Flora composition Gut flora

1 flora composition

1.1 anatomy

1.1.1 stomach flora
1.1.2 intestinal flora


1.2 age
1.3 diet
1.4 geography

flora composition
anatomy
stomach flora

due high acidity of stomach, microorganisms cannot survive there. main bacterial inhabitants of stomach include: streptococcus, staphylococcus, lactobacillus, peptostreptococcus, , types of yeast. helicobacter pylori gram-negative spiral organism establishes on gastric mucosa causing chronic gastritis , peptic ulcer disease , carcinogen gastric cancer.

intestinal flora

the small intestine contains trace amount of microorganisms due proximity , influence of stomach. gram-positive cocci , rod-shaped bacteria predominant microorganisms found in small intestine. however, in distal portion of small intestine alkaline conditions support gram-negative bacteria of enterobacteriaceae. bacterial flora of small intestine aid in wide range of intestinal functions. bacterial flora provide regulatory signals enable development , utility of gut. overgrowth of bacteria in small intestine can lead intestinal failure. in addition large intestine contains largest bacterial ecosystem in human body. 99% of large intestine , feces flora made of obligate anaerobes such bacteroides , bifidobacterium. factors disrupt microorganism population of large intestine include antibiotics, stress, , parasites.

bacteria make of flora in colon , 60% of dry mass of feces. fact makes feces ideal source test gut flora tests , experiments extracting nucleic acid fecal specimens, , bacterial 16s rrna gene sequences generated bacterial primers. form of testing preferable more invasive techniques, such biopsies. somewhere between 300 , 1000 different species live in gut, estimates @ 500. however, probable 99% of bacteria come 30 or 40 species, faecalibacterium prausnitzii being common species in healthy adults. fungi , protozoa make part of gut flora, little known activities. virome bacteriophages.

research suggests relationship between gut flora , humans not merely commensal (a non-harmful coexistence), rather mutualistic, symbiotic relationship. though people can survive no gut flora, microorganisms perform host of useful functions, such fermenting unused energy substrates, training immune system via end products of metabolism propionate , acetate, preventing growth of harmful species, regulating development of gut, producing vitamins host (such biotin , vitamin k), , producing hormones direct host store fats. extensive modification , imbalances of gut microbiota , microbiome or gene collection associated obesity. however, in conditions, species thought capable of causing disease causing infection or increasing cancer risk host.

age

it has been demonstrated there common patterns of microbiome composition evolution during life. in general, diversity of microbiota composition of fecal samples higher in adults in children, although interpersonal differences higher in children in adults. of maturation of microbiota adult-like configuration happens during 3 first years of life.

as microbiome composition changes, composition of bacterial proteins produced in gut. in adult microbiomes, high prevalence of enzymes involved in fermentation, methanogenesis , metabolism of arginine, glutamate, aspartate , lysine have been found. in contrast, in infant microbiomes dominant enzymes involved in cysteine metabolism , fermentation pathways.

diet

studies , statistical analyses have identified different bacterial genera in gut microbiota , associations nutrient intake. gut microflora composed of 3 enterotypes: prevotella, bacteroides, , ruminococcus. there association between concentration of each microbial community , diet. example, prevotella related carbohydrates , simple sugars, while bacteroides associated proteins, amino acids, , saturated fats. specialist microbes break down mucin, survive on host s carbohydrate excretions. 1 enterotype dominate depending on diet. altering diet result in corresponding change in numbers of species.

malnourished human children have less mature , less diverse gut microbiota healthy children, , changes in microbiome associated nutrient scarcity can in turn pathophysiological cause of malnutrition. malnourished children typically have more potentially pathogenic gut flora, , more yeast in mouths , throats. altering diet may lead changes in gut microbiota composition , diversity.

geography

gut microbiome composition depends on geographic origin of populations. variations in trade off of prevotella, representation of urease gene, , representation of genes encoding glutamate synthase/degradation or other enzymes involved in amino acids degradation or vitamin biosynthesis show significant differences between populations usa, malawi or amerindian origin.

the population has high representation of enzymes encoding degradation of glutamine , enzymes involved in vitamin , lipoic acid biosynthesis; whereas malawi , amerindian populations have high representation of enzymes encoding glutamate synthase , have overrepresentation of α-amylase in microbiomes. population has diet richer in fats amerindian or malawian populations have corn-rich diet, diet main determinant of gut bacterial composition.

further studies have indicated large difference in composition of microbiota between european , rural african children. fecal bacteria of children florence compared of children small rural village of boulpon in burkina faso. diet of typical child living in village largely lacking in fats , animal proteins , rich in polysaccharides , plant proteins. fecal bacteria of european children dominated firmicutes , showed marked reduction in biodiversity, while fecal bacteria of boulpon children dominated bacteroidetes. increased biodiversity , different composition of gut flora in african populations may aid in digestion of indigestible plant polysaccharides , may result in reduced incidence of non-infectious colonic diseases.

on smaller scale, has been shown sharing numerous common environmental exposures in family strong determinant of individual microbiome composition. effect has no genetic influence , consistently observed in culturally different populations.