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 permeabilization, as measured by in situ alcohol dehydrogenase activity; 4) the action of the antibiotics, cycloheximide, and amphotericin B; and 5) flocculation ability have been studied. The effects of Pluronic F-68 have been compared with those of Triton X100. Consistent with its recognized biocompatibility, Pluronic F-68 (0.1-1.0% w/v) did not affect culture growth kinetics, whereas Triton X100 initially inhibited the onset of the logarithmic phase and slowed cell senescence. The changes were not reflected by changes in the profiles of cell-associated polypeptides. Cell-permeabilizing effects of both surfactants were demonstrated by the in situ alcohol dehydrogenases assay and by enhancement of growth-inhibiting effects of sublethal doses of cycloheximide (0.1 mu g ml(-1)) or amphotericin (50 mu g ml(-1)). No evidence of surfactant-induced flocculation was observed with this strain of yeast, which has minimal inherent flocculating ability. The results are discussed in relation to the principal physicochemical properties of the surfactants (e.g., critical micelle concentration) and their affects on cell permeability.