stool
belonged to one of the most widespread
norovirus genotypes; however, the oysters
were negative and could not be linked to
the outbreak.
AgCenter scientists also looked at a
municipal secondary wastewater treatment plant on the Mississippi River in New
Orleans as a potential source of environmental contamination. For one year they
collected monthly wastewater samples from
the treatment plant both before treatment
(influent) and after secondary treatment
and chlorine disinfection (effluent). Enteric
viruses were present in both influent and
eff luent wasters year-round. Microbial
loads in the influent indicate the presence
of the pathogens, reflecting what is happening within a population. They found
that changes in concentrations of enteric
viruses may not be in accordance with the
expected epidemiological trends, and some
strains circulating among the population
have been overlooked from epidemiological standpoints. These results showed that
enteric viral pathogens are more resistant
than microbial indicators to the secondary
treatment of wastewater and chlorine disinfection (Figures 1 and 2). Furthermore, fecal
coliforms, E. coli and enterococci commonly
present in the sewage water had no remarkable changes over time. Coliphages (viruses
infecting E. coli) were the only indicators that
concentrations were similar to noroviruses,
indicating that coliphages have the potential to be used to assess the efficacy of the
treatment and disinfection of noroviruses
in sewage.
Overall, this study shed light on the safety
of Louisiana oysters and showed that norovirus might occur in the oyster even when
they are bacteriologically safe. This study
also found that raw and even secondary
treated sewage water can harbor high densities of the pathogenic viruses, which eventually enter the environmental waters. A
proper system to manage oyster harvesting
areas using more effective criteria or even
direct monitoring of enteric viruses is recommended to reduce the risk of outbreaks.
Microbial Load log CFU/100 mL or log PFU/100 mL
Figure 1. Concentration of microbial indicators in
wastewater.
7
Norovirus GI
6
Norovirus GII
5
Enteric viruses
4
3
2
1
0
Influent
Effluent
Figure 2. Concentration of enteric pathogens in
wastewater.
Acknowledgments: This research was
funded through NoroCORE, an Agriculture
and Food Research Initiative from the
U.S. Department of Agriculture National
Institute of Food and Agriculture.
Marlene Janes is a professor and Morgan Maite is a graduate assistant in the School of
Nutrition and Food Sciences. Naim Montazeri graduated from the School of Nutrition
and Food Sciences, with a Ph. D. in May 2015 and is currently working with the NoroCore
project as a post-doctoral researcher at North Carolina State University.
The LSU AgCenter research team heading out for a day of harvesting oysters. Left to right are Naim
Montazeri, Marlene Janes, Jen Shields, Morgan Maite and Jody Donewar, the captain. Photo by Liu Da
Louisiana Agriculture, Fall 2015
13
Studying Rice-Microbe-Insect Interactions
to Increase Rice Production
Lina Bernaola and Michael Stout
G
lobal needs for food and fiber are expected to increase
dramatically over the next few decades, with some
experts predicting that food production will need to
double by 2050 to meet growing demand. Some of the biggest
obstacles to increasing crop production are the challenges
presented by biotic and abiotic stressors such as nutrient
deficiencies and insect pests. One key to overcoming these
obstacles is to better understand the interactions of crop
plants with the great variety of organisms they encounter
both above and below the soil surface.
Soil microbes represent an important but often neglected
component of the soil environment. Over the past decade they
have become an increasingly important subject of innovative
research in agriculture because understanding the interactions of soil microbes with plants has the potential to lead
to novel methods for increasing plant yields and productivity under stressful environments. The LSU AgCenter rice
entomology program conducts studies to develop cost-effective management programs for insect pests that attack rice
in Louisiana. This research program led to interest in the
potential of soil microbes to increase nutrient availability,
enhance crop growth and protect against insect and disease
pests. The research focus in this area is to understand how
soil microbes influence the mechanisms and processes that
allow rice to resist or tolerate attacks by insect pests.
Soil microbes include fungi, bacteria and viruses. The
idea that these microbes can harm crops is a familiar one.
Many “good” soil microbes, however, have positive influences
on agricultural production. Among the most abundant and
common of these good microbes are the arbuscular mycorrhizae fungi (AMF). AMF are ubiquitous, soil-dwelling
fungi that form symbiotic relationships with many plant
root systems; in fact, as many as 80 percent of plant species
are thought to form associations with mycorrhizae. The
Vesicles
plant “partners” in these symbiotic associations supply photosynthetically fixed carbon to the AMF, and in exchange,
the AMF use this carbon to grow mycelial networks that
allow plant root systems to expand more in the soil and
efficiently absorb water and nutrients. Plant-AMF associations generally show positive effects on plants in natural
and agricultural ecosystems. In agriculture, these effects
include plant growth promotion through enhanced uptake
of essential nutrients, such as nitrogen and phosphorus. This
may translate to higher yields in plants colonized by AMF.
Much past research with AMF has focused on the direct
effects of AMF on plants. Interestingly, however, colonization by AMF has also been shown to alter plant resistance
to abiotic and biotic stresses. In particular, colonization of
a plant by AMF can alter the interactions of the plant with
other members of the ecological community, both above
ground and below ground, such as plant-eating insects
and plant pathogens. AMF colonization alters interactions
with these other organisms by influencing plant characteristics such as plant biomass, nutrient content and plant
chemical defenses.
Rice, like most other plant species, can form associations
with AMF. Preliminary observations of rice roots from
Louisiana and other Southern states show that rice is often
naturally colonized by AMF in the field, at least before rice is
flooded (Figure 1). The entomology program is conducting
research to understand how interactions between rice and
AMF influence interactions of rice with pests.
A four-year field study has determined the effects of AMF
on infestations of the rice water weevil, the most important
insect pest of rice in the United States. When rice was inoculated with a commercially available mixture of six species
of AMF, the fungi formed associations with the rice roots
and made rice much more susceptible to infestation by rice
Vesicles
Hyphae
Figure 1. Rice root samples collected from Mississippi and Arkansas rice fields show natural colonization by mycorrhizae. “Vesicles” and
“Hyphae” are fungal structures.
14
Louisiana Agriculture, Fall 2015
water weevil larvae. That is, populations of weevil larvae
were larger on AMF-inoculated roots. In addition, studies
evaluated the effects of AMF on rice susceptibility to the fall
armyworm, a sporadic insect pest of rice, and sheath blight,
an important disease pest of rice. Data obtained so far show
that, after inoculation with mycorrhizae, rice plants become
more susceptible to both armyworms and sheath blight.
The effects of AMF on rice resistance to pests are dependent on soil type, as both field and greenhouse experiments
have shown that rice plants inoculated with mycorrhizae
supported higher densities of rice water weevil larvae and
Densities of Weevil Larvae
20
Mycorrhizae
Mean Larvae per core sample
*
Nonmycorrhizae
15
10
5
0
*
higher relative growth rates of armyworms when grown in
soil from Crowley, Louisiana, but not when grown in soil
from Mamou, Louisiana (Figures 2 and 3). Root biomass of
AMF-colonized rice plants was also greater than non-AMF
plants in an experiment in Crowley but not Mamou. No effects
of AMF colonization on yields were observed in either location. The effects on AMF colonization on pest infestations
and root biomass, coupled with the lack of effect on yields,
suggest that AMF colonization may increase rice tolerance
to rice water weevils. Nutritional analyses of root and shoot
tissues indicated only slight differences in the concentration
of nutrients in AMF-colonized plants.
Although the fact that rice-AMF interactions can make
rice more susceptible to pests is not directly useful for managing pests, the dramatic change in rice resistance caused by
AMF colonization provides a unique window for studying
the traits or characteristics that make rice plants more susceptible to insect and pathogen attack. Studies include the
effect of AMF on the growth of rice plants and the uptake of
nutrients from the soil as well as changes in the biochemistry
and physiology of rice plants that occur following AMF colonization. This research can lead to insights into what makes
rice resistant to or tolerant of pests, and this knowledge will
ultimately contribute to developing more resistant varieties
to improve pest management programs in Louisiana rice.
Lina Bernaola is a graduate assistant and Michael Stout is
the L.D. Newsom Professor in Integrated Pest Management
in the Department of Entomology.
Crowley
2012
Crowley
2013
Mamou
2014
Mamou
2015
Figure 2. Mean numbers of rice water weevil larvae per core
sample in four years of field experiments conducted in two
locations, Crowley and Mamou. An * indicates a significant
difference between treatments.
Armyworm Growth Rates After 10 Days
0.09
0.08
Mycorrhizae
*
Nonmycorrhizae
Relative Growth Rate (g\g\d)
0.07
0.06
0.05
*
0.04
0.03
0.02
0.01
0.00
Greenhouse
soil source
Crowley
soil source
Mamou
soil source
Figure 3. Relative growth rates of armyworm larvae fed for 10 days
on rice leaves from mycorrhizae-inoculated and control plants.
Plants were grown in soil from three sources: a greenhouse soil
mix, soil from Crowley, and soil from Mamou. An * indicates a
significant difference between treatments.
Lina Bernaola, a doctoral student in the Department of
Entomology, poses in her mycorrhizae field experiment at a
research field site located in Evangeline Parish. Photo by Thais
Freitas
Louisiana Agriculture, Fall 2015
15
On-farm Food Safety Research
Helps Louisiana Growers Comply with New Law
Achyut Adhikari
T
he Food Safety Modernization Act
(FSMA) is one of the sweeping
reforms of U.S. food safety laws in
more than 70 years. The main focus of the
act is to reduce foodborne hazards by preventing microbial contamination during
production, processing, handling and
transportation of food rather than relying
on correction after problems occur. Under
FSMA, “FDA will have a legislative mandate
to require comprehensive, science-based
preventive controls across the food supply.”
FSMA requires new standards for growing, harvesting, packing and holding produce for human consumption, also known
as the “Produce Safety Rule.” The rule
identifies five routes of on-farm microbial
contamination – agricultural water, domesticated and wild animals, workers, biological soil amendments, and equipment and
tools – and sets requirements to prevent
or reduce the introduction of pathogens.
Cantaloupe irrigated with UV-C light treated
irrigation water. Photo by Achyut Adhikari
Achyut Adhikari works with students evaluating
the efficacy of ultraviolet light for surface water
treatments. Photo by Robert Williams
From left, Achyut Adhikari, Vijay Singh Chettri and Kathryn Fontenot perform microbial analysis of
watermelon samples. Photo by Kathryn Parraga
16
Louisiana Agriculture, Fall 2015
The potential introduction of foodborne
pathogens during growing, harvesting
and packing necessitates that producers
understand the on-farm sources of harmful microorganisms and apply appropriate
practices to reduce the risk of contamination. FSMA requires fresh-produce growers
to follow practices that minimizes the level
of harmful microorganisms before they
harvest or market their produce. The rule
states the waiting period between irrigation
and harvesting or during storage depends
upon the microbial quality of irrigation
water and the survival of generic E. coli on
the edible portion of the crops.
