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A microbiota is "the ecological community of commensal, symbiotic and pathogenic microorganisms that literally share our body space". Joshua Lederberg coined the term, emphasising the importance of microorganisms inhabiting the human body in health and disease. Many scientific articles distinguish microbiome and microbiota to describe either the collective genomes of the microorganisms that reside in an environmental niche or the microorganisms themselves, respectively. However, by the original definitions these terms are largely synonymous. The human body contains over 10 times more microbial cells than human cells, although the entire microbiome only accounts for about for 1-3% total body mass, with some weight-estimates ranging as high as 3 pounds (approximately 48 ounces or 1,400 grams). Research into the role that microbiota in the gut might play in the human immune system started in the late 1990s.〔Penders, J., Stobberingh, E. E., van den Brandt, P. A. and Thijs, C. (2007). "The role of the intestinal microbiota in the development of atopic disorders". ''Allergy'', 62 (11): 1223–1236. 〕 The microbiome of the gut has been characterised as a "forgotten organ",〔O'Hara, A. M. and Shanahan, F. (2006). "The gut flora as a forgotten organ. EMBO reports", 7 (7): 688–693. 〕 and the possibility has been raised that "the mammalian immune system, which seems to be designed to control microorganisms, is in fact controlled by microorganisms".〔Round, J. L. and Mazmanian, S. K. (2009). "The gut microbiota shapes intestinal immune responses during health and disease". ''Nature Reviews: Immunology'', 9 (5): 313–323. 〕 The human microbiome may have a role in auto-immune diseases like diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, fibromyalgia, and perhaps some cancers.〔Wu, Shaoguang et al. “A Human Colonic Commensal Promotes Colon Tumorigenesis via Activation of T Helper Type 17 T Cell Responses.” Nature medicine 15.9 (2009): 1016–1022. PMC. Web. 21 May 2015.〕 A poor mix of microbes in the gut may also aggravate common obesity.〔Turnbaugh, Peter J., et al. "A core gut microbiome in obese and lean twins." nature 457.7228 (2009): 480-484.〕〔Ridaura, Vanessa K., et al. "Gut microbiota from twins discordant for obesity modulate metabolism in mice." Science 341.6150 (2013): 1241214.〕〔Turnbaugh, Peter J., et al. "An obesity-associated gut microbiome with increased capacity for energy harvest." Nature 444.7122 (2006): 1027-131.〕 Since some of the microbes in the human body can modify the production of neurotransmitters known to occur in the brain, it may also relieve schizophrenia, depression, bipolar disorder and other neuro-chemical imbalances.〔 Bravo, Javier A., et al. "Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve." Proceedings of the National Academy of Sciences 108.38 (2011): 16050-16055. 〕 The microbes being discussed are generally non-pathogenic (they do not cause disease unless they grow abnormally); they exist in harmony and symbiotically with their hosts.〔 〕 Moreover, it has been stated that microbiome and host emerged as a unity along evolution by a process of integration. ==Introduction== All plants and animals, from protists to humans, live in close association with microbial organisms (see for example the human microbiome). Up until relatively recently, however, biologists have defined the interactions of plants and animals with the microbial world mostly in the context of disease states and of a relatively small number of symbiotic case studies. Organisms do not live in isolation, but have evolved in the context of complex communities. A number of advances have driven a change in the perception of microbiomes, including: * the ability to perform genomic and gene expression analyses of single cells and even of entire microbial communities in the new disciplines of metagenomics and metatranscriptonomics * massive databases making this information accessible to researchers across multiple disciplines * methods of mathematical analysis that help researchers to make sense of complex data sets Increasingly, biologists have come to appreciate that microbes make up an important part of an organism's phenotype, far beyond the occasional symbiotic case study.〔 〕 Pierre-Joseph van Beneden(1809-1894), a Belgian professor at the University of Louvain, developed the concept of commensalism during the nineteenth century. In his 1875 publication ''Animal Parasites and Messmates'', Van Beneden presented 264 examples of commensalism. His conception was widely accepted by his contemporaries and commensalism has continued to be used as a concept right up to the present day: microbiome is clearly linked to commensalism.〔Poreau B., ''( Biologie et complexité : histoire et modèles du commensalisme )''. PhD Dissertation, University of Lyon, France, 2014.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「microbiota」の詳細全文を読む スポンサード リンク
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