The Healthy Microbiome

Question 1

Microbiota

Answer 1

Microorganisms inhabiting the human body

Question 2

Microbiome

Answer 2

Genomes of microorganisms inhabiting the human body

Question 3

When does colonization of our gut microbiome begin?

Answer 3

• Starts in the birth canal
• Continues with breast feeding
• After 2-5 years, the microbiome starts resembling the adult microbiome

Question 4

What are some main influential factors that affect our gut biome throughout life?

Answer 4

• Gestational age at delivery
• NICU exposure
• Antibiotics
• Diet

Question 5

How does the microbiome differ as you go further down the GI tract?

Answer 5

The number of bacteria increases the further you go down the GI tract; for example, there are a few hundred bacteria in our stomachs and 10^12 bacteria in our colons.

Question 6

What are some main benefitis of the microbiome?

Answer 6

• Blocks colonization of pathogens via nutrient competition and direct microbial conflict
• Immune system modulation (germ-free mice have defective lymphoid tissue)
• Nutrients through microbial by-products

Question 7

What are important by-products that the microbiome produces?

Answer 7

Short-chain fatty acids (SCFAs) such as butryrate, acetate, and proprionate

Question 8

What does the microbiome fermentation of dietary fibers result in?

Answer 8

Short-chain fatty acids (SCFAs) such as butryrate, acetate, and proprionate

Question 9

How does luminal acetate and propionate made by the microbiome affect us?

Answer 9

• It affects intestinal transit and satiety
• Decreased hepatic glucose production through intestinal gluconeogenesis
• Acetate specifically decreases rate of lipolysis (breakdown of fats) in white adipose tissue

Question 10

How does butyrate made by the microbiome affect us?

Answer 10

It exerts an anti-inflammatory effect and stimulates the enteric nervous system (ENS) [which is one of the main divisions of the autonomic nervous system and governs the function of the GI tract]

Question 11

How does the microbiome influence T-cell differentiation?

Answer 11

Different bacterial species were shown to induce specific T cell differentiation pathways

Question 12

What forms a barrier between the host tissue and microbiota?

Answer 12

A mucus layer acts as the primary barrier

Question 13

What immune cell eliminates occasional microbiota that translocate into the host?

Answer 13

Macrophages

Question 14

What role do dendritic cells play in the microbiota?

Answer 14

Dendtritic cells are antigen presenting cells and differentiate microbiota-specific T-red, Th17, and IgA-producing B cells

Question 15

What role does the microbiota play when a pathogen breaks into the host?

Answer 15

The microbiota also enter the host and help ramp up the immune response and then help recover the suppressive atmosphere after recovery

Question 16

What role does Bacteroides fragilis play in maintaining the immune system status?

Answer 16

• They create a suppressive/anti-inflammatory atmosphere

- Are required for normal development of spleen, thymus, and lymph nodes

Question 17

What role does Clostridium species play in maintaining the immune system status?

Answer 17

They create a suppressive/anti-inflammatory atmosphere

Question 18

What role does Segmented filamentous bacteria play in maintaining the immune system status?

Answer 18

They are pro-inflammatory

Question 19

What are some ways that the gut microbiome can be altered?

What consequence might this have?

Answer 19

• Antibiotic use, changes in diet, etc.

- Changes in the gut microbiome can lead to altered immunity and infection