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Encyclopedia > Gut flora
Escherichia coli, one of the many species of bacteria present in the human gut.
Escherichia coli, one of the many species of bacteria present in the human gut.

The gut flora are the microorganisms that normally live in the digestive tract and can perform a number of useful functions for their hosts. Image File history File links Download high resolution version (1024x861, 165 KB)Escherichia coli: Scanning electron micrograph of Escherichia coli, grown in culture and adhered to a cover slip. ... Image File history File links Download high resolution version (1024x861, 165 KB)Escherichia coli: Scanning electron micrograph of Escherichia coli, grown in culture and adhered to a cover slip. ... E. coli redirects here. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and...


The average human body, consisting of about 1013 cells, has about ten times that number of microorganisms in the gut.[1][2][3][4][5] Bacteria make up most of the flora in the colon[5] and 60% of the mass of feces.[2] Somewhere between 300[2] and 1000 different species live in the gut,[3] with most estimates at about 500.[6][4] However, it is probable that 99% of the bacteria come from about 30 or 40 species.[7] Fungi also make up a part of the gut flora, but little is known about their activities. Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... It has been suggested that this article or section be merged with Large intestine. ... Horse feces Feces, faeces, or fæces (see spelling differences) is a waste product from an animals digestive tract expelled through the anus (or cloaca) during defecation. ... In biology, a species is one of the basic units of biodiversity. ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ...


Research suggests that the relationship between gut flora and humans is not merely commensal (a non-harmful coexistence), but rather is a mutualistic, symbiotic relationship.[3] Though people can survive with no gut flora,[4] the microorganisms perform a host of useful functions, such as fermenting unused energy substrates, training the immune system, preventing growth of harmful species,[2] regulating the development of the gut, producing vitamins for the host (such as biotin and vitamin K), and producing hormones to direct the host to store fats. However, in certain conditions, some species are thought to be capable of causing disease by causing infection or increasing cancer risk for the host.[2][5] In microbiology, flora (plural: floras or floræ) refers to the collective bacteria and other microorganisms in an ecosystem (usually an animal host or a single part of its body). ... Commensalism is an interaction between two living organisms, where one organism benefits and the other is neither harmed nor helped. ... In biology, mutualism is an interaction between two species in which both species derive benefit. ... Common Clownfish (Amphiprion ocellaris) in their Magnificent Sea Anemone (Heteractis magnifica) home. ... This article or section does not cite any references or sources. ... A scanning electron microscope image of a single neutrophil (yellow), engulfing anthrax bacteria (orange). ... Vitamin H redirects here. ... Vitamin K1 (phylloquinone). ... The term disease refers to an abnormal condition of an organism that impairs function. ... An infection is the detrimental colonization of a host organism by a foreign species. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ...

Contents

Localization

The colon has the greatest numbers of bacteria and the most different species, and the activity of these bacteria make the colon the most metabolically active organ in the body.[6] Most of the bacteria in the small intestine are Gram-positive, while those in the colon are mostly Gram-negative.[8] The first part of the colon is mostly responsible for fermenting carbohydrates,[7][6][2] while the latter part mostly breaks down proteins and amino acids.[6][2] Bacterial growth is rapid in the cecum and ascending colon, which has a low pH, and slow in the descending colon, which has an almost neutral pH.[2] The body maintains the proper balance and locations of species by altering pH, the activity of the immune system, and peristalsis.[5] A few of the metabolic pathways in a cell. ... In biology, an organ is a group of tissues which perform some function. ... Gram-positive anthrax bacteria (purple rods) in cerebrospinal fluid sample. ... Lactose is a disaccharide found in milk. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Phenylalanine is one of the standard amino acids. ... The cecum or caecum (from the Latin caecus meaning blind) is a pouch connected to the ascending colon of the large intestine and the ileum. ... In anatomy of the digestive system, the colon or large intestine or large bowel is the part of the intestine from the cecum to the rectum. ... The correct title of this article is . ... In much of the digestive tract, muscles contract in sequence to produce a peristaltic wave which forces food (called bolus while in the esophagus and chyme below the esophagus) along the alimentary canal. ...


Over 99% of the bacteria in the gut are anaerobes,[7][2][5][3][9] but in the cecum aerobic bacteria reach high densities.[2] An anaerobic organism or anaerobe is any organism that does not require oxygen. ... The cecum or caecum (from the Latin caecus meaning blind) is a pouch connected to the ascending colon of the large intestine and the ileum. ... Bacteria that require oxygen for respiration. ...


Types

Candida albicans, a dimorphic fungus which grows as a yeast in the gut.
Candida albicans, a dimorphic fungus which grows as a yeast in the gut.

Not all the species in the gut have been identified[2][3] because some cannot be cultured,[7][3][10] so DNA isolation and identification is difficult.[11] Populations of species vary widely among different individuals but stay fairly constant within an individual over time.[2] Image File history File links Microscopic image (200-fold magnification) of Candida albicans ATCC 10231, grown on cornmeal agar medium with 1% Tween80. ... Image File history File links Microscopic image (200-fold magnification) of Candida albicans ATCC 10231, grown on cornmeal agar medium with 1% Tween80. ... Binomial name Candida albicans (C.P. Robin) Berkhout 1923 Synonyms Candida stellatoidea [1] Candida albicans is a diploid asexual fungus (a form of yeast), and a causal agent of opportunistic oral and vaginal infections in humans. ...


