Question 1

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

Accepted Answer

Sterilization removes all microbial life, while disinfection only reduces the number of pathogens to safe levels.

Question 2

A scientist is trying to determine whether a microbe is a strict anaerobe. Which test would be most appropriate?

Accepted Answer

Grow the microbe in a sealed jar with no oxygen and observe for growth.

Question 3

Which of the following statements about biofilms is correct?

Accepted Answer

Biofilms protect microbes from antibiotics and can cause persistent infections.

Question 4

Which equation correctly represents the calculation of cell concentration using a direct microscopic count?

Accepted Answer

$$N = \frac{A}{V} 	imes D$$

Question 5

Pasteur’s germ theory of disease states that:

Accepted Answer

Microorganisms are the cause of many diseases.

Question 6

Which of the following is NOT a beneficial activity of bacteria?

Accepted Answer

Causing food spoilage.

Question 7

A patient is infected with a bacterium that survives boiling but is killed by autoclaving. What structure does this bacterium likely possess?

Accepted Answer

Endospore

Question 8

Which of the following best explains why Gram-negative bacteria are generally more resistant to chemical biocides than Gram-positive bacteria?

Accepted Answer

Gram-negative bacteria have an outer membrane that acts as a barrier to many chemicals.

Question 9

Which process is responsible for the transfer of genetic material from one bacterium to another via a pilus?

Accepted Answer

Conjugation

Question 10

Which of the following is a correct definition of an operon?

Accepted Answer

A cluster of genes under the control of a single promoter and operator.

Question 11

A researcher is using the streak plate method to isolate pure colonies. What is the main principle behind this technique?

Accepted Answer

Dilution of bacteria across the plate to separate individual cells.

Question 12

Which of the following is a direct method for measuring microbial cell growth?

Accepted Answer

Plate count

Question 13

Which of the following best describes the function of plasmids in bacteria?

Accepted Answer

Plasmids carry genes that can confer antibiotic resistance.

Question 14

Which of the following is a correct statement about the structure of prokaryotic cell walls?

Accepted Answer

Gram-positive cell walls have a thick peptidoglycan layer.

Question 15

Which of the following is a correct formula for calculating the generation time ($$g) of a $$bacterial culture?

Accepted Answer

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

Question 16

Which of the following is a reason why mycoplasma is resistant to antibiotics that interfere with cell wall synthesis?

Accepted Answer

Mycoplasma lacks a cell wall.

Question 17

Which of the following is a correct statement about the role of cAMP in gene regulation?

Accepted Answer

cAMP binds to CAP, allowing RNA polymerase to initiate transcription.

Question 18

Which of the following is a correct definition of emerging infectious disease?

Accepted Answer

A disease that has recently increased in incidence or geographic range.

Question 19

Which of the following is a correct statement about Koch’s postulates?

Accepted Answer

They are a set of criteria used to establish a causative relationship between a microbe and a disease.

Microbiology Core Concepts: Learning Objectives and Study Guide

Study Guide - Practice Questions