''Saccharomyces'' is a
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
fungi
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...
that includes many species of
yeast
Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...
s. ''Saccharomyces'' is from
Greek
Greek may refer to:
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group
*Greek language, a branch of the Indo-European language family
**Proto-Greek language, the assumed last common ancestor of all kno ...
σάκχαρον (sugar) and μύκης (fungus) and means ''sugar fungus''. Many members of this genus are considered very important in food production where they are known as
brewer's yeast
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been o ...
,
baker's yeast
Baker's yeast is the common name for the strains of yeast commonly used in baking bread and other bakery products, serving as a leavening agent which causes the bread to rise (expand and become lighter and softer) by converting the fermentable ...
and
sourdough starter
Sourdough is a type of bread that uses the fermentation by naturally occurring yeast and lactobacillus bacteria to raise the dough. In addition to leavening the bread, the fermentation process produces lactic acid, which gives the bread its dis ...
among others. They are unicellular and
saprotrophic
Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ...
fungi. One example is ''
Saccharomyces cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...
'', which is used in making
bread
Bread is a baked food product made from water, flour, and often yeast. It is a staple food across the world, particularly in Europe and the Middle East. Throughout recorded history and around the world, it has been an important part of many cu ...
,
wine
Wine is an alcoholic drink made from Fermentation in winemaking, fermented fruit. Yeast in winemaking, Yeast consumes the sugar in the fruit and converts it to ethanol and carbon dioxide, releasing heat in the process. Wine is most often made f ...
, and
beer
Beer is an alcoholic beverage produced by the brewing and fermentation of starches from cereal grain—most commonly malted barley, although wheat, maize (corn), rice, and oats are also used. The grain is mashed to convert starch in the ...
, and for human and animal health. Other members of this genus include the wild yeast ''
Saccharomyces paradoxus
''Saccharomyces paradoxus'' is a wild yeast and the closest known species to the baker's yeast ''Saccharomyces cerevisiae''. It is used in population genomics and phylogenetic studies to compare its wild characteristics to laboratory yeasts.
Eco ...
'' that is the closest relative to ''S. cerevisiae'', ''
Saccharomyces bayanus
''Saccharomyces bayanus'' is a yeast of the genus ''Saccharomyces'', and is used in winemaking and cider fermentation, and to make distilled beverages. ''Saccharomyces bayanus'', like ''Saccharomyces pastorianus'', is now accepted to be the resul ...
'', used in making wine, and ''
Saccharomyces cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...
''
var. ''boulardii'', used in medicine.
Morphology
Colonies
A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their '' metropole'' (or "mother country"). This separated rule was often or ...
of ''Saccharomyces'' grow rapidly and mature in three days. They are flat, smooth, moist, glistening or dull, and cream in color. The inability to use nitrate and ability to ferment various
carbohydrate
A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...
s are typical characteristics of ''Saccharomyces''.
Cellular morphology
Generally, they have a diameter of 2–8 μm and length of 3–25 μm.
Blastoconidia (cell
buds
In botany, a bud is an undeveloped or Plant embryogenesis, embryonic Shoot (botany), shoot and normally occurs in the axil of a leaf or at the tip of a Plant stem, stem. Once formed, a bud may remain for some time in a dormancy, dormant conditi ...
) are observed. They are unicellular, globose, and ellipsoid to elongate in shape. Multilateral (multipolar) budding is typical. Pseudohyphae, if present, are rudimentary.
Hyphae
A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium.
Structure
A hypha consists of one o ...
are absent.
''Saccharomyces'' produces
ascospores
In fungi, an ascospore is the sexual spore formed inside an ascus—the sac-like cell that defines the division Ascomycota, the largest and most diverse division of fungi. After two parental nuclei fuse, the ascus undergoes meiosis (halving of ...
, especially when grown on V-8 medium, acetate ascospor
agar
Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from " ogonori" and " tengusa". As found in nature, agar is a mixture of two components, t ...
, or Gorodkowa medium. These ascospores are globose and located in asci. Each ascus contains 1–4 ascospores. Asci do not rupture at maturity. Ascospores are stained with Kinyoun stain and ascospore stain. When stained with
Gram stain
Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. It may also be used to diagnose a fungal infection. The name comes ...
, ascospores appear
Gram-negative
Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...
, while vegetative cells appear
Gram-positive
In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.
The Gram stain is ...
.
History
The presence of yeast in beer was first suggested in 1680, although the genus was not named ''Saccharomyces'' until 1837. It was not until 1876 that
Louis Pasteur
Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist, pharmacist, and microbiologist renowned for his discoveries of the principles of vaccination, Fermentation, microbial fermentation, and pasteurization, the la ...
demonstrated the involvement of living organisms in fermentation and in 1883, Emil C. Hansen isolated brewing yeast and propagated the culture, leading to the discovery of the importance of yeast in brewing. The use of microscopes for the study of yeast morphology and purity was crucial to understanding their functionality.