Most bacteria come from the genera Bacteroides, Clostridium, Fusobacterium,[7][2][9] Eubacterium, Ruminococcus, Peptococcus, Peptostreptococcus, and Bifidobacterium.[2][7] Other genera such as Escherichia and Lactobacillus are present to a lesser extent.[2] Species from the genus Bacteroides alone constitute about 30% of all bacteria in the gut, suggesting that that genus is especially important in the functioning of the host.[3] Species etc. ... Species Clostridium acetobutylicum Clostridium aerotolerans Clostridium botulinum Clostridium colicanis Clostridium difficile Clostridium formicaceticum Clostridium novyi Clostridium perfringens Clostridium sordelli Clostridium tetani Clostridium piliforme Clostridium tyrobutyricum etc. ... Fusobacteria contribute to several diseases, including periodontal diseases, Lemierres syndrome, and tropical skin ulcers. ... Peptostreptococci, anaerobic streptococci, are Gram-positive cocci, a type of bacteria. ... Bifidobacteria (genus Bifidobacterium) are a group of anaerobic bacteria and a form of probiotic that is thought to have health-promoting properties for humans. ... Escherichia - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... Species L. acidophilus L. brevis L. delbrueckii subsp. ...


The currently known genera of fungi of the gut flora include Candida, Saccharomyces, Aspergillus, and Penicillium. Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... Species C. albicans C. dubliniensis C. glabrata C. guilliermondii C. kefyr C. krusei C. lusitaniae C. milleri C. oleophila C. parapsilosis C. tropicalis C. utilis Candida is a genus of yeasts. ... Species Saccharomyces bayanus Saccharomyces boulardii Saccharomyces bulderi Saccharomyces cariocanus Saccharomyces cariocus Saccharomyces cerevisiae Saccharomyces chevalieri Saccharomyces dairenensis Saccharomyces ellipsoideus Saccharomyces martiniae Saccharomyces monacensis Saccharomyces norbensis Saccharomyces paradoxus Saccharomyces pastorianus Saccharomyces spencerorum Saccharomyces turicensis Saccharomyces unisporus Saccharomyces uvarum Saccharomyces zonatus Saccharomyces is a genus in the kingdom of fungi that includes... Species Aspergillus caesiellus Aspergillus candidus Aspergillus carneus Aspergillus clavatus Aspergillus deflectus Aspergillus flavus Aspergillus fumigatus Aspergillus glaucus Aspergillus nidulans Aspergillus niger Aspergillus ochraceus Aspergillus oryzae Aspergillus parasiticus Aspergillus penicilloides Aspergillus restrictus Aspergillus sojae Aspergillus sydowi Aspergillus terreus Aspergillus ustus Aspergillus versicolor Aspergillus is a genus of around 200 filamentous fungi... Species Penicillium bilaiae Penicillium camemberti Penicillium candida Penicillium claviforme Penicillium crustosum Penicillium glaucum Penicillium marneffei Penicillium notatum Penicillium purpurogenum Penicillium roqueforti Penicillium stoloniferum Penicillium viridicatum Penicillium verrucosum Penicillium commune Penicillium is a genus of ascomyceteous fungi that includes: Penicillium bilaiae, which is an agricultural inoculant. ...


