International Journal of Systematic and Evolutionary Microbiology, Vol 52, 115-122, Copyright © 2002 by Society for General Microbiology

Taxonomic characterization of Mogibacterium diversum sp. nov. and Mogibacterium neglectum sp. nov., isolated from human oral cavities

F. Nakazawa, S. R. Poco Jr, M. Sato, T. Ikeda, S. Kalfas, G. Sundqvist and E. Hoshino
Department of Oral Microbiology, School of Dentistry, Niigata University, Niigata, 951-8514, Japan

Novel isolates, strains HM-7, HM-6, HH-31, P9a-h(T) and UJB13-d, which were isolated from tongue plaque and necrotic dental pulp, were studied taxonomically and phylogenetically. These organisms were anaerobic, non-spore-forming, Gram-positive, rod-shaped bacteria that were inert in most of the conventional biochemical tests and phenotypically resemble Mogibacterium species or asaccharolytic Eubacterium species. The G+C contents of the DNAs from the novel isolates ranged from 41 to 42 mol%. DNA--DNA hybridization studies demonstrated that these strains might be assigned to the genus Mogibacterium but not to the previously described species. It was also apparent that strain HM-7 belonged to the same species as strains HM-6 and HH-31, and that strains P9a-h(T) and UJB13-d belonged to a second species. The levels of DNA--DNA relatedness to asaccharolytic Eubacterium species, including Eubacterium brachy, Eubacterium nodatum, Eubacterium saphenum and the more recently proposed Eubacterium minutum and Eubacterium exiguum (reclassified as Slackia exigua), are less than 2%. The results of 16S rDNA sequence comparisons revealed that these organisms represent novel lineages distinct from all previously described species of Gram-positive, rod-shaped bacteria. On the basis of phenotypic characteristics, DNA--DNA hybridization data and phylogenetic analysis with 16S rRNA gene sequence data, new species are proposed, namely Mogibacterium diversum (for strains HM-7,( )HM-6 and HH-31) and Mogibacterium neglectum (for strains P9a-h(T) and UJB13-d). HM-7(T) (=ATCC 700923(T)=JCM 11205(T)) is the type strain of the former and P9a-h(T) (=ATCC 700924(T)=JCM 11204(T)) is the type strain for the latter.