Different phenotypes for the lactose utilization system in Kluyveromyces and Saccharomyces species

Analysis of the system for the utilization of lactose in some strains of yeasts belonging to the genera Kluyveromyces and Saccharomyces revealed the occurrence of several genetic variants, corresponding to mutants expected on the basis of the model of Jacob and Monod for the lac system in E. coli. These results could be useful in the taxonomic analysis and in the phylogenetic evaluation of the Saccharomycetaceae.