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20 Cards in this Set

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  • Back
What is the pH range of most natural environments? Over how broad a pH range can most microbes grow?
Natural pH is 5-9. Most organisms have 1-2 pH units of lie way
What special problem do obligate alkalophiles experience in using a proton motive force for energy requiring processes?
Difficult in high OH- environment, some use Na+ gradient provides energy for transport and motility
What structure or processes might be affected by dramatic changes in external pH (1-2 units)
Cell envelope is directly affected by changing pH disassociation protonation of macromolecules such as membrane proteins can affect membrane functions and intregrity. Weak acids are membrane permable, once inside they dissociate to A- and H+ and trapped into cytoplasm.
What physical factors determine the H2O availability in growth media
dryness, moisture content, AW=amt of salt, and sugar in environment.
How are compatible solutes used to counter osmotic effects when a microbe is placed in a high solute environment? What are the four major chemical classes of compatible solutes?
When a cell is placed in a high solute environment, the osmotic pressure forces water out of the cell. To overcome this force many cells will produce an intracellular solute, which is compatible with the cellular proteins and enzymes, to counter the osmotic force.

Four major Chemical Classes

1. Amino-Acid-type solutions
2. Carbohydrate-type solution
3. Alcohol-type solutions
4. Other
How might you distinguish a microaerophile from a anaerobe?
Microaerophile-can tolerate a little bit of oxygen, they are aerobes

Anaerobe-Can not respire oxygen. Two classes

Aerotolerant-can tolerate but wont use in e- Acceptor

Obligate anaerobe- cannot tolerate O2 and are inhibited or killed by it.

Why are most hypertherophiles anaerobes
Lower oxygen concentration at higher temperatures.
What chemical agent is often included in anaerobic growth media to remove O2?
What are the toxic forms of oxygen that are commonly formed in microbes?
-Super oxide radical

-OH radical

- H2O2
Which enzymes are involved in the detoxification of superoxide anion? How do the enzyme systems differ in aerobes and anaerobes?
Superoxide dismutase and catalase

Peroxide, superoxide reductase, because they dont produce O2
What are the chemical effects of ionizing and non-ionizing radiation on microbial cells?
Ionizing-results in the production of e-, hydroxyl radicals and hydride radicals. Each is highly reactive and damage small molecules and macromoles (protein and Nucleic acids)

Nonionizing radiation- such as UV leads to the formation of pyrimidine dimer, which if un-repaired will lead to mutations, if high mutation effects can be lethal.
is the negative log of the hydrogen ion concentration
Grow best at low pH's


Maintaining CM is important adaptation
Grow best at high pH's

found in soda lakes

Best known are bacillus

Use Na+ gradient
Water activity Aw
Where Aw is the ratio of the solution vapor pressure to the vapor pressure of water.
organisms can survive in environments with low Aw, but grow optimally at Aw > .99
are separated into 3 general groups based on the NaCl concentration in their optimal growth media
organisms that live in environments containing high sugar
organisms that thrive in very dry environments

Cereal and Candy
Positive Water Balance
cytoplasm has a high solute concentration and water flows into the cell