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The Enterobacteriaceae are a large family of Gram-negative bacteria that includes, along with many harmless symbionts, many of the more familiar pathogens, such as ''Salmonella'', ''Escherichia coli'', ''Yersinia pestis'', ''Klebsiella'' and ''Shigella''. Other disease-causing bacteria in this family include ''Proteus'', ''Enterobacter'', ''Serratia'', and ''Citrobacter''. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the phylum Proteobacteria. Phylogenetically, in the Enterobacteriales, several peptidoglycan-less insect endosymbionts form a sister clade to the Enterobacteriaceae, but as they are not validly described, this group is not officially a taxon; examples of these species are ''Sodalis'', ''Buchnera'', ''Wigglesworthia'', ''Baumannia cicadellinicola'' and ''Blochmannia'', but not former Rickettsias. Members of the Enterobacteriaceae can be trivially referred to as enterobacteria or "enteric bacteria",〔http://inst.bact.wisc.edu/inst/index.php?module=book&type=user&func=displayarticle&art_id=268〕 as several members live in the intestines of animals. In fact, the etymology of the family is enterobacterium with the suffix to designate a family (aceae) — not after the genus ''Enterobacter'' (which would be "Enterobacteraceae")— and the type genus is ''Escherichia''. ==Characteristics== Members of the Enterobacteriaceae are rod-shaped, and are typically 1-5 μm in length. They appear as small grey colonies on blood agar. Like other proteobacteria, enterobacteria have Gram-negative stains,〔(【引用サイトリンク】title=Dorlands Medical Dictionary:Enterobacteriaceae )〕 and they are facultative anaerobes, fermenting sugars to produce lactic acid and various other end products. Most also reduce nitrate to nitrite, although exceptions exist (e.g. ''Photorhabdus''). Unlike most similar bacteria, enterobacteria generally lack cytochrome C oxidase, although there are exceptions (e.g. ''Plesiomonas shigelloides''). Most have many flagella used to move about, but a few genera are nonmotile. They are not spore-forming. Catalase reactions vary among Enterobacteriaceae. Many members of this family are a normal part of the gut flora found in the intestines of humans and other animals, while others are found in water or soil, or are parasites on a variety of different animals and plants. ''Escherichia coli'' is one of the most important model organisms, and its genetics and biochemistry have been closely studied. Most members of Enterobacteriaceae have peritrichous, type I fimbriae involved in the adhesion of the bacterial cells to their hosts. Some enterobacteria produce endotoxins. Endotoxins reside in the cell cytoplasm and are released when the cell dies and the cell wall disintegrates. Some members of the Enterobacteriaeceae produce endotoxins that, when released into the bloodstream following cell lysis, cause a systemic inflammatory and vasodilatory response. The most severe form of this is known as endotoxic shock, which can be rapidly fatal. 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「Enterobacteriaceae」の詳細全文を読む スポンサード リンク
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