GENOTYPIC HETEROGENEITY AMONG LACTOBACILLUS-HELVETICUS STRAINS ISOLATED FROM NATURAL CHEESE STARTERS

A total of 23 strains of Lactobacillus helveticus isolated from natura l whey starter cultures for Italian hard cheeses, and three reference strains were characterized by plasmid profiling, ribotyping and random amplified polymorphic DNA (RAPD) fingerprinting. The data showed an i nteresting strain heterogeneity in natural cheese starters, that seeme d not only strain-dependent, but also related to the source of isolate s. Nineteen of the strains tested harboured extrachromosomal elements, whilst 11 different plasmid profiles were detected. Ribotyping with a variety of restriction enzymes differentiated Il strains and in a few cases, RAPD fingerprinting allowed differentiation amongst strains th at were not distinguished by the other two techniques.