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2A - Alimentary System > The Microbiota of the GI Tract 1 > Flashcards

The Microbiota of the GI Tract 1 Flashcards

1
Q

What is the transit time in the mouth?

A

1 minute

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2
Q

What is the transit time in the oesophagus?

A

4-8 seconds

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3
Q

What is the transit time in the stomach?

A

2-4 hours

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4
Q

What is the transit time in the small intestine?

A

3-5 hours

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5
Q

What is the transit time in the colon?

A

10 hours to several days

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6
Q

What does transit time affect?

A

Bacterial populations due to different bacterial growth rates

Intestinal cell exposure to toxins, consumed with food or produced by bacteria

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7
Q

How does the amount of bacteria change as you go down the GI tract from the stomach to the colon?

A

Increases

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8
Q

What does anaerobic mean?

A

Living in the absence of oxygen

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9
Q

What does aerobic mean?

A

Living in the presence of oxygen

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10
Q

What are different classes of anaerobic bacteria?

A

Facultative anaerobic bacteria

Obligate anaerobic bacteria

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11
Q

What are facultative anaerobic bacteria?

A

Can grow in the presence of oxygen and in the absence of oxygen (some grow poorly when oxygen is present)

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12
Q

What are obligate anaerobes?

A

Cannot grow in the presence of oxygen (many rapidly killed in the presence of oxygen)

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13
Q

What are examples of bacteria found in the stomach?

A

Lactobacillus

Candia

Streptococcus

Helicobacter pylori

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14
Q

What are examples of bacteria found in the colon?

A

Bacteroides

Clostridium

Bifidpbacterium

Enterobacteriaceae

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15
Q

What class of anaerobes are found in the stomach?

A

Faciltative anaerobes

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16
Q

What class of anaerobes is found in the colon?

A

Obligate anaerobes

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17
Q

Why do different kinds of bacteria dominate different areas of the GI tract?

A

Different oxygen concentrations

Different pH

Different transit times

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18
Q

How does the number of microbial cells compare to human cells?

A

There are more microbial cells

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19
Q

How much bacteria is there in the human gut?

A

100 trillion

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20
Q

What are the different parts of taxonomy?

A

Life

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

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21
Q

Why must meaningful comparison between bacteria be done at the genus level?

A

Bacterial comparison at the phylum level is a higher level than grouping all mammals together

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22
Q

What impact does diet have on bacteria?

A

Impacts diversity

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23
Q

What does OTU stand for?

A

Operational taxonomic unit

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24
Q

What does a higher number of OTUs mean?

