Microbiota 1 Flashcards
how many commensals in/on us?
1-2kg
microbiome provides us with extra source of?
genes
humans and microbiota are known as:
mutualists
how many bacteria in microbiota?
10^14
how many species of bacteria on us?
1000
majority of bacteria use oxygen?
99.9% are anaerobes
Gram what in
Throat and skin
Gut
Vaginal?
Throat/ skin: +ve
gut: -ve
vaginal: +ve
4 main bacteria phyla from most to least
- bacteroides
- firmicutes (clostridia, mollicutes)
- actinobacteria
- proteobacteria (E.coli)
each body site has low or high diversity of microbiota?
high
twins have the same microbiota?
share <50% of bacterial species
microbiota unstable in host?
stable but influenced by determinants
4 things microbiota contribute to:
metabolism (cellulose)
development
immunity
protection
6 factors that influence gut microbiota?
mode of delivery age (more diversity with age) diet (breast milk) antibiotics genetics/environment (rural vs. city) chronic inflammation
vaginal birth associated with rapid acquisition of?
Firmicutes Bifidobacteria
animal based diets do what to microbiota?
decrease plant metabolizing bacteria, more bile-tolerant bacteria
what does iron do to mice microbiota?
more bacteroides
less bifidobacteria
does microbiota of mice treated with amoxicillin/metronidazole and bismuth recover?
yes
which antibiotic do you not recover your diversity of microbiota?
vancomysin
microbiota provides how much calories?
10% of calories from plant CHO
microbiota in nutrition does 2 things to help us
- change our genes for CHO/lipid metabolism
2. maintain enterocyte differentiation/function
microbiota taxa varied by site, what remained stable?
metabolic pathways eg. 16S rRNA
what vitamins do microbiota make for us?
vitamin B12, K
biotin
folate
what happens to bile acid in the gut?
microbiota break it down to desoxycholic acid to reabsorb back into liver
what happens to amino acids in gut?
nitrogen recycling from lysine and threonine
what does bacterial degradation of host glycans do?
elicits synthesis of new glycans by host
how does microbiota maintain enterocyte differentiation
from production of short chain fatty acids from fibre
is angiogenesis affected by microbiota?
yes
describe the metabolism path of dietary fibre:
broken into monosaccharides>fermented into SCFAs>absorbed by colon>reaches liver>substrates for gluconeogenesis/lipgenesis
how do the colonic epithelial cells get their energy?
from fermented and absorbed SCFAs
SCFAs do more than just be energy source, explain:
control colonic gene expression via HDAC inhibition and GPCR signal regulation
mucosal immune systemis closely associated with?
intestinal microbiota
what is MALT?
mucosa-associated lymphoid tissue
SI covers how many square metres? so what?
400m2, big antigenic challenge, which is why it has the largest collection of lymphoid tissue
2 big things the MALT must be able to do
protection from pathogens (IgA)
tolerance to normal microbiota/food
what is ILFs? where are they found?
isolated lymphoid follicles in large/small intestine
where are Peyers patches? what happens there?
small intestine
induction of T, B Cells
enterocytes secrete what cytokines?
TGF-B, chemokines, anti-microbial peptides
what is lactoferrin? where does it come from on the small intestine?
on villus
from Goblet cells
inhibits bacteria growth
Paneth cells do what?
secrete defensins
what immune cells are in the lamina propria of the small intestine?
Intraepithelial lymphocytes (IEL)
2 kinds of Intraepithelial lymphocytes in the villus?
nonconventional lymphocytes
innate lymphocytes
what two cells in the small intestine play a role in tolerance?
enterocytes IEL (intraepithelial lymphocytes)
3 innate defences of gut?
peristaltic (flushing) action
acid
mucous layer to hold commensals at ‘arms length’
Describe the 3 innate defensive roles of enterocytes
- barrier: integrity is critical tight junctions
- antimicrobial factors
- cytokines/chemokines
What is a mechanism for controlled antigen access?
M Cells/ dendritic cells
innate leucocytes include:
lymphocytes
macrophages
What are ILCs? what do they do?
innate lymphoid cells
secrete cytokines
what does IL-17, IL-22 do?
recruits and activates neutrophils
What does lymphoid tissue inducer cells do?
stim DC, T, B cells, PPs, ILFs
what cytokine does IELs secrete?
IL-22
what does IL-22 do?3 things
enhances antimicrobe defence
epithelial repair
barrier integrity
What are MAIT cells? what do they do?
mucosal associated invariant T cells
rapid response to bacterial antigen
what do invariant NKT cells do?
secrete pro-inflamm cytokines like IL-22
M cell stands for? where is it?
microfold cell
directly over the lymphoid aggregates (PPs, ILFs isolated lymphoid follicles)
villi on M cells?
Nope
folded luminal surface
M-cell secrete mucous? why?
does not
microbial access easier
DCs are located directly below the M-cell, how do they sample? 2 ways:
directly (tentacle into lumen)
indirectly (via goblet/M-cells
TGF-B stands for?
transforming growth factor
tell me what DCs do in:
- steady state
- inflamm state
- induce Tregs/TGF-B
2. induce Th1/Th17
DCs bias what immunoglobulin from B-cells?
Isotype switching to IgA
inducing mucosal addressin a4B7 on T/B cells does what?
- allows to bind to MAdCAM1 on mucosal surfaces
2. also gives chemokine receptors specific for lamina propria
a4B7 activated T/Bcells are found where?
distributed through all mucosal surfaces
IELs do what to enterocytes?
may eliminate damaged ones
what happens in MALT?
stimulation
suppression
of immune cells
