INTERSPECIFIC PROTOPLAST FUSION BETWEEN CANDIDA-TROPICALIS AND CANDIDA-BOIDINII - CHARACTERIZATION OF THE FUSANTS

The polyethylene glycol (PEG) and electroporation protoplast fusion methods were applied to imperfect yeasts of the genus Candida to induce interspecific fusion. Auxotrophic strains of Candida tropicalis (an nalkane-utilizing yeast) and Candida boidinii (a methanol-utilizing yeast) were used as parental strains and fusion products were selected by complementation on minimal medium. The frequency of fusion induced by filter-sterilized PEG was high, ranging from 10(-4) to 10(-5). Scanning electron microscopy showed that the fusants varied considerably in shape, surface structure, and cell volume. Various electrophoretic karyotypes of fusants were observed, although their karyotypes were basically the same as that of C. boidinii. Morphological, biochemical, and physiological studies indicated that the characteristics of the fusants were mainly those of C. boidinii, but with some of those of C. tropicalis. The fusants could utilize methanol and n-alkane as sole carbon sources when they were first isolated, but their ability to utilize n-alkane was lost during their prolonged storage.