Question 1

Which of the following best describes the difference between a pathogen and an opportunistic pathogen?

Accepted Answer

A pathogen always causes disease in humans, while an opportunistic pathogen causes disease only in a weakened host.

Question 2

Which experiment by Louis Pasteur provided strong evidence against spontaneous generation?

Accepted Answer

He used a swan-necked flask to show that broth remained sterile unless exposed to airborne microbes.

Question 3

Which of Koch’s postulates would be violated if a microbe could not be grown in pure culture?

Accepted Answer

The organism must be isolated from the diseased host and grown as a pure culture.

Question 4

Which of the following is NOT a goal of aseptic technique in a clinical laboratory?

Accepted Answer

To ensure that only Gram-positive bacteria are cultured.

Question 5

Which scientist is credited with introducing hand washing to reduce childbed fever in hospitals?

Accepted Answer

Ignaz Semmelweis

Question 6

Which of the following best describes the difference between a scientific law and a scientific theory?

Accepted Answer

A law is a precise statement or formula that predicts a specific occurrence, while a theory explains how and why something occurs.

Question 7

Which of the following is the correct order of the taxonomic hierarchy from broadest to most specific?

Accepted Answer

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Question 8

Which of the following best describes mutualism in host–microbe interactions?

Accepted Answer

Both the microbe and the host benefit from the relationship.

Question 9

Which of the following is a real-world example of how the human microbiome can be disrupted, leading to disease?

Accepted Answer

Taking antibiotics for a urinary tract infection can reduce normal vaginal microbiota, allowing Candida albicans to cause a yeast infection.

Question 10

Which of the following statements about biofilms is TRUE?

Accepted Answer

Biofilms are more resistant to antibiotics and immune responses than planktonic cells.

Question 11

Which of the following best explains why immersion oil is used with the 100x objective lens in light microscopy?

Accepted Answer

Immersion oil has the same refractive index as glass, reducing light refraction and increasing resolution.

Question 12

Which of the following staining techniques would be most appropriate for identifying Mycobacterium tuberculosis in a clinical sample?

Accepted Answer

Acid-fast stain

Question 13

A scientist observes that a bacterial sample appears pink after Gram staining. What can be concluded about the cell wall structure?

Accepted Answer

The bacteria have a thin peptidoglycan layer and an outer membrane rich in lipids.

Question 14

Which of the following best describes the function of a mordant in a staining procedure?

Accepted Answer

It interacts with a dye and fixes it on or inside the treated specimen.

Question 15

Which of the following is a limitation of Koch’s postulates in identifying the causative agent of a disease?

Accepted Answer

Some pathogens cannot be grown in pure culture or do not cause disease in animal models.

Question 16

Which of the following best explains why proper sewage management reduced cholera cases, even though the miasma theory was incorrect?

Accepted Answer

It prevented the contamination of drinking water with Vibrio cholerae.

Question 17

Which of the following statements about the Human Microbiome Project is TRUE?

Accepted Answer

It aims to characterize all of the microbes in and on our bodies.

Question 18

Which of the following best describes the role of normal microbiota in protecting against infection?

Accepted Answer

They compete with potential pathogens, reducing their ability to colonize.

Question 19

Which of the following microscopy techniques would be most appropriate for visualizing the 3D surface structure of a bacterial cell?

Accepted Answer

Scanning electron microscopy (SEM)

Question 20

Which of the following best explains why only about 2% of bacteria can be cultured in the laboratory?

Accepted Answer

Most bacteria require complex growth environments that are difficult to replicate in the lab.

Introduction to Microbiology: Foundations, Classification, and Laboratory Techniques

Study Guide - Practice Questions