One of the long-term goals of the LSU
AgCenter is to strengthen the productivity, profitability and competitiveness of
Louisiana’s agriculture. Scientists focus on
applied research that has immediate impact
on the quality, safety and economic viability
of Louisiana-based fresh produce. This is
achieved by collaboration among scientists
from several disciplines that bring expertise
to address critical food safety issues along
the production chain.
On-farm applied research contributes
to the assessment of produce food safety
and guides development of control strategies to mitigate the risks during pre- and
Robert Williams, left, and Ron Strahan collect
watermelon samples for a food safety research
project. Photo by Achyut Adhikari
post-harvest processing. Current research
efforts focus on irrigation water treatments,
the fate and persistence of microorganisms
on fresh produce and the development of
science-based post-harvest processing techniques for food safety risk reduction.
Irrigation water is one of the important
sources of pathogen contamination. Several
methods currently are available for water
treatment, such as chlorine, ozone and
filtration. Not all are suitable for surface
water treatment, however, because of the
complexity, variability and content of suspended particles.
In one on-farm study, AgCenter researchers evaluate the efficacy of ultraviolet
light treatment on reducing the generic
Escherichia coli levels from surface water
used for irrigating cantaloupes. The preliminary results indicate significant reduction of
generic E. coli even at low doses. This means
growers who treat their water with ultraviolet light can harvest earlier because FSMA
requires producers to apply a time interval
between last irrigation and harvest using a
microbial die-off rate based on the generic
E. coli levels of irrigation water. In addition,
producers will benefit from a water treatment process that does not leave any residue
that adversely affects crop production or
soil quality. An ultraviolet light treatment
replaces use of chemical disinfectants and
leaves no residue in the water.
Pecans are native to the lower Midwest
and Midsouth. Native pecan areas have
a long-standing tradition of double-crop-
ping the land by allowing cattle to graze in
pecan groves. Cattle manure is a primary
source of foodborne pathogens such as E.
coli O157:H7, Salmonella spp. and Listeria
monocytogenes. With the potential food
safety risk associated with raw manure,
Louisiana pecan growers may not be able
to have this second source of income by
grazing cattle in pecan groves.
However, a provision in the food safety
act exempts a farm from the produce safety
rule if the produce is processed with a “kill
step.” An LSU AgCenter team of food safety
and quality specialists, pecan specialists and
economists is working on a research project to address this issue. The study aims to
optimize proper antimicrobial intervention
techniques during pecan processing that can
be regarded as a kill step and increase competitiveness of Louisiana-grown pecans.
The fate and persistence of pathogens on
the edible portion of the crops is one of the
important requirements set by the produce
safety rule. Several factors affect the survival
of pathogens, such as temperature, humidity, UV exposure and type of crops. Previous
studies in this area have been performed
in laboratory settings, simulating agriculture environmental conditions. Because of
several variables in an actual farming and
processing environment, laboratory settings may not accurately predict microbial
response and die-off rates that would be in
actual environmental conditions.
AgCenter on-farm studies with watermelons and cantaloupes are focused on
examining the die-off rate of indicator
organisms specific to Louisiana climate
and weather conditions. Results from this
applied research will help growers identify
best growing practices and conditions to
increase productivity and minimize food
safety risks.
Critical knowledge gaps exist regarding
the fate of pathogens in agricultural environments. Understanding the behavior of
indicator organisms in on-farm settings
will enable researchers to conduct pre- and
post-harvest food safety risk assessments.
The outcomes of this applied research on
produce safety will enhance researcher and
grower knowledge of the spread of foodborne hazards on fresh produce and will
help in the development of preventive control practices, allowing Louisiana growers
to comply with FSMA requirements.
On-farm study with ultraviolet light treatment of
irrigation water. Photo by Achyut Adhikari
Preparation of cantaloupe samples. Photo by
Achyut Adhikari
Using diluent to dislodge microorganism from the
surface of cantaloupe. Photo by Achyut Adhikari
Achyut Adhikari is an assistant professor in
the School of Nutrition and Food Sciences and
is in charge of training and education about
the Food Safety Modernization Act.
Louisiana Agriculture, Fall 2015
17
Bt technology
A Major Advancement in Insect Pest Control
David Kerns
M
anaging insect pests has been an ongoing struggle since the birth of agriculture some 10,000
years ago. For the most part, farmers have had
little recourse to mitigate damaging insect populations in
their fields. However, shortly following World War II, the
development of organic insecticides made it possible to
effectively manage most insect pests affecting crop production. However, these tools came with a price. Insect pests
exhibited the ability to adapt to the use of these insecticides
and develop resistance. Additionally, these insecticides
exhibit broad-spectrum activity, meaning they kill insects
indiscriminately – both bad and good insects. By removing
natural predators and parasitoids while removing the pest,
secondary pest outbreaks and resurgence of target pests are
often negative side effects. Lastly, some organic insecticides
had potentially damaging effects on the environment. In
response, over the past 20 years, agricultural researchers
have worked to develop insecticides safe to the environment
and more target-specific, thus minimizing the impact on
predators, parasitoids and pollinators.
One of the greatest advancements in insect pest control
has been through Bt technology. Bt refers to a soil-dwelling
bacterium, Bacillus thuringiensis. These bacteria produce
States. These GMO corn hybrids were highly efficacious,
so much so that corn borers are hard to find in most corn
ecosystems these days. Since these early introductions,
additional Bt genes have been introduced to corn. These
additional proteins are there to help prevent insects from
developing resistance to the Bt proteins and control other
corn pests such as corn rootworm and fall armyworm.
Advances have been made in other crops as well. In
1996, a Bt cotton, was introduced that targeted tobacco budworm and pink bollworm. Up until that time, the tobacco
budworm was a terrible pest of cotton that developed resistance to many of the commonly used insecticides. It was
not uncommon for cotton to be treated with insecticides
six to eight times for tobacco budworm. However, with Bt
cotton no insecticide sprays targeting this pest have been
necessary. Results were similar for pink bollworm. This
does not mean other pests do not affect Bt cotton. Cotton
bollworm and fall armyworm, although affected by the
Bt protein, would still cause unacceptable injury. Since
the initial introduction into cotton, additional Bt protein
genes have been introduced – much like corn – that help
alleviate single toxin weaknesses and for the prevention
of resistance.
The truth of the matter is that reputable, peer-reviewed research has
time after time demonstrated that there are no detrimental effects
of GMO crop products on humans, animals and nontarget insects.
proteins that bind to the stomach of certain insects, causing ulcers that result in death. In the 1970s, a number of
Bt strains were introduced as sprayable insecticides. These
products are extremely safe to nontarget insects and animals, and they are still used, although primarily in organic
production systems. The problem with these products is that
they have to be eaten by the insect to exhibit toxicity. Also,
they rapidly degrade in the environment. Essentially, they
just aren’t very effective unless used every few days. Because
it is the protein and not necessarily the bacterium itself
that affects the insect, researchers had the idea to remove
the gene that codes the protein and insert it into the plant.
Thus, the plant would essentially produce its own defense
mechanism based on the Bt proteins. The beauty of this
strategy is that it is nontoxic, constantly produced by the
plant, and for the most part, highly effective. Because the
plant had a foreign gene introduced into it, it was termed
a genetically modified organism, also known as a GMO.
In 1996, the first GMO corn hybrids developed to combat
corn-boring caterpillars were introduced in the United
18
Louisiana Agriculture, Fall 2015
GMO crops that express Bt toxin have had huge impacts
on the ability to manage insect pests in corn and cotton.
Since their introduction, the reliance on insecticide sprays
to manage pests has decreased dramatically. Insect predators, parasitoids and pollinators are better protected, and
outbreaks of secondary pests are much less common.
There are individuals in society who are critical of GMO
crop products, some to an extreme. They contend that
GMOs are detrimental because they are not natural; they
claim GMOs cause everything from allergies to cancer.
The truth of the matter is that reputable, peer-reviewed
research has time after time demonstrated that there are
no detrimental effects of GMO crop products on humans,
animals and nontarget insects. The U.S. food supply has
never been safer or more productive than it is today, and
GMO crops have played a key role in that development.
David Kerns is an entomologist and associate professor at
the Macon Ridge Research Station in Winnsboro and holds
the Jack Hamilton Regents Chair in Cotton Production.
Internal Regulations and Safeguards
for Biological Materials
Kenneth R. Bondioli
All teaching, diagnostic, research and extension activities
performed by LSU AgCenter faculty, students and visitors that involve
recombinant DNA or potentially hazardous biological materials
must be reviewed and approved by the Inter-Institutional Biological
and Recombinant DNA Safety Committee. This applies to all such
activities which take place on LSU AgCenter land or facilities.
The committee is composed of faculty from many academic
disciplines at LSU, nonscientific members and community
representatives not affiliated with the university. The objective
of the review is to ensure compliance with federal, state and
local guidelines and regulations, ensure the safety of faculty,
students, employees and visitors, and protect the community
and environment from any potential harm arising from these
activities.
A review is initiated by the individual responsible for the
activity, who completes an online registration and submits it
for review. Information in this registration includes the relevant
training and experience of each individual involved, the physical
location where the activity will be conducted, the specific
biological materials involved, specific procedures that will be
performed, and physical containment equipment and personal
protection equipment that will be used. Most importantly, the
principal investigator is required to do a risk assessment of the
potential hazards, if any, to individuals, agricultural crops or
animals and identify steps, such as confinement, protective
equipment and disposal methods, to be used to control these
risks. This risk assessment leads to assignment of a Biological
Safety Level that determines minimal practices necessary to
protect the individuals performing the work, the community and
the environment. Each activity is considered individually.
The final step before a proposal is approved is a physical
inspection of the laboratory or facility where the work is to be
performed to ensure that any specified physical containment
equipment and personnel protection equipment are present
and in working order. Once each year the investigator is asked
to provide any updates such as personnel changes, and every
three years a new registration must be completed and the review
process repeated.
Kenneth R. Bondioli is chair of the Inter-Institutional Biological
and Recombinant DNA Safety Committee and a professor in the
School of Animal Sciences.
Protection for Human Subjects
Michael J. Keenan
Scientists and extension specialists at LSU AgCenter
frequently work with human subjects in scientific studies or
educational programs. The LSU AgCenter has an Institutional
Review Board that reviews research with human subjects to
ensure their protection. This review ensures:
■■ Benefits of the research outweigh risks.
