Yeast

Yeast
Saccharomyces cerevisiae, a species of yeast
Cross-sectional labelled diagram of a typical yeast cell
Scientific classification
Kingdom: Fungi
Phyla and subphyla with yeast species

Ascomycota p. p.

  • Saccharomycotina (true yeasts)
  • Taphrinomycotina p. p.
    • Schizosaccharomycetes (fission yeasts)

Basidiomycota p. p.

  • Agaricomycotina p. p.
    • Tremellomycetes
  • Pucciniomycotina p. p.
    • Microbotryomycetes

Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized.[1][2][3] They are estimated to constitute 1% of all described fungal species.[4]

Some yeast species have the ability to develop multicellular characteristics by forming strings of connected budding cells known as pseudohyphae or false hyphae, or quickly evolve into a multicellular cluster with specialised cell organelles function.[5][6] Yeast sizes vary greatly, depending on species and environment, typically measuring 3–4 μm in diameter, although some yeasts can grow to 40 μm in size.[7] Most yeasts reproduce asexually by mitosis, and many do so by the asymmetric division process known as budding. With their single-celled growth habit, yeasts can be contrasted with molds, which grow hyphae. Fungal species that can take both forms (depending on temperature or other conditions) are called dimorphic fungi.

The yeast species Saccharomyces cerevisiae converts carbohydrates to carbon dioxide and alcohols through the process of fermentation. The products of this reaction have been used in baking and the production of alcoholic beverages for thousands of years.[8] S. cerevisiae is also an important model organism in modern cell biology research, and is one of the most thoroughly studied eukaryotic microorganisms. Researchers have cultured it in order to understand the biology of the eukaryotic cell and ultimately human biology in great detail.[9] Other species of yeasts, such as Candida albicans, are opportunistic pathogens and can cause infections in humans. Yeasts have recently been used to generate electricity in microbial fuel cells[10] and to produce ethanol for the biofuel industry.

Yeasts do not form a single taxonomic or phylogenetic grouping. The term "yeast" is often taken as a synonym for Saccharomyces cerevisiae,[11] but the phylogenetic diversity of yeasts is shown by their placement in two separate phyla: the Ascomycota and the Basidiomycota. The budding yeasts, or "true yeasts", are classified in the order Saccharomycetales,[12] within the phylum Ascomycota.

  1. ^ Piškur, Jure; Compagno, Concetta (2014). Molecular Mechanisms in Yeast Carbon Metabolism. Springer. p. 98. ISBN 978-3-642-55013-3. The second completely sequenced yeast genome came 6 years later from the fission yeast Schizosaccharomyces pombe, which diverged from S. cerevisiae probably more than 300 million years ago.
  2. ^ Cite error: The named reference Kurtzman-2006b was invoked but never defined (see the help page).
  3. ^ Hoffman CS, Wood V, Fantes PA (October 2015). "An Ancient Yeast for Young Geneticists: A Primer on the Schizosaccharomyces pombe Model System". Genetics. 201 (2): 403–23. doi:10.1534/genetics.115.181503. PMC 4596657. PMID 26447128.
  4. ^ Cite error: The named reference Kurtzman-2006a was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Kurtzman-2005 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Yong-2012 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Walker-2002 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Legras-2007 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Ostergaard-2000 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference HelsinkiUniTech-2007 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Kurtzman-1994 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference YeastVirtualLibrary-2009 was invoked but never defined (see the help page).
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