A

Higher diversity

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25
How are the vast majority of bacteria in the GI tract beneficial for health?
Different bacteria perform different functions Bacteria act together in a population Bacteria communicate with each other and with the host A diverse microbiota is important to maintain health
26
What are some functions of gut microbiota?
Modifications of host secretions (mucin, bile, gut receptors etc) Defence against pathogens Metabolism of dietary components Production of essential metabolites to maintain health Development of the immune system Host signalling
27
How does the gut microbiota provide defence against pathogens?
Competition Barrier function pH inhibition
28
What host secretions do the gut microbiota modify?
Mucin Bile Gut receptors
29
Why is junk food bad although it contains lots of energy (calories)?
Does not feed out gut microbes, that grow on fibres
30
What kinds of food is fibre found in?
Fruit Vegetables Pulses Whole grains
31
Where are the products created by bacteria that are derived from fibres absorbed?
Large intestine
32
As well as fibre, what else can GIT microbes use for growth?
Endogenous (host-derived) substrates
33
What are benefits of including dietary fibre in our diet?
Improves faecal bulking, eases passage, results in a shorter transit time Contains important phytochemicals, anti-oxidants and vitamins Bacterial fermentation
34
How does bacterial fermentation impact pH?
Maintains slightly acidic pH
35
What are the benefits of bacterial fermentation?
Releases additional phytochemicals Maintains slightly acidic pH that improves resistance to pathogens Essential supply of short chain fatty acids
36
What are the 3 main fatty acids provided by bacterial fermentation?
Butyrate Propionate Acetate (1:1:1 ratio)
37
What are the functions of butyrate?
Epithelial cell growth and regeneration
38
What are the functions of propionate?
Gluconeogenesis in the liver Satiety signalling
39
What are the functions of acetate?
Transported in the blood to peripheral tissues Lipogenesis
40
How does the colon change in regards to bacterial fermentation?
Proximal is carbohydrate rich, pH midly acidic and transover rapid Distal has little fermentable carbohydrates, pH neutral and turnover slow
41
How does bile acid concentration change along the bowel?
Increases going proximal to distal
42
How much carbohydrates are metabolised by bacteria per day?
About 40g/day
43
How much protein is metabolised by bacteria per day?
12-18g/day
44
What are important gut microbial activities driven by?
What we eat
45
What are the functional importance of firmicutes?
Butyrate production Polysaccharide utlisation Propionate production
46
What is the functional importance of aminomycetes?
Utilise prebiotics Lactate production
47
What is an example of an actinomycete?
Bifidobacteria
48
How does the GI microbiota provide have a barrier effect for defence?
Large number of the indigenous microbiota prevent colonisation by ingesting pathogens and inhibit overgrowth of potentially pathogenic bacteria normally resident at low levels
49
How does the GI microbiota provide active competitive exclusion for defence?
Conferred by both microbe-microbe and microbe-host interactions
50
How does the GI microbiota protect against pathogens due to pH inhibitions?
Generally pathogens grow opimally at pHs over 7
51
Is the pH greater in the proximal or distal colon?
Distal
52
What forms a barrier between the luminal bacterial population and the epithelial cells to keep the gut health?
Mucus layer
53
What are the different layers of bacteria after the mucus layer?
Inner layer and outer layer
54
What happens when the mucus bacterial of the colon disrupted?
Bacterial cells penetrate the mucus layer and the epithelial barrier
55
What is the largest lymphoid organ in the body?
Gut
56
What must be gut be able to do due to being in constant interaction with the environment?
Respond appropriately to foreign/pathogenic agents Actively down-regulate immune responses to "self" proteins, dietary antigens and the commensal microbiota Recognise and respond to pathogenic invasions
57
Why do autoimmune diseases occur in relation to the gut?
Immune system can no longer distinguish between harmful pathogens and commensal bacteria
58
What does imbalance between the gut microbiota composition lead to?
Disrupting homeostasis causing inflammation
59
What are the 2 possible effects that gut bacteria can have on inflammation?
Some are pro-inflammatory and some are anti-inflammatory
60
What are important signalling molecules that gut microbiota produce?
Short chain fatty acids
61
What impact do short chain fatty acids from bacteria have on the gut epithelial cells?
Secretes gut hormones
62
What receptors on the gut epithelium detects short chain fatty acids from bacteria?
GRP43/FFAR2 GPR/FFAR3 GPR109A
63
What does SCFA stand for?
Short chain fatty acid
64
What are GPR43/FFAR2 receptors activated by?
Acetate Propionate \> butyrate
65
What does activation of GPR43/FFAR2 receptors cause?
GLP-1 secretions (inhibits fat accumulation)
66
What does GLP-1 do?
Inhibits fat secretions
67
What does activation of GPR/FFAR3 receptors do?
Results in PYY secretion (improves insulin resistance and satiety signalling to brain)
68
What activates GPR/FFAR3 receptors?
Propionate and butyrate
69
What does PYY do?
Improves insulin resistance and satiety signalling to brain
70
What activates GPR109A receptors?
Butyrate
71
What does activation of GPR109A receptors cause?
Suppreses colonic inflammation and carcinomogenesis (anti-inflammatory cytokines such as IL-10)
72
What happens to microbial metabolites that are not utilised by gut epithelial cells?
Absorbed into the bloodstream and transported around the body
73
What can be said about microbial composition throughout life?
It changes throughout life
74
What are some different factors that influence the microbiota throughout life?
Anatomy is the same, food is different Dietary changes cause the greatest influence Our food is out microbiotas food

2A - Alimentary System (41 decks)

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