Microbiome in Health and Disease

Question 1

The collective microbiome genome is about _______ as long as the combined human genome.

Answer 1

100x

Question 2

What immune function do the commensal bacteria have?

Answer 2

• Serve as a protective barrier
• Induce IgA
• Produce antimicrobial substances like H2O2 and lactic acid

Question 3

10% of our calories go to ___________.

Answer 3

microbial fermentation (producing anti-inflammatory molecules and energy sources such as butyrate for the gut epithelium)

Question 4

Microbiomes are studied using ____________.

Answer 4

16S PCR sampling to determine relative quantities

Question 5

Compare the types of bacteria over the life course.

Answer 5

•Children younger than one year:

• Proteobacteria (Escherichia)
• Actinobacteria (Bifidobacteria)

•Older than one year to adulthood:

• Bacteroidetes (Bacteroides)
• Firmicutes (Clostridia and Lactobacilli)

Question 6

People usually acquire the lifetime maximum amount of bacteria at age ________.

Answer 6

7 days

Question 7

What is a common problem in dysbiosis research?

Answer 7

Much research on dysbiosis is correlative. Causality is not known. For instance, those with IBD may have dysbiosis, but perhaps that dysbiosis is a result of intestinal distress and malabsorption, not a cause.

Question 8

What are some risk factors for C. difficile infection?

Answer 8

• Age: older than 65
• Hospitalization
• Antibiotic usage (10x risk)

Question 9

There is a lot of anecdotal research on ___________ after fecal microbiota transplant.

Answer 9

obesity

(Obesity has been shown to be transmittable between mice using fecal microbiota transplant, particularly with excess Firmicutes and decreased Bacteroides.)

Question 10

Dysbiosis has been shown to correlate with higher risk of ________________.

Answer 10

tumorigenesis

Question 11

Gram-positive organisms are related, but Gram-negative organisms are ______________.

Answer 11

heterogeneous

Question 12

How many commensal organisms typically live on an adult host?

Answer 12

100 trillion (10^14)

Question 13

List three metabolic functions of commensal bacteria.

Answer 13

• Ferment non-digestible polysaccharides and mucus
• Synthesize vitamins: B3, B5, B6, B12, K, Biotin, Folate
• Sequester metals

Question 14

Which bacterium induces Th17 differentiation?

Answer 14

Clostridium

Question 15

Elevated __________ (which can come from dysbiosis) has been shown to contribute to NAFLD.

Answer 15

TMAO and betaine

Because of this, some people are trying to treat dysbiosis with inhibitors of the enzyme that converts TMA to TMAO.