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GI Anatomy > Microbiota of GI tract > Flashcards

Microbiota of GI tract Flashcards

(49 cards)

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1
Q

Why does transit time affect bacterial populations in different parts of the GI tract

A

Due to different bacterial growth rates

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2
Q

Transit time of food in the mouth

A

1 min max

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3
Q

Transit time of food in the oesophagus

A

4-8 secs

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4
Q

Transit time of food in the stomach

A

2-4 hrs

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5
Q

Transit time of food in the LI

A

10 hrs - several days

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6
Q

As you go down the GI tract, there’s more…

A

Bacteria

Esp obligate anaerobes because less oxygen the further down you go

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7
Q

What are facultative anaerobes + where are they found + what pH they live in

A

Grow in presence and absence of oxygen

Found in the stomach, existing at pH 1.5 - 4

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8
Q

Name some facultative anaerobes

A

Lactobacillus

H.pylori

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9
Q

What are obligate anaerobes + where are they found + what pH they live in

A

Can’t grow in presence of oxygen

Found in the colon at pH 5.5 - 6.5

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10
Q

Name some obligate anaerobes

A

Bacteroides
Clostridium groups
Enterobacteraceae

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11
Q

pH of mouth

A

6.5 - 7.5

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12
Q

pH of duodenum

A

7-8.5

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13
Q

Main function of gut microbes

A

Metabolise undigested dietary components, e.g. fibre which is not digested in stomach/SI

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14
Q

3 ways gut microbes can defend against pathogens

A

Acting as a barrier - to prevent pathogen colonisation

Active competitive exclusion - commensal bacteria can produce active compounds to kill pathogens

pH inhibition - pathogens generally grow best at ph>6, proximal colon has pH 5.5 but distal colon pH 6.5

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15
Q

More risk of pathogen colonisation in proximal or distal colon + why

A

proximal colon has pH 5.5 but distal colon usually pH 6.5 so MORE RISK OF PATHOGEN COLONISATION IN DISTAL COLON as pathogens grow best at ph>6

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16
Q

Functions of bacteria in the GI tract (6)

A 
Metabolise undigested dietary components
Defend against pathogens
Produce essential metabolites, e.g. short chain fatty acids
Modify host secretions, e.g. bile
Develop immune system
Control host signalling
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17
Q

Function of E. rectale & F. prausnitzii

A

Produce butyrate ( a SCFA)

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18
Q

Function of megasphaera

A

Produce propionate ( a SCFA)

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19
Q

Function of bactericides

A

Utilise acetate

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20
Q

Functions of bifidobacteria (2)

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A

Utilise prebiotics

Produce lactate

21
Q

Functions of lactobacilli (2)

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A

Produce lactic acid

Degrade mucin

22
Q

High bacterial diversity is a biomarker of what

23
Q

Products of microbial fermentation (5)

Study These Flashcards
A 
Short chain fatty acids/ branched chain fatty acids
Phytochemicals
Gases - CO2, H2, CH4
Other metabolites
Minerals
24
Q

3 main short chain fatty acids from carbohydrate metabolism

Study These Flashcards
A

Butyrate
Proprionate
Acetate

25
Function of butyrate (a SCFA)
involved in epithelial cell growth
26
Function of propionate
involved in gluconeogenesis
27
Function of acetate
transported in blood to peripheral tissues, involved in lipogenesis
28
Rate of butyrate:propionate:acetate
1:1:3
29
Bacterial in proximal colon ferment more carbohydrate/protein while bacteria in distal colon ferment more carbohydrate/protein
Carbohydrate Protein
30
Dysbiosis of gut microbiotia disrupts what which leads to what
Disrupts homeostasis --> gut inflammation
31
Dietary fibre improves what
Faecal bulking resulting in shorter transit time in colon
32
Fermentation of fibre by bacteria leads to what
Release of additional phytochemicals Maintains acidic pH - to resist pathogens Increases commensal bacteria Essential supply of SCFAs
33
Babies have low or high bacterial diversity
Low
34
Difference between causation and correlation with respect to microbes and disease
Microbial dysbiosis could be a cause of gut disease but it could also be the gut disease that’s causing microbial dysbiosis
35
Name some infections/disease that are caused by microbial dysbiosis (i.e. usually these bacteria live asymptomatically) (4)
MRSA (Staph aureus) infection Streptococcus throat infection C. diff infection Gastritis/ Gastric cancer- H.pylori
36
Inflammation in IBD is most likely due to what in regards to microbiota and immune response
Dysregulated immune response to gut microbiota
37
Evidence has shown that there's reduced bacterial diversity in crohn's or UC
Crohn's
38
In crohn's there may be elevated levels of what type of bacteria
Enterobacteriaceae
39
How do features of IBD itself have an impact on microbiota (4)
Antibiotic use - reduces bacterial diversity Inflammation - decreases mucus barrier --> more oxygen exposure --> changes microbial composition Diarrhoea - decreased transit time altering microbial composition Diet - desire to eat less fibre --> changes microbial composition
40
Effect of antibiotics on gut microbiota
Reduce bacterial diversity -creates selection pressure (loss of diverse bacteria, left with just a few species) resulting in the increase and spread of a bacterial resistance
41
Effect of broad spectrum antibiotics on bacteria
kill pathogenic bacteria AND kill many of the commensal, resident bacteria that may be important for health
42
What are probiotics
live micro-organisms conferring health benefit when administered adequately, e.g. Bifidobacterium
43
Frequent functions of probiotics (3)
Bioconversion Antagonistic to pathogens Stimulate immune system
44
What are probiotics
substrate used by host bacteria (food for bacteria) conferring health benefit, e.g. garlic
45
Probiotics can potentially be used to treat what disease
reduce incidence of C. diff associated diarrhoea
46
How may prebiotics may be helpful in IBD
IBD to boost numbers of Faecalibacterium prausnitzii so enhancing production of anti-inflammatory protein and reducing effects of IBD
47
Function of Faecalibacterium prausnitzii (F. prausnitzi)
production of anti-inflammatory protein
48
Potential functions of prebiotics (4)
Improve gut function by increasing faecal bulk Reduce risk of colon cancer by reducing DNA damage Used in infant formula to increase bifidobacteria numbers Increase calcium absorption
49
Explain why FMT (faecal microbial transplantation) may be more effective in treating recurrent C. difficile infection than other GI diseases
Faecal sample from healthy donor transplanted and repopulates microbiota of colon, displacing C. diff and preventing re-infection may not work in other GI diseases because success depends on whether any microbiota is present/absent -In c. diff infection, majority of microbiota is destroyed which allows FMT to work

GI Anatomy (21 decks)

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