Question 1

Which of the following statements best describes the process of binary fission in bacteria?

Accepted Answer

Binary fission is a type of cell division where a cell enlarges, replicates its DNA, and divides into two genetically identical daughter cells.

Question 2

A researcher observes a bacterium that forms a stalk at one pole and divides by producing a new cell from the tip of the stalk. Which type of cell division is this, and which genus is most likely being observed?

Accepted Answer

Budding; Caulobacter

Question 3

During rapid growth, Escherichia coli can have multiple rounds of chromosome replication occurring simultaneously. If the doubling time is 20 minutes and chromosome replication takes 40 minutes, how many replication forks are present in a single cell at any given time?

Accepted Answer

$$4$$

Question 4

Which protein is most directly responsible for forming the contractile ring at the site of bacterial cell division, and what is its eukaryotic homolog?

Accepted Answer

FtsZ; homologous to tubulin

Question 5

A mutation in the MinCDE system of E. coli leads to improper placement of the FtsZ ring. What is the most likely consequence of this mutation?

Accepted Answer

Cells may form minicells due to division near the poles.

Question 6

Which of the following best explains why biofilms are more resistant to antibiotics than planktonic bacterial cells?

Accepted Answer

The extracellular polysaccharide matrix of biofilms impedes antibiotic penetration and can harbor dormant cells.

Question 7

Which of the following is the correct sequence of events in peptidoglycan biosynthesis in rod-shaped bacteria?

Accepted Answer

Autolysin activity, precursor transport by bactoprenol, transglycosylation, transpeptidation

Question 8

A patient is infected with a strain of Staphylococcus aureus that is resistant to methicillin. Which genetic element is most likely responsible for this resistance?

Accepted Answer

Acquisition of the SCCmec island encoding MecA, an alternative penicillin-binding protein

Question 9

Which of the following antibiotics inhibits bacterial cell wall synthesis by binding to the pentapeptide precursor and preventing cross-link formation?

Accepted Answer

Vancomycin

Question 10

A culture of E. coli is exposed to ciprofloxacin, a quinolone antibiotic. What is the primary cellular target of this drug?

Accepted Answer

DNA gyrase and topoisomerase IV

Question 11

Which of the following best describes the function of toxin-antitoxin (TA) modules in bacterial persistence?

Accepted Answer

TA modules encode a toxin that inhibits cell growth and an antitoxin that neutralizes the toxin, allowing some cells to enter dormancy and survive antibiotic treatment.

Question 12

In the formation of heterocysts in Anabaena, which environmental condition triggers differentiation, and what is the main function of heterocysts?

Accepted Answer

Nitrogen limitation; nitrogen fixation

Question 13

Which of the following best explains why the generation time of E. coli can be shorter than the time required for chromosome replication?

Accepted Answer

E. coli cells can initiate new rounds of DNA replication before the previous round is complete, resulting in overlapping replication cycles.

Question 14

Which of the following is a major mechanism by which bacteria acquire antibiotic resistance genes from other species?

Accepted Answer

Horizontal gene transfer via mobile genetic elements such as plasmids

Question 15

A patient with a chronic Pseudomonas aeruginosa infection is not responding to multiple antibiotics. Which of the following mechanisms is most likely contributing to the multidrug resistance observed in this biofilm-associated infection?

Accepted Answer

Upregulation of multidrug efflux pumps and presence of a protective biofilm matrix

Question 16

Which of the following best describes the role of cyclic di-guanosine monophosphate (c-di-GMP) in bacterial biofilm formation?

Accepted Answer

c-di-GMP acts as a second messenger that regulates the transition from planktonic to biofilm growth by activating genes for extracellular matrix production.

Question 17

Which of the following antibiotics inhibits protein synthesis by binding to the A site of the 70S ribosome and causing premature chain termination?

Accepted Answer

Chloramphenicol

Question 18

A researcher is studying a bacterial mutant that cannot form a septum during cell division. Which protein is most likely defective in this mutant?

Accepted Answer

FtsZ

Question 19

Which of the following best explains the function of autolysins during peptidoglycan biosynthesis?

Accepted Answer

Autolysins hydrolyze bonds in existing peptidoglycan to allow insertion of new material.

Question 20

A bacterial cell exposed to penicillin is unable to form cross-links in its peptidoglycan. Which enzyme is directly inhibited by penicillin?

Accepted Answer

Transpeptidase

Molecular Biology of Microbial Growth: Cell Division, Budding, and Biofilms

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