Identification of diary Propionibacterium species by rRNA gene restriction patterns.

A total of 78 strains of dairy propionibacteria, 4 reference strains of Propionibacterium and 8 related bacteria were characterized by ribosomal ribonucleic acid (rRNA) gene restriction patterns (ribotyping). The patterns were obtained after cleavage of total DNA with either BamHI or ClaI restriction endonucleases and hybridization of fragments with acetylaminofluorene-labelled 16 + 23S rRNA from Escherichia coli. The four different species of dairy propionibacteria, P. freudenreichii, P. jensenii, P. thoenii and P. acidipropionici, gave different restriction patterns with species-specific fragments. Moreover, ribotyping allowed the differentiation of P. freudenreichii subsp. freudenreichii from P. freudenreichii subsp. shermanii. The patterns of dairy propionibacteria were different from those of closely related bacteria and other bacteria used in the dairy industry.