Acquisition of gut flora in human infants

The gastrointestinal tract of a normal fetus is sterile. During birth and rapidly thereafter, bacteria from the mother and the surrounding environment colonize the infant gut. Immediately after vaginal delivery, babies have bacterial strains in the upper gastrointestinal tract derived from the mothers’ feces.[12] Infants born by caesarean section may also be exposed to their mothers’ microflora, but the main exposure is from the surroundings.[13] After birth, environmental, oral and cutaneous bacteria are readily transferred from the mother to the infant through suckling, kissing, and caressing. All infants are initially colonized by large numbers of E. coli and streptococci. Within a few days, bacterial numbers reach 108 – 1010 /g feces.[13][14] During the first week of life, these bacteria create a reducing environment favorable for the subsequent bacterial succession of strict anaerobic species mainly belonging to the genera Bifidobacterium, Bacteroides, Clostridium, and Ruminococcus.[15]Breast-fed babies become dominated by bifidobacteria, possibly due to the contents of bifidobacterial growth factors in breast milk.[16] In contrast, the microflora of formula-fed infants is more diverse with high numbers of Enterobacteriaceae, enterococci, bifidobacteria, Bacteroides, and clostridia.[17][18] After the introduction of solid food and weaning, the microflora of breast-fed infants becomes similar to that of formula-fed infants. By the second year of life the fecal microflora resembles that of adults. Upper and Lower gastrointestinal tract The gastrointestinal tract (GI tract), also called the digestive tract, or the alimentary canal, is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... “Unborn child” redirects here. ... Horse feces Feces, faeces, or fæces (see spelling differences) is a waste product from an animals digestive tract expelled through the anus (or cloaca) during defecation. ... A caesarean section (AE cesarean section), or c-section, is a form of childbirth in which a surgical incision is made through a mothers abdomen (laparotomy) and uterus (hysterotomy) to deliver one or more babies. ... This article is about skin in the biological sense. ... A breastfeeding infant Breastfeeding is the practice of a woman feeding an infant (or sometimes a toddler or a young child) with milk produced from her mammary glands, usually directly from the nipples. ... Binomial name Escherichia coli T. Escherich, 1885 Escherichia coli (usually abbreviated to E. coli) is one of the main species of bacteria that live in the lower intestines of warm-blooded animals (including birds and mammals) and are necessary for the proper digestion of food. ... Species S. pneumoniae S. pyogenes S. viridans Streptococcus is a genus of spherical, Gram-positive bacteria of the phylum Firmicutes. ... Horse feces Feces, faeces, or fæces (see spelling differences) is a waste product from an animals digestive tract expelled through the anus (or cloaca) during defecation. ... A reducing environment is one chacterized by little or no free oxygen (dissolved or as a gas). ... Succession is the act or process of pooing or of following in order or sequence. ... Aerobic and anaerobic bacteria can be identified by growning them in liquid culture: 1: Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. ... Bifidobacteria (genus Bifidobacterium) are a group of anaerobic bacteria and a form of probiotic that is thought to have health-promoting properties for humans. ... Species etc. ... Species Clostridium acetobutylicum Clostridium aerotolerans Clostridium botulinum Clostridium colicanis Clostridium difficile Clostridium formicaceticum Clostridium novyi Clostridium perfringens Clostridium sordelli Clostridium tetani Clostridium piliforme Clostridium tyrobutyricum etc. ... A breastfeeding infant Breastfeeding is the practice of a woman feeding an infant (or sometimes a toddler or a young child) with milk produced from her mammary glands, usually directly from the nipples. ... A bacterial group (and probiotic) that is perceived to exert health-promoting properties within humans, specifically the colon. ... Bifidus Factor (methyl-N-acetyl D-glucosamine) is a specific factor that promotes the growth of Lactobacillius Bifidus. ... An infant being fed by bottle. ... Genera see text The Enterobacteriaceae are a large family of bacteria, including many of the more familiar pathogens, such as Salmonella and Escherichia coli. ... Species Enterococcus is a genus of bacteria of the phylum Firmicutes. ... A bacterial group (and probiotic) that is perceived to exert health-promoting properties within humans, specifically the colon. ... Species etc. ... Species Clostridium acetobutylicum Clostridium aerotolerans Clostridium botulinum Clostridium colicanis Clostridium difficile Clostridium formicaceticum Clostridium novyi Clostridium perfringens Clostridium sordelli Clostridium tetani Clostridium piliforme Clostridium tyrobutyricum etc. ... A breastfeeding infant Breastfeeding is the practice of a woman feeding an infant (or sometimes a toddler or a young child) with milk produced from her mammary glands, usually directly from the nipples. ...


Functions

Bacteria in the gut fulfills a host of useful functions for humans, including digestion of unutilized energy substrates;[19] stimulating cell growth; repressing the growth of harmful microorganisms; training the immune system to respond only to pathogens; and defending against some diseases.[2][3][20] A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ...


Carbohydrate fermentation and absorption

Without gut flora, the human body would be unable to utilize some of the undigested carbohydrates it consumes, because some types of gut flora have enzymes that human cells lack for breaking down certain polysaccharides.[3] Rodents raised in a sterile environment and lacking in gut flora need to eat 30% more calories just to remain the same weight as their normal counterparts.[3] Carbohydrates that humans cannot digest without bacterial help include certain starches; fiber; oligosaccharides and sugars that the body failed to digest and absorb[6][2][7] like lactose and sugar alcohols, mucus produced by the gut, and proteins.[6] Lactose is a disaccharide found in milk. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Polysaccharides (sometimes called glycans) are relatively complex carbohydrates. ... Food energy is the amount of energy in food that is available through digestion. ... This article or section does not cite any references or sources. ... Starch is a complex carbohydrate which is insoluble in water. ... Dietary fibers are the indigestible portion of plant foods that move food through the digestive system and absorb water. ... The term “oligosaccharide” refers to a short chain of sugar molecules (“oligo” means “few” and “saccharide” means “sugar. ... Magnification of grains of sugar, showing their monoclinic hemihedral crystalline structure. ... Lactose is a disaccharide that consists of β-D-galactose and β-D-glucose molecules bonded through a β1-4 glycosidic linkage. ... Functional group of an alcohol molecule. ... Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). ...


