Adenine auxotrophic heterozygosity in Candida krusei.

Candida krusei CK 18 carries heterozygosity for a recessive adenine biosynthesis allele, as it can be induced by UV irradiation to form adenine mutants at high frequency. The resultant mutants were characterized with the phenotype of red colony and residual growth on minimal media. The majority of the descendant prototrophic segregates were capable of continuous segregation to adenine mutants, suggesting gene conversion as one possible mechanism for the occurrence of the adenine auxotroph in the isolate.