A NOVEL HETEROTHALLIC ASCOMYCETOUS YEAST SPECIES - STEPHANOASCUS-SMITHIAE, TELEOMORPH OF CANDIDA-EDAX

The new species Stephanoascus smithiae was found to be heterothallic and to constitute the perfect state of Candida edax, a yeast of ascomycetous affinity. The presence of asci crowned with an apical cell, the formation of galeate or hemispherical ascospores, and copious development of true mycelium with denticulate conidiogenous cells, assigns the teleomorphic state to the genus Stephanoascus Smith, van der Walt et Johannsen. Morphological and physiological characters of Steph. smithiae, including the ability to utilize non-conventional sources of carbon, were compared with those of other hyphal yeast species in the genera Stephanoascus, Zygoascus, Arxula, and with other related anamorphic hyphal ascomycetous yeasts which showed striking phenotypical resemblances with the perfect forms examined. Further differentiation was based on the determination of mol% G+C content and extent of DNA relatedness. Different physiological characteristics, maximum temperatures for growth, and significantly low relative DNA reassociation values with the type strains of Steph. ciferrii (34-38 %) and Steph. farinosus (1-3 %) indicated that it represents a novel taxon. Similar phenotypic characteristics, a positive mating reaction and a high degree of DNA relatedness demonstrated conspecificity with C. edax. The description of the new teleomorph is given and possible relationships with other taxa are discussed.