Bacteria turn carbohydrates they ferment into short chain fatty acids, or SCFAs.[6][5][7] These materials can be used by host cells, providing a major source of useful energy and nutrients for humans.[6] They increase the gut's absorption of water, reduce counts of damaging bacteria, increase growth of human gut cells,[5] and are also used for the growth of indigenous bacteria.[2] The SCFAs are produced by a form of fermentation called saccharolytic fermentation[6] and include acetic acid, propionic acid, and butyric acid.[6][5][7] Gases and organic acids like lactic acid are also produced by saccahrolytic fermentation.[7] Acetic acid is used by muscle, propionic acid helps the liver produce ATP, and butyric acid provides energy to gut cells and may prevent cancer.[6] Short chain fatty acids are a sub-group of fatty acids with aliphatic tails of less than six carbons. ... Acetic acid, also known as ethanoic acid, is an organic chemical compound best recognized for giving vinegar its sour taste and pungent smell. ... Propionic acid (systematically named propanoic acid) is a naturally occurring carboxylic acid with chemical formula CH3CH2COOH. In the pure state, it is a colorless, corrosive liquid with a pungent odor. ... Butyric acid, (from Greek βουτυρος = butter) IUPAC name n-Butanoic acid, or normal butyric acid, is a carboxylic acid with structural formula CH3CH2CH2-COOH. It is notably found in rancid butter, parmesan cheese, and vomit, and has an unpleasant odor and acrid taste, with a sweetish aftertaste (similar to ether). ... An organic acid is an organic compound that is an acid. ... For the production of milk by mammals, see Lactation. ... A top-down view of skeletal muscle Muscle (from Latin musculus little mouse [1]) is contractile tissue of the body and is derived from the mesodermal layer of embryonic germ cells. ... The liver is an organ present in vertebrates and some other animals. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Cancer is a class of diseases or disorders characterized by uncontrolled division of cells and the ability of these to spread, either by direct growth into adjacent tissue through invasion, or by implantation into distant sites by metastasis (where cancer cells are transported through the bloodstream or lymphatic system). ...


Another, less favorable type of fermentation, proteolytic fermentation, breaks down proteins like enzymes, dead host and bacterial cells, and collagen and elastin found in food, and can produce toxins and carcinogens in addition to SCFAs. Thus a diet lower in protein lowers exposure to toxins.[2][5] Tropocollagen triple helix. ... Elastin, also known as elasticin, is a protein in connective tissue that is elastic and allows skin to return to its original position when it is poked or pinched. ... The hazard symbol for carcinogenic chemicals in the Globally Harmonized System. ...


Evidence also suggests that bacteria enhance the absorption and storage of lipids.[3] Bacteria also produce and help the body absorb needed vitamins like vitamin K. In addition, the SCFAs they produce help the body absorb nutrients such as calcium, magnesium, and iron.[2] Figure 1: Basic lipid structure. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Standard atomic weight 40. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ...


Trophic effects

Another benefit of SCFAs is that they increase growth of intestinal epithelial cells and control their proliferation and differentiation.[2] They may also cause lymphoid tissue near the gut to grow. Bacterial cells also alter intestinal growth by changing the expression of cell surface proteins such as sodium/glucose transporters.[3] In addition, changes they make to cells may prevent injury to the gut mucosa from occurring.[20] In zootomy, epithelium is a tissue composed of a layer of cells. ... In mammals including humans, the lymphatic vessels (or lymphatics) are a network of thin tubes that branch, like blood vessels, into tissues throughout the body. ... The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. ...


Repression of pathogenic microbial growth

C. difficile colonies on a blood agar plate. The overgrowth of C. difficile in the gut can be harmful to the host.
C. difficile colonies on a blood agar plate. The overgrowth of C. difficile in the gut can be harmful to the host.

Another important role of helpful gut flora is that they prevent species that would harm the host from colonizing the gut, an activity termed the "barrier effect". Yeasts and harmful bacterial species such as Clostridium difficile (the overgrowth of which can cause pseudomembranous colitis) are unable to grow too much due to competition from helpful gut flora species, thus animals without gut flora are infected very easily. The barrier effect protects humans from both invading species and species normally present in the gut at low numbers, whose growth is usually inhibited by the gut flora.[2] Image File history File links Clostridium_difficile_01. ... Image File history File links Clostridium_difficile_01. ... An agar plate streaked with microorganisms isolated from a deep-water sponge. ... Typical divisions Ascomycota (sac fungi) Saccharomycotina (true yeasts) Taphrinomycotina Schizosaccharomycetes (fission yeasts) Basidiomycota (club fungi) Urediniomycetes Sporidiales Yeasts are a growth form of eukaryotic microorganisms classified in the kingdom Fungi. ... Binomial name Clostridium difficile Hall & OToole, 1935 Clostridium difficile or CDF/cdf (Template:Audo, alternatively ) (also referred to as C. diff or C-diff) is a species of bacteria of the genus Clostridium which are gram-positive, anaerobic, spore-forming rods (bacillus). ... Pseudomembranous colitis is an infection of the colon often, but not always, caused by the bacterium Clostridium difficile. ... An infection is the detrimental colonization of a host organism by a foreign species. ...


Helpful bacteria prevent the growth of pathogenic species by competing for nutrition and attachment sites to the epithelium of the colon. Symbiotic bacteria are more at home in this ecological niche and are thus more successful in the competition. The indigenous bacteria send chemical signals to the host about the amount of nutrients they need, and the host provides only that much, so harmful bacteria are starved out. Indigenous gut flora also produce bacteriocins, substances which kill harmful microbes and the levels of which can be regulated by enzymes produced by the host.[2] Types of epithelium This article discusses the epithelium as it relates to animal anatomy. ... Bacteriocins are proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s). ...


The process of fermentation, since it produces fatty acids, also serves to lower the pH in the colon, preventing the proliferation of harmful species of bacteria and facilitating that of helpful species. The pH may also enhance the excretion of carcinogens.[6] In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail (chain), which is either saturated or unsaturated. ...


