USE OF RAPD AND MITOCHONDRIAL-DNA RFLP FOR TYPING OF CANDIDA ZEYLANOIDES AND DEBARYOMYCES-HANSENII YEAST STRAINS ISOLATED FROM CHEESE

In order to evaluate the genetic diversity of the yeast flora in North ern Spain cheese, we adapted two molecular techniques devised for Sacc haromyces, RAPD and RFLP of mitochondrial DNA, to type 27 Candida zeyl anoides strains and 28 Debaryomyces hansenii strains isolated from Ron cal and Idiazabal cheese at different stages of manufacture in differe nt dairies. RAPD with (GTG)(5) primer, although very reproducible, onl y defined 2 groups of strains for both species. On the other hand, mtD NA RFLP proved to be more discriminating and defined 5 groups pf strai ns for both species. In addition, the strains from the minor RAPD grou ps in both species corresponded to specific groups defined by mtDNA RF LP. Overall, this analysis has revealed an important genetic diversity , considering the limited sample of different biotopes tested. Neverth eless, the mt DNA RFLP results indicate that a large majority of the s trains appeared closely related, suggesting little variability between cheese and dairies. This work has demonstrated that rapid identificat ion methods (the typing of strains can be achieved in two days) can be applied to these poorly characterized yeast species, allowing a rapid evaluation of genetic diversity of these species in different biotope s.