PCAT Microbiology 4

Question 1

Which bacterium uses a type III secretion system to inject effector proteins directly into host cell cytoplasm?

Accepted Answer

Salmonella enterica

Answer

Salmonella uses its type III secretion system (injectisome) to deliver effector proteins into epithelial cells, triggering actin rearrangement and bacterial uptake.

Question 2

In a continuous culture system (chemostat), bacterial growth rate is controlled by:

Accepted Answer

Dilution rate of limiting nutrient

Answer

In a chemostat, the dilution rate determines the growth rate because the limiting nutrient is supplied at a fixed rate, maintaining steady-state culture conditions.

Question 3

Which characteristic distinguishes a temperate bacteriophage from a lytic bacteriophage?

Accepted Answer

Ability to integrate into the host chromosome as a prophage

Answer

Temperate phages can integrate their DNA into the bacterial chromosome (becoming a prophage) and remain dormant, while lytic phages always lyse the host immediately.

Question 4

Clostridium botulinum toxin causes flaccid paralysis by:

Accepted Answer

Cleaving SNARE proteins to prevent acetylcholine release

Answer

Botulinum toxin is a zinc-dependent protease that cleaves SNARE proteins (SNAP-25, synaptobrevin, syntaxin), preventing vesicle fusion and acetylcholine release.

Question 5

Which Plasmodium species can form hypnozoites in the liver, enabling relapse months after initial infection?

Accepted Answer

Plasmodium vivax

Answer

P. vivax (and P. ovale) form dormant hypnozoites in hepatocytes; primaquine is required to eliminate them and prevent relapse.

PCAT - Pharmacy College Admission Test Practice Test

PCAT - Pharmacy College Admission Test Practice Test

PCAT Microbiology 4