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MICRB 265 > 6-3: Environmental effects on microbial growth > Flashcards

6-3: Environmental effects on microbial growth Flashcards

1
Q

What environmental factors that need to be suitable for microbial growth

A

Temperature, pH, water, osmolarity, O2 levels, radiation levels, lack of toxic substances

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2
Q

All organisms have ________,_________ and _________ temperatures for growth

A

Minimal, optimal, maximal

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3
Q

What do higher temperatures do to microbial growth?

A

Increase rates of enzymatic reactions, but at a point proteins start to denature, membrane loses integrity

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4
Q

What do lower temperatures do to microbial growth?

A

Reactions proceed slowly, membrane fluidity becomes an issue, transport inefficient

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5
Q

What is the typical growth range for a microbe?

A

Less than 40 degrees C

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6
Q

What microbes have an optimal growth rate below 15C?

A

Psychrophile

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7
Q

What microbes have the most widespread organisms, grow at intermediate temperatures (8 to 48 degrees C)?

A

Mesophile

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8
Q

What do you call microbes with optimal growth rate above 45 degrees C?

A

Thermophile

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9
Q

What do you call microbes with optimal growth rate above 80C?

A

Hyperthermophile

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10
Q

What are psychrophiles?

A

Psychrophiles grow optimally at low temperatures

eg. Snow algae, Chlamydomonas nivalis

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11
Q

What are psychrotolerant organisms?

A

Can grow at low temperatures, but grrow optimally as mesophiles (20-40 degrees C)

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12
Q

Where do psychrophiles live?

A

The oceans, arctic, the antarctic, glaciers (areas that are always cold)

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13
Q

What happens when psychrophiles are exposed to moderate temperatures

A

They are killed

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14
Q

What adaptations do psychrophiles have

A

Increased short fatty acid chains and unsaturated fatty acids in cell membranes = fluidity
Cold shock proteins to help protein/RNA folding
Cryoprotectants to prevent ice formation

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15
Q

What do cold temperatures do to bacteria, compared to excessive heat?

A

Cold doesn’t always kill, unlike excessive heat. Actually prevents growth (eg. storing bacteria in 10% glycerol at -80)

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16
Q

Where do thermophiles/hyperthermophiles live

A

Surface soils, compost piles in sunlight
Hot springs, hydrothermal vents

17
Q

What is the only domain of microbe that can grow at temperatures above 60C?

A

Prokaryotes

18
Q

What temperature can bacteria grow up to? What temperature can archaea grow up to?

A

Bacteria - 95 degrees
Archaea - 122 degrees

19
Q

How are thermophiles/hyperthermophiles adapted to high temperatures

A

Increased number and strength of intermolecular protein interaction
Heat stable solutes that support proteins
Longer more saturated f.a. hold membrane together (archaea have lipid monolayer)
Heat-stable enzymes/solutes (eg. Taq pol)

20
Q

What are acidophiles?

A

Microbes that prefer low pH (acidic conditions)

21
Q

What are alkaliphiles?

A

Microbes that prefer higher pH (alkaline conditions)

22
Q

What is the cytoplasmic pH in alkaliphiles and acidophiles?

A

Maintained close to neutral (6-8)

23
Q

What is the point of the low pH of the stomach?

A

Barrier that protects us from infection by consuming contaminated food/water

24
Q

What does acid tolerance of enteric pathogens influence?

A

Infectious dose (minimum number of organisms needed to get sick), Buffering or increasing stomach pH = lower infectious dose

25
Q

What is the most significant osmotic factor?

A

Salt concentrations

26
Q

What are halophiles

A

Organisms that live in high salt environments (eg. hypersalinated lakes), may require high salt concentrations

27
Q

What are compatible solutes

A

Solutes produced by cell in high solute environments to increase cytoplasmic solute concentration. Do not interfere with the cell’s biochemical processes (highly water soluble and inert).

28
Q

List some common cytoplasmic compatible solutes

A

Glu/Pro, Sucrose, KCl, Glycerol

29
Q

What are facultative anaerobes

A

O2 not required, but grow better with it. Use aerobic and anaerobic respiration.

30
Q

What are microaerophilic microbes

A

Excel in low O2 environments, use aerobic respiration

31
Q

Give some examples of anoxic environments.

A

Sediments, bogs, marshes, subsurface, animal intestinal tracts (microaerobic)

32
Q

What are obligate anaerobes?

A

Microbes that would die in the presence of O2

33
Q

Why is oxygen toxic to obligate anaerobes?

A

Can produce reactive oxygen species (toxic). Aerobic/aerotolerant organisms can detoxify these molecules.

MICRB 265 (34 decks)

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