CHROMOSOMAL-POLYMORPHISM AND ADAPTATION TO SPECIFIC INDUSTRIAL ENVIRONMENTS OF SACCHAROMYCES STRAINS

Several industrial Saccharomyces strains, including bakers', wine, bre wers' and distillers' yeasts, have been characterized with regards to their DNA content, chromosomal polymorphism and homologies with the DN A of laboratory strains. Measurement of the DNA contents of cells sugg ested that most of the industrial yeasts were aneuploids. Polymorphism s in the electrophoretic chromosomal pattern were so large that each s train could be individually identified. However, no specific changes r elating to a particular group were observed. Hybridization using diffe rent probes from laboratory strains was very strong in all cases, indi cating that all industrial strains possess a high degree of DNA homolo gy with laboratory yeasts. Probes URA3, CUP1, LEU2, TRP1, GAL4 or ADC1 demonstrated the presence of one or two bands, two especially in bake rs' strains. Also, results indicate that all hybridized genes are loca ted on the same chromosomes both in laboratory and industrial strains. Translocation from chromosome VIII to XVI seems to have occurred in a distillers' strain, judging by the location of the CUP1 probe. Finall y, when the SUC2 probe is used, results indicate a very widespread pre sence of the SUC genes in only bakers' and molasses alcohol distillers ' strains. This clearly suggests that amplification of SUC genes is an adaptive mechanism conferring better fitness upon the strains in thei r specific industrial conditions. The widespread presence of Ty1 and T y2 elements as well as Y' subtelomeric sequences could account for the inter-and intrachromosomal changes detected.