Rapid Differentiation of Phenotypically Similar Yeast Species by Single-Strand Conformation Polymorphism of Ribosomal DNA

Systematic Mycology and Lichenology Laboratory, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; Graduate school of the Chinese Academy of Sciences, Beijing 100039, China

^* To whom correspondence should be addressed. Email: baify{at}im.ac.cn.

	Abstract

Single-strand conformation polymorphism (SSCP) of ribosomal DNA was investigated for rapid differentiation of phenotypically similar yeast species. Sensitive tests indicated that some yeast strains with one, most strains with two, and all strains with three or more nucleotide differences in the internal transcribed spacer 1 (ITS1) or ITS2 region, could be distinguished by PCR SSCP analysis. The discriminative power of SSCP in yeast species differentiation was demonstrated by comparative studies on representative groups of yeast species from ascomycetes and basidiomycetes, including Saccharomyces species, medically important Candida species, and phylloplane basidiomycetous yeast species. Though the species within each group selected are closely related and have relatively similar rDNA sequences, they were clearly differentiated by PCR SSCP analysis of the ITS1 region, given the amplified fragments were less than 350 bp in sizes. By using SSCP analysis for rapid screening of yeast strains with different rDNA sequences, species diversity existing in a large collection of yeast strains from natural sources were effectively and thoroughly investigated with substantially reduced time and cost in subsequent DNA sequencing.