Use in brewing
Brewing yeasts are
polyploid
Polyploidy is a condition in which the biological cell, cells of an organism have more than two paired sets of (Homologous chromosome, homologous) chromosomes. Most species whose cells have Cell nucleus, nuclei (eukaryotes) are diploid, meaning ...
and belong to the genus ''Saccharomyces''. The brewing strains can be classified into two groups; the ale strains (''
Saccharomyces cerevisiae
''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...
'') and the lager strains (''
Saccharomyces pastorianus
''Saccharomyces pastorianus'' is a yeast used industrially for the production of lager beer, and was named in honour of Louis Pasteur by the German Max Reess in 1870. This yeast's complicated genome appears to be the result of Hybridisation (bio ...
'' or ''
Saccharomyces carlsbergensis
''Saccharomyces pastorianus'' is a yeast used industrially for the production of lager beer, and was named in honour of Louis Pasteur by the German Max Reess in 1870. This yeast's complicated genome appears to be the result of hybridisation be ...
'' in the old taxonomy). Lager strains are a hybrid strain of ''S. cerevisiae'' and ''
S. eubayanus'' and are often referred to as bottom fermenting. In contrast, ale strains are referred to as top fermenting strains, reflecting their separation characteristics in open square fermenters. Although the two species differ in a number of ways, including their response to temperature, sugar transport and use, the ''S. pastorianus'' and ''S. cerevisiae'' species are closely related within the genus ''Saccharomyces''.
''Saccharomyces'' yeasts can form symbiotic matrices with bacteria, and are used to produce
kombucha
Kombucha (also tea mushroom, tea fungus, or Manchurian mushroom when referring to the Microbiological culture, culture; Latin name ''Medusomyces gisevii'') is a fermented beverage, fermented, effervescent, Sweetened beverage, sweetened black ...
,
kefir
Kefir ( ; alternative spellings: kephir or kefier; ; ; ) is a Fermented milk products, fermented milk drink similar to a thin yogurt or ayran that is made from kefir grains, a specific type of mesophilic SCOBY, symbiotic culture. It is prep ...
and
ginger beer
Traditional ginger beer is a sweetened and carbonated, usually non-alcoholic beverage. Historically it was produced by the natural fermentation of prepared ginger spice, yeast and sugar.
Modern ginger beers are often mass production, manufactur ...
.
''Saccharomyces fragilis'', for example, is part of kefir cultures and is being grown on the
lactose
Lactose is a disaccharide composed of galactose and glucose and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from (Genitive case, gen. ), the Latin word for milk, plus the suffix ''-o ...
contained in
whey
Whey is the liquid remaining after milk has been curdled and strained. It is a byproduct of the manufacturing of cheese or casein and has several commercial uses. Sweet whey is a byproduct resulting from the manufacture of rennet types of hard c ...
(as a byproduct in
cheesemaking
Cheesemaking (or caseiculture) is the craft of making cheese. The production of cheese, like many other food preservation processes, allows the nutritional and economic value of a food material, in this case milk, to be preserved in concentrate ...
) to be used as animal
fodder
Fodder (), also called provender (), is any agriculture, agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, domestic rabbit, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food ...
itself.
Pathology
''Saccharomyces'' cause food spoilage of sugar-rich foods, such as maple sap, syrup, concentrated juices and
condiments
A condiment is a preparation that is added to food, typically after cooking, to enhance the flavour, to complement the dish or to impart a specific flavor. Such specific flavors generally add sweetness or pungency, or sharp or piquant flavors. ...
.
Case report suggest extended exposure to ''S. cerevisiae'' can cause
hypersensitivity
Hypersensitivity (also called hypersensitivity reaction or intolerance) is an abnormal physiological condition in which there is an undesirable and adverse immune response to an antigen. It is an abnormality in the immune system that causes Imm ...
in humans.
See also
*
Mating of yeast
The mating of yeast, also known as yeast sexual reproduction, is a biological process that promotes genetic diversity and adaptation in yeast species. Yeast species, such as ''Saccharomyces cerevisiae'' (baker's yeast), are single-celled eukaryot ...
*
''Saccharomyces cerevisiae'' virus L-A
*
''Schizosaccharomyces pombe'' (fission yeast)
References
External links
''Saccharomyces'' at Milk the Funk Wiki''Saccharomyces'' Genome Database
{{Authority control
Ascomycota genera
Gut flora
Yeasts used in brewing
Taxa described in 1838
Taxa named by Franz Meyen