Summary auto-generated
This study describes two novel bacterial species isolated from human oral cavities. Five strains (HM-7, HM-6, HH-31, P9a-hT, and UJB13-d) recovered from tongue plaque and necrotic dental pulp were subjected to comprehensive taxonomic analysis. These organisms are anaerobic, non-spore-forming, Gram-positive rods that are phenotypically inert, showing negative results in most conventional biochemical tests. DNA analysis revealed G-C content of 41-42 mol%, consistent with the genus Mogibacterium. DNA-DNA hybridization confirmed the five strains represent two distinct species: strains HM-7, HM-6, and HH-31 (76-106% reassociation) constitute one species, while strains P9a-hT and UJB13-d (high reciprocal reassociation) form another. Both species showed low relatedness (<3%) to other asaccharolytic Eubacterium species and 16S rRNA sequence analysis demonstrated they represent phylogenetically distinct lineages. Both species produce phenylacetate as their sole metabolic end product. Based on phenotypic characteristics, DNA hybridization, and phylogenetic analysis, the authors propose Mogibacterium diversum sp. nov. and Mogibacterium neglectum sp. nov. as new species with designated type strains.
Key findings
- Two novel Mogibacterium species were identified from human oral isolates and designated M. diversum (strains HM-7, HM-6, HH-31) and M. neglectum (strains P9a-hT, UJB13-d) based on DNA-DNA hybridization and 16S rRNA sequence analysis.
- Both new species are obligately anaerobic, phenotypically inert Gram-positive rods with DNA G-C content of 41-42 mol% and produce phenylacetate as their sole metabolic end product.
- The novel species are phylogenetically distinct from previously described asaccharolytic oral bacteria, showing <3% DNA relatedness to other Eubacterium species and forming separate branches in the evolutionary tree.
- 16S rRNA gene sequencing confirmed these organisms belong to subcluster XI-A within Clostridium cluster XI but show sequence similarity <96.2% to established Mogibacterium species.
- Strains were isolated from human sources (tongue plaque and necrotic dental pulp) and demonstrate the presence of previously unrecognized bacterial diversity in the human oral cavity.
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Abstract
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.