Question 1

A patient is infected with a bacterium that can grow both in the presence and absence of oxygen, but grows faster when oxygen is available. Which term best describes this organism?

Accepted Answer

Facultative anaerobe

Question 2

During which phase of the bacterial growth curve are cells most susceptible to antibiotics that target cell wall synthesis, and why?

Accepted Answer

Exponential (log) phase, because cells are actively dividing and synthesizing new cell walls

Question 3

A microbiologist is culturing a halophilic bacterium. Which of the following conditions would best support its growth?

Accepted Answer

A medium with 3.5% NaCl

Question 4

Which of the following statements about sterilization is correct?

Accepted Answer

Sterilization eliminates all bacteria, viruses, and endospores

Question 5

A researcher uses ethylene oxide to sterilize medical equipment. What is the primary mechanism by which ethylene oxide achieves sterilization?

Accepted Answer

It damages proteins and nucleic acids

Question 6

Which of the following best describes the difference between competitive and non-competitive enzyme inhibitors?

Accepted Answer

Competitive inhibitors bind to the active site, while non-competitive inhibitors bind to a regulatory site and change the shape of the active site

Question 7

Which of the following equations correctly represents the net ATP yield from glycolysis per molecule of glucose?

Accepted Answer

$$2 	imes 	ext{ATP}$$

Question 8

A patient is diagnosed with tuberculosis. Which biosafety level (BSL) laboratory is required to safely handle Mycobacterium tuberculosis?

Accepted Answer

BSL-3

Question 9

Which of the following best describes an opportunistic pathogen?

Accepted Answer

A microbe that only causes disease when the host is weakened

Question 10

Which of the following statements about exotoxins and endotoxins is correct?

Accepted Answer

Exotoxins are secreted from the cell; endotoxins are released when the cell wall is broken

Question 11

A patient is prescribed ciprofloxacin for a bacterial infection. What is the mechanism of action of this drug?

Accepted Answer

Inhibits DNA gyrase

Question 12

Which of the following best explains why a bacterium with acquired resistance to an antibiotic may survive treatment?

Accepted Answer

It has gained resistance through genetic mutation or acquisition of resistance genes

Question 13

Which of the following is a correct description of an amphilbolic pathway?

Accepted Answer

A pathway that has both catabolic and anabolic components

Question 14

A culture medium that contains ingredients to suppress the growth of Gram-negative bacteria while allowing Gram-positive bacteria to grow is best described as:

Accepted Answer

Selective medium

Question 15

Which of the following best describes the function of superoxide dismutase and catalase in obligate aerobes?

Accepted Answer

They break down harmful oxygen species

Question 16

A patient is infected with a pathogen that requires only a small number of cells to establish infection in 50% of exposed hosts. This number is referred to as:

Accepted Answer

Infectious dose-50 (ID50)

Question 17

Which of the following best explains why placing a mesophile at 70°C results in cell death?

Accepted Answer

Enzymes and proteins denature at temperatures above the maximal growth temperature

Question 18

Which of the following drugs inhibits protein synthesis by binding to the 50S ribosomal subunit and blocking translocation?

Accepted Answer

Erythromycin

Question 19

A hospital outbreak of a disease is traced to a zoonotic pathogen. Which of the following best describes a zoonotic disease?

Accepted Answer

A disease that spreads from animals to humans

Question 20

Which of the following is NOT a mechanism by which bacteria can evade the effects of antimicrobial drugs?

Accepted Answer

Increasing the permeability of the cell membrane to the drug

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

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