Human Microbiome

Question 1

What is commensal bacteria?

Answer 1

Supplies the host with essential nutrients and protects host against opportunisitic pathogens without causing harm to our health. They form part of the normal microbial flora

Question 2

What is a microbiome?

Answer 2

Community of bacteria

Question 3

Which commensal bacteria is present in the gut microbiome?

Answer 3

Lactobaccilius and escherischia coli

Question 4

How does the gut microbiome develop?

Answer 4

Babies are sterile until delivery when they travel through the birth canal where the vagina is rich in lactobaccilius bacteria and gain maternal bacteria, alongside breastfeeding. It changes in composition and becomes more diverse during development

Question 5

What affects composition of gut microbiota?

Answer 5

Diet, medication like antibitoics, chronic inflammation, hygeine and lifestyle

Question 6

How does the density of bacteria change?

Answer 6

Greatest in the large intestine, specifically, the proximal transverse colon

Question 7

Which type of bacteria is present in gut microbiome?

Answer 7

Gram positive, anaerobic.

Question 8

What is the difference in microbiota between infants born vaginally vs C-section?

Answer 8

Vaginally: commensal bacteria such as prevotella, sneathius and lactobaccilius

Question 9

What is the microbiota of infants born by C section?

Answer 9

Harmful bacteria such as streptococcus, corynebacterium and propionibacterium

Question 10

Where is the majoirty of serotoinin produced?

Answer 10

Intestines

Question 11

What is the role of the gut microbiome?

Answer 11

Protection against pathogens, immune system development, modulation of CNS

Question 12

What prevents interaction between gut microbiota and intestinal cells?

Answer 12

Thick layer of mucus on top of enterocytes contaning IgA antibodies

Question 13

Which vitamins are produced by the gut microbiome?

Answer 13

Production of vitamin K and B12/folate, and B2.

Question 14

How does the gut microbiome affect metabolism?

Answer 14

It increases metabolism of xenobiotics and drugs, by promoting absorptive capacity of enterocytes through increasing intestinal angiogenesis. Increases adiposity. It increases fermentation and lipogenesis

Question 15

Why are the metabolites of the gut microbiome important?

Answer 15

Signalling molecules for biochemical communication between enteric system and CNS.

Question 16

What provides majority of energy to colon cells?

Answer 16

Fermentation of dietary fibre/ non-digestable carbohydrates -> short chain fatty acids such as butyrate

Question 17

How does gut microbiome affect lipid levels?

Answer 17

Increases lipid storage and adiposity by promoting lipogenesis

Question 18

How does gut microbiome affect the morphology of the gut?

Answer 18

It increases mucus thickness, levels of IgA antibodies, development of lymphoid tissue.
It increases intestinal angiogenesis, lipogenesis, production of short chain fatty acids by metabolsim of dietary fibre.

Question 19

How does the gut microbiome protect against pathogens?

Answer 19

Via colonisation resistance. Bacteria which survive low stomach pH establish colonisation through replication and resist peristalsis. Gut promotes immune defences through metabolic products, nutrient competition, direct toxicity and immune induction

Question 20

How do metabolic products provide protection against pathogens?

Answer 20

Bile salts disrupt bacterial membranes; short chain fatty acids regulate virulence factors. These provide indirect protection against clostridium and e.coli

Question 21

How does gut microbiome affect immune response?

Answer 21

Promotes production of defensins from epithelial cell lining of GI tract which inhibit bacterial growth of enterococcus and listeria. This is indirect.

Question 22

How does gut microbiome provide direct protection against pathogens?

Answer 22

Nutrient competition with pathogens for sialic acid and fucose in intestinal mucus. Gut microbiota produces the toxin bacteriococcilin and uses type VI secretion.

Question 23

What is type VI secretion?

Answer 23

Mode of transport of toxins from gut microbiota into target cell membrane/cyptoplasm/

Question 24

How can commensal bacteria cause infection?

Answer 24

Spread into sterile areas of the body or replicate if normal numbers are disturbed and increase in population

Question 25

What causes increase in population of commensal bacteria?

Answer 25

Immune deficiency, pH imbalance, decrease in mucus. This can lead to infection because population must be low to prevent harm

Question 26

What is clostridium dificile?

Answer 26

Gram positive anaerobic Bacteria which composes a small proportion of commensal flora when in low levels. It forms spores and transmitted from faecal to mouth causing bowel infection.

Question 27

How does antibiotic treatment affect gut microbiome?

Answer 27

Non discriminatavely eliminates both commensal and harmful bacteria

Question 28

What is antibiotic selective pressure?

Answer 28

Use of antibiotics leaves only bacteria with mutation for resistance to survive

Question 29

What is pseudomembranous colitis?

Answer 29

Inflammation of colon with elevated yellow-white plaques on mucosa, caused by clostridium dificle when antibitoic selective pressure increases their population. This causes diarrhoea

Question 30

What is fecal microbial transplant?

Answer 30

Transfer of healthy bacteria from processed stool of healthy donor to intestine via a tube. This is to restore gut bacteria and control infection from clostridium dificile.

Question 31

What is dysbiosis?

Answer 31

Imablance in gut microbiome associated with disease due to changes in micorbe abundance which cause harm to the host.

Question 32

What are prebiotics?

Answer 32

Non digestable food ingredient as dietary fibre which promotes activity/growth of colonic bacteria by providing nutrients, improving host health without being destroyed during digestion

Question 33

What are probiotics?

Answer 33

Living non- pathogenic organisms in food to improve host health