Question 1

Which of the following best describes the function of teichoic acids in the cell wall of Gram-positive bacteria?

Accepted Answer

They provide structural support and contribute to the negative charge of the cell wall.

Question 2

A patient presents with a fever and is diagnosed with septic shock caused by Gram-negative bacteria. Which component of the bacterial cell is most likely responsible for this condition?

Accepted Answer

Lipopolysaccharide (LPS)

Question 3

Which of the following equations correctly represents the calculation of generation time ($g$) for a bacterial culture, given the number of generations ($n$) and the total time of exponential growth ($t$)?

Accepted Answer

$g = \frac{t}{n}$

Question 4

During a laboratory experiment, a culture of E. coli is grown in a batch culture. The optical density (OD) is measured every hour. Which phase of growth is characterized by a constant rate of cell division and a straight line when plotting $\log_{10}$ of cell number versus time?

Accepted Answer

Exponential (log) phase

Question 5

A microbiologist is testing the effect of a new antibiotic on Staphylococcus aureus. After treatment, the cells are stained with crystal violet and iodine, then washed with alcohol and counterstained with safranin. The cells appear purple under the microscope. What does this indicate about the bacterial cell wall?

Accepted Answer

The cells are Gram-positive and have a thick peptidoglycan layer.

Question 6

Which of the following best explains why endospores are more resistant to heat and chemicals than vegetative cells?

Accepted Answer

Endospores contain dipicolinic acid and a dehydrated core.

Question 7

A culture of Bacillus subtilis is exposed to UV light. Which DNA repair mechanism is most likely to be activated to correct thymine dimers formed by the UV exposure?

Accepted Answer

Photoreactivation

Question 8

Which of the following statements about bacterial plasmids is correct?

Accepted Answer

Plasmids often carry genes for antibiotic resistance.

Question 9

A patient is diagnosed with tuberculosis. Which unique component of the Mycobacterium tuberculosis cell wall is responsible for its acid-fast property?

Accepted Answer

Mycolic acid

Question 10

Which of the following best describes the function of the bacterial capsule in pathogenesis?

Accepted Answer

It protects the bacterium from phagocytosis by host immune cells.

Question 11

A culture of bacteria is growing in a chemostat at steady state. Which of the following parameters is controlled to maintain the growth rate?

Accepted Answer

Dilution rate

Question 12

Which of the following equations correctly represents the relationship between the initial number of cells ($N_0$), the final number of cells ($N$), and the number of generations ($n$) in a bacterial culture?

Accepted Answer

$N = N_0 	imes 2^n$

Question 13

A hospital outbreak is traced to a strain of Klebsiella pneumoniae that produces extended-spectrum beta-lactamases (ESBLs). Which of the following best explains the clinical significance of this enzyme?

Accepted Answer

It confers resistance to a wide range of beta-lactam antibiotics.

Question 14

Which of the following best describes the process of bacterial conjugation?

Accepted Answer

Direct transfer of plasmid DNA through a pilus

Question 15

A microbiologist is culturing a thermophilic bacterium. At which temperature range would you expect optimal growth for this organism?

Accepted Answer

55-70 $^\circ$C

Question 16

Which of the following best explains why obligate anaerobes are killed by exposure to oxygen?

Accepted Answer

They lack enzymes such as superoxide dismutase and catalase to detoxify reactive oxygen species.

Question 17

A bacterial culture is found to have a generation time of 30 minutes. If the initial population is $1 	imes 10^3$ cells, how many cells will be present after 3 hours of exponential growth? (Assume no cell death.)

Accepted Answer

$6.4 	imes 10^4$

Question 18

Which of the following is a key difference between prokaryotic and eukaryotic ribosomes?

Accepted Answer

Prokaryotic ribosomes are 70S, while eukaryotic ribosomes are 80S.

Question 19

A patient is infected with a bacterium that lacks a cell wall. Which antibiotic would be ineffective against this organism?

Accepted Answer

Penicillin

Question 20

Which of the following best describes the role of the FtsZ protein in bacterial cell division?

Accepted Answer

It forms a contractile ring at the future site of septum formation.

Microbiology Reading Assignment Schedule (Brock 16th Edition)

Study Guide - Practice Questions