Genetic (RAPD-PCR) and technological diversities among wild Lactobacillus helveticus strains

Diversity in 25 Lactobacillus helveticus strains isolated from natural whey cultures for Argentinian hard cheese production was studied by means of RAPD-PCR patterns and technological parameters (acidifying and proteolytic activities, salt tolerance, diacetyl, H2O2 and slime production, phage sensitivity). In the RAPD diversity study, 10 Lact. helveticus strains from the CNRZ collection were also included. The clustering of RAPD patterns from the Argentinian strains revealed the existence of two Lact. helveticus biotypes. Cluster 1 contained 22 strains (15 wild and seven CNRZ collection strains), Cluster 2 grouped 10 wild strains and Cluster 3 contained only three CNRZ collection strains. RAPD groups could be related to specific cheese-making characteristics (cheese plants). Analysis of technological characteristics in the Argentinian strains showed the occurrence of different natural variants. According to their capacity for growing in milk, they were classified as 'fast', 'intermediate' and 'slow' variants. Among the strains, low salt tolerance and widespread phage resistance were demonstrated. The genetic diversity (RAPD-PCR clustering) did not show any clear relationship with phenotypical diversity. Study of genetic and technological diversity allows a better characterization of mild strains belonging to Lact. helveticus.