Strain and species identification by restriction fragment length polymorphisms in the ribosomal DNA repeat of Candida species

Restriction fragment length polymorphisms in the ribosomal DNA (rDNA) have been shown to be a useful criterion for distinguishing among various isolates of Candida albicans. In a sample of 12 clinical isolates, we found six different classes based on variations in the fragments produced from genomic DNA by EcoRI and visualized after Southern transfer by being probed with a plasmid containing Saccharomyces cerevisiae rDNA. Some of the classes appeared to be heterozygous at the rDNA locus. Similar digestion of other Candida species showed that each could be identified on the basis of its restriction patterns. Since these are highly reiterated genes, the differences were apparent on ethidium bromide-stained gels; Southern transfers were not necessary. EcoRI restriction maps of the rDNA of C. albicans, C. stellatoidea, C. tropicalis, and C. guilliermondii were determined.