Benefits & Mischiefs from Normal Microbiota 1 Flashcards
Which type of bacteria is predominant in the gut?
gram negative bacteria
Are the bacteria in the gut predominantly aerobes or anaerobes?
anaerobes
In which part of the gut is most of the microbiota?
The colon
What are the most common aerobic microbiota in the gut?
staphylococcus, streptococcus, lactobacillus, enterobacteriaciae
What are the most common anaerobic microbiota in the gut?
bacteriodes, streptococcus, bifidobacterium, clostridium
What are the four main phyla in the gut?
Mostly bacteriodetes, firmicutes with some actinobacteria and few proteobacteria
What do the genes of the microbiota contribute to?
metabolic activity, development, immune system function and protection against pathogens
What factors influence gut microbiota?
mode of delivery (vaginal vs caesarian), age, diet, antibiotics, genetics, environment, chronic inflammation
Which phyla of bacteria is most prominent in the microbiota in the first few years of life?
fermicutes
At what age will there be sufficient microbiota to utilise plant base products?
a few months
At what age is the microbiota the same that it will be throughout the rest of life/
2.5 years
What diet changes affect microbiota?
changing from a high fat/low fibre diet to a low fat/high fibre diet
What will happen to the microbiota on an animal based diet?
There will be an increase in bile tolerant bacteria such as bacteroides
What will happen to the microbiota on an iron free diet?
There will be an increase in bifidobacterium and clostridium and a decrease in bacteroides
What happens to microbiota after antibiotic treatment?
It goes back to normal
Which antibiotic may effect the microbiota so that it doesn’t go back to normal after treatment is stopped?
vancomycin
What role does microbiota have in providing nutrition?
Directly supplying nutrients as well as altering metabolic machinery by inducing changes in genes and maintaining enterocyte differentiation
How do microbiota help with the metabolism of carbohydrates?
They break lactose and cellulose down into short chain fatty acids
Which vitamins are absorbed with the help of microbiota?
vitamin B2, vitamin K, biotin, folate
How do microbiota help break down bile acids?
By dehydroxylation which then allows reabsorption back into the liver
Which amino acids particularly need the help of microbiota?
lysine and threonine are broken down to urea
Why is important that bacteria degrades host glycans (such as mucin)?
Because it induces synthesis
What are some functions of short chain fatty acids as a product of metabolism by bacteria?
they maintain entrocyte differentiation and alter host genes to maintain angiogenesis
What are the main short chain fatty acids?
acetate, propionate and butyrate
How is butyrate an energy source?
it is absorbed by the colon and is an energy source for colonic epithelial cells
How is acetate and propionate an energy source?
They are transported to the liver where they are substrates for gluconeogenesis and lipogenesis
What enzyme is inhibited by short chain fatty acids?
histone deacetylase
Which antibody is most common in the gut MALT?
IgA
What are Peyer’s patches and isolated lymphoid follicles (ILFs)?
aggregates of lymphoid tissue in the small and large intestine - they are the site of induction of T and B cell activation
What is the immune function of enterocytes?
secretes cytokines, chemokines ant anti-microbial peptides
What is the immune function of goblet cells?
Secrete mucins, lysozyme and lactoferin
What is the immune function of paneth cells?
secrete defensins
What are IELs?
intra epithelial lymphocytes - these are non conventional lymphocytes
What are the innate defences of the gut?
peristalsis, acid, mucus, enterocyte barrier, antimicrobial factors, cytokines and chemokines, innate leukocytes
What are ILCs?
Innate lymphoid cells - including LTis, IELs, NK cells, MAIT cells, invariant NKT cells and macrophages
What are LTis?
lymphoid tissue inducer cells - stimulate recruitment of dendritic cells, T and B cells to Peyer’s patches and isolate lymphoid follicles
What is the function of IL-22?
enhances antimicrobial defence, epithelial repair and barrier integrity
What cells produce IL-22?
NK cells and IELs and MAIT cells
What are MAIT cells?
mucosal associated invariant T cells - unknown function
Why are macrophages in the gut harder to stimulate?
Because they have lower amounts of TLRs and PRRs
What is an M cell?
The cell located directly over the site of organised lymphoid aggregates to deliver antigens directly to these cells
What are the features of M cells?
a folded luminal surface (no villi) and a thick glycocalyx (no mucus)
What are the two ways that dendritic cells sample antigens from the mucosa?
directly or indirectly via goblet cells and M cells
Under normal conditions what type of T cell differentiation do dendritic cells produce?
Treg and Th2
Under inflammatory conditions what type of T cell differentiation do dendritic cells produce?
Th1 and Th17
How do B and T cells find their way back to the gut?
because they are induced to express mucosal addressin alpha4beta7 which binds to the mucosal endothelial integrin MAdCAM1
What is the role of IELs?
eliminated damaged enterocytes
