6-3: Environmental effects on microbial growth

Question 1

What environmental factors need to be suitable for microbial growth

Answer 1

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

Question 2

All organisms have ________,_________ and _________ temperatures for growth

Answer 2

Minimal, optimal, maximal

Question 3

What do higher temperatures do

Answer 3

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

Question 4

What happens at lower temperatures

Answer 4

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

Question 5

Microbes with optimal growth rate below 15C

Answer 5

Psychrophile

Question 6

Most widespread organisms, grow at intermediate temperatures

Answer 6

Mesophile

Question 7

Microbes with optimal growth rate above 45C

Answer 7

Thermophile

Question 8

Microbes with optimal growth rate above 80C

Answer 8

Hyperthermophile

Question 9

Psychrophiles vs psychrotolerant

Answer 9

Psychrophiles grow optimally at low T, psychrotolerant organisms can grow at low T, but optimally as mesophiles

Question 10

Psychrophiles live in

Answer 10

The oceans, arctic, the antarctic, glaciers

Question 11

What happens when psychrophiles are exposed to moderate temperatures

Answer 11

They are killed

Question 12

What adaptations do psychrophiles have

Answer 12

Increased short f.a. chain and unsaturated f.a. in cell membranes = fluidity
Cold shock proteins to help protein/RNA folding
Cryoprotectants to prevent ice formation

Question 13

Where do thermophiles/hyperthermophiles live

Answer 13

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

Question 14

The only microbe that can grow at T above 60C

Answer 14

Prokaryotes

Question 15

What microbe can grow up to 122C

Answer 15

Archaea

Question 16

How are thermophiles/hyperthermophiles adapted to high temperatures

Answer 16

Longer more saturated f.a. hold membrane together (archaea have lipid monolayer)
Heat-stable enzymes/solutes

Question 17

Microbes that prefer low pH (acidic conditions) are

Answer 17

Acidophiles

Question 18

Microbes that prefer higher pH (alkaline conditions) are

Answer 18

Alkaliphiles

Question 19

What are acid-tolerant organisms

Answer 19

Tolerate low pH, prefer neutral

Question 20

Cytoplasmic pH in alkaliphiles and acidophiles is…

Answer 20

Maintained close to neutral (6-8)

Question 21

What is the point of the low pH of the stomach

Answer 21

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

Question 22

What does acid tolerance of enteric pathogens influence

Answer 22

Infectious dose (minimum # needed to get sick), increasing stomach pH = lower infectious dose

Question 23

What does high concentrations of solutes in the environment lead to

Answer 23

Water leaves cell = shrinking, dehydration

Question 24

What does low concentrations of solutes in the environment lead to

Answer 24

Water flows into cell = bursts

Question 25

What is the most significant osmotic factor

Answer 25

Salt concentrations

Question 26

What are halophiles

Answer 26

Live in high salt environments, may require high concentrations

Question 27

What are compatible solutes

Answer 27

Solutes produced by cell in high solute environments to increase cytoplasmic solute conc.

Question 28

What are facultative anaerobes

Answer 28

O2 not required, but grow better with it

Question 29

What are microaerophilic microbes

Answer 29

Excel in low O2 environments

Question 30

Obligate anaerobes are…

Answer 30

Microbes that would die in the presence of O2

Question 31

Some anoxic environments…

Answer 31

Sediments, bogs, marshes, animal intestinal tracts

Question 32

Aerobic/aerotolerant organisms produce enzymes to detoxify what molecules

Answer 32

Reactive oxygen species (toxic) present when O2 is present