Molecular diversity within Lactobacillus helveticus as revealed by genotypic characterization.

Lactobacillus helveticus is a homofermentative thermophilic lactic acid bacterium that is used in the manufacture of Swiss type and long-ripened Italian cheeses, such as Emmental, Grana, and Provolone cheeses. Substantial differences in several technologically important characteristics are found among L. helveticus strains isolated from natural dairy starter cultures. In the present study we investigated the genotypic diversity of 74 strains isolated from different dairy cultures used for manufacturing Grana and Provolone cheeses and six collection strains. A restriction fragment length polymorphism analysis of both total genomic DNA and the 16S rRNA gene (ribotyping) was used as genotypic fingerprinting. A multivariate statistical analysis of the data enabled us to identify significant genotypic heterogeneity in L. helveticus. We found that genotypic fingerprinting could be used to distinguish strains; in particular, it was possible to associate the presence of specific strain genotypes with dairy ecosystem sources (e.g., Grana or Provolone cheese). Our data contribute to the description of microbial heterogeneity in L. helveticus and provide a more solid basis for understanding the functional and ecological significance of the presence of different L. helveticus biotypes in natural dairy starter cultures.