Justification of the “Classical” Propionibacterium Species Concept by Ribotyping

Abstract

Summary The rRNA gene restriction patterns of 135 “classical” Propionibacterium strains were determined by hybridization with a 16S rDNA digoxigenin-labelled probe from P. freudenreichii subsp. freudenreichii (ATCC 6207). The combination of the Hae II and Sma I restriction endonuclease patterns resulted in the elucidation of 16 distinctly different ribotype profiles. Two ribotype profiles corresponding to the old species “P. pentosaceum” (ribotype A) and “P. arabinosum” (ribotype B) were observed for all P. acidipropionici strains. The P. freudenreichii species was homogeneous, with the various subspecies all displaying an identical ribotype profile (ribotype C). A large degree of rRNA restriction pattern heterogeneity was observed for all strains phenotypically identified as P. jensenii , with nine ribotype profiles (ribotype D-L). Four ribotype profiles (ribotype M-P) were observed for all strains phenotypically identified as P. thoenii . With the exception of the incorrect consolidation of “P. rubrum” and “P. sanguineum” strains into the P. thoenii species, the results of this study validate and justify the “classical” species concept within the genus Prop ionibacterium. However, based on phenotypic, restriction endonuclease profiles of polymerase chain reaction amplified 16S rDNA and ribotyping data, a revision of the P. acidipropionici, P. jensenii and P. thoenii species is shown to be required, as the existence of additional groups within these species is apparent.