■■ Subjects consent to voluntary participation.
■■ Vulnerable populations – such as children, the elderly,
pregnant women and prisoners – are protected.
There are three possible types of review by the board. The first
type is called “exempt” and is done by one member for six categories of research types. For example, one category is for children
in the normal educational setting, such as school or 4-H. The second type is called “expedited” and includes, for example, studies with collection of blood samples. This review is also done by
one member of the Institutional Review Board. These two categories of review are only allowed if the risk is deemed minimal and
not different from most everyday activities. The third type of review is by the full committee when the research is not exempt or
expedited. The board will determine the category of risk to be
minimal, uncertain or more than minimal. All of these regulations
have been established by the federal government. Also, no human subject can be used to benefit another if there is risk for the
research subject and no benefit for the research subject. For example, the testing of a new high-risk drug to regulate blood glucose would only be used in subjects that had very poor glucose
regulation because they may benefit, and the benefit-to-risk ratio
was beneficial for them.
For review of programs of LSU AgCenter extension specialists,
there is a checklist to determine if the program is research or not.
If the program is not research and approved as not research by
the extension specialist’s supervisor, the board will not review the
program. Any possible risk would then be in the purview of risk
management and LSU AgCenter administration. This is the level
of protection of human subjects in programs that are not considered research. Thus, human subjects who participate in either scientific research studies or programs not deemed to be research
are protected from any risk greater than their possible benefit.
Michael J. Keenan is a professor in the School of Nutrition and
Food Science.
Louisiana Agriculture, Fall 2015
19
Resistant Starch Fermentation
and Human Health
Michael J. Keenan
I
n 2003, LSU AgCenter researchers first became aware
of the use of resistant starch to reduce body fat in rats.
Resistant starch, which is not digested in the small
intestine, is a fermentable fiber found in peas, beans,
lentils and some grain products.
Since then, research conducted at the AgCenter has
demonstrated many beneficial health effects of resistant
starch in the diet of rodents. These include:
1) Reduced body fat when the control diet without
resistant starch has the same energy as the
diet with resistant starch. This is the effect
of fermentation in which bacteria feed on the
resistant starch.
2) Increased production of blood levels of
hormones from the intestines that promote
increased energy expenditure and other health
parameters beyond the intestine.
3) Improved insulin sensitivity and blood glucose
control.
4) A healthier large intestine demonstrated by
measures of fermentation of resistant starch.
5) Increased gene expression for proteins that
improve the function and structure of the
large intestine.
6) Increased levels of a serum peptide, adiponectin,
which prevent inflammation.
7) A healthier microbiota, which is the community
of microbes, in the gastrointestinal tract.
LSU AgCenter research focuses on the study of the
microbes in the gastrointestinal tract. These microbes
consist of bacteria, bacteria-like organisms, viruses
and single-celled organisms. Bacteria are the dominant
entity. Some have described this community of microbes,
or microbiota, as essentially another organ of the body
because there are more bacterial cells in the gastrointestinal tract than cells in the body. Thus, making the
microbiota healthier would be good for overall health.
Initially, researchers demonstrated that fermentation of resistant starch resulted in major changes to
the bacterial populations in the large intestine of rats.
However, this was fairly early in the development of the
science of bioinformatics, which aids in identification
of genetic material of bacterial genes, DNA. The next
step in studying the effects of resistant starch on the
microbiota occurred after the science of bioinformatics had advanced, and researchers could measure the
different types of bacteria involved in fermentation of
resistant starch.
Researchers then used an advanced technique called
high throughput microbial DNA analysis to assess the
entire bacterial community in the large intestine of a
mouse model fed resistant starch. By this time bioinformatics for the microbiota had advanced greatly. The
microbiota composition of obese mice has been shown
to have a different microbiota than lean mice.
One of the most recent projects involved the investigation of the microbiota in Zucker Diabetic Fatty rats.
These are obese rats that possess a defective leptin
receptor. Leptin is primarily produced in white fat and
is a major signal to the brain for the level of body fat. The
research group found that this rat model did ferment
resistant starch and demonstrated what appears to be
a healthier microbiota, even though these rats did not
have reduced body fat, which is typical in other studies
in rodents with sufficient leptin signaling.
Researchers have found that the composition of
healthy microbiota is different among different organisms – human, pig or rodent – and is affected by different dietary fermentable fibers. Resistant starch is one
type of fermentable fiber.
One further note is that AgCenter researchers have
found that feeding resistant starch in a high fat diet, in
which 42 percent of the dietary energy comes from fat,
reduced the fermentation. Future studies will include
microbiota analyses for rodents fed resistant starch in
a high fat diet.
Michael J. Keenan is a professor and researcher in the
School of Nutrition and Food Sciences.
Acknowledgements: The author would like to thank his research group – Roy Martin, formerly with the LSU AgCenter and now at U.S.
Department of Agriculture Human Research Center in Davis, California; Diana Coulon, manager of the Rodent Bioassay Core Lab for
the AgCenter and a veterinarian; Anne Raggio, research associate; Justin Guice, Ryan Page and Diana Obanda, graduate students; and
Felicia Goldsmith, a former graduate student and now a post-doctoral researcher at the Pennington Biomedical Research Institute; and
collaborators Marlene Janes, professor in the School of Nutrition and Food Sciences, and Claudia Husseneder, professor in the Department
of Entomology; Maria Marco at the University of California at Davis; and David Welsh at the LSU Health Sciences Center in New Orleans.
20
Louisiana Agriculture, Fall 2015
Scientist Helps Ensure Safety for LSU
AgCenter Food Incubator Products
Olivia McClure
W
hen food entrepreneurs first
become tenants at the LSU
AgCenter Food Incubator, they
must begin transforming their recipe from
a home kitchen version to something commercially viable. Often, that can mean scaling up the recipe to make larger quantities
or replacing ingredients to make the product
shelf stable.
But one of the most important early steps
incubator tenants must take is ensuring their
product is safe for consumers, said AgCenter
food scientist Luis Espinoza.
“Food safety is all about preventing
foodborne pathogens,” he said. “Your processing has to be designed to kill the target
pathogen.”
After reviewing a tenant’s recipe and process, Espinoza determines which U.S. Food
and Drug Administration product category
it falls into. The different categories, which
include everything from low-acid canned
foods to dairy products, each have their
own set of rules for processing.
The process depends on the product because every product is different,
Espinoza said.
Pickled products, for example, must be
thermally processed, he said. Those products, along with any others that are cooked,
have to reach a certain temperature that is
maintained for a designated holding time.
Next, samples are tested to verify there are
no pathogens present.
Cooked products should be packed while
they’re still hot — above 185 degrees — and
gradually cooled down.
“If you cool it down before packing and
it’s exposed to the environment, the air
is full of food spoilage microorganisms,”
Espinoza said. “Something’s going to get in
there. While it’s still hot, they won’t develop.”
There is a well-established process for
dairy products, which must reach and stay
at a minimum of 145 degrees for 30 minutes
in a pasteurizer.
But some products — like the new ones
Food Incubator tenants are known for crafting — don’t neatly fit into the FDA’s categories or existing rules. That’s when Espinoza
starts doing trials in his lab to find ways to
Luis Espinoza tests product safety at the LSU AgCenter Food Incubator. Photo by Olivia McClure
eliminate dangerous pathogen populations
and meet regulations.
The FDA and state Department of Health
and Hospitals are kept in the loop throughout the process. Espinoza helps tenants write
a process authority review letter — known
as a “PA letter” — that includes a product
description and processing instructions
with weights, temperatures and pH levels.
The FDA requires the letter for processors
of low-acid and acidified foods, or those
with acid added to them.
While the letter is a requirement, it also
gets tenants in the habit of keeping documentation of how they process their products, Espinoza said.
“It will help you have a consistent quality
and a safe product,” he said.
Sometimes, recipes have to be changed
to ensure their safety. In those cases, it
is especially important to help tenants
understand food safety and why it matters,
Espinoza said.
The AgCenter’s School of Nutrition
and Food Sciences hosts a four-day Better
Process Control School twice a year — in
June and January. Attendees of the program are certified per FDA guidelines for
supervising the production of low-acid
and acidified foods. AgCenter experts teach
the courses.
Olivia McClure is a graduate assistant with
LSU AgCenter Communications.
Louisiana Agriculture, Fall 2015
21
Plant Pathogens Threaten the Louisiana Plant World
Lawrence E. Datnoff
The disease-conducive environment in Louisiana and the frequent incursions of new
pathogens into the state make it clear that plant diseases are, and will continue to be,
one of the most limiting factors in crop production. Plant pathologists will continue to
address future threats with a comprehensive approach, including the development of
resistant varieties and other methods of control. They will increase the use of molecular
methods to aid in rapid, precise diagnosis and the use of GPS and other new technologies
to monitor and predict spread of new diseases. The goal is to develop methods of disease
management that are effective and environmentally friendly.
P
lant diseases caused by microbes – including plant pathogenic
fungi, bacteria, viruses and nematodes – have seriously limited
the development and production of agronomic and horticultural crops in Louisiana. Although a number of control strategies
have been developed, new disease threats continually appear. This can
occur because of changes in crop varieties and production practices
or because new plant pathogens are introduced into Louisiana from
other states or countries. Each time a new pathogen arrives or a new
disease outbreak occurs in Louisiana, LSU AgCenter scientists in the
Department of Plant Pathology and Crop Physiology, operating the
only program of its type in the state, provide leadership for generating knowledge and applied solutions for managing these diseases.
Following are examples of important pathogens causing continuing
plant disease threats to agricultural production.
Brown Rust of Sugarcane
Brown rust of sugarcane (Figure 1), caused by a fungus named
Puccinia melanocephala, has been in Louisiana since the late 1970s.
The disease causes reddish-brown leaf lesions that result in reduced
yield. Severe winters limit this pathogen because it must survive from
season to season in living leaf tissue. In the early 2000s, a series of mild
winters resulted in brown rust becoming the most important disease
problem in what is the most valuable row crop in Louisiana. Rust fungi
are highly adaptable plant pathogens that are able to overcome host
plant resistance. Breeding for resistant varieties is the primary control
measure for brown rust. However, resistance has been overcome in
11 of the last 13 varieties released, probably due to pathogenic variability in the population of the pathogen. Therefore, LSU AgCenter
plant pathologists developed a controlled conditions inoculation
system to further evaluate resistance. Experiments proved that specialization existed within the pathogen population to varieties. The
test results also revealed that one variety that has remained resistant
under cultivation exhibited quantitative resistance to all isolates of
the pathogen. This type of resistance is often conferred by multiple
genes and may be more durable. Research is in progress to identify
genes associated with quantitative resistance and develop molecular
markers to use in parent and progeny selection. The employment of
quantitative resistance in combination with markers previously developed to a major resistance gene could provide effective and durable
resistance to brown rust.
