History
In 1899, Henri Tissier, a French paediatrician, pediatrician at the Pasteur Institute in Paris, isolated a bacterium characterised by a Y-shaped morphology ("bifid") in the intestinal microbiota of breast-fed infants and named it "bifidus". In 1907, Élie Metchnikoff, deputy director at the Pasteur Institute, propounded the theory that lactic acid bacteria are beneficial to human health. Metchnikoff observed that the longevity of Bulgarians was the result of their consumption of fermented milk products. Metchnikoff also suggested that "oral administration of cultures of fermentative bacteria would implant the beneficial bacteria in the intestinal tract".Metabolism
The genus ''Bifidobacterium'' possesses a unique fructose-6-phosphate phosphoketolase pathway employed to ferment carbohydrates. Much metabolic research on bifidobacteria has focused on oligosaccharide metabolism, as these carbohydrates are available in their otherwise nutrient-limited habitats. Infant-associated bifidobacterial phylotypes appear to have evolved the ability to ferment Human milk oligosaccharide, milk oligosaccharides, whereas adult-associated species use plant oligosaccharides, consistent with what they encounter in their respective environments. As breast-fed infants often harbor bifidobacteria-dominated gut consortia, numerous applications attempt to mimic the bifidogenic properties of milk oligosaccharides. These are broadly classified as plant-derived fructooligosaccharides or dairy-derived galactooligosaccharides, which are differentially metabolized and distinct from milk oligosaccharide catabolism.Response to oxygen
The sensitivity of members of the genus ''Bifidobacterium'' to O2 generally limits probiotic activity to anaerobic habitats. Recent research has reported that some ''Bifidobacterium'' strains exhibit various types of wikt:oxic, oxic growth. Low concentrations of O2 and CO2 can have a stimulatory effect on the growth of these ''Bifidobacterium'' strains. Based on the growth profiles under different O2 concentrations, the ''Bifidobacterium'' species were classified into four classes: O2-hypersensitive, O2-sensitive, O2-tolerant, and microaerophilic. The primary factor responsible for aerobic growth inhibition is proposed to be the production of hydrogen peroxide (H2O2) in the growth medium. A H2O2-forming NADH oxidase was purified from O2-sensitive ''Bifidobacterium bifidum'' and was identified as a ''b''-type dihydroorotate dehydrogenase. The kinetic parameters suggested that the enzyme could be involved in H2O2 production in highly aerated environments.Genomes
Members of the genus ''Bifidobacterium'' have genome sizes ranging from 1.73 (''Bifidobacterium indicum'') to 3.25 Mb (''Bifidobacterium biavatii''), corresponding to 1,352 and 2,557 predicted protein-encoding open reading frames, respectively. Functional classification of ''Bifidobacterium'' genes, including the pan-genome of this genus, revealed that 13.7% of the identified bifidobacterial genes encode enzymes involved in carbohydrate metabolism.Clinical uses
