Trichosporon

Abstract

The yeast Trichosporon cutaneum belongs to the genus Trichosporon Behrend, which was described as early as 1890 (Behrend 1890). This genus includes yeasts which are characterized by budding cells of various shapes, a more or less developed pseudomycelium, or a true mycelium and arthrospores (Fig. 1). Trichosporon yeasts may form asexual endospores, but sexual reproduction has not been demonstrated so far (Do Carmo-Sousa 1970). Biochemical characteristics such as hydrolysis of urea, utilization of mono-, di-, tri-, or polysaccharides, etc., as well as studies concerning DNA base composition and DNA relatedness, led Guého et al. (1984) to propose that Trichosporon yeasts should be classified into two separate groups. The first group, which appears to be related to the Ascomycetes, includes 13 species with a G+C content lower than 50% (34.7–48.8%) and lacks urease, with T. margaritiferum being an exception. The second group appears to be related to the Basidiomycetes and contains 15 species with a G+C content higher than 50% (57–64%) including T. cutaneum, T. beigelii, and T. pullulans, and has the ability to hydrolyze urea. The basidiomycetous nature of some of the Trichosporon yeasts is demonstrated by the lamellar structure of the cell walls (Kreger-Van Rij and Veenhuis 1971) and the presence of xylose (Weijman 1979). Furthermore, the diazonium blue B test (van der Walt and Hopsu-Havu 1976) has been applied to a number of T. beigelii strains (Kemker et al. 1991). The positive test results are in agreement with the described basidiomycetous affinity of these strains.