Question 1

Which of the following statements best describes the distribution of dominant bacterial groups across the most heavily colonized human body sites?

Accepted Answer

One group of bacteria tends to dominate each site, but the dominant group is different for each site.

Question 2

The human microbiome is estimated to contain approximately how many microbial cells?

Accepted Answer

$$10^{13}$$

Question 3

Which bacterial genus is primarily responsible for maintaining the acidic environment of the adult female vaginal tract?

Accepted Answer

Lactobacillus

Question 4

A disruption in the balance of vaginal microbiota can lead to which of the following conditions?

Accepted Answer

Bacterial vaginosis

Question 5

Which of the following is a function of the mucosal layer in the gastrointestinal tract?

Accepted Answer

It forms a barrier that retains host secretions and inhibits microbial attachment.

Question 6

Which enzyme found in saliva is responsible for cleaving peptidoglycan bonds in bacterial cell walls?

Accepted Answer

Lysozyme

Question 7

Why are infants delivered by Cesarean section at increased risk for atopic diseases and asthma compared to those delivered vaginally?

Accepted Answer

They are introduced to skin flora rather than vaginal microbes, leading to abnormal microbial colonization and disrupted immune system development.

Question 8

Which of the following best explains the role of short-chain fatty acids (SCFAs) produced by gut microbiota?

Accepted Answer

SCFAs are absorbed by the host and play a role in energy metabolism and immune regulation.

Question 9

Which of the following is a plausible consequence of a decrease in gut microbial diversity in elderly individuals?

Accepted Answer

Increased susceptibility to metabolic diseases such as type 2 diabetes and obesity.

Question 10

Which of the following statements about the human virome is correct?

Accepted Answer

The human virome is unique to each individual and generally stable over time.

Question 11

Endogenous retroviruses (HERVs) make up approximately what percentage of the human genome?

Accepted Answer

$$5-8\%$$

Question 12

Which of the following is a protective function of bacteriophages in the human microbiome?

Accepted Answer

They kill bacteria before crossing the mucous barrier, providing defense against pathogens.

Question 13

Which of the following is TRUE regarding the colonization of the infant gut microbiome?

Accepted Answer

The infant gut is colonized immediately after birth, with a natural succession of microbial communities as the microbiome matures.

Question 14

Which of the following is a plausible effect of a Western diet (high in protein, carbohydrates, and fats) on the gut microbiome?

Accepted Answer

It promotes the production of ammonia, phenols, and hydrogen sulfide by the intestinal microbiota, which can contribute to colon inflammation.

Question 15

Which of the following is a major function of Propionibacterium acnes in the skin microbiome?

Accepted Answer

It hydrolyzes triglycerides in sebaceous follicles, producing free fatty acids that can promote inflammation and acne.

Question 16

Which of the following is a plausible outcome of an overabundance of Propionibacterium acnes on the skin?

Accepted Answer

Development of acne due to increased inflammation.

Question 17

Which of the following best describes the role of the immune system in relation to the human microbiome?

Accepted Answer

Exposure to microorganisms during and after birth is essential for developing immune tolerance and recognizing pathogens.

Question 18

Which of the following is a plausible effect of missing microbial genes in the gut microbiome?

Accepted Answer

Reduced ability to synthesize certain vitamins and nutrients, impacting host health.

Question 19

Which of the following is a plausible consequence of an imbalanced oral microbiome?

Accepted Answer

Development of gum inflammation and periodontal disease due to loss of mutualistic balance.

Question 20

Which of the following best explains why the colon is considered strictly anoxic?

Accepted Answer

The colon contains enormous numbers of anaerobic bacteria and very little oxygen.

Microbial Symbioses with Humans: The Human Microbiome and Its Impact

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