Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 12/25/2004
Publication Date: 3/1/2006
Citation: Kurtzman, C.P., Piskur, J. 2006. Taxonomy and phylogenetic diversity among the yeasts. In: Sunnerhagen, P. and Piskur, J., editors. Comparative Genomics: Using Fungi as Models. Vol. 15. Berlin: Springer-Verlag, Berlin. p. 29-46.
Technical Abstract: Yeasts are fungi that predominantly exist as unicellular organisms. However, some yeasts can become multicellular through formation of strands of elongated buds known as pseudohyphae, or through the formation of true hyphae that have well developed crosswalls like those seen in typical filamentous fungi. Yeasts are found among both the ascomycetes and the basidiomycetes. Ascomycetous yeasts, such as Saccharomyces, are found in just one of the three major ascomycete genetic lineages, whereas basidiomycetous yeasts are distributed among all three major basidiomycete lineages. All yeasts share in common vegetative reproduction by budding or fission and sexual states that are unenclosed in fruiting bodies. Yeasts are often difficult to identify and the most reliable method is through gene sequencing. Multiple genes are required for an in-depth understanding of species boundaries, but the partial sequence of the gene for large subunit ribosomal RNA is effective for rapid identification of most species and forms the basis for a variety of commercial identification systems. Understanding species relationships requires comparisons of sequences from a wide variety of genes, and this is necessary to define genera and to guide genomic and proteomic studies. At present, it is estimated that less than one percent of all yeasts are known. However, in the last 10 years, the number of known species has about doubled, primarily because of the availability of gene sequence databases.