Question 1

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

Accepted Answer

A process where a single cell divides after enlarging to twice its minimum size, producing two genetically identical daughter cells.

Question 2

During peptidoglycan biosynthesis, which molecule is responsible for transporting peptidoglycan precursors across the cytoplasmic membrane?

Accepted Answer

Bactoprenol

Question 3

Which enzyme is directly inhibited by the antibiotic penicillin, thereby preventing bacterial cell wall synthesis?

Accepted Answer

Transpeptidase

Question 4

A bacterial culture is inoculated with $10^3$ cells. If the generation time is 30 minutes, how many cells will there be after 3 hours of exponential growth? Use the formula $N = N_0 	imes 2^n$, where $n$ is the number of generations.

Accepted Answer

$N = 10^3 	imes 2^6 = 64,000$

Question 5

Which of the following best explains why autolysins are essential during bacterial cell wall growth?

Accepted Answer

They create small openings in the existing cell wall to allow insertion of new peptidoglycan material.

Question 6

In a chemostat, which parameter controls the growth rate of the microbial population?

Accepted Answer

Dilution rate

Question 7

Which of the following adaptations would you expect to find in the cytoplasmic membrane of a thermophilic bacterium?

Accepted Answer

High content of saturated fatty acids

Question 8

A microbiologist is using a spectrophotometer to measure the optical density (OD) of a bacterial culture. What is a major limitation of this method?

Accepted Answer

It cannot distinguish between live and dead cells.

Question 9

Which of the following best describes the function of compatible solutes in halophilic microorganisms?

Accepted Answer

They are synthesized or accumulated to balance the osmotic pressure and prevent water loss.

Question 10

Which of the following statements about the FtsZ protein is correct?

Accepted Answer

It forms a ring at the center of the cell and is related to tubulin.

Question 11

A facultative aerobe is best described as an organism that:

Accepted Answer

Can live with or without oxygen, using it when available.

Question 12

Which of the following toxic oxygen species is neutralized by the enzyme catalase?

Accepted Answer

Hydrogen peroxide ($H_2O_2$)

Question 13

Which of the following best explains why UV radiation is effective for surface decontamination but not for sterilizing liquids or solids?

Accepted Answer

UV radiation cannot penetrate solid, opaque, or light-absorbing surfaces.

Question 14

A batch culture of bacteria is observed to have a lag phase, exponential phase, stationary phase, and death phase. What is the primary reason for the onset of the stationary phase?

Accepted Answer

Accumulation of toxic waste products or depletion of an essential nutrient.

Question 15

Which of the following is NOT a limitation of microscopic cell counts?

Accepted Answer

It is highly accurate for counting only viable cells.

Question 16

Which of the following best describes the effect of increasing the concentration of a limiting nutrient in a chemostat?

Accepted Answer

It increases the cell yield (biomass) but not the growth rate.

Question 17

Which of the following is a correct statement about the minimum inhibitory concentration (MIC) of an antimicrobial agent?

Accepted Answer

It is the smallest amount of an agent needed to inhibit the growth of a microorganism.

Question 18

Which of the following adaptations is most likely to be found in the enzymes of psychrophilic microorganisms?

Accepted Answer

More a-helices and fewer weak bonds for greater flexibility.

Question 19

Which of the following best describes the action of autoclaving in microbial control?

Accepted Answer

It uses steam under pressure to achieve temperatures above 100°C, denaturing macromolecules.

Question 20

A microbiologist is working with a bacterium that grows best at 25°C but can survive at 4°C. This organism is best classified as a:

Accepted Answer

Psychrotolerant mesophile

Microbial Growth and Control: Cell Division and Peptidoglycan Biosynthesis

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