Isolation of Candida tropicalis auxotrophic mutants

An enrichment scheme using nystatin was designed for the isolation of auxotrophic mutants from the diploid-alkane-utilizing yeast Candida tropicalis. A collection of 194 auxotrophs representing 7 phenotypes was isolated. One class of mutants was identified as having a defect in histidinol dehydrogenase activity and a second class of mutants was identified as having a defect in orotidine monophosphate decarboxylase activity. These strains are good candidates to be carrying mutations corresponding to the HIS4 and URA3 genes of Saccharomyces cerevisiae.