Saccharomyces

Taxobox


image_width = 320px
name = "Saccharomyces"
regnum = Fungi
phylum = Ascomycota
subphylum = Saccharomycotina
classis = Saccharomycetes
ordo = Saccharomycetales
familia = Saccharomycetaceae
genus = "Saccharomyces"
genus_authority = (E.C. Hansen 1838) Meyen
subdivision_ranks = Species
subdivision =
* "Saccharomyces bayanus"
* "Saccharomyces boulardii"
* "Saccharomyces bulderi"
* "Saccharomyces cariocanus"
* "Saccharomyces cariocus"
* "Saccharomyces cerevisiae"
* "Saccharomyces chevalieri"
* "Saccharomyces dairenensis"
* "Saccharomyces ellipsoideus"
* "Saccharomyces martiniae"
* "Saccharomyces monacensis"
* "Saccharomyces norbensis"
* "Saccharomyces paradoxus"
* "Saccharomyces pastorianus"
* "Saccharomyces spencerorum"
* "Saccharomyces turicensis"
* "Saccharomyces unisporus"
* "Saccharomyces uvarum"
* "Saccharomyces zonatus"

"Saccharomyces" is a genus in the kingdom of fungi that includes many species of yeast. "Saccharomyces" is from Latin meaning "sugar fungi". Many members of this genus are considered very important in food production. One example is "Saccharomyces cerevisiae", which is used in making wine, bread, and beer. Other members of this genus include "Saccharomyces bayanus", used in making wine, and "Saccharomyces boulardii", used in medicine.

Morphology

Colonies of "Saccharomyces" grow rapidly and mature in 3 days. They are flat, smooth, moist, glistening or dull, and cream to tannish cream in color. The inability to utilize nitrate and ability to ferment various carbohydrates are typical characteristics of "Saccharomyces".

Cellular morphology

Blastoconidia (cell buds) are observed. They are unicellular, globose, and ellipsoid to elongate in shape. Multilateral (multipolar) budding is typical. Pseudohyphae, if present, are rudimentary. Hyphae are absent.

"Saccharomyces" produces ascospores, especially when grown on V-8 medium, acetate ascospor agar, 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, ascospores are gram-negative while vegetative cells are gram-positive.

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 demonstrated the involvement of living organisms in fermentation and in 1888, Hansen isolated brewing yeast and propagated leading to 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 yeast are polyploid and belong to the "Saccharomyces" genera. The brewing strains can be classified into two groups; the ale strains ("Saccharomyces cerevisiae", generally used for ale and stout) and the lager strains ("Saccharomyces pastorianus" or "Saccharomyces uvarum"). Lager strains are a hybrid strain of "S. cerevisiae" (ale strains) and "S. bayanus" (wine strains) 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 utilisation, the "S. pastorianus" and "S. cerevisiae" species are closely related within the "Saccharomyces" genus.

"Saccharomyces" yeasts can form symbiotic matrices with bacteria, and are used to produce kombucha, kefir and ginger beer.

Pathology

Saccharomyces cause food spoilage of sugar-rich food, such as maple sap, syrup, concentrated juices and condiments. [ [http://gchava.myweb.uga.edu/organisms.html MICROBES INVOLVED IN FOOD SPOILAGE] Authors: Gabriel Chavarria, Julia Neal, Parul Shah, Katrina Pierzchala, Bryant Conger]

Long exposure to S. cerevisiae can result in hypersensitivity [cite journal |author=Yamamoto Y, Osanai S, Fujiuchi S, "et al" |title= [Saccharomyces-induced hypersensitivity pneumonitis in a dairy farmer: a case report] |language=Japanese |journal=Nihon Kokyuki Gakkai Zasshi |volume=40 |issue=6 |pages=484–8 |year=2002 |pmid=12325333 |doi=]

ee also

*Mating of yeast
*Yeast
*Saccharomyces cerevisiae virus L-A

References

External links

* [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=4930 "Saccharomyces" at NCBI taxonomy browser]