Adding ''Bifidobacterium'' as a probiotic to conventional treatment of ulcerative colitis has been shown to be associated with improved rates of remission and improved maintenance of remission. Some ''Bifidobacterium'' strains are considered as important probiotics and used in the food industry. Different species and/or strains of bifidobacteria may exert a range of beneficial health effects, including the regulation of intestinal microbial homeostasis, the inhibition of pathogens and harmful bacteria that colonize and/or infect the gut mucosa, the modulation of local and systemic immune responses, the repression of procarcinogenic enzymatic activities within the microbiota, the production of vitamins, and the bioconversion of a number of dietary compounds into bioactive molecules. Bifidobacteria improve the gut mucosal barrier and lower levels of lipopolysaccharide in the intestine. Bifidobacteria may also improve abdominal pain in patients with irritable bowel syndrome (IBS) though studies to date have been inconclusive. Naturally occurring ''Bifidobacterium'' spp. may discourage the growth of gram-negative bacteria, Gram-negative pathogens in infants. A mother's milk contains high concentrations of lactose and lower quantities of phosphate (pH buffer). Therefore, when mother's milk is fermented by lactic acid bacteria (including bifidobacteria) in the infant's gastrointestinal tract, the pH may be reduced, making it more difficult for Gram-negative bacteria to grow.Bifidobacteria and the infant gut
The human infant gut is relatively sterile up until birth, where it takes up bacteria from its surrounding environment and its mother. The microbiota that makes up the infant gut differs from the adult gut. An infant reaches the adult stage of their microbiome at around three years of age, when their microbiome diversity increases, stabilizes, and the infant switches over to solid foods. Breast-fed infants are colonized earlier by ''Bifidobacterium'' when compared to babies that are primarily formula-fed. ''Bifidobacterium'' is the most common bacteria in the infant gut microbiome. There is more variability in genotypes over time in infants, making them less stable compared to the adult ''Bifidobacterium''. Infants and children under three years old show low diversity in microbiome bacteria, but more diversity between individuals when compared to adults. Reduction of ''Bifidobacterium'' and increase in diversity of the infant gut microbiome occurs with less breast-milk intake and increase of solid food intake. Mammalian milk all contain oligosaccharides showing natural selection . Human milk oligosaccharides are not digested by enzymes and remain whole through the digestive tract before being broken down in the colon by microbiota. ''Bifidobacterium'' species genomes of ''Bifidobacterium longum, B. longum, B. bifidum, Bifidobacterium breve, B. breve'' contain genes that can hydrolyze some of the human milk oligosaccharides and these are found in higher numbers in infants that are breast-fed. Glycans that are produced by the humans are converted into food and energy for the ''B. bifidum.'' showing an example of coevolution.Species
The genus ''Bifidobacterium'' comprises the following species: * ''Bifidobacterium actinocoloniiforme, B. actinocoloniiforme'' Killer et al. 2011 * ''Bifidobacterium adolescentis, B. adolescentis'' Reuter 1963 (Approved Lists 1980) * ''Bifidobacterium aemilianum, B. aemilianum'' Alberoni et al. 2019 * ''Bifidobacterium aerophilum, B. aerophilum'' Michelini et al. 2017 * ''Bifidobacterium aesculapii, B. aesculapii'' Modesto et al. 2014 * ''Bifidobacterium amazonense, B. amazonense'' Lugli et al. 2021 * ''Bifidobacterium angulatum, B. angulatum'' Scardovi and Crociani 1974 (Approved Lists 1980) * ''Bifidobacterium animalis, B. animalis'' (Mitsuoka 1969) Scardovi and Trovatelli 1974 (Approved Lists 1980) * ''Bifidobacterium