Week 4.2 - The Gut Microbiota Flashcards
What is the pH in the mouth, stomach, duodenum and colon?
- mouth 6.5-7.5 - aerobic
- stomach 1.5-5 - aerobic and anaerobic
- duodenum 7-8.5
- colon 5.5-6.5 - obligate anaerobes
What factors change the dominant bacteria in the Gi tract?
- o2 concentrations
- pH
- transit times
What determines the composition of our microbiota?
- each individual is unique
- our diet
What is the role of bacteria in the large intestine? (4)
- ferment dietary fibre
- produce metabolites to communicate with other bacteria and the host
- prime the immune system keeping it in homeostasis
- prevent pathogen colonisation
How does the microbiota help with the development of the immune system?
microbiota develops alongside immune system so we have immunity as we recognise cells as self cells.
What are the benefits of dietary fibre?
- increased faecal bulking
- decreased transit time
- release antioxidants, vitamins and phytochemicals
- bacterial fermentation maintains slightly acidic pH resistance to pathogens + release additional phytochemicals and short chain fatty acids
Carb metabolism in the colon and its importance?
- occurs in proximal
- produces short chain fatty acids acetate, propionate and butyrate.
- also gas production
What nutrients are metabolised in distal colon? whats the importance?
- proteins and fats
- produce harmful branched chain amino acids and harmful gasses like ammonia and hydrogensulphate. also inflammation
Whats the significance of short chain amino acids?
- acetate used in lipogenesis
- butyrate for epithelial growth and regeneration in gut
- propionate important for glyconeogenesis in liver and satiety signals
How does the pH change along the colon and why is this important?
- proximal is 5.5 due to carb metabolism. inhibits pathogens and increases Ca absorption
- distal is 6.5 - due to protein and fat fermnetation - less bacterial fermentation of carbs
What pH do pathogens generally grow?
over pH6
What is disease likeliness in proximal and distal colon?
less disease in proximal due to:
- quicker transit of faeces,
- low pH,
- high substrate conc.
- high fermentation rates
- short chain fatty acids.
all opposite in distal so more disease
What are prebiotics and probiotics?
- pre-biotics are substrate that is utilised by host microorganisms giving health benefit
- probiotics is live substrate that you administer - correct one for requirements you’re looking for
What is dysbiosis?
inbalance of pre-inflammatory and post-inflammatory bacterioa, causing altered immune response
How does a decrease in the mucus barrier lead to disease?
decrease in mucus barrier leads to o2 penetration on epithelium in bowel, causing death of microbiota obligate anaerobes, changing composition causing inflammation further decreasing mucus barrier. cycle.
