Differentiation of Lactobacillus sanfranciscensis strains by randomly amplified polymorphic DNA and pulsed-field gel electrophoresis

Genetic diversity of Lactobacillus sanfranciscensis strains isolated from naturally fermented sourdoughs of different origin was evaluated by using randomly amplified polymorphic DNA (RAPD). Computer-assisted comparison of the RAPD patterns revealed a clear separation of L. sanfranciscensis from other obligately heterofermentative Lactobacillus species closely related or normally present in sourdough. Six clusters, five of them constituted by strains of the same origin, were recognized at a similarity level of 63%. Pulsed-field gel electrophoresis (PFGE) results on strains chosen as representative were generally in good agreement with the grouping obtained by RAPD. Both techniques showed a high degree of discriminatory power and indicated the existence of a remarkable genetic polymorphism within the species. Furthermore, the chromosome size of L. sanfranciscensis was estimated by PFGE to be about 1.4 Mb.