Microbiota of the GI Tract Flashcards
What does anaerobic mean?
Living in the absence of air
What does aerobic mean?
Living in the presence of air
What is facultative anaerobic bacteria?
Can grow in the presence of oxygen AND absence of oxygen
What is an obligate anaerobe?
Cannot grow in the presence of oxygen
What is the normal range of pH in the mouth?
6.5 - 7.5
What is the normal range of pH in the stomach?
1.5 - 4
What is the normal range of pH in the duodenum?
7 - 8.5
What is the normal range of pH in the distal ileum?
4 - 7
What is the normal range of pH in the colon?
5.5 - 6.5
Where are facultative anaerobes found?
Stomach
Where are obligate anaerobes found?
Colon
What does the GIT microbiota do?
Metabolism of dietary components Modification of host secretions Defence against pathogens Production of essential metabolites Immune system development Host signalling
What types of food do GIT microbes come from?
Fibre (fruit, vegetables, pulses, whole grains)
How much energy is absorbed in the stomach/small intestine?
> 70%
How much energy is absorbed in the large intestine?
5-10%
What are the benefits of fibre in the diet?
Improves faecal bulking, eases passes, slower transit time
Contains phytochemicals, anti-oxidants and vitamins
Bacterial fermentation
What are the 3 main short chain fatty acids?
Butyrate
Propionate
Acetate
What are the functions of butyrate?
Epithelial cell growth and regeneration
What are the functions of propionate?
Gluconeogenesis in the liver
Satiety signalling
What is the functions of acetate?
Transport in blood to peripheral tissues
Lipogenesis
What is the barrier effect?
Microbiota prevents colonisation of pathogens
Inhibit overgrowth of pathogenic bacteria
What does the outer mucus layer of the gut do?
Barrier effect
What does the inner mucus layer of the gut do?
Prevents bacterial penetration
What is the effect of dysbiosis of the gut microbiota composition?
DIsrupts homeostasis and can lead to gut inflammation
What is GPR43/FFAR2 activated by and what is the result?
Activated by acetate, propionate, butyrate
Result: GLP-1 secretion
Inhibits fat accumulation
What is GPR/FFAR3 activated by and what is the result?
Activated by propionate and butyrate
Result: PYY secretion
Improves insulin resistance and satiety signalling to brain
What is GPR109A activated by and what is the result?
Activated by butyrate
Suppresses colonic inflammation and carcinogenesis
What are the different factors that influence the microbiota through life?
Birth Feeding Weaning Diet expansion Diet contraction DIet maintenance
