Ribosomal DNA Restriction Fragment Analysis as a Taxonomic Tool in Separating Physiologically Similar Basidiomycetous Yeasts

The taxonomic potential of restriction fragment analysis of the basic unit of the tandemly repeated ribosomal RNA genes was investigated. Four related basidiomycetous yeasts, Cryptococcus humicolus, Trichosporon cutaneum and two different tremelloid yeasts isolated out of the agarics Asterophora lycoperdoides and Asterophora parasitica were analysed with regard to their physiological standard characteristics, DNA homology and rDNA restriction maps, including localization of the regions coding for the 5.8S and the large and the small ribosomal RNA. Although physiologically almost identical, both DNA methods indicated that these strains belong to four different species. DNA-DNA hybridization could only be used to exclude conspecificity, whereas rDNA restriction analysis may be useful in establishing more general taxonomic relationships. Results indicate that different species have different restriction enzyme sites in the rDNA spacer regions. Regions specifying rRNA species on the other hand display greater similarity. The similarities in the rDNA restriction maps of these four species are also discussed in relation to the rDNA maps of two mycelial Homobasidiomycetes published elsewhere.