Chapter 5 Lec.2.2

Question 1

Molecular adaptations to psychrophily

Answer 1

Production of enzymes that function optimally in cold.

Transport processes function optimally at low temperature.

Question 2

Microbial life at high temperatures

Answer 2

Above 65, only prokaryotes exist.
Thermophiles: growth optima between 45-80.
Hyperthermophiles: growth optima above 80.

Question 3

Studies of thermal habitats have revealed…

Answer 3

Prokaryotes are able to grow at high temps better than eukaryotes.
Archaea have highest temp optima.

Question 4

Thermophily

Answer 4

Enzyme and proteins function optimally at high temps, features that provide thermal stability.
-Heat tolerant amino acids
-Increased number of ionic bonds.
-Solutes help stabilize proteins.
Modifications to cytoplasmic membrane to ensure heat stability.

Question 5

Hyperthermophiles and industry

Answer 5

Produce enzymes widely used in industrial microbiology.

-Taq polymerase: PCR

Question 6

pH

Answer 6

Relative acidity in solution.

Question 7

Microbial growth at high or low pH

Answer 7

pH greatly affects microbial growth.

Most organisms grow between 6-8.

Question 8

Microbial growth at high or low pH: Types

Answer 8

Acidophiles- 0-5.5.

Neutrophiles- 5.5-7

Alkaliphiles- 8.5 11.5

Question 9

Microbial growth at high or low pH: Internal pH and acid tolerance

Answer 9

Most microbes maintain internal environment close to neutral.
-Exchange ions for protons
Acid tolerance response.
-pump protons out of cell.

Question 10

High Pressure

Answer 10

High hydrostatic pressure.
Barotolerant- adversely affected by pressure.
Barophilic- require or grow in increased pressure.

Question 11

Water activity (aw)

Answer 11

Ratio of vapor pressure of air in equilibrium with substance or solution to the vapor pressure of pure water.

Question 12

Solutes and water activity

Answer 12

Water activity

• amount of water available to organisms
• reduced by interaction with solute molecules
• higher solutes –>lower aw
• reduced by adsorption to surface

Question 13

The dead sea

Answer 13

1. Tectonic basin
   - lowest point on the surface of the planet
2. salinity
   - One of the saltiest naturally occurring bodies of water.
3. pH ~6

Question 14

The dead sea: mostly dead, slightly alive

Answer 14

Believed devoid of life until 1930’s.

Wilkansky, 1936, showed living microorganisms.

Question 15

Don Juan pond

Answer 15

More salinic than The Dead Sea.

-No life.

Question 16

Solutions

Answer 16

Isotonic solution
-same concentration inside as outside 
Hypotonic 
-more concentrated inside the cell
Hypertonic 
-more concentrated outside the cell

Question 17

Halophiles

Answer 17

Organisms that grow best at reduced water potential, requirement for NaCl.
Extreme halophiles: require high levels.
Halotolerant- reduction in water activity.

Question 18

Solutes in cytoplasm

Answer 18

Cytoplasm > concentration then surrounding environment.

-water moves into cell

Question 19

Halophile defense mechanisms: High salinity coping mechanisms.

Answer 19

Two high salinity coping mechanisms

1. Organic
   - energetically expensive
   - does not require protein alteration.
2. Salt in
   - energetically cheap
   - requires protein alteration
   - Used by all haloarchaea and two lineages of bacteria.

Question 20

Halophile defense mechanisms

Answer 20

Increasing internal solute concentration by:

• pumping ions from environment into cell.
• synthesis or concentration of solutes.

Question 21

Similar to Halophiles

Answer 21

Osmophiles: organisms that live in environments high in sugar as solute.
Xerophiles: organisms able to grow in very dry environments.

Question 22

Oxygen and microorganisms

Answer 22

Aerobes- require oxygen.
Anaerobes- do not require oxygen.
Facultative organisms- can live with or without oxygen.
Aerotolerant anaerobes- can tolerate oxygen and grow in its presence even though they cannot use it.
Microaerophiles- can use oxygen only when it is present at levels reduced from the air.

Question 23

Thioglycolate broth

Answer 23

Complex medium that separates microbes based on oxygen requirements.
Reacts with oxygen so oxygen can only penetrate top of tube.

Question 24

Toxic forms of oxygen in cell

Answer 24

Single oxygen
Superoxide anion
hydrogen peroxide
hydroxyl radical

Question 25

Toxic oxygen enzymes

Answer 25

Catalase
Peroxidase
Superoxide dismutase