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''Butyrivibrio'' is a genus of bacteria in Class Clostridia. Bacteria of this genus are common in the gastrointestinal systems of many animals. Genus ''Butyrivibrio'' was first described by Bryant and Small (1956) as anaerobic, butyric acid-producing, curved rods (or vibroids). ''Butyrivibrio'' cells are small, typically 0.4 – 0.6 µm by 2 – 5 µm. They are motile, using a single polar or subpolar monotrichous flagellum. They are commonly found singly or in short chains but it is not unusual for them to form long chains. Despite historically being described as Gram-negative,〔Bryant & Small, 1956〕 their cell walls contain derivatives of teichoic acid,〔Cheng & Costerton, 1977〕 and electron microscopy indicates that bacteria of this genus have a Gram-positive cell wall type.〔〔Beveridge, 1990〕 It is thought that they appear Gram-negative when Gram stained because their cell walls thin to 12 to 18 nm as they reach stationary phase.〔 ''Butyrivibrio'' species are common in the rumens of ruminant animals such as cows, deer and sheep, where they are involved in a number of ruminal functions of agricultural importance in addition to butyrate production.〔Miller & Jenesel, 1979〕 These include fibre degradation, protein breakdown, biohydrogenation of lipids and the production of microbial inhibitors.〔Blackburn & Hobson, 1962〕〔Kalmokoff & Teather, 1997〕〔Kepler et al., 1966〕〔Dehority & Scott, 1967〕〔Polan et al., 1964〕 Of particular importance to ruminant digestion, and therefore productivity, is their contribution to the degradation of plant structural carbohydrates, principally hemicellulose.〔〔Morris & Van Gylswyk, 1980〕 ''Butyrivibrio'' species are metabolically versatile and are able to ferment a wide range of sugars〔Stewart et al., 1997〕 and cellodextrins.〔Russell, 1985〕 Some strains have been reported to break down cellulose,〔Shane et al., 1969〕 although their ability to sustain growth on cellulose appears to be lost during in vitro culturing. Most isolates are amylolytic〔Cotta, 1988〕 and are able to degrade xylan by producing xylanolytic〔Hespell et al., 1987〕〔Sewell et al., 1988〕 and esterase enzymes.〔Hespell & O'Bryan-Shah, 1988〕〔Lin & Thomson, 1991〕 The induction of xylanase enzymes varies between strains; in group D1 strains (49, H17c, 12) xylanase expression appears to be constitutively expressed, while groups B1 (113) and C (CF3) are induced only by growth on xylan, and those of group B2 are induced by growth on xylan or arabinose.〔Hespell & Whitehead, 1990〕 A number of genes encoding glycoside hydrolases (GH) have been identified in ''Butyrivibrio'' species including endocellulase (GH family 5 and 9); β-Glucosidase (GH family 3); endoxylanase (GH family 10 and 11); β-Xylosidase (GH family 43); and α-Amylase (GH family 13) enzymes. Several carbohydrate binding modules (CBM) have also been identified that are predicted to bind glycogen (CBM family 48); xylan or chitin (CBM family 2); and starch (CBM family 26).〔Krause et al., 2003〕〔Cantarel et al., 2008〕 The ''Butyrivibrio'' genus encompasses over 60 strains that were originally confined to the species ''Butyrivibrio fibrisolvens'' based on their phenotypic and metabolic characteristics. However, phylogenetic analyses based on 16S ribosomal RNA (rRNA) gene sequences has divided the genus ''Butyrivibrio'' into six families.〔Kopecny et al., 2003 (fig. 1.1)〕 These families include the rumen isolates ''Butyrivibrio fibrisolvens'', ''B. hungateii'', ''B. proteoclasticus'', ''Pseudobutyrivibrio xylanivorans'', and ''P. ruminis'' and the human isolate ''B. crossotus''. The families ''B. fibrisolvens'', ''B. crossotus'', ''B. hungateii'' as well as ''B. proteoclasticus'' all belong to the ''Clostridium'' sub-cluster XIVa.〔Willems et al., 1996〕 ==Butyrivibrio proteoclasticus B316T== ''Butyrivibrio proteoclasticus'' B316T was the first ''Butyrivibrio'' species to have its genome sequenced.〔Kelly W. J., et al. (2010). (2010). . PLoS One 5(8): e11942〕 It was first isolated and described by Attwood et al. (1996),〔Attwood et al., 1996〕 and was originally assigned to the genus ''Clostridium'' based on its similarity to ''Clostridium aminophilum'', a member of the ''Clostridium'' sub-cluster XIVa. Further analysis has shown that it is more appropriately placed within the genus ''Butyrivibrio'' and the organism was given its current name.〔Moon et al., 2008〕 Within this genus its 16S rDNA sequence is most similar to, but distinct from, that of ''B. hungateii''. ''B. proteoclasticus'' is found in rumen contents at significant concentrations of from 2.01 x 106/ml to 3.12 x 107/mL as estimated by competitive PCR〔Reilly & Attwood 1998〕 or 2.2% to 9.4% of the total eubacterial DNA within the rumen, as estimated by real time PCR.〔Paillard et al., 2007)〕 ''B. proteoclasticus'' cells are anaerobic, slightly curved rods, commonly found singly or in short chains, but it is not unusual for them to form long chains. They possess a single sub-terminal flagellum, but unlike other ''Butyrivibrio'' species, they are not motile. They are ultrastructurally Gram-positive, although as with all ''Butyrivibrio'' species, they stain Gram-negative〔 ''B. proteoclasticus'' has been shown to have an important role in biohydrogenation, converting linoleic acid to stearic acid.〔Wallace et al., 2006〕 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「Butyrivibrio」の詳細全文を読む スポンサード リンク
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