Summary points from Lecture 2:
Fungi & fungi-like protists, reproductive phase of flagella-driven zoospores.
 Oomycota (= Oomycetes) are in a group “Stramenopiles” (= with two,
unequal flagella) of the Protista (Chromista are a Kingdom not recognized by
everyone) with:
 Filamentous vegetative cells and absorptive nutrition (like fungi),
 BUT with a Cellulose-like compound in cell walls (unlike fungi),
reproductive zoospores with 2 kinds flagella (tinsel and whiplash = Protista,
unlike the fungi),
and a lysine AA pathway unlike the fungi,
 Oomycotans have mainly diploid lifecycles (compare with humans).
 Terrestrial Oomycotans have evolved non-motile, air dispersed sporangia
that function like mold spores, in addition to zoospores that require water.
Chytridiomycota (= Chytridiomycetes or “chytrids”) are true fungi with
 Chitin-walled filamentous vegetative cells or very a simple one-celled thallus
and reproductive cells zoospores with one posterior whiplash flagellum.
 Chytrids usually have mainly haploid lifecycles, but some
are have alternation of generations (= multicellular 1N and 2N phases).
 Chytrids reproduce only by zoospores that require water.
World-wide, frog declines (die-offs) are caused by a chytrid called
Batrachochytrium (or new viruses). This is an example of an Emerging
Infectious Disease (EID). Bullfrogs cultivated for meat around the world are
symptomless carriers – evidence of worldwide disease transmission..
NOTE that zoospores are easily dispersed, facilitating disease transmission.
Fungi are eukaryotes:
Fungi are most closely related to animals:
There are five main groups of fungi (recognized as phyla or classes)
http://tolweb.org/tree?group=Fungi&contgroup=Eukaryotes
http://tolweb.org/tree?group=Zygomycota&contgroup=Fungi
You can determine what a name means by ending
and whether it is italicized:
Kingdom: EUMYCOTA
Phylum: Dikaryomycota
Subphylum: Basidiomycotina
Class: Holobasidiomycetes
Order: Agaricales
Family: Agaricaceae
Genus: Agaricus
Species: Agaricus brunnescens
-- the edible (supermarket) mushroom.
From your Text, “The Fifth Kingdom”
Lecture 3: Molds I – The Zygomycota
Reading – Text chapter 3;
http://tolweb.org/Zygomycota/20518
http://tolweb.org/Glomeromycota
http://en.wikipedia.org/wiki/Arbuscular_mycorrhiza
http://blog.mycology.cornell.edu/2006/12/14/pilobolus-and-the-lungworm
Objectives: To recognize (when you see them) this important group of
airborne and soil-, dung-, debris-inhabiting, composting, mycorrhizaforming, food-producing, food-spoiling, and human disease-causing group
of moulds.
Key features of the Zygomycetes:
• Haploid
• Filamentous or yeast vegetative state; no regular
crosswalls in hyphae (aseptate).
• Both sexual and asexual sporangia producing spores.
• Sex by fusion of sex organs (gametangial fusion) to form
zygosporangia.
Zygomycete The name of the class comes from the type of sexual
union- fusion or conjugation - of morphologically similar gametangia to form
a zygosporangium. 'Zygos' is Greek for a yoke or joining.
Zygosporangia usually develop thick walls, and act as resting spores.
http://www2.uni-jena.de/biologie/mikrobio/fportraits/phycomy3.htm; also your TEXT
Zygospores of Mucorales
These structures represent the sexually reproductive spores of several genera of
Mucorales. They are usually dark, roughened, 1-celled, and connected to the filaments by
short cells called suspensors. They rarely occur apart from asexual fruiting structures and
are not normally used exclusively for identification purposes. Ref: Schipper, Samson, and
Stalpers 1975; Zycha and Siepmann 1970
http://www.botany.utoronto.ca/ResearchLabs/MallochLab/Malloch/Moulds/Zygos
pores_of_Mucorales.html
Yeast cells (left) and hyphae (right) are the two types of fungal vegetative
cells. Some fungal species are dimorphic. Here, both types of cells are
roughly the same width but the magnification is different. Yeasts are 5-20um
in size, Bacteria are less than 1 um (DIAGNOSTIC LAB clue #1).
Diagnostic lab clue #2:
(yeast vs. bacteria size was clue #1):
Zygomycetes have coenocytic, aseptate hyphae:
One cell with many nuclei and no septa
- photo below.