22
Louisiana Agriculture, Fall 2015
Bacterial Panicle Blight of Rice
Bacterial panicle blight of rice is a major limiting factor for stable
rice production in Louisiana and the southeastern United States. This
disease is caused by two similar rice pathogenic bacteria, Burkholderia
glumae and B. gladioli, with the former usually more virulent and
problematic than the other. LSU AgCenter plant pathologists are
studying bacterial panicle blight of rice with three major research
aspects. First, molecular genetics and genomics studies of the major
pathogen, B. glumae, have been performed to better understand the
virulence mechanism of this pathogen. Several components that
regulate the virulence of B. glumae have been identified and characterized. Second, genetics and molecular biology associated with the
rice disease resistance to bacterial panicle blight have been studied.
Research projects to help further elucidate methods of control include
genetic mapping of rice genes associated with the disease resistance
and molecular characterization of rice defense pathways against B.
glumae. AgCenter plant pathologists are also studying induced rice
disease resistance to panicle blight under field conditions.
Virus-tested Sweet Potatoes
Because sweet potato plants are vegetatively propagated, pathogens
– especially viruses – accumulate in the “seed” causing a decline in
yields and quality over several years. Over the past 20 years, AgCenter
plant pathologists have determined that four viruses – Sweet potato
feathery mottle virus, Sweet potato virus G, Sweet potato virus C and
Sweet potato virus 2 – that are rapidly spread by aphids are common
in sweet potatoes in the southeastern U.S.
During the 1990s, they found that infection with any one of these
viruses had minimal effect on yield of Beauregard sweet potatoes. But
as the number of viruses infecting a plant increased (Figure 2), the
yields decreased by up to 25 percent to 40 percent. Therefore in 1999,
the LSU AgCenter foundation seed program was converted entirely
to virus-tested seed production. The AgCenter sweet potato breeding lines and varieties are cleaned of viruses by re-growing plants in
tissue cultures from meristem tips, thoroughly tested to ensure that
the resulting plants are free of viruses, and then increased in tissue
culture. These plants are then provided to the Sweet Potato Research
Station at Chase, where they are increased to eventually produce foundation seed, which is sold to farmers.
AgCenter plant pathologists soon learned that producing virustested tissue cultures alone is not sufficient to produce virus-free seed.
They have been working for the past five years to develop tactics to
prevent re-infection with the common viruses. Currently, they are
adapting molecular testing methods that they hope will allow testing
of growers’ seed to help decide when seed needs to be replaced. This
program has provided not only a way to manage viruses that have
been chronic problems in the Louisiana crop, but has also provided a
way to keep two whitefly-transmitted viruses that have been found in
other sweet potatoes in the U.S. out of Louisiana production systems.
Nematodes
The reniform nematode (Figure 3), Rotylenchulus reniformis, has
emerged from relative obscurity to become an important pathogen
to cotton, soybeans and sweet potatoes in Louisiana. LSU AgCenter
plant pathologists have been studying whether precision agriculture
can be applied to better manage this nematode pest. The reniform
nematode is often widespread within a field but may occur in areas
where soil texture favors more damage by the nematode. Most fields
within Louisiana have considerable variability in soil texture across
the field, either at the surface or down several feet. This variability
can be identified with soil mapping equipment such as the Veris EC
3100, which measures how much electrical current soil conducts. Clay
soils will conduct more current than sand or silt. After a field has been
mapped for electrical conductivity, this information can then be used
to develop management zones within a field based on soil texture.
Research with the reniform nematode on cotton has shown that
when electrical conductivity values are low at the surface and down
through the profile, fumigant nematicides have been very effective
in reducing the nematode and providing a significant yield response.
When electrical conductivity values are higher in a field, fumigant
nematicides reduced the nematodes but failed to provide a significant
increase in yield. This information can be used to develop management zones where fumigants can be applied only to specific areas
within a field.
Lawrence E. Datnoff is the head of the Department of Plant Pathology
and Crop Physiology.
Figure 2. Potyvirus symptoms on infected sweet potato leaf. Photo provided
by Christopher Clark
Figure 1. Sugarcane rust. Photo by Jeff Hoy
Figure 3. Reniform nematode feeding on cotton roots. Photo by Charles
Overstreet
Louisiana Agriculture, Fall 2015
23
Photo by Oliva McClure
Linking Soil Microbes and Ecosystem
Functions
Lisa Fultz
L
eonardo DaVinci said it best when he stated, “We
know more about the movement of the celestial
bodies than about the soil underfoot.” A tablespoon of soil contains one of the most biologically
diverse ecosystems on Earth, and, so far, scientists have
identified less than 5 percent of the billons of organisms
in that tablespoon. The microbes are an intricate and
vital component of soil. Microbial diversity enhances
multiple critical soil functions including promoting
plant growth, nutrient cycling, water holding capacity
and filtration, aggregate stability, accumulation of soil
organic matter, and physical stability.
LSU AgCenter research is focused on linking soil
management practices, soil microbial communities,
the functions they are directly responsible for, and how
these processes all interact to maintain and improve
soil health. Soil health, a growing field of study, is
the capacity of the soil to function within ecosystem
boundaries to sustain biological productivity. In particular, AgCenter scientists are trying to determine
how soil microbial communities respond to management practices such as prescribed burns, tillage,
use of cover crops, and double cropping. The quick
response of the dynamic microbial communities and
biological processes to environmental changes make
them sensitive indicators of soil health.
While some organisms are able to subsist on inorganic material, a majority of microbes get their life
requirements from organic carbon in vegetation and
24
Louisiana Agriculture, Fall 2015
other organisms. As they break this material down,
some of the carbon is released into the atmosphere
as carbon dioxide (respiration), some is incorporated
into microbial bodies (assimilation), and still more
is digested and incorporated into organic material.
Some bacterial byproducts of these processes include
organic glues like geosmin, which is an organic compound responsible for the “earthy” smell of soil. Fungi
produce appendages known as mycelia (Figure 1) that
physically bind the soil particles together, improving
aggregate stability and decreasing potential losses
from soil erosion.
As microbes break down the organic material, they
are releasing and recycling soil nutrients – including
nitrogen, potassium and phosphorus – to be taken up
by microbes and plants alike. When they cannot get the
nutrients they need from the soil, some microbes have
the ability to take nitrogen from the atmosphere for
themselves and make it available to plants. This process
is called nitrogen fixation. These organisms include
free-living bacteria like cyanobacteria, or blue-green
algae, and those in symbiotic relationships with plants,
such as legumes and rhizobia. Legumes, in turn, are
desirable not only because they require less nitrogen
fertilizer inputs, but they also act as “green manures,”
supplying a readily degradable nitrogen source when
used as a cover crop, all from their relationship with soil
microbes. Trees and many other plants – in addition
to agricultural crops – profit from relationships with
microbes, which offer access to nutrients,
water and disease protection.
Soil microbes are also central to biological processes for remediating contaminated environments. These processes can
address a wide range of contaminants and
are cost-effective with low environmental impact. While bacteria and fungi are
responsible for many plant diseases, there
are those that aid in disease protection and
suppression. Organisms from the Bacillus
genus have been used for the biocontrol of
Rhizoctonia solani, responsible for root rot
and damping off, and Alternaria helianthi,
responsible for seedling blight in sunflowers. Overall, microbes fulfill multiple roles
in soil ecosystems and are drivers of critical
soil functions.
Lisa Fultz is an assistant professor of soil
microbiology of cropping systems in the
School of Plant, Environmental and Soil
Sciences.
Figure 1. Electron microscope image of plant root and fungal hyphae
intermixed with soil particles. These roots and hyphae work to
physically and chemically hold soil aggregates together, improving
stability and decreasing losses due to soil erosion. Photo by Lisa Fultz
Use of Microbes As Expression Systems
Ted Gauthier
N
early every property that defines
a living organism is determined
by proteins. They guide the many
biochemical processes that make life possible. Proteins can be classified by their
many different biological functions. Some
are transport proteins that move electrons
so that photosynthesis can occur in plants.
Some are enzymes that speed up biochemical
reactions. Still other proteins store nutrients,
defend against invasion by foreign species or
regulate cellular activity. Proteins also play a
critical role in many diseases such as cancer
and diabetes. Because of their importance
in biological systems, it is critical that proteins are studied in detail. To do that, proteins must be produced in the laboratory.
It is often not practical to try to isolate the
protein from the organism that produces it
naturally or to chemically synthesize the
protein. The researcher has several tools in
his or her toolbox to overcome this problem.
One of these tools is called protein expression and is usually carried out in a microbial
system using organisms such as bacteria or
yeast. The most common bacterial expres-
sion system uses Escherichia coli (E. coli for
short) while the most common yeast expression system uses either Saccharomyces cerevisiae or Pichia pastoris.
In the E. coli expression system, the gene
(comprised of DNA), which will direct the
production of the needed protein, is normally introduced via a plasmid expression
vector. In a process called transformation,
the vector is positioned inside the bacterial cells. The bacterial cells are allowed to
grow and replicate. At the same time, the
gene introduced into the bacteria in the
earlier step is also being replicated. Each
copy of the gene will direct the machinery
of each bacterial cell to produce the protein
of interest. Since E. coli grow at a rapid rate,
this expression system can produce large
amounts of protein in a short time. From
a cost perspective, the E. coli expression
system is also relatively inexpensive.
One disadvantage of the E. coli expression
system is that it is limited to producing relatively simple proteins. Oftentimes, research
requires the production of more complex
proteins. Yeast expression systems are
usually very good at producing more complicated proteins. The most common yeast
organisms used in this expression system
are Saccharomyces cerevisiae and Pichia
pastoris. Yeast cells are a more advanced
form of life than bacterial cells. As a result,
they can produce proteins that are more
similar to proteins naturally produced in
more advanced organisms such as plants and
animals. The procedure to express proteins
in yeast is similar to that of bacteria. Yeast
grow moderately fast so protein production
is relatively quick, and the cost is about the
same as that of bacteria.
Protein expression using microbial systems is a cost-effective and efficient procedure that allows scientists to study proteins
that direct biological processes. This may
lead to improved animal and plant products and intervention into diseases that
negatively affect living things.
Ted Gauthier is an associate professor with
the AgCenter Biotechnology Laboratory.
