Question 1

Which bacterial protein is functionally analogous to tubulin in eukaryotic cells, and what is its primary role?

Accepted Answer

FtsZ; initiates cell division

Question 2

A rod-shaped bacterium suddenly becomes spherical after a genetic mutation. Which protein is most likely inactivated, and what is its eukaryotic analog?

Accepted Answer

MreB; actin

Question 3

During binary fission, which protein complex is responsible for synthesizing both the cytoplasmic membrane and the peptidoglycan cell wall at the division site?

Accepted Answer

Divisome

Question 4

Which of the following best explains why penicillin is effective against many bacteria but not against human cells?

Accepted Answer

Penicillin inhibits the synthesis of peptidoglycan, a component absent in human cells.

Question 5

A patient with a persistent Pseudomonas aeruginosa infection is treated with antibiotics, but the infection returns after treatment. Which phenomenon best explains this recurrence?

Accepted Answer

Persistence due to dormant cells surviving treatment

Question 6

Which of the following antibiotics acts by inhibiting DNA gyrase, thereby blocking DNA replication in bacteria?

Accepted Answer

Quinolones

Question 7

What is the primary function of the MinC, MinD, and MinE proteins during bacterial cell division?

Accepted Answer

They ensure the FtsZ ring forms at the cell midpoint.

Question 8

Which molecule is responsible for transporting peptidoglycan precursors across the bacterial cell membrane, and which antibiotic specifically inhibits this process?

Accepted Answer

Bactoprenol; bacitracin

Question 9

A researcher observes that a bacterial mutant cannot form a crescent shape and instead appears as a straight rod. Which protein is most likely missing?

Accepted Answer

Crescentin

Question 10

Which of the following best describes the role of c-di-GMP in bacterial biofilm formation?

Accepted Answer

High c-di-GMP promotes biofilm formation by reducing flagella activity and increasing matrix production.

Question 11

Which of the following is a correct sequence of events during endospore formation in Bacillus species?

Accepted Answer

Environmental stress → Spo0A activation → asymmetric division → endospore formation

Question 12

Which of the following best explains why efflux pumps can confer multidrug resistance in bacteria?

Accepted Answer

They export a wide range of antibiotics out of the cell, reducing intracellular drug concentration.

Question 13

A patient is infected with MRSA, which is resistant to β-lactam antibiotics. What is the molecular basis for this resistance?

Accepted Answer

Alteration of the penicillin-binding protein by the mecA gene

Question 14

Which of the following best describes the stringent response in bacteria?

Accepted Answer

It is triggered by amino acid starvation and leads to dormancy by reducing macromolecule synthesis.

Question 15

Which of the following is a direct target of β-lactam antibiotics such as penicillin?

Accepted Answer

Transpeptidase enzyme

Question 16

Which of the following best explains why antibiotics that target the bacterial ribosome do not affect human ribosomes?

Accepted Answer

Bacterial ribosomes are 70S, while human ribosomes are 80S.

Question 17

A bacterial cell is exposed to bacitracin. Which step in peptidoglycan synthesis is directly inhibited?

Accepted Answer

Transport of peptidoglycan precursors across the membrane

Question 18

Which of the following scenarios best illustrates the concept of metabolic bypass as a mechanism of antibiotic resistance?

Accepted Answer

A bacterium expresses an alternative enzyme that performs the same function as the antibiotic target.

Question 19

Which of the following is a correct description of the HipA–HipB toxin-antitoxin system?

Accepted Answer

HipA is the toxin that inhibits cell growth, while HipB is the antitoxin that neutralizes HipA.

Question 20

A hospital-acquired infection is caused by a bacterium that forms strong biofilms and is highly resistant to antibiotics. Which of the following mechanisms is LEAST likely to contribute to this resistance?

Accepted Answer

Increased permeability of the cell membrane to antibiotics

Microbial Cell Structure, Division, Biofilm Formation, and Antibiotic Targets

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