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The relationships among 65 basidiomycetous yeast strains were determined by one-dimensional electrophoresis of SDS-solubilized whole-cell proteins. Protein profiles were compared by the Pearson product moment correlation coefficient (r). The strains investigated represented species from the genera Cystofilobasidium, Filobasidium, Filobasidiella, Kondoa, Leucosporidium, Mrakia and Rhodosporidium. Except for the genus Mrakia, all species constituted separate protein electrophoretic clusters. The species of the genus Mrakia (M. frigida, M. gelida, M. nivalis and M. stokesii) show highly similar protein patterns, suggesting that these four species may be synonymous. Strains of two varieties of Filobasidiella neoformans, F. neoformans var. neoformans and F. neoformans var. bacillispora, could not be differentiated by protein electrophoresis. For the delineation of the protein electrophoretic clusters of the yeasts studied, literature data relying on other criteria, such as DNA base composition, carbon source utilization patterns, enzymatic protein electrophoregrams, ubiquinone systems, DNA-DNA homology and rRNA sequence data were used. It was demonstrated that a database of SDS-protein patterns provides a valuable tool for the identification of yeasts.

A numerical analysis was performed on one-dimensional whole-cell protein electrophoretic fingerprints of 107 strains belonging to the basidiomycetous yeast genera Rhodosporidium and Rhodotorula. This technique allowed evaluation of taxonomic relationships at the species level. In particular for the anamorphic genus Rhodotorula, the electrophoretic groupings did not correspond in all cases with the existing species. Heterogeneity of strains within the anamorphic species Rhodotorula acheniorum, RtR aurantiaca, RtR araucariae, RtR foliorum, RtR glutinis, RtR graminis and Rt. minuta was found. There was a good correlation between the grouping obtained by numerical analysis of protein patterns, the mol% G + C content and the coenzyme Q type. Furthermore, the results obtained with the different techniques used suggest possible close interspecific and/or intergeneric relationships. Most Rhodotorula glutinis strains, including the type strain, and the type strain of Rhodotorula graminis were highly similar to strains of Rhodosporidium diobovatum. For other investigated strains of Rhodotorula glutinis, a high similarity was found with strains of Rhodosporidium kratochvilovae, Rs. sphaerocarpum, Rs. toruloides and Rhodotorula mucilaginosa, respectively. Most of the Rhodotorula graminis strains could not be differentiated from Rhodosporidium paludigenum strains.