Ethanol is one of the products of the metabolism of glucose by Candida albicans. The amount produced is directly related to the concentration of glucose in the medium. The fungus utilizes ethanol as a sole source of carbon but is relatively intolerant of ethanol in its environment. Ethanol induces germ tube formation by blastoconidia of C. albicans. Germination was not seen under fermentation conditions even though the amount of ethanol produced was in the range form stress proteins that are similar to heat shock proteins. The possibility that stress proteins may regulate germ tube formation by C. albicans is discussed.

At elevated temperatures, yeast cells of Candida albicans synthesized nine heat-shock proteins (HSPs) with apparent molecular masses of 98, 85, 81, 76, 72, 54, 34, 26 and 18 kDa. The optimum temperature for the heat-shock response was 45 degrees C although HSPs were detected throughout the range 41-46 degrees C. Protein synthesis was not observed in cells kept at 48 degrees C. Yeast cells survived exposure to an otherwise lethal temperature of 55 degrees C when they had previously been exposed to 45 degrees C. The thermotolerance induced during incubation at 45 degrees C required protein synthesis, since protection was markedly reduced by trichodermin. Mercury ions induced a set of three stress proteins, one of which corresponded in size to an HSP, and cadmium ions evoked one stress protein seemingly unrelated to the HSPs observed after temperature shift.

Some of the phenotypic characteristics of a slow-growing, nongerminating variant of a commonly studied strain of Candida albicans are described. The variant arose as a chance isolate. The rate of occurrence was about 0 X 1% and the reversion rate was about 1 per 10(6) cells. The colony size was typically smaller than that of the parent and the yeast cells tended not to separate from one another so that catenulate strands of cells (pseudohyphae) were formed. Under standard conditions the generation time of the small-colony variant in liquid shake cultures was about twice that of the parental strain. Growth of the variant was suppressed by antimycin A, indicating that the small colony form was not the consequence of a defect in the cytochrome system. The colony size of the variant was not influenced by chlorobenzotriazole, which suggested that adenine metabolism was not involved in the small-colony phenotype. The pseudohyphal growth pattern was not relieved by high concentrations of utilizable carbohydrates, which means the catenulate microscopic appearance of the yeast cells was not simply an exaggeration of the normal growth pattern of isolates of C. albicans but more probably represented the growth of a cell-cycle mutant defective at the cell separation step. The cytoplasmic proteins of the variant and the parent were very similar though some unique peptides were displayed by each.

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