STUDIES ON THE SEXUALITY OF RHODOTORULA

Abstract

A sexual interaction was discovered between two strains of Rhodotorula glutinis considered as haploid. The nutritionally prototrophic mycelial colony was obtained by the conjugation and plasmogamy of cells of their auxotrophic mutants. The mycelial development was also found in the couple of their wild type cells. The mycelium has septa with clamp-connections, and consists of dikaryotic cells. It produces terminally brown pear-shaped resting spores which are regarded as diploid. The resting spore germinates to form a promycelium, on which haploid sporidia bud off laterally. Single sporidium propagates by budding and develops to the same haploid yeast as that of the original Rhodotorula strains. Among monosporidial yeasts, there are two mating types. The same mycelial stage appears again by conjugation of the two mating types. For the perfect stage of these strains of Rhodotorula, a life history is proposed schematically. It was concluded that this organism was related to the order Ustilaginales of Basidiomycetes.
After the examination for sexual interaction in many couples of the authentic strains of Rhodotorula, the same mating reactions were found between IFO. 0559, IFO. 0413, or IFO. 0871 and IFO. 0880 or IFO. 1236. The mating types of the former three and the latter two were designated by symbols A and a, respectively.
A monotypic new genus, Rhodosporidium, was proposed and a new species, Rhodosporidium toruloides, was given to the perfect stage of these Rhodotorula strains.