ARS | Publication request: OVERVIEW OF THE YEASTS AND THEIR CLASSIFICATION

Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: August 2, 2003
Publication Date: N/A

Technical Abstract: The word yeast is synonymous with bread, beer and wine, products that would not be possible without the fermentative activities of yeasts. For all practical purposes, the taxonomic history of yeasts begins with the name Saccharomyces, which was first proposed for bread and beer yeasts by Meyen in 1838, and defined as a genus by Reess in 1870. Yeasts are found in two groups of fungi, the Ascomycotina and the Basidiomycotina. One of the major scientific questions has been how are the yeasts related to other ascomycetes and basidiomycetes. Are they primitive subgroups or are they reduced forms scattered among the higher fungi? Only recently have there been answers to these questions, which have come from gene sequence analyses. Traditionally, yeasts have been classified from morphology, and from their fermentation of selected sugars and growth reactions on a large variety of carbon and nitrogen compounds. However, the taxonomic conclusions drawn from these tests are often contradictory to relationships determined from traditional genetic crosses and from gene sequence comparisons. The first of the quantitative molecular comparisons was nuclear DNA reassociation and results from these studies demonstrated that many species were incorrectly defined from phenotype. Gene sequence analyses followed and have allowed analyses of broader relationships not possible from nDNA reassociation. These advances are providing a phylogenetic framework for yeast classification and form the basis for many rapid identification tests.