Question 1

Which of the following statements best describes the relationship between the human host and its microbiome?

Accepted Answer

The human host and its microbiome form a supraorganism, with mutual influences on health and disease.

Question 2

A patient undergoes a course of broad-spectrum antibiotics, which significantly reduces the population of obligate anaerobes in their colon. Which of the following is a likely consequence?

Accepted Answer

An increase in the abundance of facultative aerobes such as Escherichia coli due to reduced competition.

Question 3

Which of the following best explains why the stomach, despite its low pH, contains a distinct core microbiome?

Accepted Answer

Certain bacteria, such as Helicobacter pylori, are highly acid-tolerant and can colonize the stomach, forming a stable community.

Question 4

Which of the following is a major function of short-chain fatty acids (SCFAs) produced by gut microbiota?

Accepted Answer

SCFAs serve as signaling molecules that regulate immune responses and cellular metabolism in the host.

Question 5

A researcher is studying the effect of diet on the gut microbiome. She finds that a high-fiber diet increases the abundance of bacteria that ferment plant polysaccharides. Which of the following is a likely metabolic product of these bacteria?

Accepted Answer

Butyrate, a short-chain fatty acid

Question 6

Which of the following best describes the role of bacteriophages in the human virome?

Accepted Answer

They are the most abundant viruses in the human body and can provide a first line of defense against bacterial pathogens.

Question 7

A newborn delivered by cesarean section is more likely to have which of the following features in their early gut microbiome compared to a vaginally delivered infant?

Accepted Answer

Enrichment of Staphylococcus and Streptococcus species due to colonization from skin and oral microbes.

Question 8

Which of the following mechanisms helps maintain the anoxic environment of the colon, favoring the growth of obligate anaerobes?

Accepted Answer

Facultative aerobes such as Escherichia coli consume residual oxygen, preventing its accumulation.

Question 9

Which of the following statements about the oral microbiome is correct?

Accepted Answer

The oral microbiome is as diverse as the gut microbiome, with most species growing as biofilms on teeth and gums.

Question 10

A patient presents with recurrent urinary tract infections caused by Proteus mirabilis. Which of the following features of this bacterium contributes to its pathogenicity in the urinary tract?

Accepted Answer

Production of urease, which generates ammonia and raises urine pH.

Question 11

Which of the following best explains why breastfed infants have a gut microbiome dominated by Bifidobacterium species?

Accepted Answer

Human milk contains unique oligosaccharides that only Bifidobacterium species can efficiently metabolize.

Question 12

Which of the following is a plausible consequence of a decrease in butyrate-producing bacteria in the colon?

Accepted Answer

Increased oxygen availability in the colon, favoring facultative aerobes and potentially leading to inflammation.

Question 13

Which of the following statements about the skin microbiome is correct?

Accepted Answer

Different skin microenvironments (moist, dry, oily) support distinct microbial communities dominated by specific genera.

Question 14

Which of the following is a key difference between the upper and lower respiratory tracts in terms of microbial colonization?

Accepted Answer

The upper respiratory tract harbors a diverse microbiota, while the lower respiratory tract is nearly sterile in healthy adults.

Question 15

Which of the following best describes the concept of 'enterotypes' in the human gut microbiome?

Accepted Answer

Distinct gut community types characterized by the dominance of specific bacterial genera such as Bacteroides, Prevotella, or Ruminococcus.

Question 16

A researcher is using 16S rRNA gene sequencing to study the diversity of bacteria in the human colon. Which of the following is a major advantage of this method over traditional culture-based techniques?

Accepted Answer

It allows detection of bacteria that cannot be readily cultured in the laboratory.

Question 17

Which of the following is a likely effect of excessive hygiene during infancy on the development of the immune system?

Accepted Answer

A poorly trained immune system that is more likely to attack beneficial organisms, increasing the risk of autoimmune conditions.

Question 18

Which of the following best explains the stability of the adult gut microbiome over long periods?

Accepted Answer

A core set of bacterial species, especially Bacteroidetes and Actinobacteria, persist for years or decades in an individual.

Question 19

Which of the following is a plausible mechanism by which bacteriophages in the human gut can influence bacterial pathogenicity?

Accepted Answer

By transferring toxin genes to bacteria through lysogeny, making them pathogenic.

Structure and Function of the Healthy Adult Gastrointestinal and Oral Microbiomes

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