hsp60 gene sequences were determined for members of the genus Bacteroides and sequence similarities were compared with those obtained for the 16S rRNA gene. Among the 29 Bacteroides type strains, the mean sequence similarity of the hsp60 gene (84.5 %) was significantly less than that of the 16S rRNA gene (90.7 %), indicating a high discriminatory power of the hsp60 gene. Species of the genus Bacteroides were differentiated well by hsp60 gene sequence analysis, except for Bacteroides pyogenes JCM 6294 T , Bacteroides suis JCM 6292 T and Bacteroides tectus JCM 10003 T . The hsp60 gene sequence analysis and the levels of DNA-DNA relatedness observed demonstrated that these three type strains are a single species. Consequently, B. suis and B. tectus are heterotypic synonyms of B. pyogenes. This study suggests that the hsp60 gene is an alternative phylogenetic marker for the classification of species of the genus Bacteroides. INTRODUCTIONOrganisms of the genus Bacteroides are part of the indigenous microbiota of human and animal gastrointestinal tracts, but different species in this group are commonly associated with a variety of human and animal infections. The genus Bacteroides is important in clinical bacteriology. Although species of the genus Bacteroides are isolated frequently from hospitalized patients, it can be difficult to identify every clinical isolate to the species level. In the past, because of poor definition of the genus, more than 50 species of the genus Bacteroides have been included in this group. The taxonomy of the genus Bacteroides has undergone significant changes in the last two decades (Dewhirst et al., 1990;Moore & Moore, 1994;Rautio et al., 2003;Sakamoto et al., 2002Sakamoto et al., , 2007Sakamoto & Benno, 2006;Shah & Collins, 1988. It has also been reported that 16S rRNA gene sequencing is useful for the identification of isolates of clinically significant species of the genus Bacteroides (Song et al., 2005).To date, a multilocus sequence typing (MLST) approach has been widely used to infer the phylogeny of organisms (Alexandre et al., 2008; Itoh et al., 2006;Shah et al., 2007;Yamamoto & Harayama, 1995). However, only limited information has been accumulated for species of the genus Bacteroides. It has been reported that housekeeping gene sequences, e.g. rpoB, could be used to clarify interspecies phylogenetic relationships within the genus Bacteroides (Ko et al., 2007). The ad hoc committee for the re-evaluation of the species definition in bacteriology has recommended evaluation of protein-coding gene sequence analysis for its applicability to genomically circumscribe the taxon species and differentiate it from neighbouring species detected by 16S rRNA gene sequence analysis (Stackebrandt et al., 2002).Hsp60, also known as Cpn60 or GroEL, is a member of the heat-shock protein (Hsp) family. The hsp60 gene has been shown to be more discriminative than the 16S rRNA gene for the identification of Streptococcus suis serotypes (Brousseau et al., 2001) and species of the genus Prevotella (Saka...

Two anaerobic, pigmented, non-spore-forming, Gram-stain-negative, rod-shaped strains isolated from the human oral cavity, OMA31 T

Three bacterial strains that had been isolated from human blood cultures, MS-1 T , MS-2 and MS-3, were characterized for their phenotypic and biochemical features, cellular fatty acid profiles, menaquinone profiles and phylogenetic positions based on 16S rRNA gene sequence analysis. 16S rRNA gene sequence analysis showed that the isolates were members of the genus Parabacteroides. These isolates were most closely related to Parabacteroides goldsteinii JCM 13446 T , with 95.9 % 16S rRNA gene sequence similarity. The levels of sequence similarity among the three strains were 99.7-100 %. The isolates were obligately anaerobic, nonpigmented, non-spore-forming, non-motile, Gram-negative and rod-shaped. The strains grew on media containing 20 % bile. These strains could be differentiated from P. goldsteinii by their ability to ferment L-arabinose and inabilities to ferment cellobiose, L-rhamnose and trehalose or to hydrolyse aesculin. The major menaquinone of the isolates was MK-10. Based on these data, we propose a novel Parabacteroides species, Parabacteroides gordonii sp. nov. The type strain is MS-1 T (5JCM 15724 T 5CCUG 57478 T ).