Question 1

Which of the following best describes the difference between resident and transient microbiota?

Accepted Answer

Resident microbiota are always present on or in the body, while transient microbiota are only temporarily found and do not permanently colonize.

Question 2

A patient taking broad-spectrum antibiotics develops a Clostridioides difficile infection. This is an example of:

Accepted Answer

An opportunistic pathogen causing disease due to disruption of the normal microbiota.

Question 3

Which of the following best defines 'mutualism' in the context of the human microbiome?

Accepted Answer

Both the host and the microbe benefit from the relationship.

Question 4

Which of the following is NOT a benefit provided by the normal microbiota?

Accepted Answer

Direct destruction of host cells for nutrients.

Question 5

Which of the following best describes the role of bacteriocins in the human microbiome?

Accepted Answer

They are antimicrobial peptides produced by bacteria to inhibit the growth of closely related bacterial species.

Question 6

A newborn is breastfed and develops a healthy gut microbiome. Which genera are most likely to be dominant in the infant's gut due to breastmilk?

Accepted Answer

Streptococcus and Lactobacillus

Question 7

Which of the following is a limitation faced by gut microbiome organisms, and what is one adaptation they have developed?

Accepted Answer

Low oxygen levels; adaptation: anaerobic metabolism

Question 8

Which of the following best describes the process of competitive exclusion by the normal microbiota?

Accepted Answer

Normal microbiota outcompete pathogens for nutrients and attachment sites, preventing pathogen colonization.

Question 9

Which of the following is a correct sequence of ecological succession in the development of dental plaque?

Accepted Answer

Streptococcus species colonize first, followed by Actinomyces, then anaerobic bacteria such as Porphyromonas.

Question 10

Which of the following statements about biofilms is TRUE?

Accepted Answer

Biofilms provide protection to microbes from environmental stresses and antibiotics.

Question 11

A patient presents with inflamed gums and bone loss around the teeth. Which of the following best describes the likely condition and its microbial cause?

Accepted Answer

Periodontal disease caused by anaerobic bacteria in the gingival crevice.

Question 12

Which of the following is a major antimicrobial component of saliva, and what is its mechanism of action?

Accepted Answer

Lysozyme; it hydrolyzes the $$\beta-1$$,4 glycosidic bonds in peptidoglycan.

Question 13

Which of the following best describes the role of glycoproteins on a clean tooth surface?

Accepted Answer

They form a pellicle that facilitates initial bacterial attachment and biofilm formation.

Question 14

Which method is most commonly used to study oral microbiome populations that cannot be cultured in the laboratory?

Accepted Answer

DNA sequencing of 16S rRNA genes

Question 15

A cariogenic diet high in sucrose increases the risk of dental caries. Which of the following best explains the mechanism?

Accepted Answer

Streptococcus mutans metabolizes sucrose to produce lactic acid, which lowers pH and leads to decalcification of enamel.

Question 16

Which of the following best defines 'dysbiosis'?

Accepted Answer

An imbalance in the normal microbiota that can lead to disease.

Question 17

Which of the following is NOT a typical environmental condition of the oral cavity that influences microbial colonization?

Accepted Answer

High oxygen concentration throughout the entire mouth

Question 18

Which of the following is a correct statement about the dynamic nature of the oral microbiome?

Accepted Answer

The composition of the oral microbiome changes over time in response to factors such as diet, hygiene, and age.

Question 19

Which of the following best describes the process of decalcification in dental caries?

Accepted Answer

Acid produced by bacteria dissolves the $$\mathrm{Ca$$^{2+}$$}$$ ions from hydroxyapatite in tooth enamel.

Question 20

Which of the following is a key step in the development of a biofilm?

Accepted Answer

Attachment of microbes to a surface, followed by production of extracellular polymeric substances (EPS).

Human Microbiome and Oral Microbiology: Study Guide

Study Guide - Practice Questions

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