Propionibacterium acidifaciens sp. nov., isolated from the human mouth.

Three strains of anaerobic, pleomorphic, Gram-positive-staining bacilli, which were isolated from human carious dentine, were subjected to a comprehensive range of phenotypic and genotypic tests and were found to comprise a homogeneous group. The strains were saccharolytic and produced acetic and propionic acids in large amounts, and succinic acid in moderate amounts, as the end products of fermentation. 16S rRNA gene and RpoB protein sequence analyses revealed that the strains constituted a novel group within the genus Propionibacterium, most closely related to Propionibacterium australiense but sharing only 8 % DNA-DNA relatedness with the type strain of that species. Therefore, a novel species, Propionibacterium acidifaciens sp. nov., is proposed to accommodate these strains. The DNA G+C content of the type strain is 70 mol%. The type strain is C3M_31(T) (=DSM 21887(T) =CCUG 57100(T)).