Phenotypic Characteristics of a Slow-growing, Nongerminating Variant of Candida albicans

Abstract

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.

Multiple chromosomal and phenotypic changes in spontaneous mutants of Candida albicans

“…(ii) Germ tube formation and chlamydospore production Each of the germination-deficient mutants has retained the non-germination phenotype for many years (Howard et al, 1986). Although each of the non-germinative mutants formed chlamydospores and pseudohyphae when studied initially (unpublished observation), strains 302,307D, 3 1 1 and 3 12 have subsequently lost the ability to form chlamydospores (Table l), though they all still form pseudohyphae.…”

“…in parental strain 300 or induced mutants, 31 1 or 312. Spontaneous mutant 300-SG was initially identified by its small colony size and was described as a slow-growing mutant (Howard et al, 1986), but over time during maintenance at 4 "C in a refrigerator both normal growth rate and colonial size have been restored (Fig. 5).…”

“…Non-germinative mutants of the sort represented by 301,302 and 303 have been reported to occur at a frequency of 1-2 % (Buckley et al, 1982). Strain 300-SG was observed at a single instance amongst lo3 colonies of strain 300 (Howard et al, 1986). Group B consisted of the NTG-and UVinduced non-germinative mutants and their parental strains 307 and 310, respectively.…”

“…The strain 300-SG was a spontaneous mutant observed because of its small colony size among customary-sized colonies of strain 300 streaked on GPA and incubated at room temperature for 48 h (Howard et al, 1986).…”

“…Because of instabilities of the strains, the special method of maintenance (-70 "C) and growth of strains was used in these studies (Rustchenko-Bulgac, 1991). The recipes for yeast extract peptone dextrose (YPD) medium, GPA and Lee-Buckley-Campbell (LBC) synthetic medium have been published (Sherman et ul., 1986;Howard et al, 1986). Bismuth sulphite glucose glycine yeast (BiGGY) agar was prepared in accordance with the manufacturer's instructions (Difco).…”