Chapter 7
Microbial Nutrition,
Ecology, and Growth
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• Be sure to note which of the words are
bold and purple we’ll be using them for
something later
2
Microbial Nutrition
Nutrition – process by which chemical substances
(nutrients) are acquired from the environment and
used in cellular activities
Essential nutrients – elements or molecules that
must be provided to an organism b/c they can’t be
synthesized by the organism
For Humans?
Fats-Omega 3 fatty acids
Amino Acids-Tryptophan
Vitamins- A, B,
Dietary Minerals- Ca, Cu, Na, Fe,
3
Growth Factors: Essential Organic
Nutrients
• Growth factors organic compounds that must
be provided as a nutrient
– Organism cannot make it on its own
– Essential amino acids, vitamins, and nucleic
acids
4
Microbial Nutrition
Macronutrients
o required in large
quantities
o cell structure/ metabolism
o EX: Proteins,
carbohydrates
Micronutrients
o Aka trace elements –
required in small
amounts
o protein
structure/enzyme
function
o EX: Manganese, zinc,
nickel
5
Nutrients
• Organic nutrients – contain carbon and
hydrogen atoms
– EX: methane (CH4), macromolecules
• Inorganic nutrients – No C-H
– Metals and their salts (magnesium sulfate, ferric
nitrate, sodium phosphate), gases (oxygen, carbon
dioxide) and water
6
Chemical Analysis of Cell Contents
Organic
(97%),
29.1
Water (70%),
70
Other, 30
Inorganic
(3%), 0.9
7
Essential Biological Nutrients
8
PROCESS BOX 7-1
• Why is a combination of macronutrients
and micronutrients required for
organisms? Why are these both
considered essential nutrients?
3 LINE MINIMUM!
Nutritional Types
• Main determinants of nutritional type are:
– Carbon source
– Energy source
10
Sources of Essential Nutrients
• Main determinants of nutritional type are:
– Carbon source
• Heterotroph – must obtain carbon in an
organic form made by other living organisms
• Autotroph – an organism that uses CO2, an
inorganic gas as its carbon source
–Not nutritionally dependent on other living
things
11
Heterotrophs and Their Energy Sources
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Two categories
– Saprobes: free-living
microorganisms that feed on
organic detritus from dead
organisms
• Opportunistic pathogen
• Facultative parasite
– Parasites: derive nutrients from
host
• Pathogens
• Some are obligate parasites
12
Nutritional Types
• Main determinants of nutritional type are:
– Energy source
• Chemotroph – gain energy from chemical
compounds
• Phototrophs – gain energy through
photosynthesis
13
PROCESS BOX 7-2
• What “troph” combination would best
describe an organism is degrading large
organic molecules to get both carbon and
energy? Why?
2 LINE MINIMUM!
• Draw a concept map, outline, or graphic
organizer that shows the relationships
between the bold purple words from the
previous slides
15
16
Put it all together!
Mode of Nutrition
Energy Source
Carbon Source
Photoautotroph
Light
CO2
Chemoautotroph
Inorganic chemicals
CO2
Photoheterotroph
Light
Organic chemicals
Chemoheterotroph
Organic chemicals
Organic chemicals
17
Active and Passive Transport
18
Crash Course Biology
• “Membranes and Transport”
19
Transport: Movement of Chemicals
Across the Cell Membrane
• Passive transport – does not require energy; substances
exist in a gradient and move from areas of higher
concentration toward areas of lower concentration
– Diffusion
– Osmosis – diffusion of water
– Facilitated diffusion – requires a carrier
• Active transport – requires energy and carrier proteins;
gradient independent
– Active transport
– Group translocation – transported molecule chemically
altered
– Bulk transport – endocytosis, exocytosis, pinocytosis,
phagocytosis
20
Diffusion – Net Movement of Molecules Down
Their Concentration Gradient (Passive Transport)
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21
Osmosis - Diffusion of Water (Passive Transport)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
22
Response to solutions of different osmotic content
23
Osmosis in the
kidney
24
25
Group Translocation
26
Endocytosis: Eating and Drinking by Cells
• Endocytosis: bringing substances into the cell
through a vesicle or phagosome
– Phagocytosis ingests substances or cells
– Pinocytosis ingests liquids
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
27
Review
1) What is a difference between active and
passive transport?
