A polyphasic taxonomic study was performed on two strains of an unknown Gram-positive, asaccharolytic, nonspore-forming, obligately anaerobic coccus-shaped bacterium isolated from oral subgingival plaque of Labrador retriever dogs. Comparative 16S rRNA gene sequencing confirmed that these isolates were highly related to each other and formed a hitherto unknown linage within the clostridial rRNA XI cluster of organisms. Pairwise analysis demonstrated that the novel organism to be most closely related to members of the genus Peptostreptococcus with 16S rDNA gene sequence similarity values between 92.8% and 96.7%, respectively. The G + C DNA base composition was 30.8 mol% and the major cellular fatty acids included iso-C14:0, iso-C16:0, and iso-C16:0 DMA. Based on biochemical, chemotaxonomic, and phylogenetic evidence it is proposed that the unknown bacterium be classified as a new species, Peptostreptococcus canis sp. nov. The type strain is CCUG 57081T.
- 16S RNA