Louisiana Agriculture, Fall 2015
25
Plant Diagnostic Center Serves Louisiana
Raj Singh
I
n Louisiana, millions of dollars are lost
every year in crop yield and quality to
plant diseases, insect pests and competition from weeds. In addition to this
direct loss, increased production costs due
to management of diseases, insects and
weeds result in economic hardships. Plant
problems caused by different biotic (plant
diseases, insect pests or nematodes) and
abiotic (environmental extremes, nutrient
deficiencies or chemical phytotoxicities)
agents may exhibit similar symptoms, or
those caused by similar agents may show
different symptoms. Misdiagnosis and
delayed identification of these problems
may add to an increase in cost of production and a decrease in profits. Therefore,
effective management of plant diseases
and pests starts with accurate and rapid
identification.
The mission of the Plant Diagnostic
Center at the LSU AgCenter is to provide
accurate and rapid diagnosis of plant health
problems and to recommend best management practices to solve these problems. The
Plant Diagnostic Center is one-stop shopping for all plant health problems and provides services for ornamentals, vegetables,
fruits, agronomic crops, trees and turfgrass.
In addition to providing routine diagnostic
services, the center is involved in detection,
testing, surveying and extension outreach
of high impact plant pathogens and pests.
Currently, the center is involved with the
following pathogens and pests of significant importance to Louisiana agriculture.
Horticulture and Fruit
Tree Diseases
Citrus canker and greening are regulatory
diseases, and the citrus industry is facing major
economic impact because of the restriction on
inter- and intrastate movement of any citrus
plant material including fruits from quarantine zones. The Plant Diagnostic Center
provides citrus canker and greening testing
to the Louisiana Department of Agriculture
and Forestry.
Texas Phoenix palm decline (TPPD) is
threatening palms worth millions of dollars
in New Orleans and surrounding areas. It is a
fatal disease that can rapidly kill the infected
palms. Recently, the Plant Diagnostic Center
was awarded a grant of nearly $100,000 by
the U.S. Department of Agriculture to study
TPPD in southern Louisiana.
26
Louisiana Agriculture, Fall 2015
Raj Singh, director of the LSU AgCenter Plant Diagnostic Center, is known as the “plant doctor.” Photo by
Olivia McClure
Last year, LSU AgCenter plant pathologists reported boxwood dieback caused by
Colletotrichum theobromicola for the first
time in the U.S. The center is conducting
further research on detection, host range
and management strategies, which will be
useful to commercial landscapers and home
gardeners. Recently, the diagnostic center
confirmed the Rose rosette disease of roses
in Louisiana for the first time.
Other important plant diseases that
have been detected but not confirmed yet
in Louisiana include bacterial leaf scorch
of blueberry, loquat, sweet olives, olives
and tea; bacterial leaf spot of crape myrtle;
lilac chastetree; and bacterial stem gall of
loropetalums.
Agronomic Crops Diseases
The Plant Diagnostic Center collaborates with extension field faculty in identifying and reporting important diseases of
agronomic crops. Goss’s wilt of corn was
reported in 2013, and research is underway to report sudden death syndrome of
soybeans and target spot of cotton.
Detection of Plant Pathogens
of Economic Importance
In 2014, an AgCenter pathology student
in the Plant Diagnostic Center developed
a loop-mediated isothermal amplifica-
tion for early and accurate detection of
bacterial panicle blight of rice caused by
Burkholderia glumae. It has been reported
to cause losses as high as 70 percent in rice
production in Louisiana. This summer a
horticulture graduate student in the Plant
Diagnostic Center successfully documented
that Phytophthora palmivora is the primary
causal agent of this disease.
Leaf and crown rot of liriope has been
a major problem for commercial nurseries
specializing in ground covers. This summer,
a plant pathology graduate student successfully documented that Phytophthora
palmivora is the primary causal agent of
this disease.
Extension Outreach Program
The Plant Diagnostic Center participates
in delivering educational programs about
newly detected plant problems in Louisiana,
such as the laurel wilt disease and the emerald ash borer insect, both of which cause
destruction to trees. The center participates
in the Louisiana Master Gardener program
and is a member of the National Clean Plant
Network and the National Plant Diagnostic
Network.
Raj Singh is an assistant professor in
the Department of Plant Pathology and
Crop Physiology and director of the Plant
Diagnostic Center.
Rose Disease Found for First Time in Louisiana
Johnny Morgan
A
devastating disease of roses called
rose rosette caused by the Rose
rosette virus has been confirmed
for the first time in Louisiana by two LSU
AgCenter scientists, Allen Owings and
Raj Singh.
Rose rosette was found on landscape
shrub roses growing in a commercial landscape in Bossier City, said Singh, who is a
plant pathologist and director of the LSU
AgCenter Plant Diagnostic Clinic.
“Modern roses, which include our hybrid
tea, grandiflora, floribunda and landscape
shrub cultivars along with antique old
garden roses are equally susceptible to the
disease,” Owings said. “Naturalized plantings of the wild species of rose called multiflora are serving as host plants around
the country.”
Rose rosette disease produces a range
of symptoms, depending on the variety or
species of the rose and the plant’s age. Some
of the more recognizable symptoms of rose
rosette disease include excessive thorniness, thickened new canes and abnormal
discoloration or excessive reddening of
new foliage.
Infected roses produce a cluster of new
shoots from a single point on the parent
canes. The new shoots, which elongate rapidly, have a broom-like appearance called
“witch’s broom.”
Infected canes produce excessive thorns
that are green or red and soft in the beginning but later harden off as the disease
progresses.
“These symptoms can be used to potentially recognize rose rosette disease, but
positive confirmation of the disease requires
molecular testing,” Singh said.
Although rose rosette disease produces
unique symptoms on roses, those symptoms
can be confused with symptoms caused
by other diseases, pests, stresses and other
factors.
Improper use of herbicides such as glyphosate may result in distortion and clustering of new growth that looks like witch’s
broom.
Abnormal discoloration and distortion
of new foliage have been associated with
rose rosette disease, but feeding injury
from chilli thrips, which is a significant
rose-growing issue in Louisiana, also cause
similar symptoms.
Excessive thorns that are soft and green on
infected new growth of Knock Out rose in Bossier
City. Photo by Raj Singh
Witch’s broom symptoms caused by rose rosette disease on Knock Out
rose in Bossier City. Photo by Raj Singh
Similarly, excessive reddening of new
growth is a normal characteristic of some
rose varieties.
Rose rosette disease is transmitted by a
tiny eriophyid mite or by grafting, Singh
said.
“Management of rose rosette disease in
infected roses is not possible. Once a rose
is infected, there is no cure,” Singh said.
Several precautions can be taken, however, to avoid introduction of the disease or
to reduce its spread from infected to healthy
roses. Go to www.LSUAgCenter.com and
search for rose rosette.
If rose rosette disease is suspected,
consult Singh at 225-578-4562 or email
[email protected].
Johnny Morgan is a communications
specialist and professor with LSU AgCenter
Communications.
Louisiana Agriculture, Fall 2015
27
Studies on the Transmission of Insect-borne Viruses
That Cause Hemorrhagic Disease in Deer, Cattle
Lane Foil, Michael Becker, Willie Andrew Forbes, Glen T. Gentry, James M. LaCour, Stephanie R. Ringler and
Jonathan L. Roberts
Researchers from the LSU AgCenter
and state agencies are conducting studies
on the transmission of insect-borne viruses
that cause hemorrhagic disease in deer and
cattle at the LSU AgCenter Bob R. JonesIdlewild Research Station, which houses the
Bob Jones Wildlife Research Institute. The
two viruses that cause hemorrhagic disease
are epizootic hemorrhagic disease virus and
bluetongue virus, which are orbiviruses.
There are many different strains of these
two viruses, and unfortunately immunity to
one strain does not provide protection from
other strains. The symptoms of hemorrhagic
disease in small ruminants such as whitetailed deer and sheep include cyanosis (the
skin is blue due to a lack of oxygen in the
blood), internal hemorrhaging, lameness,
high fever and dehydration. Mortality rates
can exceed 90 percent in infected whitetailed deer populations. Cattle infected with
these orbiviruses normally do not develop
clinical disease and are considered to be
reservoirs of the viruses; however, in some
cases, symptoms such as heavy salivation,
weight loss, a decrease in lactation, coronitis, and stillbirths or abortions can occur.
Because cattle do not suffer clinical hemor-
rhagic disease, testing is not required unless
animals are shipped internationally to an
area that requires orbivirus testing prior
to entry. Therefore, infected cattle are routinely shipped to other domestic locations
and can be the source of new virus strains
in these areas.
Outbreaks of hemorrhagic disease occur
when susceptible animals are introduced
into regions where these viruses are endemic
or when the viruses spread into susceptible ruminant populations. For example, a
bluetongue disease outbreak in Europe in
2006-2007 resulted in the death of tens of
thousands of sheep and affected more than
30,000 farms. In the U.S., transmission of
epizootic hemorrhagic disease virus and
bluetongue virus can cause extreme mortality in both wild deer and farmed deer
herds. The deer farming industry is rapidly
expanding in the United States, including
Louisiana. In 2007, the estimated value of
U.S. deer farming was near $3 billion, and
it accounted for 29,000 jobs. Probably the
most important health problem facing deer
farms today is hemorrhagic disease due to
the transmission of epizootic hemorrhagic
disease virus and bluetongue virus. This
Deer at the Bob R. Jones-Idlewild Research Station in Clinton. Photo by Johnny Morgan
28
Louisiana Agriculture, Fall 2015
transmission is not independent of wild
white-tailed deer or cattle herds. Records
are not available for the number of deaths
associated with hemorrhagic disease that
occur annually on these deer farms, but
there are recent examples of these outbreaks
in wild deer populations.
In the United States, outbreaks in wild
white-tailed deer populations have been
devastating. During 2012, one of the largest
outbreaks of hemorrhagic disease recorded
in U.S. history occurred in South Dakota,
where the Game, Fish and Parks department
issued refunds for hunting licenses due to
the high level of deer mortality. Deer deaths
attributed to hemorrhagic disease were
estimated at 15,000 in Michigan, 10,000 in
Missouri and 6,000 in Nebraska, resulting
in a 30 percent decline in the white-tailed
deer harvest in that state. In Louisiana,
while wild deer deaths were reported from
some areas, the magnitude of the outbreak
was less than in the more northern states.
In spite of the effect on wild deer populations, deer farmers, hunters and wildlife
services, no information is available on the
vectors associated with the 2012 outbreak.
Furthermore, for wild deer populations,
there often is no proof of the cause of death;
the time of year and location of the carcasses
in or near water lead wildlife personnel to
attribute the deaths to hemorrhagic disease.