2) What will happen to a cell placed in a hypotonic
solution?
3) What is the difference between diffusion and
facilitated diffusion? Similarity?
4) Group translocation vs bulk transport?
5) Phagocytosis vs pinocytosis?
6) Endocytosis vs exocytosis?
28
Summary of Transport Processes
29
PROCESS BOX 7-3
• A cell is in a concentrated glucose solution
and the glucose is moving into the cell
through a carrier protein would be an
example of what type of cell transport?
How do you know?
2 LINE MINIMUM!
Environmental Factors That
Influence Microbes
• Niche: totality of adaptations organisms make to
their habitat
• Environmental factors affect the function of
metabolic enzymes
– Factors include:
•
•
•
•
•
Temperature
Oxygen requirements
pH
Osmotic pressure
Barometric pressure
31
3 Temperature Adaptation Groups
Psychrophiles – optimum temperature below 15oC; capable of
growth at 0oC
Mesophiles – optimum temperature 20o-40oC; most human
pathogens
Thermophiles – optimum temperature greater than 45oC
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32
Temperature and Disease
• Body isn’t evenly heated.
– Extremities are at 30 – 35ºC and
scrotum at 32ºC.
– Cooler areas are more prone to
diseases such as:
• Hansen’s disease (Leprosy-Mycobacterium leprae)
• Syphilis (Treponema
pallidum).
–Used to treat syphilis by
inducing fever (with
malaria) and hot springs
Gas Requirements
• Oxygen is not as wonderful as we think!
• Very destructive molecule
– Why fruits (with antioxidants) are important
• There are enzymes to detoxify O2
Culturing by Oxygen Requirement
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Photo by Keith Weller, USDA/ARS
© Terese M. Barta, Ph.D.
Categories of Oxygen Requirement
• Aerobe – utilizes oxygen and can detoxify it
• Aerotolerant anaerobes – do not utilize oxygen but
can survive and grow in its presence
• Anaerobe – does not utilize oxygen
• Facultative anaerobe – utilizes oxygen but can also
grow in its absence
• Microaerophilic – requires only a small amount of
oxygen
• Obligate aerobe – cannot grow without oxygen
• Obligate anaerobe – lacks the enzymes to detoxify
oxygen so cannot survive in an oxygen environment
36
Categories of Oxygen Requirement
• Aerobe vs Anaerobe?
• Aerotolerant anaerobes vs Microaerophilic ?
• Obligate aerobe vs Obligate anaerobe ?
• Obligate anaerobe vs Facultative anaerobe ?
37
PROCESS BOX 7-4
• Rank all of the terms related to gas
requirements from needing the most
oxygen to needing the least oxygen
a.
b.
c.
d.
e.
Aerotolerant anaerobes
Microaerophilic
Obligate aerobe
Obligate anaerobe
Facultative anaerobe
Environmental Factors That
Influence Microbes
“PHILE”
Niche
39
Take a guess
• Acidophiles vs Alkalinophiles?
40
Effects of pH
• Majority of
microorganisms grow at a
pH between 6 and 8
(neutrophiles)
• Acidophiles – grow at
extreme acid pH
• Alkalinophiles – grow at
extreme alkaline pH
41
Osmotic Pressure
• Most microbes exist under hypotonic or isotonic
conditions
• Halophiles
• – require a high concentration of salt
• Osmotolerant
• – do not require high concentration of solute but
can tolerate it when it occurs
42
Other Environmental Factors
• Barophiles
• – can survive under extreme pressure and will
rupture if exposed to normal atmospheric
pressure
43
PROCESS BOX 7-5
• Chlamydomonas nivalis
grows on Alaskan
glaciers and it’s
photosynthetic pigments
give the snow a red crust.
