Morphological commitment in Candida albicans.

Stationary phase yeast cells of the dimorphic fungus albicans can reinitiate growth under appropriate conditions either as yeasts through bud formation or as hyphae through germ tube formation and elongation. Stationary phase yeast cells resuspended in fresh medium at 37 degrees C form germ tubes and those resuspended at 25 degrees C form buds. Temperature shift experiments have been used to observe when cells become committed to germ tube formation and yeast budding growth under conditions favorable to each form. The two commitment processes appear to be independent and, once initiated, occur at characteristic rates with commitment to germ tube formation preceding commitment to yeast bud formation. The rate of commitment to germ tube formation was consistent with a random process or first-order kinetics. A relationship between cell volume and commitment to yeast growth and bud emergence was consistent with observations of cell volume distribution both in stationary phase cultures and between budded and unbudded cells during resumption of growth at 25 degrees C.