anseris, B. anseris'' Lugli et al. 2018 * ''Bifidobacterium apousia, B. apousia'' Chen et al. 2022 * ''Bifidobacterium apri, B. apri'' Pechar et al. 2017 * ''Bifidobacterium aquikefiri, B. aquikefiri'' Laureys et al. 2016 * ''Bifidobacterium asteroides, B. asteroides'' Scardovi and Trovatelli 1969 (Approved Lists 1980) * ''Bifidobacterium avesanii, B. avesanii'' Michelini et al. 2019 * ''Bifidobacterium biavatii, B. biavatii'' Endo et al. 2012 * ''Bifidobacterium bifidum, B. bifidum'' (Tissier 1900) Orla-Jensen 1924 (Approved Lists 1980) * ''Bifidobacterium bohemicum, B. bohemicum'' Killer et al. 2011 * ''Bifidobacterium bombi, B. bombi'' Killer et al. 2009 * ''Bifidobacterium boum, B. boum'' Scardovi et al. 1979 (Approved Lists 1980) * ''Bifidobacterium breve, B. breve'' Reuter 1963 (Approved Lists 1980) * ''Bifidobacterium callimiconis, B. callimiconis'' Duranti et al. 2019 * ''Bifidobacterium callitrichidarum, B. callitrichidarum'' Modesto et al. 2018 * ''Bifidobacterium callitrichos, B. callitrichos'' Endo et al. 2012 * ''Bifidobacterium canis, B. canis'' Neuzil-Bunesova et al. 2020 * ''Bifidobacterium castoris, B. castoris'' Duranti et al. 2019 * ''Bifidobacterium catenulatum, B. catenulatum'' Scardovi and Crociani 1974 (Approved Lists 1980) * ''Bifidobacterium catulorum, B. catulorum'' Modesto et al. 2018 * ''Bifidobacterium cebidarum, B. cebidarum'' Duranti et al. 2020 * ''Bifidobacterium choerinum, B. choerinum'' Scardovi et al. 1979 (Approved Lists 1980) * ''Bifidobacterium choladohabitans, B.choladohabitans '' Chen et al. 2022 * ''Bifidobacterium choloepi, B. choloepi'' Modesto et al. 2020 * ''Bifidobacterium colobi, B. colobi'' Lugli et al. 2021 * ''Bifidobacterium commune, B. commune'' Praet et al. 2015 * ''Bifidobacterium criceti, B. criceti'' Lugli et al. 2018 * "''Bifidobacterium crudilactis, B. crudilactis''" Delcenserie et al. 2007 * ''Bifidobacterium cuniculi, B.cuniculi '' Scardovi et al. 1979 (Approved Lists 1980) * ''Bifidobacterium dentium, B. dentium'' Scardovi and Crociani 1974 (Approved Lists 1980) * ''Bifidobacterium dolichotidis, B. dolichotidis'' Duranti et al. 2019 * "''Bifidobacterium eriksonii, B. eriksonii''" Cato et al. 1970 * ''Bifidobacterium erythrocebi, B. erythrocebi'' Neuzil-Bunesova et al. 2021 * ''Bifidobacterium eulemuris, B. eulemuris'' Michelini et al. 2016 * ''Bifidobacterium faecale, B. faecale'' Choi et al. 2014 * ''Bifidobacterium felsineum, B. felsineum'' Modesto et al. 2020 * ''Bifidobacterium gallicum, B. gallicum'' Lauer 1990 * ''Bifidobacterium gallinarum, B. gallinarum'' Watabe et al. 1983 * ''Bifidobacterium globosum, B. globosum'' (ex Scardovi et al. 1969) Biavati et al. 1982 * ''Bifidobacterium goeldii, B. goeldii'' Duranti et al. 2019 * ''Bifidobacterium hapali, B. hapali'' Michelini et al. 2016 * ''Bifidobacterium imperatoris, B. '' Lugli et al. 2018 * ''Bifidobacterium indicum, B. indicum'' Scardovi and Trovatelli 1969 (Approved Lists 1980) * ''Bifidobacterium italicum, B. italicum'' Lugli et al. 2018 * ''Bifidobacterium jacchi, B. jacchi'' Modesto et al. 2019 * ''Bifidobacterium lemurum, B. lemurum'' Modesto et al. 2015 * ''Bifidobacterium leontopitheci, B. leontopitheci'' Duranti et al. 2020 * ''Bifidobacterium longum, B. longum'' Reuter 1963 (Approved Lists 1980) * ''Bifidobacterium magnum, B. magnum'' Scardovi and Zani 1974 (Approved Lists 1980) * ''Bifidobacterium margollesii, B.margollesii '' Lugli et al. 2018 * ''Bifidobacterium merycicum, B. merycicum'' Biavati