Published Online: 15 NOV 2011
Copyright © 2001 John Wiley & Sons, Ltd. All rights reserved.
How to Cite
Lachance, M.-A. 2011. Yeasts. eLS. .
- Published Online: 15 NOV 2011
Yeasts are a group of eukaryotic fungi with a well-defined cell wall whose growth is either entirely unicellular or a combination of hyphal and unicellular reproduction. The approximately 1500 known yeast species belong to two distinct fungal phyla, the Ascomycota and the Basidiomycota. Within each these phyla, yeasts can be found in several subphyla or classes, reflecting the enormous diversity of their evolutionary origins and biochemical properties. In nature, yeasts are found mainly in association with plants or animals but are also present in soil and aquatic environments. Yeasts grow rapidly and have simple requirements, for which reason they have been used as model systems in biochemistry, genetics and molecular biology. They were the first microorganisms to be domesticated for the production of beer, bread or wine, and they continue to be used for the benefit of humanity in the production of recombinant proteins and other materials.
Yeasts share in common a primarily unicellular mode of reproduction.
Yeasts are phylogenetically diverse, being classified in several classes of two fungal phyla.
The concept of yeast is rooted in history and does not always follow logical biological lines.
Yeasts have a rigid cell wall primarily made up of β-(1–3)-glucan.
Sexual reproduction in yeasts involves the formation of internally formed ascospores or externally formed basidiospores.
Current yeast classification is based on phylogenetic relationships inferred by gene sequencing.
Yeasts grow in nature primarily in association with the plant–insect interface or with warm-blooded animals, but also occur in soil and aquatic habitats.
Yeasts serve as important industrial model systems in research.
Yeasts are of great importance in biotechnology. The main products are alcohol, yeast biomass and recombinant proteins.
A few yeast species cause infections in humans and other animals, but most yeasts act in an opportunistic fashion, in individuals that are immunocompromised.