L27 - Gut Microbiome

Question 1

The gut contains 10 times more or less bacteria than there are cells in the human body?

Answer 1

More

*They are also more diverse - low diversity leads to increased likelyhood of diabetes and obesity

Question 2

In colon, almost exclusively aerobic/anaerobic?

Answer 2

Anerobic

Question 3

In caecum, about 20% aerobic/anaerobic?

Answer 3

Aerobic

Question 4

By what age do you already have your adult gut bacteria?

Answer 4

7

Question 5

Antibiotics have a major short term effect on microbiota - allows certain diseases to take over as such as ___ which is supressed by normal microbiota (which is affected during ingestion of antibiotics)

Answer 5

Clostridium difficile colitis - antibiotic diarrhoea induced disease

Question 6

T/F: Bacteria in mucus associated with epithelium are the same as those in the lumen itself

Answer 6

F

Question 7

Tools for study of gut microbiome (3)

Answer 7

•16S ribosomal RNA sequencing and other next generation sequencing methods for identifying presence of different species
•Metabolomics
–Identification of the full suite of metabolic products produced by colonic bacteria
•Germ-free mice (mice with no microbiota AT ALL)
–Behavioural studies
–Functional studies at single neuron level
–Can introduce whole microbiome (faecal transplant) or single bacterial strains (probiotic)

Question 8

Vancomycin treats gram _ bacteria. In the colon, it suppresses _ and in the colon and duodenum it supresses_. In preterm babies (

Answer 8

Vancomycin treats gram negative bacteria. In the colon, it suppresses bacteriodetes and in the colon and duodenum it supresses actinobacteria

Question 9

GABA is a metabolite of certain bacteria associated with Clostridium difficile colitis infection. In high amounts, it increases the likelihood of this infection. It activates cells in the mucosa such as the endochromatin cells that release serotonin.

Answer 9

GABA is a metabolite of certain bacteria associated with Clostridium difficile colitis infection. In high amounts, it increases the likelihood of this infection. It activates cells in the mucosa such as the endochromatin cells that release serotonin.

Question 10

GABA – excitatory or inhibitory for both enteric neurons and extrinsic primary afferent neurons?

Answer 10

Excitatory

Question 11

Serotonin – excites or inhibits enteric neurons and terminals of extrinsic primary afferent neurons

Answer 11

Excites

Question 12

Histamine

Answer 12

Inflammatory mediator

Question 13

Lipopolysaccharide (LPS)

Answer 13

Cell wall component that is neuroactive, can act on enteroendocrine cells and enters the blood

Question 14

Short chain fatty acids (acetate, butyrate, proprionate) can excite/inhibit intrinsic sensory neurons and EE cells via specific ____

Answer 14

Excite via GPCR

Question 15

What is the effects of probiotic JB-1 on a myenteric neuron?

Answer 15

JB-1 changes overall function of mucosa (more easily excitable) and also excites vagal afferent axons and has psychogenic effects in germ free mice

Question 16

Stress modifies microbiome via

Answer 16

Cortisol

Question 17

Microbiome modifies central mood, etc via?

Answer 17

Cytokines, tryptophan metabolites

–Probably also via primary afferent neurons

Question 18

Can antibiotics be used to achieve germ free status?

Answer 18

NO

Question 19

Are germ free mice more or less anxious?

Answer 19

Less anxious

Question 20

Largest study gives different conclusion
–No difference in microbiomes between patients and “neurotypical” siblings
–No difference in microbiota between ASD patients with GI symptoms, neurotypical siblings and ASD patients without GI symptoms

Answer 20

Largest study gives different conclusion
–No difference in microbiomes between patients and “neurotypical” siblings
–No difference in microbiota between ASD patients with GI symptoms, neurotypical siblings and ASD patients without GI symptoms

Question 21

Recall that NL – 3 mice have a single point mutation in a synaptic protein not expressed anywhere but in neurons (Enteric and central); so it appears that this point mutation is capable of producing a change in the microbiome, increasing the levels of what happens to be a neuroactive strain of bacteria (Lactobacillus )

It is possible that there are environmental factors that can lead to changes in behaviours, and are associated with a microbiome change.

Answer 21

Recall that NL – 3 mice have a single point mutation in a synaptic protein not expressed anywhere but in neurons (Enteric and central); so it appears that this point mutation is capable of producing a change in the microbiome, increasing the levels of what happens to be a neuroactive strain of bacteria (Lactobacillus )

It is possible that there are environmental factors that can lead to changes in behaviours, and are associated with a microbiome change.