Currently, the only known vectors of
epizootic hemorrhagic disease virus and
bluetongue virus are biting midges in the
genus Culicoides. Some common names
of these flies include sand flies, punkies,
no-see-ums, midges and biting midges. In
south Louisiana, they are more commonly
referred to as gnats. In Louisiana, more
than 25 species of Culicoides have been
reported. One species, C. sonorensis, has
been shown to transmit orbiviruses and has
been the focus of many studies. The biology
and control of this species, primarily found
near intensive cattle production systems, is
well known. Unfortunately, that species is
not present in most of the locations where
outbreaks occur in wild populations or
farmed deer herds.
Research aims and techniques
The research project goals are to fill in
the knowledge gaps that exist regarding the
transmission of the viruses that cause hemorrhagic disease. Particular objectives are
to identify the insects involved during the
active transmission season of summer and
fall and determine how the viruses persist
between transmission seasons. Additional
studies have been conducted to improve
diagnostic techniques for determining the
probable cause of death of wild deer when
carcasses are found and begin to estimate
the percentage of deer that survive exposure
to orbiviruses.
The study was initiated in fall 2011 at
the Bob R. Jones-Idlewild Research Station
where reproductive herds of cattle and
white-tailed deer are managed specifically
for the purposes of the project. The studies use serological techniques to determine
exposure to and molecular techniques to
determine the presence of the different
viruses. At least once each year, all animals are tested for exposure to the different
viruses during the previous transmission
season. Blood samples from clinically ill animals and spleen and bone marrow samples
from dead deer are tested for the presence
and serotype identification of the viral RNA.
Scientists conduct research on deer at the Bob R. Jones-Idlewild Research Station. Photo by Johnny
Morgan
Insect collections are made weekly during
the transmission season and monthly
during the winter period, and the insects
are identified and tested. Virus culture also
is conducted on positive samples from ruminants and insects. These techniques have
been used to capture valuable information
regarding orbivirus transmission.
Findings
An outbreak of clinical hemorrhagic
disease occurred in white-tailed deer in
2012, and symptoms were observed in some
cattle. There were cases of both epizootic
hemorrhagic disease virus and bluetongue
virus in the deer herds. Thirteen species
of Culioides were tested for both epizootic
hemorrhagic disease virus and bluetongue
virus, and three bluetongue virus-positive Culioides species and their population
peaks coincided with the deaths of deer
confirmed to be bluetongue virus positive.
The death patterns of the deer showed that
epizootic hemorrhagic disease virus transmission peaks preceded bluetongue virus
transmission, and no Culioides were found
to be epizootic hemorrhagic disease virus
positive. At least 25 percent of the captive
deer exposed to bluetongue virus and epizootic hemorrhagic disease virus survived.
Research showed that bone marrow samples
collected from deer carcasses can be used
to determine if the deer had been exposed
to bluetongue virus for up to four months
postmortem, thus increasing the likelihood
of determining the cause of death to be
hemorrhagic disease.
Applications
The research shows that at least three
species of Culioides are important in the
transmission of the viruses that cause hemorrhagic disease in deer. Studies also have
determined the larval habitats of these insect
species as well as their yearly and daily flight
activity periods. The findings of those studies can be used by deer population managers
to determine habitat management methods
for the immature stages of the vectors and
insecticide application periods for adult
vector control. The studies also indicate
that alternate vectors exist for epizootic
hemorrhagic disease virus and bluetongue
virus, and researchers are in the process
of examining those differences. The finding that captive deer survived exposuure
to viruses could point the way to future
studies on the genetics of susceptibility to
orbiviruses and deer herd immunity. The
bone marrow study provides a diagnostic
tool for deer population managers who want
to determine a probable cause of death for
deer carcasses found after collection of other
tissues is not possible.
Lane Foil is a professor and Pennington Regents Chair for Wildlife Research at the Bob R. Jones-Idlewild Research Station and Department of
Entomology; Michael Becker is a research associate in the Department of Entomology; Willie Andrew Forbes is a research associate and Glen
T. Gentry is an associate professor at the Bob R. Jones-Idlewild Research Station; James M. LaCour, DVM, is state wildlife veterinarian in the
Louisiana Department of Wildlife and Fisheries; Stephanie R. Ringler is a research associate in the Department of Entomology; Jonathan L.
Roberts, DVM, is a veterinary medical officer in the Office of Animal Health and Food Safety, Louisiana Department of Agriculture and Forestry.
Louisiana Agriculture, Fall 2015
29
Use of Microbes in Oil Spill Cleanup
Andy Nyman
F
ollowing an oil spill, we sometimes hear about commercial products based on microbes that are bred to
consume the oil. Such consumption often is called
biodegradation. Before addressing microbial consumption
of oil, it helps to begin with the role of other microbes in
creating oil. Oil and other fossil fuels contain solar energy
captured by plants millions of years ago. Most of the
biomass produced then did not become fossil fuels but
instead was consumed by microbes and converted into
carbon dioxide and water as microbes used the energy
in the biomass. The same thing happens to most biomass
today. Whether it is forest or crop residue, this consumption requires oxygen. However, biomass that ends up in the
sediments of wetlands, lakes and oceans cannot be completely consumed because oxygen moves too slowly through
water to meet the demand of all the microbes. Numerous
microbes that do not need oxygen greatly alter the biomass
as they consume what they can. But most of the biomass
becomes immune to such consumption because it is highly
altered. The biomass will remain immune to microbial
consumption as long as there is no oxygen. Eventually this
biomass becomes fossil fuels. Later, people mine fossil fuels
and subsequently occasionally spill oil.
Oil that is exposed to oxygen becomes susceptible to
microbial consumption. Microbes capable of consuming
oil occur in a wide variety of environments that contain
oxygen. The microbial species that win the competition
for oil differ from place to place and even differ over time
within a place as temperature, salinity and nutrient availability change. Most microbial scientists agree that resident
oil-eating microbes will almost always consume more oil at
particular a site than oil-eating microbes from another site
unless the two sites are virtually identical in fluctuations
of temperature, moisture, pH, nutrients, etc. Microbial consumption of oil can be enhanced when
natural conditions do not provide enough oxygen or nutrients. Thus, upland soils and some beaches sometimes are
plowed or scraped to bring oily soil into contact with oxygen.
Nutrient additions accelerate microbial consumption of
oil where oxygen is plentiful but nutrients are scarce, such
as in some upland soils and some beaches. In Louisiana’s
coastal wetlands, however, oxygen is available only at the
soil surface. But nutrients are naturally abundant there,
too. Thus, nutrients are not recommended as a response
to oil spills in Louisiana’s coastal wetlands. Microbial processes other than biodegradation of oil
also are important. Nitrate dissolves well in water and is
a common form of fertilizer and a component of fertilizer runoff. But nitrogen gas is virtually inert and makes
30
Louisiana Agriculture, Fall 2015
up about 78 percent of the air that we breathe. In wetlands, some microbes can convert nitrate into nitrogen
gas. This reaction is called denitrification. Farmers generally want to minimize denitrification, whereas people
charged with reducing water pollution generally want to
maximize denitrification. An AgCenter researcher has
estimated that 14 percent of the nitrogen that flows into
the Atchafalaya River is removed before the river reaches
the Gulf of Mexico. In the Atchafalaya Basin, denitrification removes about 14 percent of the nitrogen in the water
that enters the basin before being discharged into coastal
waters. Another AgCenter researcher and his collaborators
saw that crude oil reduced denitrification rates by about
half in coastal marsh soils. Microbial consumption of oil is one of the motivations
for dispersing spilled oil because it is hoped that changing
a surface layer of oil into submerged drops of oil will create
more surface area for microbial attack. It is clear that dispersed oil spreads out and travels to different places than
undispersed oil, but the effects on biodegradation have been
inconsistent in research literature. Dispersants allow oil
and water to mix because they contain substances known
as surfactants, which is a contraction of surface-active. A
surfactant allows oil and water to mix because one end
of the molecule dissolves in water whereas the other end
dissolves in oil.
Some microbes produce natural surfactants known as
surfactin. Some companies design microbes that cannot
reproduce and do very little other than produce surfactin. Surfactin would not be a good ingredient in a dispersant, however, because surfactin does not dissolve well in
water. Scientists working at Modular Genetics, Inc. designed
a new surfactant called FA-Glu and designed microbes to
produce it. An AgCenter researcher found that FA-Glu
was less toxic than surfactin; his collaborators at Columbia
University found that FA-Glu was a better surfactant than
surfactin. Using microbes to produce surfactants on a
commercial basis requires competing with petroleum
chemists who can change crude oil into a wide variety of
chemicals. Such efficiency generally requires sugar as a food
for the microbes. One AgCenter researcher has identified
pretreatments that increase the efficiency of microbial
production when using sugarcane bagasse as food for the
microbes. It is hoped that in the future, microbial scientists will design more efficient, less toxic surfactants and
ways to use agricultural waste products to produce them. Andy Nyman is a professor in the School of Renewable
Natural Resources.
Ruminants and Their Rumen Microbes
Guillermo Scaglia
R
uminants are one of the most successful
groups of herbivorous mammals on the
planet, with around 200 species represented by approximately 75 million wild and
3.5 billion domesticated individuals worldwide. Cattle, sheep and goats constitute about
95 percent of domestic ruminant populations.
Ruminants have the distinguishing feature of
a four-chambered stomach: reticulum, rumen,
omasum and abomasum (or true stomach).
Ruminants are defined by their mode of plant
digestion: a fermentation process for which
they have evolved a forestomach, the rumen,
which allows partial microbial digestion of
feed before it enters the abomasum.
Ruminants themselves do not produce the
enzymes needed to degrade most complex
plant polysaccharides. The rumen provides
an environment for a rich and dense consortium of anaerobic microbes that fulfill this
metabolic role. These rumen microbes ferment feed to form major nutrient sources for
the host animal and contribute significantly
to ruminant productivity. The host animal
also uses microbial biomass and some unfermented feed components once these exit the
rumen to the remainder of the digestive tract.
The rumen has evolved to digest various
plant materials by a complex community
of microbes consisting of bacteria, archaea,
protozoa and fungi. Within this community, bacteria are the dominant group and
make the greatest contribution to digestion.
Most of ruminal archaea produce methane,
a potent greenhouse gas that is implicated in
climate change. Both bacterial and archaeal
populations can be affected by many factors,
such as species and age of host animals, diets,
feeds, feed additives, seasons and geographic
regions. Distinct bacterial communities have
developed in the rumens of cattle associated
with eating bermudagrass hay versus those
grazing on winter wheat. These results clearly
identify the tremendous variation in ruminal
microbial ecosystems that respond to the composition of grass forage diets.