Immunity

Gut flora have a continuous and dynamic effect on the host's gut and systemic immune systems. The bacteria are key in promoting the early development of the gut's mucosal immune system both in terms of its physical components and function and continue to play a role later in life in its operation. The bacteria stimulate the lymphoid tissue associated with the gut mucosa to produce antibodies to pathogens. The immune system recognizes and fights harmful bacteria, but leaves the helpful species alone, a tolerance developed in infancy.[2][10][4][5]


As soon as an infant is born, bacteria begin colonizing its digestive tract. The first bacteria to settle in are able to affect the immune response, making it more favorable to their own survival and less so to competing species; thus the first bacteria to colonize the gut are important in determining the person's lifelong gut flora makeup. However, there is a shift at the time of weaning from predominantly facultative aerobic species such as Streptococci and Escherichia coli to mostly obligate anaerobic species.[2][3] A request has been made on Wikipedia for this article to be deleted in accordance with the deletion policy. ... A breastfeeding infant Breastfeeding is the practice of a woman feeding an infant (or sometimes a toddler or a young child) with milk produced from her mammary glands, usually directly from the nipples. ... An aerobic organism or aerobe is an organism that has an oxygen based metabolism. ... Species S. pneumoniae S. pyogenes S. viridans Streptococcus is a genus of spherical, Gram-positive bacteria of the phylum Firmicutes. ... E. coli redirects here. ... ...


Recent findings have shown that gut bacteria play a role in the expression of Toll-like receptors (TLRs) in the intestines, molecules that help the host repair damage due to injury. TLRs cause parts of the immune system to repair injury caused for example by radiation.[3][20] Toll-like receptors (TLRs) are primary transmembrane proteins of immune cells that serve as a key part of the innate immune system; in addition they show a link between the innate and adaptive immune systems in vertebrates. ... Radiation as used in physics, is energy in the form of waves or moving subatomic particles. ...


Bacteria can influence the phenomenon known as oral tolerance, in which the immune system is less sensitive to an antigen (including those produced by gut bacteria) once it has been ingested. This tolerance, mediated in part by the gastrointestinal immune system and in part by the liver, can reduce an overreactive immune response like those found in allergies and auto-immune disease.[21] This article does not cite any references or sources. ... ‹ The template below (Taginfo) is being considered for deletion. ... Autoimmune diseases arise from an overactive immune response of the body against substances and tissues normally present in the body. ...


Some species of gut flora, such as some of those in the Bacteroides genus, are able to change their surface receptors to mimic those of host cells in order to evade immune response. Bacteria with neutral and harmful effects on the host can also use these types of strategies. The host immune system has also adapted to this activity, preventing overgrowth of harmful species.[2][4]


Preventing allergy

Bacteria are also implicated in preventing allergies,[1] an overreaction of the immune system to non-harmful antigens. Studies on the gut flora of infants and young children have shown that those who have or later develop allergies have different compositions of gut flora from those without allergies, with higher chances of having the harmful species C difficile and S aureus and lower prevalence of Bacteroides and Bifidobacteria.[1] One explanation is that since helpful gut flora stimulate the immune system and "train" it to respond properly to antigens, a lack of these bacteria in early life leads to an inadequately trained immune system which overreacts to antigens.[1] On the other hand, the differences in flora could be a result, not a cause, of the allergies.[1] ‹ The template below (Taginfo) is being considered for deletion. ... This article does not cite any references or sources. ...


Preventing inflammatory bowel disease

Another indicator that bacteria help train the immune system is the epidemiology of Inflammatory Bowel Disease, or IBD, such as Crohn's Disease (CD). Some authors suggest that SCFAs prevent IBD. In addition, some forms of bacteria can prevent inflammation.[22] The incidence and prevalence of IBD is high in industrialized countries with a high standard of living and low in less economically developed countries, having increased in developed countries throughout the twentieth century. The disease is also linked to good hygiene in youth; lack of breastfeeding; and consumption of large amounts of sucrose and animal fat.[22] Its incidence is inversely linked with poor sanitation during the first years of life and consumption of fruits, vegetables, and unprocessed foods.[22] Also, the use of antibiotics, which kill native gut flora and harmful infectious pathogens alike, especially during childhood, is associated with inflammatory bowel disease.[19] On the other hand, using probiotics, bacteria consumed as part of the diet that impart health benefits (aside from just nutrition), helps treat IBD. Epidemiology is the study of factors affecting the health and illness of populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine. ... In medicine, inflammatory bowel disease (IBD) is a group of inflammatory conditions of the large intestine and, in some cases, the small intestine. ... Crohns disease (also known as regional enteritis) is a chronic, episodic, inflammatory condition of the gastrointestinal tract characterized by transmural inflammation (affecting the entire wall of the involved bowel) and skip lesions (areas of inflammation with areas of normal lining in between). ... An abscess on the skin, showing the redness and swelling characteristic of inflammation. ... ... The Standard of living refers to the quality and quantity of goods and services available to people and the way these services and goods are distributed within a population. ... Green usually considered third world, yellow sometimes considered third world Third World was a term first coined by Jawaharlal Nehru (First Prime Minister of India), originally to distinguish nations that aligned with neither the West or with the East during the Cold War, including many members of the Non-Aligned... Probiotics are dietary supplements containing potentially beneficial bacteria or yeast, with lactic acid bacteria (LAB) as the most common microbes used. ... The updated USDA food pyramid, published in 2005, is a general nutrition guide for recommended food consumption. ...


