Question 1

Which of the following best describes a chemotroph, and which is a correct example?

Accepted Answer

An organism that uses organic or inorganic chemicals as an energy source; example: Nitrosomonas

Question 2

Which of the following statements correctly differentiates oxygenic and anoxygenic photosynthesis?

Accepted Answer

Oxygenic photosynthesis produces $$\mathrm{O_2$} as a $$byproduct, while anoxygenic photosynthesis does not; cyanobacteria perform oxygenic photosynthesis.

Question 3

A bacterium is found growing in a hot spring at $$70^\circ\mathrm{C}$$ and a pH of 2. Which term best describes its growth requirements?

Accepted Answer

Thermophile and acidophile

Question 4

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

Accepted Answer

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

Question 5

A hospital patient develops a persistent infection on a catheter despite regular cleaning. Which microbial property most likely contributes to this problem?

Accepted Answer

The ability of bacteria to form biofilms, which protect them from disinfectants and immune responses.

Question 6

Which phase of the bacterial growth curve is characterized by a balance between cell division and cell death, resulting in no net increase in cell number?

Accepted Answer

Stationary phase

Question 7

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization destroys all forms of microbial life, including endospores; disinfection eliminates most pathogens but not necessarily endospores.

Question 8

A laboratory technician uses an autoclave to sterilize media. Which physical method is being used, and what is its primary limitation?

Accepted Answer

Moist heat; cannot be used for heat-sensitive materials

Question 9

Which of the following statements about the use of radiation in microbial control is correct?

Accepted Answer

Ionizing radiation causes breaks in DNA strands, leading to cell death; it is used to sterilize medical equipment.

Question 10

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

Accepted Answer

Alcohols

Question 11

A patient with a fungal infection is prescribed amphotericin B. Which mode of action does this drug use?

Accepted Answer

Disrupts plasma membrane integrity by binding to ergosterol

Question 12

Which of the following best explains why selective toxicity is more difficult to achieve with eukaryotic pathogens than with bacteria?

Accepted Answer

Eukaryotic pathogens share more cellular structures and metabolic pathways with human cells.

Question 13

Which of the following is a correct example of a broad-spectrum antibiotic and an appropriate clinical use?

Accepted Answer

Tetracycline; used when the causative agent of infection is unknown

Question 14

A bacterial strain is resistant to an antibiotic due to the presence of an efflux pump. Which resistance mechanism is this an example of?

Accepted Answer

Active removal of the drug from the cell

Question 15

Which process is most likely responsible for the rapid spread of antibiotic resistance genes among different bacterial species in a hospital setting?

Accepted Answer

Horizontal gene transfer via conjugation

Question 16

A food processing plant uses high concentrations of salt to preserve meat. Which principle of microbial control is being applied?

Accepted Answer

Osmotic pressure causes plasmolysis, inhibiting microbial growth

Question 17

Which of the following best describes the action of sulfonamides?

Accepted Answer

Inhibit essential metabolite synthesis by acting as competitive inhibitors of para-aminobenzoic acid (PABA)

Question 18

A patient is prescribed a bacteriostatic drug for a urinary tract infection. In which scenario would a bactericidal drug be preferred instead?

Accepted Answer

The patient is immunocompromised and cannot clear inhibited bacteria effectively.

Question 19

Which of the following is a limitation of pasteurization as a method of microbial control?

Accepted Answer

It does not sterilize; some thermoduric organisms and endospores may survive.

Question 20

Which of the following best describes the action of ethylene oxide in sterilization?

Accepted Answer

It is a gaseous agent that alkylates proteins and nucleic acids, leading to microbial death.

Microbial Metabolism, Growth, Control, and Antimicrobial Drugs: Study Guide

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