The Microbiota of the GI Tract

Question 1

transit time along the mouth

Answer 1

1 min

Question 2

transit time along the oesophagus

Answer 2

4-8 sec

Question 3

transit time along stomach

Answer 3

2-4 h

Question 4

transit time along small intestine

Answer 4

3-5h

Question 5

transit time along colon/large intestine

Answer 5

10h to several days

Question 6

what does transit time effect?

Answer 6

bacterial populations due to different bacterial growth rates

intestinal cell exposure to toxins- consumed with food or produced by bacteria

Question 7

what is Facultative anaerobic bacteria

Answer 7

Facultative anaerobic bacteria

Question 8

what is Obligate anaerobe

Answer 8

Cannot grow in the presence of oxygen

– many rapidly killed in the presence of any oxygen

Question 9

ph of Mouth

Answer 9

6.5-7.5

Question 10

ph of stomach

Answer 10

1.5-4

Question 11

ph of duodenum

Answer 11

7-8.5

Question 12

ph of distal ileum

Answer 12

4-7

Question 13

ph of colon

Answer 13

5.5-6.5

Question 14

what does the GIT microbiota do?

Answer 14

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

Question 15

where is the energy from junk food absorbed?

Answer 15

small intestine

Question 16

where is the energy from fibre in veg and fruit absorbed?

Answer 16

large intestine

Question 17

benefits of including dietary fibre in our diet

Answer 17

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

Question 18

function of butyrate?

Answer 18

epithelial cell growth and regeneration

Question 19

function of propionate?

Answer 19

gluconeogenesis in the liver

satiety signalling

Question 20

function of acetate

Answer 20

transported in blood
to peripheral tissues
lipogenesis

Question 21

what is colonisation resistance?

Answer 21

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

2. Active competitive exclusion
   conferred by both microbe-microbe and microbe-host interactions

Question 22

what ph does pathogens grow optimally at?

Answer 22

> 6

Question 23

differences between proximal colon to distal colon?

Answer 23

high substrate concentrations

high fermentation rates

high SCFA production and absorption

low pH

pathogen exclusion

quicker transit

high epithelial cell turnover

Question 24

what is the most densely populated body site colonised with anaerobic bacteria?

Answer 24

large intestine

Question 25

how does bacteria in the large intestine ferment dietry fibre?

Answer 25

the metabolites produced like SCFA are important for health and circulate round the body having effects outside the gut

Question 26

how does the resident bacteria prevent pathogen colonisation

Answer 26

lowering pH, creating a physical barrier, prime immune system, produce active compounds that kill incoming pathogens