Alterations in balance

Effects of antibiotic use

Altering the numbers of gut bacteria, for example by taking broad-spectrum antibiotics, may affect the host's health and ability to digest food.[23] People may take the drugs to cure bacterial illnesses or may unintentionally consume significant amounts of antibiotics by eating the meat of animals to which they were fed.[23] Antibiotics can cause antibiotic-associated diarrhea (AAD) by irritating the bowel directly, changing the levels of gut flora, or allowing pathogenic bacteria to grow.[7] Another harmful effect of antibiotics is the increase in numbers of antibiotic-resistant bacteria found after their use, which, when they invade the host, cause illnesses that are difficult to treat with antibiotics.[23] A broad-spectrum antibiotic is so called due to its activity against a wide range of infectious agents. ... Staphylococcus aureus - Antibiotics test plate. ... Pseudomembranous colitis is an infection of the colon caused by the bacterium Clostridium difficile. ... The intestine is the portion of the alimentary canal extending from the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine. ... A pathogen or infectious agent is a biological agent that causes disease or illness to its host. ... Antibiotic resistance is the ability of a microorganism to withstand the effects of an antibiotic. ...


Changing the numbers and species of gut flora can reduce the body's ability to ferment carbohydrates and metabolize bile acids and may cause diarrhea. Carbohydrates that are not broken down may absorb too much water and cause runny stools, or lack of SCFAs produced by gut flora could cause the diarrhea.[7] Bile (or gall) is a bitter, yellow or green alkaline fluid secreted by hepatocytes from the liver of most vertebrates. ...


A reduction in levels of native bacterial species also disrupts their ability to inhibit the growth of harmful species such as C. difficile and Salmonella kedougou, and these species can get out of hand, though their overgrowth may be incidental and not be the true cause of diarrhea.[7][23][2]


Gut flora composition also changes in severe illnesses, due not only to antibiotic use but also to such factors as ischemia of the gut, failure to eat, and immune compromise. Negative effects from this have led to interest in selective digestive tract decontamination (SDD), a treatment to kill only pathogenic bacteria and allow the reestablishment of healthy ones.[24] In medicine, ischemia (Greek ισχαιμία, isch- is restriction, hema or haema is blood) is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. ...


Probiotics & Prebiotics

Since the lack of gut flora can have such harmful health effects, the use of probiotics has anti-inflammatory effects in the gut and may be useful for improving health. Prebiotics are dietary components that can help foster the growth of microorganisms in the gut, which may lead to better health.[22] Probiotics are dietary supplements containing potentially beneficial bacteria. ... An abscess on the skin, showing the redness and swelling characteristic of inflammation. ... Prebiotics are a category of functional food, defined as: Non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thus improve host health. ...


Role in disease

Bacteria in the digestive tract have pathogenic properties in addition to their health-inducing ones: they can produce toxins and carcinogens[5] and have been implicated in such conditions as multisystem organ failure, sepsis, colon cancer, and IBD.[2] A major factor in health is the balance of bacterial numbers; if the numbers grow too high or low, it will result in harm to the host. The host has enzymes to regulate this balance.[5] This article or section does not cite any references or sources. ... The hazard symbol for carcinogenic chemicals in the Globally Harmonized System. ... Multiple organ dysfunction syndrome MODS; previously known as multiple organ failure (MOF) is altered organ function in an acutely ill patient requiring medical intervention to maintain homeostasis. ... Sepsis (in Greek Σήψις, putrefaction) is a serious medical condition, resulting from the immune response to a severe infection. ... Diagram of the stomach, colon, and rectum Colorectal cancer includes cancerous growths in the colon, rectum and appendix. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ...


Cancer

Some genera of bacteria, such as Bacteroides and Clostridium, have been associated with an increase in tumor growth rate, while other genera like Lactobacillus and Bifidobacteria are known to prevent tumor formation.[2] For other uses, see Genus (disambiguation). ... Tumor or tumour literally means swelling, and is sometimes still used with that meaning. ...


Translocation

Helpful bacteria can be very harmful to the host if they get outside of the intestinal tract.[3][5][9] Translocation, which occurs when bacteria leave the gut through its mucosal lining, the border between the lumen of the gut and the inside of the body,[4][25] can occur in a number of different diseases.[9][22] It can be caused by too much growth of bacteria in the small intestine, reduced immunity of the human, or increased gut lining permeability.[22] The gut can become more permeable in diseases like cirrhosis, which is damaging due in part to the activity of gut flora.[26] Chromosomal translocation of the 4th and 20th chromosome. ... The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. ... Lumen can mean: Lumen (unit), the SI unit of luminous flux Lumen (anatomy), the cavity or channel within a tubular structure Thylakoid lumen, the inner membrane space of the chloroplast 141 Lumen, an asteroid discovered by the French astronomer Paul Henry in 1875 Lumen (band), an American post-rock band... Cirrhosis of the liver is a consequence of chronic liver disease characterized by replacement of liver tissue by fibrotic scar tissue as well as regenerative nodules, leading to progressive loss of liver function. ...


