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

The new species Stephanoascus smithiae was found to be heterothallic a nd to constitute the perfect state of Candida edax, a yeast of ascomyc etous affinity. The presence of asci crowned with an apical cell, the formation of galeate or hemispherical ascospores, and copious developm ent 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. smithi ae, including the ability to utilize non-conventional sources of carbo n, were compared with those of other hyphal yeast species in the gener a Stephanoascus, Zygoascus, Arxula, and with other related anamorphic hyphal ascomycetous yeasts which showed striking phenotypical resembla nces with the perfect forms examined. Further differentiation was base d on the determination of mol% G+C content and extent of DNA relatedne ss. Different physiological characteristics, maximum temperatures for growth, and significantly low relative DNA reassociation values with t he type strains of Steph. ciferrii (34-38 %) and Steph. farinosus (1-3 %) indicated that it represents a novel taxon. Similar phenotypic cha racteristics, a positive mating reaction and a high degree of DNA rela tedness demonstrated conspecificity with C. edax. The description of t he new teleomorph is given and possible relationships with other taxa are discussed.