DNA base composition and DNA relatedness among species of Trichosporon Behrend.

The nuclear DNA of 28 species (30 strains investigated) of yeasts classified currently or previously in the genus Trichosporon. was analysed for its molar percentage of guanine + cytosine (mol% G + C). This criterion, together with biochemical characteristics, suggested the separation of the organisms studied into two groups. The first group, which appears related to the Ascomycetes, includes thirteen species with a G + C content lower than 50 mol% (34.7-48.8), and lacks urease (except T. margaritiferum). The second group appears related to the Basidiomycetes and includes fifteen species with a G + C content higher than 50 mol% (57-64) and has the ability to hydrolyse urea. A DNA homology experiment with T. beigelii and twelve other species of the second group showed very low values of complementarity with T. beigelii-labeled DNA. All these species must be considered as taxa other than T. beigelii.