RECAP questions

Question 1

1) what part of the cell is the one “controlling” binary fission? ie what is making the cut/septum?

2) what enzyme makes the cut?

3) what are the 4 phases of growth when you do batch culture?

4) can you determine the number of viable cells via turbidimetry?

5) what methods can you use to determine the number of viable cells?

Answer 1

1) peptidoglycan! is remodelled to split the cell
2) autolysins
3) lag phase, log phase, stationary phase, death phase
4) no! only gives you a rough estimate based on the opacity of the solution + some bacteria could be dead
5) use staining + microscopy or plating (pouring or spreading)

Question 2

1) why is mannitol salt plate selective?
2) why is MacConkay plate differential?
3) what is a growth factor?

Answer 2

1) because it contains lots of NaCl! and not all bacteria (ie gram neg and some gram pos) can grow on it!
2) differentiate btw lactose fermenters (pink) and lactose non-fermenters (colorless):
*lactose –> glucose + galactose
*glucose –> glycolytic pathway –> fermentation –> lactate (lactic acid) –> reduce pH –> pink!
3) microorganism needs it for growth but cannot synthesize by itself! (ie fastidious bacteria)

Question 3

ADD review Qs of 1, 2, 3 and 3

Question 4

• what kind of metabolism does anaerobe tolerant have?
• do anaerobe tolerants have a lot of superoxide dismutase?
• what is the purpose of disinfection?
• what is the decimal reduction time?

Answer 4

• not aerobic respiration –> fermentation OR anaerobic respiration
• yes! bc live in presence of O2: need superoxide dismutase to detoxify
• to remove all pathogens
• time needed to kill 90% of population

Question 5

• how does UV kill bacteria?
• how does chlorine kill bacteria?
• what is selective toxicity?
• does penicillin exhibit selective toxicity?
• what pathway is targeted by sulfonamide?

Answer 5

• creates thymine dimers and messes up DNA
• oxidizes everything! NO selective toxicity
• doesn’t kill everything bc targets smtg specific
• yes! inhibits transpeptidase (only in bacteria)
• folic acid synthesis

Question 6

• how do resistant bacteria protect themselves against penicillin?
• how do resistant bacteria protect themselves from aminoglycosides? (?)

Answer 6

• b-lactamase! cleaves penicillin
• modification of ribosomes! bind fo 30S ribosomal subunit + impair proofreadings = faulty proteins