If the gut is perforated, bacteria can invade the body, causing a potentially fatal infection. Aerobic bacteria can make infection by anaerobes worse by using up all available oxygen and creating an environment favorable to anaerobes.[9]


Inflammatory bowel disease

Some suspect that IBD is due to a reduction in immune tolerance and subsequent overreaction of the host's immune system to harmful or non-harmful bacteria. IBD may be caused by all of the gut flora together or some specific types.[27][19]


It has been noted that though Ulcerative Colitis and Crohn's disease (two types of IBD) probably have genetic components, they are not inherited in a Mendelian fashion and are thus probably due to a complex set of factors rather than solely to a gene.[27] Though neither bacterial colonization nor genetics is sufficient to cause the disease, bacteria probably play a role in these disorders.[27] Crohns disease (also known as regional enteritis) is a chronic, episodic, inflammatory condition of the gastrointestinal tract characterized by transmural inflammation (affecting the entire wall of the involved bowel) and skip lesions (areas of inflammation with areas of normal lining in between). ... DNA, the molecular basis for inheritance. ... Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent organisms to their children; it underlies much of genetics. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... DNA, the molecular basis for inheritance. ...


Some suspect that inflammation in IBD is due to increased permeability of the inner lining of the colon, which may allow bacteria to invade the tissues and cause an immune reaction that leads prolonged inflammation.[4][25] Abnormal tight junctions, which are supposed to prevent permeability, have been found in cells of patients with IBD.[25] Because of the potentially harmful role of these bacteria, antibiotics are frequently prescribed to treat Crohn’s disease.[20] However, inflammation could occur first and cause the increased intestinal permeability found in diseases such as Crohn's, so the causative role of bacteria is not clear.[25] Diagram of Tight junction. ...


Colitis

It has been suggested that commensal bacteria are responsible for the development of colitis, since mice raised in a sterile environment do not get the disease.[28] However, while some bacterial strains such as C. difficile[22] and even normal gut bacteria cause colitis,[28] others prevent the disease in mice.[22] Colitis is a digestive disease characterized by inflammation of the colon. ... Aseptic technique refers to a procedure that is performed under sterile conditions. ...


