Morphology, Physiology, and Virulence of Some Mutants of Candida albicans.

Five mutagens were used to induce mutants of Candida albicans. Ultraviolet light, N-nitroso-N'-methyl-N-nitrosoguanidine, and N-nitroso-N-methylurethane were effective mutagens which induced stable auxotrophs. N-nitroso-N-methylurethane produced the largest number and variety of mutants. Nitrous acid and hydroxylamine were ineffective as mutagens although they killed C. albicans. All mutagenic agents employed induced colonial variants, especially small colony forms. The morphology, physiology, and virulence of one methionine and two adenine auxotrophs was compared to that of the prototroph. The auxotrophs exhibited yeast-like morphology in complex media and had sugar fermentation patterns typical of C. albicans, and all were agglutinated by C. albicans antiserum. Chlamydospore production was absent in the nonpigmented adenine mutant, and the chlamydospores produced by the methionine auxotroph were distorted. Germ tubes were formed in human serum by the auxotrophs and prototroph. Virulence for mice was retained by all auxotrophs but generally at a reduced level. The methionine auxotroph, only slightly less virulent than the prototroph, was more virulent than a pigmented adenine mutant and a practically avirulent nonpigmented adenine auxotroph.