Nystatin-induced changes in Saccharomyces cerevisiae.

Nystatin (5 to 10 mug/ml) was fungicidal to Saccharomyces cerevisiae NCYC 361. There was an initial rapid uptake of nystatin by the yeast cells at 30 C, the uptake being pH dependent, with a maximum at low pH values (3 to 4). Photomicrographs indicated that nystatin-treated cells became granular. The effect of growth temperature on the subsequent sensitivity of the yeast cells to nystatin was investigated. Cells grown at 20 C were the most susceptible to all concentrations of nystatin tested; as the pretreatment growth temperature increased, the subsequent uptake of antibiotic by such cells decreased both in intensity and in overall extent, the most marked difference occurring between 20 and 25 C grown cells. Leakage of K(+) and the optical density of suspensions treated with nystatin were similarly affected by growth temperature. Differences in the electrophoretic mobilities of cells grown at different temperatures were also observed. The total ergosterol content of 20 C grown cells was markedly higher than that of 40 C grown cells, with 30 C grown cells having an intermediate value.