SOME PROPERTIES OF SACCHAROMYCES KLUYVERI

Four isolates of a Saccharomyces species which differed from S. kluyveri by their ability to use cellobiose were analyzed genetically in relation to the latter species. Isolated single spores had low viability. Spore tetrads segregated mating types 2 : 2, with sexual agglutination occurring between complementary mating types. All single-spore isolates assimilated cellobiose indicating that these isolates were not naturally occurring hybrids between S. kluyveri and a cellobiose assimilating Saccharomyces species. Two cell types were exhibited by single-spore cultures of S. kluyveri, one granulated (G-type) and one vacuolated (g-type). G-type cultures formed fertile hybrids with complementary mating types of both G- and g-type cultures. Hybrids between two g-type cultures were sterile. They would, however, give fertile hybrids when mixed with G-type cultures. Sporulating hybrids between Saccharomyces sp. and S. kluyveri were produced. However the percentage spore germination was low. Single-spore cultures examined had cell types atypical of either parent. The ability to assimilate cellobiose was dominant and appeared to segregate with mating type and cell type. Weak mating reactions occurred when the (+) and (-) mating types of Saccharomyces sp. were mixed with (a) and (α) mating types of S. cerevisiae, respectively. The species of Saccharomyces isolated from the Pacific Coast are designated as strains of S. kluyveri. © 1969 Swets & Zeitlinger.