On right are septate hyphae found in
Ascomycetes and Basidiomycetes
http://botit.botany.wisc.edu/images/130/Fungi/Zygomycota_Images/Rhizopus_Images/Coenocytic_hyphae_2_MC.low.jpg
http://biology.unm.edu/ccouncil/Biology_203/Images/Fungi/hyphae.gif
http://www.fungionline.org.uk/images/1intro/mycelc.jpg
Class Zygomycetes. 7 orders, 30 families, 125 genera, almost 900 species.
I will introduce you to four of the orders: the Mucorales Entomophthorales - Kickxellales and Glomales.
Order Mucorales 13 families, 56 genera, 300 species. This order includes all
the common saprobic zygomycetes. Here belong the ubiquitous bread mould,
Rhizopus stolonifer (below), and the equally common genus Mucor
Sexual zygospore of Rhizopus:
note it is melanized, thick-walled,
and spiny.
Asexual sporangium of Rhizopus
Rhizopus is used to ferment soybeans to make tempeh
Rhizopus lifecycle:
A mainly haploid lifecycle
with asexually produced
sporangia and spores
(mitospores),
plus sexually produced
zygospores that produce
zygosporangia(meiospores).
Homothallic species can go
through whole lifecycle from
one meiospore.
Heterothallic species cannot;
must mate.
Image from your Text
Mucorales are generally saprobic and are common moulds that
cause serious commercial food loss.
Rhizopus Rot, Rhizopus spp.
Rhizopus rot is a soft fungal rot
of harvested or over-ripe stone
fruits. Fungal growth and fruit
decay are greatly retarded in
cold storage but advance rapidly
at warm temperatures, allowing
loss of many fruit within the
shipping container.
http://www.caf.wvu.edu/kearneysville/disease_descriptions/omrhizop.html
Mucorales are saprobes:
Spinellus fusiger
Infected Mycena cap
http://www2.uni-jena.de/biologie/mikrobio/fportraits/fportraits.htm
Sept. 14, 2003
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Mucormycosis (Zygomycosis) is a fungal infection of the sinuses, brain, or lungs that
occurs primarily in people with immune disorders. The most common species causing
disease are Absidia corymbifera, Rhizomucor pusillus, and Rhizopus arrhizus.
Causes, incidence, and risk factors:
Mucormycosis is caused by common fungi frequently found in the soil and amongst
decaying vegetation. Most individuals are exposed to these fungi on a daily basis -but people with immune disorders may be more susceptible to infection.
Conditions most commonly associated with mucormycosis include diabetes mellitus,
chronic steroid use, metabolic acidosis, organ transplantation, leukemia/lymphoma,
treatment with deferoxamine, and AIDS.
http://www.northarundel.com/ency/article/000649.htm
Syndromes associated with mucormycosis include:
*
Rhinocerebral infection (infection sinuses & brain)
*
May start as a sinus infection
*
May progress to involve inflammation of cranial nerves
*
May cause blood clots that block vessels to the brain (thrombosis)
*
Pulmonary mucormycosis (lung involvement)
-- rapidly progressive pneumoniamay spread to chest cavity, heart,& brain.
*
Mucormycosis of the gastrointestinal tract, skin, and kidneys.
Pilobolus crystallinus is an atypical but fascinating coprophilous (anmal dung-inhabiting)
member of the order Mucorales. It grows very rapidly, and is one of the first fungi to fruit in the
extended succession that occurs on dung (see Chapter 11). Its unbranched sporangiophores are 24 cm tall, and have a unique explosive dispersal mechanism.
Jens H. Petersen, Department of Systematic Botany, Biological Institute, University of Aarhus, Denmark
http://www.mycokey.com/AAU/Systematics/SystematicsZygo.html#anchor382268
Beneath the black apical mitosporangium is a lens-like subsporangial vesicle, with a lightsensitive `retina' at its base that aims growth of the sporangiophore very precisely toward any light
source. It is phototropic.
Osmotically active compounds cause pressure in the sporangiophore and the subsporangial vesicle
to build up until it is more than 7 kilograms per cm2. This eventually causes the vesicle to explode,
hurling the black sporangium up to 2 metres, toward light, . 0-20 mph in 2 u sec. . Subsporangial
vesicle goes with the sporangium, and glue it to whatever it lands on. Animal parasites ride along!
Other Mucorales families often have fewer spores per sporangium,
and their sporangia have no columella (trend to reduction).
All images from Text
Order Entomophthorales often attack insects.
