Test I QUESTIONS Flashcards
What is the difference between fimbri and flagella?
Fimbri are smaller, thinner and may be powered by ATP. In general, only bacteria have true flagella powered by the proton motive force. Archaeans have flagella that resemble fimbri in the sense that they are powered by ATP. They are also solid instead of hollow, so they lengthen from the base.
What is the purpose of bacterial conjugation?
Horizontal gene transfer allows for more unique variation in a particular population, specifically with the transfer of new traits in the form of plasmids. A “sex pilus” is used to transfer genetic information from the male (donor) to the female (recipient). The pilus is used both for transfer and to bring the participants close to each other.
How do fimbri aid in adherence to surfaces or objects?
All adherence is controlled by adhesin proteins, which recognize GLYCOLIPIDS on the adhesed-to surface. The adhesion of a cell may be inhibited by compounds such as MANNOSE, which bind to the surface and inhibit the binding of adhesins. E. coli’s FimH adhesins are an example of a binding that is inhibited by mannose.
What happens when you spin down a Gm+ cell vs a Gm- cell?
Regardless of gram status, the EPS will spin off whereas the capsule stays on. The main difference is in the peptidoglycan. Gm+ retains its PG because it is tightly integrated in the cell membrane. Gm- loses its thin layer of PG as a sac, along with all its external LPS.
Why does E. coli change from a rod to a cocci shape during the log phase?
Different amino acids are incorporated during PG synthesis and also in glycoproteins in S-layer. This changes the surface composition of the cell and also how it interacts with its surroundings.
When might a cell use a peptidoglycan hydrolase?
When they need to break their cell wall to expand or grow. The cell wall is very rigid so it must be broken with the enzymes that dissolve the murine bond. Some eukaryotes use pg hydrolases as a defense against bacteria!
What might be a possible way to combat MRSA? Why does this work better than existing antibiotics?
MRSA is a strep that is immune to the effect of some beta-lactams because of its unique PBP protein, 2a. When this protein performs PG synthesis, it cannot be stopped by antibiotics. One possible attack against MRSA would be to break down its murine bonds manually with some kind of enzyme or hydrolase!
