Cryptobacterium curtum gen. nov., sp nov., a new genus of Gram-positive anaerobic rod isolated from human oral cavities

Novel Eubacterium-like isolates, strains 12-3(T) and KV43-B, which were iso lated from the periodontal pocket of an adult patient with periodontal dise ase and necrotic dental pulp, respectively, were studied taxonomically and phylogenetically. The morphological and differential biochemical characteri stics of these organisms are also described in this paper. These organisms were Cram-positive, anaerobic, non-spore-forming, rod-shaped bacteria that were inert in most of the conventional biochemical tests and closely resemb led members of asaccharolytic oral Eubacterium species. On the other hand, protein profiles of whole cells in SOS-PAGE and Western immunoblotting reac tion analysis distinguished these isolates from strains of the previously d escribed genus Eubacterium. The G + C content of the DNAs from the novel is olates was 50 and 51 mol%, respectively. The levels of DNA-DNA relatedness to other asaccharolytic oral Eubacterium species, including Eubacterium bra chy, Eubacterium lentum, Eubacterium nodatum, Eubacterium timidum, Eubacter ium saphenum, Eubacterium minutum and Eubacterium exiguum, was less than 11 %. These organisms also exhibited a very low level of reassociation with t he DNA of Eubacterium limosum, the type species of the genus Eubacterium. T he results of 16S rDNA sequence comparisons revealed that these organisms r epresent a novel lineage distinct from all previously described genera of G ram-positive, rod-shaped bacteria. On the basis of our results, it is sugge sted that strains 12-3(T) and KV43-B should be classified in a new genus an d species, for which the name Cryptobacterium curtum gen. nov., sp. nov. is proposed. The type strain of Cryptobacterium curtum is 12-3(T)(= ATCC 7006 83(T)).