Propionibacterium species diversity in Leerdammer cheese

Thirteen 'classical' Propionibacterium strains, isolated from Leerdammer cheese samples, using three different media were characterized phenotypically. The phenotypic data of 74 tests, conducted on 27 propionibacteria, including four type, 10 reference strains and the 13 cheese isolates were analysed by numerical taxonomical techniques, using the simple matching coefficient and single linkage cluster analysis. All the strains were grouped in four major clusters, with a final linkage at the 81% S-level. The clusters were equated with the 'classical' P. acidipropionici, P. freudenreichii, P. jensenii and P. thoenii species. The species were identified by relating them to specific type strains and by comparison of phenotypic characteristics. Differential characteristics of each cluster were determined. Strains of P. acidipropionici, P. freudenreichii and P. jensenii, but no P. thoenii strains were isolated from the Leerdammer cheese samples. No 'cutaneous' propionibacteria were isolated. The largest cluster, representing 46% of the cheese isolates was equated with P. jensenii. Various red/brown pigmented strains, which could be identified as the old 'P. rubrum' species were isolated from the cheese. These strains were, however, phenotypically identified as P. jensenii and also grouped in the P. jensenii cluster.