Entomophthora muscae infects, and eventually
kills, houseflies. Dying flies, riddled by the fungus,
usually crawl into exposed situations -- I find them
on windows, and on the growing tips of shrubs in
my garden -- where the fungal infection bursts
through the insects' exoskeleton and produces
tightly-packed masses of sporangiophores (right).
Each sporangiophore bears one unicellular, sticky mitosporangium that is shot away at
maturity. When the fly dies on a window, this barrage produces a whitish halo of
mitosporangia on the glass. These sporangia can infect other unsuspecting flies that come to
pay their last respects. As you may already have guessed, species of Entomophthora are
being investigated for their potential in biological control of insect pests (see Chapter 14).
Order Kickxellales (Named after a mycologist called Kickx). Members of this order are
atypical of the Zygomycetes in that they often have regularly septate hyphae.
I have found Coemansia (left) on bat dung from a cave. Its tall sporangiophore bears
many fertile side branches called sporocladia. Each of these produces a row of lateral
cells called pseudophialides (true phialides are discussed in Chapter 4). Finally, from the
apex of each pseudophialide arises an elongate, one-spored mitosporangium (a
sporangiole). From your Text.
Order Glomales. These soil-inhabiting fungi were placed in the Zygomycota only
tentatively, since almost none of them form zygosporangia.
Nevertheless, they are extremely important, because their hyphae enter the living root cells
of perhaps 90% of all higher plants and establish with them obligate mutualistic symbioses
called arbuscular mycorrhizae (AM) or
endomycorrhizae (Chapter 17).
arbuscules
vesicles
Many of the Glomales produce both arbuscules and lipid-filled structures
called vesicles or intramatrical spores inside plant roots, as this
photomicrograph of a root squash shows..
http://tolweb.org/tree?group=fungi
http://tolweb.org/Glomeromycota (Dirk Redecker)
Glomus desertica outside rose roots
http://mycorrhiza.ag.utk.edu/augeva2.htm
http://tolweb.org/tree?group=Glomeromycota&contgroup=Eukaryotes
Molecular identification and phylogeny of arbuscular mycorrhizal fungi
Dirk Redecker Institute of Botany, University of Basel, Switzerland
The fossil record and molecular data show that the evolutionary history of arbuscular
mycorrhizal fungi (Glomales) goes back at least to the Ordovician (460 million years
ago), coinciding with the colonization of the terrestrial environment by the first land
plants. At that time the land flora only consisted of plants on the bryophytic level.
Ribosomal DNA sequences also indicate that the diversity within the Glomales on the
family and genus level is much higher than previously expected from morphology-based
taxonomy. Two deeply divergent lineages were found and described in two new genera,
Archaeospora and Paraglomus, each in its own family.
Based on the fast-growing number of available DNA sequences, several systems for
molecular identification of the Glomales within roots have been designed and tested in
the past few years. These detection methods have opened up entirely new perspectives for
studying the ecology of arbuscular mycorrhiza.
http://www.waite.adelaide.edu.au/Soil_Water/3ICOM_ABSTs/Abstracts/R/D.%20Redecker.html
http://www.berkeley.edu/news/media/releases/2000/09/14_funghi.html
http://tolweb.org/tree?group=Glomeromycota&contgroup=Eukaryotes
Lecture 3:
Molds I – The Zygomycota
Reading – Text chapter 3
Objectives: To recognize (when you see them) this important group of
airborne and soil-, dung-, debris-inhabiting, composting, mycorrhizaforming, food-producing, food-spoiling, and human disease-causing group
of moulds.
Key features of the Zygomycetes:
• Haploid
• Filamentous or yeast vegetative state; no regular
crosswalls in hyphae (aseptate).
• Both sexual and asexual sporangia producing spores.
• Sex by fusion of sex organs (gametangial fusion) to form
zygosporangia.
Lecture 4
Mushrooms, etc.- Basidiomycotans with one-celled basidia
Reading: Text, beginning of Chapter 4, all of Chapter 5 (Lectures 4-8);
Suggested: Anderson JB & Kohn LM. 2007. Dikaryons, dipolids and evolution.
Sex in Fungi: molecular determination and evolutionary implications. Edited by
Heitman J, Casselton L, Taylor JW,& Kronstad J.
Objectives: Understand what a dikaryon is and consider its significance. In
lecture and lab get the basic lifecycle of mushroom-forming fungi in the
Basidiomycota and learn basic mushroom structure.
http://tolweb.org/tree?group=Basidiomycota&contgroup=Fungi