Functions Gut flora

1 functions

1.1 direct inhibition of pathogens
1.2 development of enteric protection , immune system
1.3 metabolism
1.4 host-gut microbiota-xenobiotic interaction
1.5 gut-brain axis

functions

when gut flora first started studied, thought have 3 key roles: directly defending against pathogens, fortifying host defense role in developing , maintaining intestinal epithelium , inducing antibody production there, , metabolizing otherwise indigestible compounds in food; subsequent work discovered role in training developing immune system, , yet further work focused on role in gut-brain axis.

direct inhibition of pathogens

the gut flora community plays direct role in defending against pathogens colonizing space, making use of available nutrients, , secreting compounds kill or inhibit unwelcome organisms compete nutrients it. disruption of gut flora allows competing organisms clostridium difficile become established otherwise kept in abeyance.

development of enteric protection , immune system

microfold cells transfer antigens (ag) lumen of gut gut-associated lymphoid tissue (galt) via transcytosis , present them different innate , adaptive immune cells.

in humans, gut flora similar adult s formed within 1 2 years of birth. gut flora gets established, lining of intestines – intestinal epithelium , intestinal mucosal barrier secretes – develop well, in way tolerant to, , supportive of, commensurate microorganisms extent , provides barrier pathogenic ones. specifically, goblet cells produce mucosa proliferate, , mucosa layer thickens, providing outside mucosal layer in friendly microorganisms can anchor , feed, , inner layer these organisms cannot penetrate. additionally, development of gut-associated lymphoid tissue (galt), forms part of intestinal epithelium , detects , reacts pathogens, appears , develops during time gut flora develops , established. galt develops tolerant gut flora species, not other microorganisms. galt becomes tolerant food infant exposed, digestive products of food, , gut flora s metabolites produced food.

the human immune system creates cytokines can drive immune system produce inflammation in order protect itself, , can tamp down immune response maintain homeostasis , allow healing after insult or injury. different bacterial species appear in gut flora have been shown able drive immune system create cytokines selectively; example bacteroides fragilis , clostridia species appear drive anti-inflammatory response, while segmented filamentous bacteria drive production of inflammatory cytokines. gut flora can regulate production of antibodies immune system. 1 function of regulation cause b cells class switch iga. in cases b cells need activation t helper cells induce class switching; however, in pathway, gut flora cause nf-kb signaling intestinal epithelial cells results in further signaling molecules being secreted. these signaling molecules interact b cells induce class switching iga. iga important type of antibody used in mucosal environments gut. has been shown iga can diversify gut community , helps in getting rid of bacteria cause inflammatory responses. ultimately, iga maintains healthy environment between host , gut bacteria. these cytokines , antibodies can have effects outside gut, in lungs , other tissues.

the immune system can altered due gut bacteria s ability produce metabolites (molecules formed metabolism) can effect cells in immune system. example short chain fatty acids (scfa) can produced gut bacteria through fermentation. scfas stimulate rapid increase in production of innate immune cells neutrophils, basophils , eosinophils. these cells part of innate immune system try limit spread of infection.

metabolism

without gut flora, human body unable utilize of undigested carbohydrates consumes, because types of gut flora have enzymes human cells lack breaking down polysaccharides. rodents raised in sterile environment , lacking in gut flora need eat 30% more calories remain same weight normal counterparts. carbohydrates humans cannot digest without bacterial include starches, fiber, oligosaccharides, , sugars body failed digest , absorb lactose in case of lactose intolerance , sugar alcohols, mucus produced gut, , proteins.

bacteria turn carbohydrates ferment short-chain fatty acids (scfas) form of fermentation called saccharolytic fermentation. products include acetic acid, propionic acid , butyric acid. these materials can used host cells, providing major source of useful energy , nutrients humans, helping body absorb essential dietary minerals such calcium, magnesium , iron. gases , organic acids, such lactic acid, produced saccharolytic fermentation. acetic acid used muscle, propionic acid helps liver produce atp, , butyric acid provides energy gut cells , may prevent cancer. evidence indicates bacteria enhance absorption , storage of lipids , produce , facilitate body absorb needed vitamins vitamin k.

gut flora synthesize vitamins biotin , folate, , absorption of dietary elements including magnesium, calcium , iron. methanogenic archaea such methanobrevibacter smithii involved in removal of end products of bacterial fermentation such hydrogen.

host-gut microbiota-xenobiotic interaction

apart carbohydrates, gut microbiota can metabolize other xenobiotic such drugs, phytochemicals, , food toxicants. more 30 drugs have been shown metabolized gut microbiota. microbial metabolism of drugs can inactivate drug.

gut-brain axis

the gut-brain axis biochemical signaling takes place between gastrointestinal tract , central nervous system. term has been expanded include role of gut flora in interplay; term microbiome-gut-brain axis used describe paradigms explicitly including gut flora. broadly defined, gut-brain axis includes central nervous system, neuroendocrine , neuroimmune systems including hypothalamic–pituitary–adrenal axis (hpa axis), sympathetic , parasympathetic arms of autonomic nervous system including enteric nervous system, vagus nerve, , gut microbiota.

a systematic review 2016 examined preclinical , small human trials have been conducted commercially available strains of probiotic bacteria , found among tested, bifidobacterium , lactobacillus genera (b. longum, b. breve, b. infantis, l. helveticus, l. rhamnosus, l. plantarum, , l. casei), had potential useful central nervous system disorders.