Hybridization of Pichia stipitis with its presumptive imperfect partner Candida shehatae

Summary A triauxotrophic strain of the D-xylose fermenting yeast Pichia stipitis, was hybridized with diauxotrophic strains of its presumptive imperfect partner Candida shehatae through polyethylene glycol (PEG) induced protoplast fusion. A small fraction of prototrophic clones, selected on specific media, appeared to be partial hybrids as determined by cellular diphenylamine DNA quantitations after three passages on a complex medium. The hybrid nature of the Pichia-resembling fusants was confirmed by cell volume estimation, analysis of nuclear condition and the isolation of a variety of mutant recombinant phenotypic segregants by meiotic segregation, as well as induced and spontaneous mitotic segregation.