Microbial Growth Flashcards
How does a hyperthermophile differ from a psychrophile?
Optimum temperature, cell membrane composition, enzyme composition.
What are the cardinal temperatures for E. coli? To what temperature class does it belong?
8, 39 and 48 degrees. It’s mesophilic.
How do psychrotolerant organisms differ from psychrophilic organisms?
Their optimum temperature are between 20 and 40 degrees.
What molecular adaptations to the cell membrane are seen in psychrophiles, and why are they necessary?
The fatty acids are unsaturated so they remain fluid in low temperatures.
Which domain of organisms include species that can grow above 100 degrees celsius?
Archaea.
What is the structure of membranes of hyperthermophilic Archaea and why might this structure be useful for growth at high temperature?
Isoprene linked to glycerol phosphate forming a lipid monolayer that makes the membrane resistant to melting and permit growth.
What is the increase in concentration of protons when going from pH 7 to 3?
10,000.
What are buffers and why are they needed?
Solutions that maintain a stable pH range permitting microorganism growth.
What is the aw of pure water?
1.
What is a compatible solute and why is it needed?
It’s an organic or inorganic compound such as mannitol, glycerol and KCl, that is accumulated in the cell in order to increase its osmolarity.
What is the compatible solute for Halobacterium?
KCl.
What is a facultative aerobe?
It’s a microorganism whose growth is not affected by the presence of absent of oxygen.
How does a reducing agent work? Give an example of a reducing agent.
They react with oxygen converting it to H2O and maintaing the medium anoxic. Thioglycolate is a reducing agent.
How does superoxide dismutase protect a cell from toxic oxygen?
It converts it into water and triplet oxygen.
How does the activity of superoxide dismutase differ from that of superoxide reductase?
The former produces oxygen and the latter yields water to avoid oxygen exposure since it is present in obligate anaerobes.