Because of the complex and interlinked
nature of the rumen microbial community,
a more drastic change in diet – for example a high level of fiber versus a high level
of grain – has a cascading effect on rumen
microbial metabolism. Rumen acidosis and
bovine methane production are examples of
how the interaction between rumen microbial
metabolism and diet influence animal performance. In intensive livestock production
systems, diets are often grain-based and rich
in fermentable carbohydrates. This leads to
enhanced microbial production of lactic acid
and a consequent lowering of ruminal pH
with harmful consequences to the animal.
Intestinal methane production also represents
a loss of energy to the animal and is significant
in terms of its impact as a greenhouse gas. In
particular, high levels of dietary fiber typical
for a beef cow are associated with increased
methane production.
Ruminants allow conversion of human-indigestible plant material into readily accessible animal products, especially dairy
products, meat and useful fibers. Ruminants
have thus played a vital role in sustaining and developing many human cultures,
as well as being used as draft animals
and having religious and status values.
Beyond sustaining an animal, the rumen provides a unique genetic resource for the discovery of plant cell wall-degrading microbial
enzymes for use in biofuel production, presumably because of coevolution of microbes
and plant cell wall types.
Guillermo Scaglia is an associate professor
at the Iberia Research Station, Jeanerette,
Louisiana.
Using Microbes to Fight Disease in Catfish
Ron Thune
E
dwardsiella ictaluri is a serious bacterial pathogen of channel catfish
that costs the catfish aquaculture
industry millions of dollars in losses every
year. LSU AgCenter researchers have been
studying the disease condition, known as
enteric septicemia of catfish, or ESC, since
the late 1990s. This effort resulted in a live,
attenuated vaccine derived from live, mutant
bacteria patented in in 2000. The vaccine is
delivered by adding it to the water, whereupon it can move into the internal organs of
catfish as soon as 15 minutes later – essentially “injecting” itself and protecting the
fish against subsequent exposure to the
wild-type E. ictaluri. The fish, however, were
able to clear the vaccine strain in only two
to four days, reducing the level of exposure
and subsequent protection, which precluded
commercial development.
The concept of a live attenuated
vaccine, however, led to several U.S.
Department of Agriculture competitive grants. The grant-funded research
developed a model that explains the initial disease process when the bacterium
infects immune-related cells known as
macrophages. The job of the macrophage
is to ingest and destroy invading bacterial
cells. E. ictaluri, however, evolved a set
of at least 42 genes that encode proteins
that make up a system that allows it to
not only survive but to replicate itself in
these macrophages that are set to destroy
it. Several of these proteins, known as
effector proteins, are actually injected
from the bacterium into the host-cell
cytoplasm, where they manipulate the
catfish immune response to their own
advantage. Constructing mutant strains
of E. ictaluri that selectively knock out
the function of these effector proteins has
led to testing new live, attenuated vaccine
strains that persist up to 18 days in the
fish tissue and provide a much stronger,
longer-lasting immune response. Work
is ongoing to further improve the strain,
which will eventually lead to another
patent application.
Ron Thune, a professor in the Department
of Pathobiological Sciences in the LSU
School of Veterinary Medicine and the
Aquaculture Research Station in the LSU
AgCenter, has been studying the disease
condition known as enteric septicemia of
catfish, or ESC, since the late 1990s.
Louisiana Agriculture, Fall 2015
31
Pending FDA Rules Could Increase Demand
for AgCenter-developed Cattle Vaccine
Rick Bogren
P
ending regulations from the U.S. Food
and Drug Administration could significantly expand the market for a bovine
vaccine developed in the LSU AgCenter more
than 20 years ago.
For years, cattle producers have used chlortetracycline in animal feed as a preventative
for the disease anaplasmosis. The drug, a
broad-spectrum antibiotic, will no longer be
available in feed after January 1, 2017, through
restrictions provided in a Veterinary Feed
Directive from the FDA.
An alternative is an anaplasmosis vaccine
developed in the early 1990s by LSU AgCenter
researchers Gene Luther, Lewis T. Hart and
William Todd. The vaccine is produced and
marketed by University Products LLC, of
Baton Rouge, which is operated by Luther, a
veterinarian and AgCenter professor emeritus.
Anaplasmosis has never been a feedlot disease because chlortetracycline has been used
in cattle diets, Luther said. The anaplasmosis
vaccine, however, has been used with beef and
dairy cattle. Because chlortetracycline in milk
of dairy cows darkened children’s teeth, milk
contaminated with chlortetracycline is prohibited from the human food chain.
The vaccine is a “killed vaccine,” which
means it uses the dead Anaplasma organism to
create immunity in cattle. When the vaccine is
injected, the animal’s body creates antibodies
and “cell-mediated immunity, which we think
actually gives the protection,” Luther said.
Anaplasmosis, a disease caused by an intracellular microorganism, causes the destruction
of red blood cells in cattle. It occurs primarily
in tropical and subtropical areas, but it has
spread to other parts of the country with the
distribution of cattle.
“It’s probably in every state of the union,”
Luther said. “It has steadily moved north.”
Infected animals suffer severe and profound
anemia, and the mortality rate escalates as animals become older and have a higher need for
oxygen, Luther said. The greatest problems are
with pregnant and nursing cows. Acute cases
show no signs until an animal has lost about 50
percent of its red blood cells and 40 to 60 percent of the remaining cells are infected and lost.
“When you see a cow that’s sick, it’s almost
too late to treat the animal,” Luther said. The
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Louisiana Agriculture, Fall 2015
disease has a 21- to 28-day incubation period.
As the animal becomes anemic, it can become
aggressive and may attempt to fight. The stress
of the fighting can result in the animal collapsing and dying from lack of oxygen.
Typical responses are that cows will go dry
or abort their fetus, and mortality increases
with animal age and weight. “It takes a cow
about 120 days to recover if it survives infection,” Luther said.
“Our vaccine is the best option for prevention,” he said. “Animal owners should vaccinate all mature cows and replacement animals
when they are 12 to 14 months old.”
The anaplasma bacterium is spread by ticks
and horseflies. If an animal survives a natural
case of anaplasmosis, its immune system will
protect against the organism for the life of the
animal. Cattle that recover from anaplasmosis, however, are carriers that can spread the
disease to susceptible cows.
After the researchers developed the vaccine, the AgCenter licensed it to PitmanMoore, which began the process of getting
USDA approval to market it. During the U.S.
Department of Agriculture licensing process,
Pitman-Moore was acquired by Mallinckrodt,
which finished the USDA process and began
marketing the vaccine as Plazvax. A few years
later, Mallinckrodt was bought by ScheringPlough, which elected not to produce and
market Plazvax. No commercially available
vaccine for anaplasmosis was then available.
After Schering-Plough took the vaccine
off the market, Luther said, a large dairy in
Florida petitioned the USDA to allow the use
of the vaccine, and the product was granted
experimental status. The USDA is the regulatory agency for veterinary biological products.
The anaplasmosis vaccine is the only killed
vaccine available in the United States, Luther
said. The USDA allows its sale as an experimental product that can be sold only to licensed
veterinarians.
University Products is in the final steps of
building a new lab in Baton Rouge that should
meet the USDA requirements for a licensed
facility. They will then proceed to attain a fully
USDA-licensed anaplasmosis vaccine.
Rick Bogren is a science writer and professor
with LSU AgCenter Communications.
Gene Luther, center, holds bottles of an anaplasmosis vaccine he developed with two LSU AgCenter
colleagues in the early 1990s. Luther is flanked by his sons Gene, left, and Don, who work with him in
University Products LLC, which markets the vaccine. Photo by Rick Bogren
Prevent Foodborne Illness at Home
Wenqing Xu
F
oods provide valuable nutrients, flavors,
satisfaction and pleasure. They represent
diverse cultures from different countries
around the world. However, there is one thing
about food that people are not familiar with
or don’t want to think about, and that is that
all foods carry risks. Compared with physical
and chemical risks, microbiological risk is one
that sometimes gets overlooked.
According to Centers for Disease Control
and Prevention, millions of Americans
suffer from foodborne illness every year.
When you think about the fact that food
provides nutrients, it is not hard to believe
that it also provides nutrients for microorganisms. Some foods naturally have a
higher risk while others are relatively safer
due to properties such as acidity and water
content. However, from farm to fork, risk
exists everywhere and can be magnified
or reduced depending on what we do to
manage it.
Consumers have many potential risks
beyond personal control. For example,
the seeds of our favorite sprouts may not
be pathogen free; irrigation water for our
spinach may have been contaminated; wild
animal feces with E. coli O157:H7 may have
dropped on our lettuce; a packer who carries
Norovirus without any symptoms may have
picked our strawberries; the equipment in
the ice cream processing facility may have
had Listeria persistence; the thermostat for
our canned green beans may not have been
properly calibrated so the processing temperature was wrong.
Standing at the end of the food supply
chain, consumers are vulnerable. Yet people
actually have a lot of power to control risks
associated with their food. Never overlook
food safety at home because it is the last
opportunity to manage risk before it’s too
late. Through effective risk management
practices, people can reduce risk and make
our food safer.
Separate, clean, cook and chill are the
four key words for home food safety. From
grocery shopping to the food on our plate,
these four actions play an important role at
every single step.
Separating raw meats, poultry or seafood from fruits and vegetables prevents
cross-contamination. This applies to shopping cart and shopping bags in the store,
as well as cutting boards and refrigerators
in the kitchen. Separate pet foods from
human foods, especially if pets are given a
raw-food diet.
Cleaning starts with clean hands when
selecting fresh produce at grocery stores.
Thoroughly wash hands before preparing
foods, after touching raw meats, poultry or
seafood, and after using restrooms; wash
fruits and vegetables before consuming;
routinely clean the kitchen, including countertop and refrigerator; clean and sanitize
all kitchen tools, such as cutting boards and
knives, after each use.
Cooking food to the required internal
temperature is extremely important. Use a
food thermometer to determine if food has
been cooked sufficiently. Timers and visual
appearance may not always be reliable.
Take making hamburgers, for example. The initial temperature of the patties,
cooking methods, the power output of the
oven or stove, and even the temperature of
the environment all affect cooking time.
Microwaving some food can also be tricky.
Food may appear fully cooked but actually
be raw inside. Always use a thermometer to
make sure the center of the food reaches the
required temperature. And don’t forget to
calibrate the thermometer to ensure accuracy is maintained over time.
