Question 1

Which of the following best describes a chemotroph?

Accepted Answer

An organism that obtains energy from the oxidation of chemical compounds.

Question 2

Cyanobacteria are capable of which type of photosynthesis, and what is a key byproduct?

Accepted Answer

Oxygenic photosynthesis; oxygen

Question 3

A bacterium that grows best at a pH of 3 and is unable to survive at neutral pH is classified as a(n):

Accepted Answer

Acidophile

Question 4

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

Accepted Answer

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

Question 5

During which phase of the bacterial growth curve does the population size remain constant as the rate of cell division equals the rate of cell death?

Accepted Answer

Stationary phase

Question 6

A hospital-acquired infection is traced to a biofilm on a catheter. Which property of biofilms most contributes to their medical significance?

Accepted Answer

Biofilms protect bacteria from antibiotics and the immune system.

Question 7

Which of the following best describes the action of moist heat in microbial control?

Accepted Answer

It denatures proteins by breaking hydrogen bonds.

Question 8

A laboratory technician needs to sterilize a solution that is heat-sensitive. Which method is most appropriate?

Accepted Answer

Filtration through a membrane with $$0.22\ \mu m$$ pores

Question 9

Which of the following statements about ionizing radiation is correct?

Accepted Answer

It sterilizes by generating hydroxyl radicals that damage cellular components.

Question 10

Which chemical disinfectant acts by denaturing proteins and disrupting membranes, and is commonly used as a skin antiseptic?

Accepted Answer

Alcohol (e.g., ethanol or isopropanol)

Question 11

A bacteriostatic agent is most appropriate in which of the following scenarios?

Accepted Answer

Preserving food by inhibiting microbial growth without killing cells

Question 12

Which of the following best describes the principle of selective toxicity?

Accepted Answer

A drug that targets microbial structures or functions not found in host cells.

Question 13

Which of the following drugs inhibits bacterial cell wall synthesis?

Accepted Answer

Penicillin

Question 14

A patient is infected with a Gram-negative bacterium that is resistant to multiple antibiotics. Which mechanism of resistance is most likely if the bacterium possesses an efflux pump?

Accepted Answer

Active transport of the drug out of the cell

Question 15

Which of the following is a major reason why it is more difficult to develop drugs with selective toxicity against fungi than against bacteria?

Accepted Answer

Fungi are eukaryotic and share more similarities with human cells.

Question 16

Which of the following best describes horizontal gene transfer by conjugation?

Accepted Answer

Transfer of DNA from one bacterium to another via a pilus.

Question 17

Which of the following is an example of misuse of antibiotics that can contribute to resistance?

Accepted Answer

Using antibiotics to treat viral infections.

Question 18

A patient is prescribed a broad-spectrum antibiotic. Which of the following is a potential risk associated with this treatment?

Accepted Answer

Increased risk of superinfection due to disruption of normal microbiota.

Question 19

Which of the following best explains why pasteurization does not achieve sterilization?

Accepted Answer

It kills most pathogens but does not destroy all endospores.

Question 20

Which of the following is a correct match between a drug and its mode of action?

Accepted Answer

Polymyxin B: Disrupts plasma membrane integrity

Microbiology Exam 2 Study Guide: Microbial Metabolism, Growth, Control, and Antimicrobial Drugs

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