Sources and notes

  1. ^ a b c d e Björkstén B, Sepp E, Julge K, Voor T, and Mikelsaar M. 2001. Allergy development and the intestinal microflora during the first year of life. Journal of Allergy and Clinical Immunology, Volume 108, Issue 4, Pages 516-520. Accessed January 9, 2007
  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac Guarner F and Malagelada JR. 2003b. Gut flora in health and disease. The Lancet, Volume 361, Issue 9356, 8 February 2003, Pages 512-519. Accessed January 7, 2007
  3. ^ a b c d e f g h i j k l m n o Sears CL. 2005. A dynamic partnership: Celebrating our gut flora. Anaerobe, Volume 11, Issue 5, Pages 247-251. Accessed January 7, 2007
  4. ^ a b c d e f g Steinhoff U. 2005. Who controls the crowd? New findings and old questions about the intestinal microflora. Immunology Letters, Volume 99, Issue 1, 15 June , Pages 12-16. Accessed January 9, 2007
  5. ^ a b c d e f g h i j k l m University of Glasgow. 2005. The normal gut flora. Available through web archive. Accessed December 26, 2006
  6. ^ a b c d e f g h i j k l Gibson RG. 2004. Fibre and effects on probiotics (the prebiotic concept). Clinical Nutrition Supplements, Volume 1, Issue 2, Pages 25-31.
  7. ^ a b c d e f g h i j k l m Beaugerie L and Petit JC. 2004. Microbial-gut interactions in health and disease. Antibiotic-associated diarrhoea. Best Practice & Research Clinical Gastroenterology, Volume 18, Issue 2, Pages 337-352. Accessed January 9, 2007
  8. ^ Riordan SM, McIver CJ, Wakefield D, Duncombe VM, Thomas MC, and Bolin TD. 2001. Small intestinal mucosal immunity and morphometry in luminal overgrowth of indigenous gut flora. The American Journal of Gastroenterology, Volume 96, Issue 2, Pages 494-500. Accessed January 9, 2007
  9. ^ a b c d e Vedantam G and Hecht DW. 2003. Antibiotics and anaerobes of gut origin. Current Opinion in Microbiology, Volume 6, Issue 5, Pages 457-461. Accessed January 9, 2007
  10. ^ a b Shanahan F. 2002. The host–microbe interface within the gut. Best Practice & Research Clinical Gastroenterology, Volume 16, Issue 6, Pages 915-931. Accessed January 7, 2007
  11. ^ Nordgård L, Traavik T, and Nielsen KM. 2005. Nucleic Acid Isolation from Ecological Samples—Vertebrate Gut Flora. Methods in Enzymology, Volume 395, Pages 38-48. Accessed January 9, 2007
  12. ^ Bettelheim KA, Breadon A, Faiers MC, O'Farrell SM, Shooter RA. 1974. The origin of O serotypes of Escherichia coli in babies after normal delivery. J Hyg (Lond).72:67-70.[
  13. ^ a b Schwiertz A, Gruhl B, Lobnitz M, Michel P, Radke M, Blaut M. 2003. Development of the intestinal bacterial composition in hospitalized preterm infants in comparison with breast-fed, full-term infants. Pediatr Res. 54:393-9.
  14. ^ Mackie RI, Sghir A, Gaskins HR. 1999. Developmental microbial ecology of the neonatal gastrointestinal tract. Am J Clin Nutr. 69:1035S-1045S.
  15. ^ Favier CF, Vaughan EE, De Vos WM, Akkermans AD. 2002. Molecular monitoring of succession of bacterial communities in human neonates. Appl Environ Microbiol. 68:219-26.
  16. ^ Coppa GV, Bruni S, Morelli L, Soldi S, Gabrielli O. 2004. The first prebiotics in humans: human milk oligosaccharides. J Clin Gastroenterol. 38(6 Suppl):S80-3.
  17. ^ Harmsen HJ, Wildeboer-Veloo AC, Raangs GC, Wagendorp AA, Klijn N, Bindels JG, Welling GW. 2000. Analysis of intestinal flora development in breast-fed and formula-fed infants by using molecular identification and detection methods. J Pediatr Gastroenterol Nutr. 30:61-7.
  18. ^ Fanaro S, Chierici R, Guerrini P, Vigi V. 2003. Intestinal microflora in early infancy: composition and development. Acta Paediatr Suppl. 91(441):48-55.
  19. ^ a b c Wynne AG, McCartney AL, Brostoff J, Hudspith BN, Glenn GR and Gibson G. 2004. An in vitro assessment of the effects of broad-spectrum antibiotics on the human gut microflora and concomitant isolation of a Lactobacillus plantarum with anti-Candida activities. Anaerobe, Volume 10, Issue 3, Pages 165-169. Accessed January 9, 2007
  20. ^ a b c d Keeley J. 2004. Good bacteria trigger proteins to protect the gut. Howard Hughes Medical Institute. EurekAlert. Accessed January 9, 2007
  21. ^ Jewell AP. 2005. Is the liver an important site for the development of immune tolerance to tumours? Medical Hypotheses, Volume 64, Issue 4, Pages 751-754. Accessed January 9, 2007
  22. ^ a b c d e f g h Guarner F and Malagelada JR. 2003a. Role of bacteria in experimental colitis. ‘’Best Practice & Research Clinical Gastroenterology’’, Volume 17, Issue 5, October 2003, Pages 793-804. Accessed January 7, 2007
  23. ^ a b c d Carman RJ, Simon MA, Fernández H, Miller MA, and Bartholomew MJ. 2004. Ciprofloxacin at low levels disrupts colonization resistance of human fecal microflora growing in chemostats. Regulatory Toxicology and Pharmacology, Volume 40, Issue 3, December, Pages 319-326. Accessed January 7, 2007
  24. ^ Knight DJW and Girling KJ. 2003. Gut flora in health and disease. The Lancet, Volume 361, Issue 9371, Page 1831. Accessed January 7, 2007
  25. ^ a b c d Suenaert P, Bulteel V, Lemmens L, Noman M, Geypens B, Assche GV, Geboes K, Ceuppens JL and Rutgeert P. 2002. Anti-tumor necrosis factor treatment restores the gut barrier in Crohn’s disease. The American Journal of Gastroenterology, Volume 97, Issue 8, Pages 2000-2004. Accessed January 7, 2007
  26. ^ Garcia-Tsao G and Wiest R. 2004. Gut microflora in the pathogenesis of the complications of cirrhosis. Best Practice & Research Clinical Gastroenterology, Volume 18, Issue 2, Pages 353-372. Accessed January 9, 2007
  27. ^ a b c Hugot JP. 2004. Inflammatory bowel disease: a complex group of genetic disorders. Best Practice & Research Clinical Gastroenterology, Volume 18, Issue 3, Pages 451-462. Accessed January 9, 2007
  28. ^ a b Veltkamp C, Tonkonogy SL, De Jong YP, Albright C, Grenther WB, Balish E, Terhorst C, and Sartor RB. 2001. Continuous stimulation by normal luminal bacteria is essential for the development and perpetuation of colitis in Tg(epsilon26) mice. Gastroenterology, Volume 120, Issue 4, Pages 900-913. Accessed January 7, 2007

  Results from FactBites:
 
Foundation for Integrated Medicine - Leaky Gut Syndromes (5590 words)
Leaky Gut Syndromes are usually provoked by exposure to substances which damage the integrity of the intestinal mucosa, disrupting the desmosomes which bind epithelial cells and increasing passive, para-cellular absorption.
Immune sensitization to the normal gut flora is an important form of dysbiosis that has been implicated in the pathogenesis of Crohn's disease and ankylosing spondylitis[67-81].
Altering gut flora through the use of antibiotics, synthetic and natural, probiotics, and diet is a third strategy for breaking the vicious cycle in Leaky Gut Syndromes.
Bacteria in the human body - Wikipedia, the free encyclopedia (387 words)
Though normal flora are found on all surfaces exposed to the environment (on the skin and eyes, in the mouth, nose, small intestine, and colon), the vast majority of bacteria live in the large intestine.
Many of the bacteria in the digestive tract, collectively referred to as gut flora, are able to break down certain nutrients such as carbohydrates that humans otherwise could not digest.
Escherichia coli is a bacterium that lives in the colon; it is an extensively studied model organism and probably the best understood organism of all.
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