The Family Lachnospiraceae, Including the Genera Butyrivibrio, Lachnospira and Roseburia
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The Family Lachnospiraceae, Including the Genera Butyrivibrio, Lachnospira and Roseburia MICHAEL COTTA AND ROBERT FORSTER
Butyrivibrio Introduction Members of the genus Butyrivibrio are nonspore forming, anaerobic, motile, curved rodshaped bacteria that are commonly isolated from the gastrointestinal tract of mammals. The Gram-negative staining of these organisms in no way reflects the true nature of the cell wall structure. Chemical and electron microscopic analyses of Butyrivibrio cells have revealed a thin, Gram-positive ultrastructure (Cheng and Costerton, 1977; Hespell et al., 1993). The genus is composed of two species, B. fibrisolvens and B. crossotus. Ruminal butyrivibrios characteristically produce butyric acid and degrade plant fibers such as xylans. Hence, the name Butyrivibrio fibrisolvens is quite descriptive (Bryant and Small, 1956a). Butyrivibrio strains isolated from human fecal material differ in substrate utilization and flagellar arrangement from B. fibrisolvens. These strains have been designated as B. crossotus to reflect the presence of “tasseled,” multiple flagella (Moore et al., 1976). Phylogenetic (DNA–DNA hybridization and 16S rDNA gene sequence) analyses indicate B. fibrisolvens strains are a genetically heterologous group of organisms, likely comprised of several species and numerous unrelated strains (Table 1; Mannarelli, 1988; Forster et al., 1996; Mannarelli et al., 1990b; Willems et al., 1995). However, these strains obviously have enough phenotypic similarities to be used to presumptively identify new isolates as B. fibrisolvens. These findings are not entirely surprising as it has been known for some time that B. fibrisolvens strains differ greatly in serological properties (Margherita and Hungate, 1963; Margherita et al., 1964; Hazlewood, et al., 1986) and in nutritional properties (Bryant and Small, 1956a; Bryant and Robinson, 1962).
Phylogeny The Butyrivibrio are phylogenetically placed within Cluster XIVa of the Clostridium subphy-
lum, as defined by Collins et al., 1994. Cluster XIVa contains a diverse array of Gram-positive bacteria including members of the Clostridium, Coprococcus, Lachnospira, Eubacterium, Ruminococcus, Syntrophococcus, Roseburia and “Acetitomaculum.” The Butyrivibrio belong to three phylogenetically distinct groups (Fig. 1) within this cluster (Forster et al., 1996; Willems et al., 1995). Although the majority of the Butyrivibrio will stain Gram-negative, the phylogenetic placement of the group among the low mol% GC content Gram-positive bacteria supports studies that demonstrated a Gram-positive type cell wall structure (Cheng and Costerton, 1977; Hespell et al., 1993). The strains of B. fibrisolvens designated to be in group I are those strains that cluster with the type strain, D1 (ATCC 19171). The strains within this group have 16S rDNA similarities of ≥92% and include the recently described C. proteoclasticum (Attwood et al., 1998).
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