[W3] Gut Microbiology

Question 1

What are the 4 dominant bacterial phyla in the human gut?

Answer 1

Firmicutes, Actinobacteria, Bacteroidetes, Proteobacteria

Question 2

What are key genera in the gut microbiota?

Answer 2

Bacteroides, Eubacterium, Bifidobacterium, Clostridium, Ruminococcus, Lactobacillus, Escherichia, Peptostreptococcus

Question 3

What physiological roles does the microbiota influence?

Answer 3

Immune system, Digestive function, Metabolism

Question 4

What conditions are linked to microbiota imbalance?

Answer 4

IBD (Crohn’s, UC), IBS, Obesity, ASD, Colorectal cancer, Antibiotic-associated diarrhoea (AAD)

Question 5

What gases are produced from carbohydrate fermentation?

Answer 5

H₂, CO₂, H₂S

Question 6

What are the main short-chain fatty acids (SCFAs) produced?

Answer 6

Acetate, Propionate, Butyrate

Question 7

What are metabolic byproducts of protein fermentation?

Answer 7

Ammonia, amines, phenols, branched-chain fatty acids

Question 8

What can compromise gut microbiota?

Answer 8

Antibiotics, Stress, Poor diet, Ageing, Infection, International travel

Question 9

What is a probiotic?

Answer 9

Live microorganisms which, when administered in adequate amounts, confer a health benefit on the host

Question 10

What are common probiotic genera?

Answer 10

Lactobacillus (e.g. L. rhamnosus, L. plantarum), Bifidobacterium (e.g. B. longum, B. breve)

Question 11

What are properties of Lactobacillus spp.?

Answer 11

Facultative anaerobes, GRAS, good technological properties, commonly used

Question 12

What are properties of Bifidobacterium spp.?

Answer 12

Strict anaerobes, GRAS, good biological effects but harder to formulate

Question 13

What GI conditions may benefit from probiotics?

Answer 13

IBD (UC, Crohn’s), IBS, Lactose intolerance, C. difficile infection, Constipation, Pouchitis, Acute diarrhoea

Question 14

What probiotic strains helped reduce AAD and C. difficile?

Answer 14

L. casei Shirota, L. casei DN114001

Question 15

What effect did L. rhamnosus HN001 have on immunity?

Answer 15

Increased macrophage phagocytic and NK cell activity in elderly individuals

Question 16

What is the evidence for probiotics in respiratory infections?

Answer 16

Mixed results – reduced duration but not incidence

Question 17

What is the role of probiotics in traveller’s diarrhoea (TD)?

Answer 17

Reduce severity or duration, Improve recovery in athletes, Limited by strain variation and environmental stability

Question 18

What is a prebiotic?

Answer 18

A substrate that is selectively utilized by host microorganisms conferring a health benefit

Question 19

What are common prebiotics?

Answer 19

Fructo-oligosaccharides (FOS), Galacto-oligosaccharides (GOS), Inulin, Lactulose

Question 20

What are the key actions of prebiotics?

Answer 20

Stimulate growth of beneficial bacteria, Inhibit pathogens, Enhance immune responses, Improve bowel function

Question 21

What effects did GOS have in IBS patients?

Answer 21

Improved stool consistency, reduced bloating, flatulence, anxiety

Question 22

How did FOS affect traveller’s diarrhoea?

Answer 22

Reduced severity of diarrhoea episodes

Question 23

What did GOS show in a placebo-controlled TD trial?

Answer 23

Lower incidence, reduced abdominal pain and diarrhoea duration

Question 24

How do prebiotics support gut health?

Answer 24

Selective stimulation of bifidobacteria, Colonisation resistance, Suppression of inflammation, Modulation of immune signaling

Question 25

Where do prebiotics come from?

Answer 25

Human milk oligosaccharides, Natural sources (onion, banana, asparagus), Manufactured (e.g. GOS)

Question 26

What is the nature of probiotics?

Answer 26

They are live microorganisms

Question 27

What is the nature of prebiotics?

Answer 27

They are non-digestible, selectively fermented carbohydrates

Question 28

What is required for probiotic effectiveness?

Answer 28

The microorganisms must be alive to be effective

Question 29

Are prebiotics affected by heat or acid?

Answer 29

No — prebiotics are stable and not affected by acid or temperature

Question 30

How do probiotics function?

Answer 30

They introduce beneficial bacteria into the host

Question 31

How do prebiotics function?

Answer 31

They feed and promote the growth of existing beneficial bacteria in the gut

Question 32

What is the research volume on probiotics?

Answer 32

Over 45,000 published studies

Question 33

What type of studies are most informative for prebiotics?

Answer 33

In vivo studies are preferred for evaluating their effects