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''Bacteroides'' is a genus of Gram-negative, obligate anaerobic bacteria. ''Bacteroides'' species are non-endospore-forming bacilli, and may be either motile or non-motile, depending on the species. The DNA base composition is 40-48% GC. Unusual in bacterial organisms, ''Bacteroides'' membranes contain sphingolipids. They also contain meso-diaminopimelic acid in their peptidoglycan layer. ''Bacteroides'' are normally mutualistic, making up the most substantial portion of the mammalian gastrointestinal flora, where they play a fundamental role in processing of complex molecules to simpler ones in the host intestine. As many as 1010-1011 cells per gram of human feces have been reported. They can use simple sugars when available; however, the main sources of energy for ''Bacteroides'' species in the gut are complex host-derived and plant glycans. Studies indicate that long-term diet is strongly associated with the gut microbiome composition - those who eat plenty of protein and animal fats have predominantly ''Bacteroides'' bacteria, while for those who consume more carbohydrates the ''Prevotella'' species dominate. One of the most important clinically is ''Bacteroides fragilis''. ''Bacteroides melaninogenicus'' has recently been reclassified and split into ''Prevotella melaninogenica'' and ''Prevotella intermedia''. ==Pathogenesis== ''Bacteroides'' species also benefit their host by excluding potential pathogens from colonizing the gut. Some species (''B. fragilis'', for example) are opportunistic human pathogens, causing infections of the peritoneal cavity, gastrointestinal surgery, and appendicitis via abscess formation, inhibiting phagocytosis, and inactivating beta-lactam antibiotics. Although ''Bacteroides'' species are anaerobic, they are transiently aerotolerant and thus can survive in the abdominal cavity. In general, ''Bacteroides'' are resistant to a wide variety of antibiotics — β-lactams, aminoglycosides, and recently many species have acquired resistance to erythromycin and tetracycline. This high level of antibiotic resistance has prompted concerns that ''Bacteroides'' species may become a reservoir for resistance in other, more highly pathogenic bacterial strains. 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「Bacteroides」の詳細全文を読む スポンサード リンク
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