Studies on the 'osmophilic' yeast saccharomyces rouxii and an obligate osmophilic mutant.

An obilagte osmophilic mutant (strain BI/4) of Saccharomyces rouxii has been isolated that fails to grow at osmotic pressures corresponding to 20 per cent (w/v) sucrose or less. In 30 percent sucrose the yeast is filamentous and grows slowly. In 40percent sucrose it is mainly filamentous and has over twice the normal diameter. In 60 percentsucrose it grows in the yeast form with a growth rate twic that of the cultrue in 40 per cent sucrose. This mutant is lysed by a suddren drop in the osmotic pressure of the environment. Cell enveoples of the parent strain contained glucose and manose in the ratio I.2; Iand contained 3-8percent (w/v) hexosamine, whereas the envelopes of the mutatn contained 0-8 percent hexosaime. Cell envelopes of the mutant grown in 40 per cent sucrose contained glucose and mannose in the ratioI.9; I, wheras for envelopes of the yeast grown in 60 percent sucrose the ratio was I.2; I. Neutral lipids from whole cells and those from the envelopes of the mutant strain generally contained more unsaturated fatty acids than the corresponding fractions from the parent strain.