Non-radioactive dot-blot DNA reassociation for unequivocal yeast identification

Unequivocal and rapid classification of yeast cultures cannot be accomplish ed exclusively on the basis of unstable phenotypic traits, but requires mol ecular tests relating to the whole genome (or the largest possible portion of it). DNA-DNA reassociation meets this requirement, although many procedu res proposed for calculating overall sequence similarity are expensive and time-consuming, thus restricting the possibility of unequivocal classificat ion to a few specialized laboratories. A novel method, based on non-radioac tive dot-blot hybridization of whole genomic DNA, has shown high and reprod ucible proportionality between the detected signal and the amount of double -stranded DNA effectively present on the membrane. This procedure has been optimized to obtain, within two working days. DNA relatedness values betwee n unknown cultures and the type strains of the species previously indicated by a few conventional tests. The effective ability of the method to discri minate strains belonging to different species has been tested within taxono mic models consisting of yeast type cultures already certified by spectroph otometric reassociation.