EFFECT OF GASEOUS ENVIRONMENT AND TEMPERATURE ON ASCOSPORE FORMATION IN SACCHAROMYCES CEREVISIAE HANSEN

Abstract

The effect on ascospore formation in bakers'' yeast of varying degrees of aeration and of O2, CO2, and N2 individually and in mixtures was studied. In the absence of CO2, ascospore formation was stimulated by concns. of O2 up to 12.0% but was depressed slightly at 41.1% and more so at 68.8% and at 100%. CO2 inhibited ascospore formation; very few were found when the concentration was 25% or greater. O2 did not overcome the inhibitory effect of CO2. Ethyl alcohol vapor so markedly inhibited sporulation that ascospores were rarely observed in cultures exposed to the vapor from a 5% solution of ethyl alcohol. Ascospore formation was observed at temperatures from 3.0 to 33.3[degree]C. Of 2 strains studied in one expt., one showed highest sporulation at 24.0[degree]C and the other at 27.5[degree]C. Cells exposed for 14 days to temperatures of 2.5, -3.5, and -18.0[degree]C, and cells multiplied at 37.5[degree]C , showed reduced sporulation at room temp.