Submitted to: Yeasts International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: March 29, 2002
Publication Date: N/A
Technical Abstract: For yeasts, as well as for many other groups of microorganisms, use of morphological and physiological properties for species identification and the prediction of natural relationships has often lead to erroneous conclusions. Application of gene sequence analyses provides a genetic means for reliable identification of species and the reconstruction of phylogenetic histories. Practical benefits of this work include databases for development of probes for rapid identification of clinical, agricultural and industrial strains, accurate naming of patent strains and the discovery of new species. Additionally, the predictiveness derived from phylogenetic comparisons can put direction on searches for new species of use in biotechnology. Primary questions include reliable recognition of species and the resolution of deep lineages. The 600-nucleotide D1/D2 domain of 26S rDNA has been sequenced for all known yeasts and provides a ready means for identification of most species. For the D1/D2 domain, conspecific strains show less than 1% divergence, whereas separate species differ by 1% or more substitutions. However, recently evolved species, as well as hybrids, may not be recognized by the preceding criteria. An example is Saccharomyces pastorianus, which is a hybrid of S. cerevisiae and S. bayanus, but has the rDNA repeat of the latter species, and will be identified as S. bayanus when only the rDNA sequences are analyzed. Consequently, several gene sequences may be needed for accurate identification of closely related species. Relationships more distant than the genus level are not well resolved from analysis of a single gene, but analysis of combined gene sequences will give an accurate portrayal of deeper lineages.