Chilling brings food out of the temperature danger zone of 40 to 140 degrees, the
range in which microorganisms can grow
faster. Some things to do include not leaving foods on the countertop for a whole
afternoon; not thawing meats or seafood
at room temperature; not leaving groceries
in the car on a normal Louisiana day for an
extended period of time; keeping refrigerators at 40 degrees or lower and freezers at
0 degrees or lower.
Keep food safety in mind when handling food, whether it’s purchasing, storing,
cooking or reheating. Food always carries
risks, but as consumers, we have the power
to reduce that risk.
Wenqing Xu is the extension food safety
specialist.
Food Safety at Home
Controlling the micobiological risk at home
SEPARATE
•Separate
•
foods when
shopping, storing and during
preparation.
CLEAN
•Clean
•
hands when selecting fresh
produce at the grocery store.
•Wash
•
hands before preparing
foods
•Wash
•
fruits and vegetables before
consuming.
•Routinely
•
clean the kitchen,
countertops and refrigerator.
•Clean
•
and sanitize kitchen tools,
cutting boards and knives.
COOK
•Cook
•
food to the required
internal temperature.
•Always
•
use a thermometer.
CHILL
•Don’t
•
leave food at room
temperature for more than two
hours.
•Keep
•
refrigerators at 40 degrees or
lower; freezer at 0 degrees or lower.
Louisiana Agriculture, Fall 2015
33
AgCenter Scientists at the Forefront
of Brucellosis Eradication
Sue D. Hagius and Philip H. Elzer
B
rucellosis is a bacterial infection that
affects both animal and human health.
Known as “Bang’s Disease” in animals
and “undulant fever” in people, it is considered
a zoonotic agent – one which passes between
animals and humans. In animals, brucellosis
results in abortions, infertility and decreased
milk production. Symptoms in people are flulike and may progress to a serious illness if not
treated. Anthropological studies have found
evidence of the organism in carbonized cheese
and bone lesions in human remains from areas
affected by the eruption of Mount Vesuvius in
79 AD. People are generally infected through
contact with animals or animal products contaminated with the bacteria. Animals transmit
the disease to each other through exposure to
the infectious organism during reproduction,
delivery and lactation. Bovine brucellosis in
the United States has been managed through
the use of vaccination and an eradication program, although wildlife reservoirs still harbor
the bacteria. Bison and elk in the Yellowstone
National Park area are infected with Brucella
abortus, and feral swine throughout the U.S.
are carriers of B. suis.
Animal brucellosis is classically a reproductive disease of livestock and may cause
abortions, stillborns and weak offspring.
Infected animals have problems with fertility
and milk production. Chronically infected
animals may exhibit no clinical signs but are
still a threat to animals and their handlers. The
presence of the disease in a region or country
results in regulations restricting animal move-
34
Louisiana Agriculture, Fall 2015
ment and adversely affects exports and the
trade economy. Management of animal disease
is the first step in human disease prevention.
The genus Brucella contains six classical
species designated by their host preference: B.
abortus (cattle); B. melitensis (goats and sheep);
B. suis (pigs); B. canis (dogs); B. ovis (sheep);
and B. neotomae (desert wood rat). Human
brucellosis may be caused by B. melitensis, B.
abortus, B. suis and B. canis. Relatively new
species have been isolated from marine mammals. Two species – B. pinnipedialis (seals,
sea lions and walruses) and B. ceti (whales,
porpoises and dolphins) – are of unknown
significance but have been known to infect
humans. Brucella microti – which was found
in the common vole, red foxes, and the soil
in some areas of Europe – has not yet been
detected in man or livestock. Through the use
of new technologies, several atypical species
have been proposed because of their genetic
similarities to the classical brucellae. Two
such strains identified as B. inopinata have
been cultured from humans, and a Baboon
strain was isolated.
Although they have a distinct preference
for their chosen host, the bacteria may infect
other hosts. Cattle disease is generally caused
by B. abortus and results in abortion and
infertility, but B. suis from feral swine can
also infect cattle. These reactions trigger a
full epidemiological investigation, which is
expensive and time-consuming, but without
these investigations, producers and states
would go into a quarantine situation. This is
not only detrimental to the U.S. eradication
program, but it would have a huge economic
impact on the beef industry.
Several of the brucellae are considered
“select agents” by the federal government,
which means they are viewed as a possible
threat to public health and safety. As a potential biological weapon, these bacteria are under
strict security and government regulation. The
Centers for Disease Control (CDC) and U.S.
Department of Agriculture require laboratories to receive special licensing to work with
these pathogens. The brucellosis scientific
community has been negatively affected by the
governmental restrictions on their research;
increased cost for security and procedures
has placed a financial burden on institutions,
which has caused many to choose not to maintain select agent labs. This has had an adverse
effect on the training of new scientists as the
next generation of brucellosis researchers.
The LSU AgCenter has been conducting
brucellosis research for more than 40 years.
Projects have involved cattle, goats, sheep,
pigs and young bison. Through collaboration
with other universities and governmental
agencies, the disease has also been studied in
mature bison, elk, deer, antelope and reindeer.
Initially, the focus was on the control of the
disease because of its negative effect on the
cattle industry. A plan for the eradication of
the disease from cattle in the southwestern
marshes of coastal Louisiana was implemented
and was successful in controlling the problem. AgCenter researchers participated in the
Using Microorganisms in the
Manufacture of Dairy Foods
evaluation and testing of the current bovine
brucellosis vaccine B. abortus RB51. This live
but less infectious strain was studied for its
safety in pregnant animals and its ability to
protect young cattle from disease later in life.
RB51, unlike the previous vaccine, B. abortus
strain 19 (S19), does not interfere with the laboratory diagnostic tests used in disease surveillance. The approval of RB51 as the official
vaccine in 1996 was an important addition to
the USDA eradication program, which began
in 1934. In 2009, all 50 states were declared
bovine brucellosis free.
Although goat brucellosis is not a problem
in the United States, goats and sheep are worldwide providers of food and fiber, and they are
the main source of human infection in many
countries. AgCenter researchers studied the
disease in goats and demonstrated the goat to
be an excellent disease model because of the
similarity of the infection in other animals,
the economics of a less expensive animal with
a shorter pregnancy cycle, and the ability to
increase animal numbers in research projects. Several universities collaborating with
AgCenter scientists benefited from this novel
disease model. The search continues for a vaccine that would be useful in both domestic and
wild animals, and the goat brucellosis model
will be an important aspect of future research.
The AgCenter brucellosis laboratories are
continuing vaccine, animal modeling and
diagnostic studies. Currently, an effort to
use a nonselect agent Brucella as an effective
challenge strain in vaccine efficiency trials
is being evaluated. Testing of new diagnostic
techniques using both serological assays and
bacteriological procedures is being pursued.
As subject matter experts, AgCenter scientists are involved in trainings for national and
international scientists. Working with governmental and industry agencies, the laboratory
strives to stay abreast of all recent developments in brucellosis research to remain an
active force in the effort to eradicate this
human and animal disease.
Sue D. Hagius is a research associate and
coordinator in the School of Animal Sciences;
Philip H. Elzer is the associate vice president
for animal science and natural resource
programs and a professor in the School of
Animal Sciences.
Kayanush J. Aryana and Luis Vargas
C
ulture and fermentative microorganisms have been identified as
“good” microorganisms that help
start the milk fermentation process and
have played a role in the manufacture of
cultured and fermented dairy products
for centuries. These functions include:
• Fermentat ion of suga rs by
microorganisms leads to the
formation of acids that lower the
acidity of fluid milk, thickening it
or converting it to a curd.
• Acids produced impart a distinctive sour taste.
• Acidic conditions and in some
instances the production of
bacteriocins (toxins produced by
bacteria to inhibit growth of other
bacteria) prevent the growth of
some pathogens and some spoilage
organisms.
• Fermentative microorganisms
are responsible for the production of volatile compounds that
contribute to the flavor of dairy
products.
• Alcohol may also be produced
as a result of microbial fermentation, which is essential during
the manufacture of koumiss and
kefir.
• Fermentative microorganisms
possess enzymes that are desirable
for the maturation of certain
cheeses.
In the manufacture of various cultured
or fermented dairy products, specific culture microorganisms are associated with
the product; precise conditions are used
during their fermentation and the milk
or milk base has specific composition
and treatment.
Cultured dairy products can be manufactured using: lactic acid bacteria or lactic
fermentations; mold-lactic fermentations;
yeast-lactic fermentations.
Various culture bacteria have reported
health benefits. Consuming cultured
dairy foods reduces counts of most culture bacteria when they reach the lower
gastrointestinal tract. Microbial susceptibility to stomach acids and bile conditions are important contributors to these
lowered numbers of the health-beneficial
bacteria. Improving the acid and bile
tolerances of culture bacteria is important, along with increased emphasis on
diets containing less carbohydrate, less
fat and more protein. Whey proteins
contain branched chain amino acids,
which play a role in muscle building
and are popu lar a mong at hletes.
A study was conducted to determine
whether incremental additions of whey
protein isolate would improve acid and
bile tolerances of two yogurt culture bacteria – Streptococcus thermophilus and
Lactobacillus bulgaricus.
Whey protein isolate was added to
broths with each bacterium in concentrations ranging from 0 percent to
3 percent. All were evaluated for acid
and bile tolerances. In the final results,
whey protein isolate improved acid and
bile tolerances of both culture bacteria.
Bile salts can cross the cell membrane,
damage proteins and DNA and result in
leakage of intracellular material. Whey
proteins may slow down the damage of the
bacterial cell proteins or facilitate protein
repair. In addition, bile emulsifies fats
and the lipid membrane of bacterial cells.
Whey proteins may function as a barrier
or a partial barrier between the bile and
the lipid membrane of the bacterial cell.
Whey protein isolate is a good source
of amino acids needed by bacteria. This
research has identified a new role of whey
protein isolate with a potential added
advantage to consumption of whey protein isolates.
Kayanush J. Aryana is a professor of
dairy foods technology in the School
and Animal Sciences, and Luis Vargas is
one of his former graduate students and
now a Ph.D. student in agricultural and
biological engineering at the University of
Illinois at Urbana-Champaign.
Louisiana Agriculture, Fall 2015
35
Inside:
In the case of termites, microbiome
engineering has the ultimate goal of
pest control. See Page 8
Noroviruses do not grow in foods; they
are merely transmitted to food, where
they linger for an extended period of
time. See Page 12
Understanding the behavior of
indicator organisms in on-farm settings
will enable researchers to conduct
pre- and post-harvest food safety risk
assessments. See Page 16
Plant pathologists will continue to
address future threats with a comprehensive approach, including the development of resistant varieties and other
methods of control. See Page 22
LSU AgCenter
128 Knapp Hall
Baton Rouge, LA 70803