| Abstract: | The redistribution of ergosterol molecules which occurs during bud and germ tube formation (dimorphism) in Candida albicans was studied using filipin, a sterol-specific antibiotic, and examined by the freeze-fracture technique. When cells were fixed in a glutaraldehyde solution containing 50 micrograms/ml of filipin, filipin-ergosterol complexes, which were recognized as either pits on the exoplasmic fracture face or protuberances on the protoplasmic fracture face, were homogeneously distributed on the yeast plasma membranes. The plasma membrane of young budding yeast cells demonstrated few filipin-ergosterol complexes compared to the parent yeast plasma membrane. In addition, at a certain time during enlargement of budding yeast cells, the complexes became virtually absent from the constricted region between daughter and parent yeast cell. On the other hand, when germ tubes emerged as cylindrical outgrowths from the parent yeast cells, filipin-ergosterol complexes were heterogeneously redistributed on the plasma membrane. These results suggest that ergosterol molecules may be in lower concentration in the plasma membrane at the constricted region of yeast cell than elsewhere on the plasmalemma of the yeast cell. |
