Antigenic differences among strains of Saccharomyces cerevisiae Hansen 1883 and Saccharomyces uvarum Beijerinck 1898 were analyzed with respect to the proton magnetic resonance spectra of alkali-extracted mannans and the gel filtration profiles of the oligosaccharides of these mannans obtained by acetolysis. The strains of both species could be divided into serotypes Ia, Ib, and II. The serological relationships of these strains were found to correlate with the proton magnetic resonance spectra of the cell wall mannans. The gel filtratin profiles of the acetolysis oligosaccharides of type Ia, Ib, and II strains of both species were also characteristic for each type or subtype. Based on these findings, it is proposed that S. cerevisiae and S. uvarum be combined into one species with two main serotypes. S. uvarum is thus a later subjective synonym of S. cerevisiae.
Although Aessosporon salmonicolor was described with a homothallic life cycle, mating studies of strains of A. salmonicolor and Sporobolomyces spp. demonstrated a heterothallic life cycle typical of other basidiomycetous yeasts.
Two new species of the yeast genus Pichia were isolated from frass obtained from loblolly pines growing in Mississippi. The new taxa, designated Pichia amylophila and Pichia mississippiensis, are heterothallic, and Candida obtusa var. arabinosa proved to be a haploid member of the latter species. The species show interspecific mating, but ascospores from the crosses are infertile. The nuclear deoxyribonucleic acids from the species differ by 2 mol% in guanine plus cytosine content and exhibit low (25%) base sequence complementarity. Deoxyribonucleic acid relatedness was determined spectrophotometrically, and the methodology is given in detail.
Strains of Pichia ohmeri that form either spherical or hat-shaped ascospores comprise a well-defined assemblage, distinct in deoxyribonucleic acid base sequence and composition from other phenotypically similar yeasts. Thus, spore morphology, usually a stable systematic character, is not invariably reliable as a major taxonomic criterion among yeasts.