What would be a good
“phile” term to describe
this organism and why?
2 LINE MINIMUM!
Types of symbiotic
relationships?
45
Ecological Associations Among
Microorganisms
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46
Examples
• Mutualism
– Cows and bacteria that produce cullulase
– Rhizobium and legume plants
• Commensalism
– Some of the bacteria in our stomach
– Mites on the skin
• Parasitism
–
–
–
–
Tapeworm (fungus)
Hookworm
Cholera bacteria
Small box bacteria
• Can change
– Streptococcus pyogenes Com-Par
47
The Study of Microbial Growth
• Microbial growth occurs at two levels:
– increase in cellular size
– increase in population size
• Division of bacterial cells occurs mainly through
binary fission (transverse)
–
-
Parent cell enlarges
Duplicates its chromosome
forms a central transverse septum
divides the cell into two daughter cells
– Similar to what process in animal/plant cells?
48
Binary Fission
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49
Rate of Population Growth
• Time required for a complete fission cycle is called
the generation, or doubling time (12 cells)
• Each new fission cycle increases the population
by a factor of 2 – exponential growth
• Generation times vary from minutes to days
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50
51
Review
• If the doubling time is 20minutes, how
many Salmonella could be on your food if
left out for 5 hours
52
Viable Plate Count
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Flask inoculated
Samples taken at equally spaced intervals
(0.1 ml)
60 min
500 ml
120 min
180 min
240 min
300 min
360 min
420 min
480 min
540 min
600 min
135
230
0.1
ml
Sample is
diluted in
liquid agar
medium
and poured
or spread
over surface
of solidified
medium
Plates are
incubated,
colonies
are counted
None
Number of
colonies (CFU)
per 0.1 ml
<1*
2
4
7
13
23
45
80
Total estimated
cell population
in flask
<10,000
5,000
20,000
35,000
65,000
115,000
225,000
400,000
*Only means that too few cells are present to be assayed.
675,000 1,150,000
Growth Curve
54
PROCESS BOX 7-6
• Based on what you saw with the graph on
the previous slide, describe why you think
there is a LAG, a LOG, a STATIONARY,
and a DEATH phase.
3 LINE MINIMUM!
The Population Growth Curve
In laboratory studies, populations typically display a
predictable pattern over time – growth curve
Stages in the normal growth curve:
1. Lag phase
2. Exponential growth phase
3. Stationary phase
4. Death phase – as limiting factors intensify, cells die
exponentially
Lag Phase
• “flat” period at start
– Time to adjust to new environment
– Cells enlarge and prepare to split
– Growth > death
Log Phase
• “curved” exponential period
– Bacteria are growing at their maximum rate
– Will continue as long as space and nutrients
are good
– Growth >> Death
Stationary Growth Phase
• “plateau” period in middle
• Survival mode
– Nutrients/space VERY limited
– Too many toxins
• Growth = Death
Death Phase
• “Downward curve” period
• Death occurring at an exponential rate
– Not as fast as growth
• Cells can still survive for a long time at this
point
• Growth < Death
Put it all together
Methods of Analyzing Population Growth
• Turbidometry – most simple
– Cloudiness(turbidity) reflects the relative population
size
– How Spectrophotometer works:
https://www.youtube.com/watch?v=pxC6F7bK8CU
62
Methods of Analyzing Population Growth
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Enumeration of bacteria:
– Viable colony count
– Direct cell count – count all
cells present; automated or
manual
– How to use
Hemocytometer
–
https://www.youtube.com/watch?v=pP0xERLUhyc
63
PROCESS BOX 7-7
• What was the easiest thing you learned
this chapter and why? What was the most
difficult think you learned this chapter and
why?
2 LINE MINUMUM!