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20 Cards in this Set
- Front
- Back
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What is the pH range of most natural environments? Over how broad a pH range can most microbes grow?
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Natural pH is 5-9. Most organisms have 1-2 pH units of lie way
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What special problem do obligate alkalophiles experience in using a proton motive force for energy requiring processes?
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Difficult in high OH- environment, some use Na+ gradient provides energy for transport and motility
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What structure or processes might be affected by dramatic changes in external pH (1-2 units)
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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.
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What physical factors determine the H2O availability in growth media
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dryness, moisture content, AW=amt of salt, and sugar in environment.
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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?
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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 |
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How might you distinguish a microaerophile from a anaerobe?
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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. Anaerobe- |
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Why are most hypertherophiles anaerobes
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Lower oxygen concentration at higher temperatures.
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What chemical agent is often included in anaerobic growth media to remove O2?
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NaBH4
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What are the toxic forms of oxygen that are commonly formed in microbes?
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-Super oxide radical
-OH radical - H2O2 |
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Which enzymes are involved in the detoxification of superoxide anion? How do the enzyme systems differ in aerobes and anaerobes?
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Superoxide dismutase and catalase
Peroxide, superoxide reductase, because they dont produce O2 |
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What are the chemical effects of ionizing and non-ionizing radiation on microbial cells?
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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. |
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pH
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is the negative log of the hydrogen ion concentration
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Acidophiles
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Grow best at low pH's
Fungus Maintaining CM is important adaptation |
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Alkaliphiles
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Grow best at high pH's
found in soda lakes Best known are bacillus Use Na+ gradient |
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Water activity Aw
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Where Aw is the ratio of the solution vapor pressure to the vapor pressure of water.
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Halotolerant
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organisms can survive in environments with low Aw, but grow optimally at Aw > .99
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Halophiles
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are separated into 3 general groups based on the NaCl concentration in their optimal growth media
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Osmophiles
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organisms that live in environments containing high sugar
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Xerophiles
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organisms that thrive in very dry environments
Cereal and Candy |
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Positive Water Balance
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cytoplasm has a high solute concentration and water flows into the cell
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