YEAST RESPONSES TO NONIONIC SURFACTANTS

The effects of the nonionic surfactant Pluronic F-68 in batch cultures of Saccharomyces cerevisiae (X 2180 1B) on 1) culture growth and cell viability; 2) whole-cell polypeptide profiles; 3) membrane permeabili zation, as measured by in situ alcohol dehydrogenase activity; 4) the action of the antibiotics, cycloheximide, and amphotericin B; and 5) f locculation ability have been studied. The effects of Pluronic F-68 ha ve been compared with those of Triton X100. Consistent with its recogn ized biocompatibility, Pluronic F-68 (0.1-1.0% w/v) did not affect cul ture growth kinetics, whereas Triton X100 initially inhibited the onse t of the logarithmic phase and slowed cell senescence. The changes wer e not reflected by changes in the profiles of cell-associated polypept ides. Cell-permeabilizing effects of both surfactants were demonstrate d by the in situ alcohol dehydrogenases assay and by enhancement of gr owth-inhibiting effects of sublethal doses of cycloheximide (0.1 mu g ml(-1)) or amphotericin (50 mu g ml(-1)). No evidence of surfactant-in duced flocculation was observed with this strain of yeast, which has m inimal inherent flocculating ability. The results are discussed in rel ation to the principal physicochemical properties of the surfactants ( e.g., critical micelle concentration) and their affects on cell permea bility.