Osmotic sensitivity and tolerance and proteinase production in a strain of Saccharomyces.

A brewing yeast strain, NCYC 1085, unusual in that it sporulated freely and produced diploid spores, was sensitive to the degree of osmotic tension induced by the addition of 1.5 M KC1 or 2.5 M ethylene glycol to yeast extract-peptone glucose medium, but its progeny, obtained on sporulation and dissection of the resulting asci, included a number of osmotic-tolerant strains, the percentage of which increased as these strains were also sporulated and dissected. In addition, after repeated isolation of single-spore clones for three or four generations, clones producing zones of liquefaction of gelatin ranging in size from zero to large (approximately 1.5 cm) appeared, with the intensity of hydrolysis increasing in clones obtained from the later generations. The isolation of erythromycin-resistant mutants by manganese treatment was also accompanied by the appearance of osmotic-tolerant and gelatin-liquefying clones.