and Mattarelli 1991 * ''Bifidobacterium miconis, B. miconis'' Lugli et al. 2021 * ''Bifidobacterium miconisargentati, B. miconisargentati'' Lugli et al. 2021 * ''Bifidobacterium minimum, B. minimum'' Biavati et al. 1982 * ''Bifidobacterium mongoliense, B. mongoliense'' Watanabe et al. 2009 * ''Bifidobacterium moraviense, B. moraviense'' Neuzil-Bunesova et al. 2021 * ''Bifidobacterium moukalabense, B. moukalabense'' Tsuchida et al. 2014 * ''Bifidobacterium myosotis, B. myosotis'' Michelini et al. 2016 * ''Bifidobacterium oedipodis, B. oedipodis'' Neuzil-Bunesova et al. 2021 * ''Bifidobacterium olomucense, B. olomucense'' Neuzil-Bunesova et al. 2021 * ''Bifidobacterium panos, B. panos'' Neuzil-Bunesova et al. 2021 * ''Bifidobacterium parmae, B. parmae'' Lugli et al. 2018 * "''Bifidobacterium platyrrhinorum, B. platyrrhinorum''" Modesto et al. 2020 * ''Bifidobacterium pluvialisilvae, B. pluvialisilvae'' Lugli et al. 2021 * ''Bifidobacterium polysaccharolyticum, B. polysaccharolyticum'' Chen et al. 2022 * ''Bifidobacterium pongonis, B. pongonis'' Lugli et al. 2021 * ''Bifidobacterium porcinum, B. porcinum'' (Zhu et al. 2003) Nouioui et al. 2018 * ''Bifidobacterium primatium, B. primatium'' Modesto et al. 2020 * ''Bifidobacterium pseudocatenulatum, B. pseudocatenulatum'' Scardovi et al. 1979 (Approved Lists 1980) * ''Bifidobacterium pseudolongum, B. pseudolongum'' Mitsuoka 1969 (Approved Lists 1980) * ''Bifidobacterium psychraerophilum, B. psychraerophilum'' Simpson et al. 2004 * ''Bifidobacterium pullorum, B. pullorum'' Trovatelli et al. 1974 (Approved Lists 1980) * ''Bifidobacterium ramosum, B. ramosum'' Michelini et al. 2017 * ''Bifidobacterium reuteri, B. reuteri'' Endo et al. 2012 * ''Bifidobacterium rousetti, B. rousetti'' Modesto et al. 2021 * "''Bifidobacterium ruminale, B. ruminale''" Scardovi et al. 1969 * ''Bifidobacterium ruminantium, B. ruminantium'' Biavati and Mattarelli 1991 * ''Bifidobacterium saguini, B. saguini'' Endo et al. 2012 * ''Bifidobacterium saguinibicoloris, B. saguinibicoloris'' Lugli et al. 2021 * "''Bifidobacterium saimiriisciurei, B. saimiriisciurei''" Modesto et al. 2020 * ''Bifidobacterium samirii, B. samirii'' Duranti et al. 2019 * ''Bifidobacterium santillanense, B. santillanense'' Lugli et al. 2021 * ''Bifidobacterium scaligerum, B. scaligerum'' Modesto et al. 2020 * ''Bifidobacterium scardovii, B. scardovii'' Hoyles et al. 2002 * ''Bifidobacterium simiarum, B. simiarum'' Modesto et al. 2020 * ''Bifidobacterium simiiventris, B. simiiventris'' Lugli et al. 2021 * ''Bifidobacterium stellenboschense, B. stellenboschense'' Endo et al. 2012 * ''Bifidobacterium subtile, B. subtile'' Biavati et al. 1982 * ''Bifidobacterium thermacidophilum, B. thermacidophilum'' Dong et al. 2000 * ''Bifidobacterium thermophilum, B. thermophilum'' corrig. Mitsuoka 1969 (Approved Lists 1980) * ''Bifidobacterium tibiigranuli, B. tibiigranuli'' Eckel et al. 2020 * ''Bifidobacterium tissieri, B. tissieri'' corrig. Michelini et al. 2016 * ''Bifidobacterium tsurumiense, B. tsurumiense'' Okamoto et al. 2008 * "''Bifidobacterium urinalis, B. urinalis''" Hojo et al. 2007 * ''Bifidobacterium vansinderenii, B. vansinderenii'' Duranti et al. 2017 * ''Bifidobacterium vespertilionis, B. vespertilionis'' Modesto et al. 2021 * ''Bifidobacterium xylocopae, B. xylocopae'' Alberoni et al. 2019See also
* List of bacterial vaginosis microbiota * Probiotic * Proteobiotics * Prebiotic (nutrition), PrebioticsReferences
External links