Auxotrophic heterozygosities and the ploidy of Candida parapsilosis and Candida krusei

Abstract

Evidence is presented that the type strain of Candida parapsilosis, ATCC 22019, is heterozygous MET/met and that Candida krusei Y 10930 is heterozygous URA/ura. This URA gene determines orotidine-5′-phosphate decarboxylase activity. Because each of these strains is demonstrably disomic for at least one chromosome, they are not haploid but must be diploid or aneuploid.