Yeasts are eukaryotic microorganisms classified in the kingdom Fungi, with 1,500 species currently described (estimated to be 1% of all fungal species). Yeasts are unicellular, although some species with yeast forms may become multicellular through the formation of a string of connected budding cells known as pseudohyphae, or false hyphae, as seen in most molds. Yeast size can vary greatly depending on the species, typically measuring 3–4 µm in diameter, although some yeasts can reach over 40 µm. Most yeasts reproduce asexually by mitosis, and many do so by an asymmetric division process called budding.
By fermentation, the yeast species Saccharomyces cerevisiae converts carbohydrates to carbon dioxide and alcohols – for thousands of years the carbon dioxide has been used in baking and the alcohol in alcoholic beverages. It is also a centrally important model organism in modern cell biology research, and is one of the most thoroughly researched eukaryotic microorganisms. Researchers have used it to gather information about the biology of the eukaryotic cell and ultimately human biology. Other species of yeast, 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, and 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, but the phylogenetic diversity of yeasts is shown by their placement in two separate phyla: the Ascomycota and the Basidiomycota. The budding yeasts ("true yeasts") are classified in the order Saccharomycetales.
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... In yeast, acyl-CoAsterol acyltransferase (ASAT) is functionally equivalent to ACAT ... Although studies in vitro and in yeast suggest that the acyl-CoA binding protein (ACBP) may modulate long-chain fatty acyl-CoA (LCFA-CoA) distribution, the ... Researchers have identified two genes in yeast, SAT-1 and SAT-2, that encode for the different isozymes of ASAT ...
... It has been highly studied in the budding yeast S ... cerevisiae, and the fission yeast S ... that phosphorylate a variety of target substrates (over 75 have been identified in budding yeast) phosphorylation of these proteins leads to cell cycle progression ...
... Numerous yeast-like, round, thick-walled cells are visualized ... Chains of yeast cells are typically formed ... Little tube-like connections are visible between the yeast cells ...
... practice throughout the medieval period, bottom-fermenting yeast seems to have emerged as a hybridization in the early fifteenth century ... that Saccharomyces eubayanus, a yeast native to Patagonia, is responsible for creating the hybrid yeast used to make lager ...
... Yeasts are able to grow in foods with a low pH, (5.0 or lower) and in the presence of sugars, organic acids and other easily metabolized carbon sources ... During their growth, yeasts metabolize some food components and produce metabolic end products ... The growth of yeast within food products is often seen on their surface, as in cheeses or meats, or by the fermentation of sugars in beverages, such as juices, and semi-liquid ...