The Microbiota of the GI Tract Flashcards
transit time along the mouth
1 min
transit time along the oesophagus
4-8 sec
transit time along stomach
2-4 h
transit time along small intestine
3-5h
transit time along colon/large intestine
10h to several days
what does transit time effect?
bacterial populations due to different bacterial growth rates
intestinal cell exposure to toxins- consumed with food or produced by bacteria
what is Facultative anaerobic bacteria
Facultative anaerobic bacteria
what is Obligate anaerobe
Cannot grow in the presence of oxygen
– many rapidly killed in the presence of any oxygen
ph of Mouth
6.5-7.5
ph of stomach
1.5-4
ph of duodenum
7-8.5
ph of distal ileum
4-7
ph of colon
5.5-6.5
what does the GIT microbiota do?
metabolism of dietary components
production of essential metabolites to maintain health
development of immune system
host signalling
defence againts pathogens-competition, barrier function, ph imhinition
modification of host secretion
where is the energy from junk food absorbed?
small intestine
where is the energy from fibre in veg and fruit absorbed?
large intestine
benefits of including dietary fibre in our diet
Improves faecal bulking, eases passage, results in shorter transit time
➢Contains important phytochemicals, anti-oxidants and vitamins
➢Bacterial fermentation:
➢Releases additional phytochemicals
➢Maintains slightly acidic pH
➢Increased commensal bacterial population and pH improves resistance to pathogens
➢Essential supply of short chain fatty acids
function of butyrate?
epithelial cell growth and regeneration
function of propionate?
gluconeogenesis in the liver
satiety signalling
function of acetate
transported in blood
to peripheral tissues
lipogenesis
what is colonisation resistance?
Barrier effect
The large numbers of the indigenous microbiota prevent colonisation by ingested pathogens AND inhibit overgrowth of potentially pathogenic bacteria normally resident at low levels
- Active competitive exclusion
conferred by both microbe-microbe and microbe-host interactions
what ph does pathogens grow optimally at?
> 6
differences between proximal colon to distal colon?
high substrate concentrations
high fermentation rates
high SCFA production and absorption
low pH
pathogen exclusion
quicker transit
high epithelial cell turnover
what is the most densely populated body site colonised with anaerobic bacteria?
large intestine
how does bacteria in the large intestine ferment dietry fibre?
the metabolites produced like SCFA are important for health and circulate round the body having effects outside the gut
how does the resident bacteria prevent pathogen colonisation
lowering pH, creating a physical barrier, prime immune system, produce active compounds that kill incoming pathogens
