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Yeast (Saccharomyces Cerevisiae): Difference between revisions
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'''''Saccharomyces cerevisiae''''' ('''brewer's yeast''' or '''baker's yeast''') is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been originally isolated from the skin of grapes. It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like ''[[Escherichia coli]]'' as the model bacterium. ''S. cerevisiae'' cells are round to ovoid, 5–10 μm in diameter. It reproduces by budding.<ref>{{cite book|last=Feldmann|first=Horst|title=Yeast. Molecular and Cell bio|date=2010|publisher=Wiley-Blackwell|isbn=978-3527326099}}</ref> | '''''Saccharomyces cerevisiae''''' ('''brewer's yeast''' or '''baker's yeast''') is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been originally isolated from the skin of grapes. It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like ''[[Escherichia coli]]'' as the model bacterium. ''S. cerevisiae'' cells are round to ovoid, 5–10 μm in diameter. It reproduces by budding.<ref>{{cite book|last=Feldmann|first=Horst|title=Yeast. Molecular and Cell bio|date=2010|publisher=Wiley-Blackwell|isbn=978-3527326099}}</ref> | ||
==Model Organism== | |||
[[File:S cerevisiae under DIC microscopy.jpg|thumb|''S. cerevisiae'', [[Differential interference contrast microscopy|differential interference contrast]] image]] | [[File:S cerevisiae under DIC microscopy.jpg|thumb|''S. cerevisiae'', [[Differential interference contrast microscopy|differential interference contrast]] image]] | ||
[[Image:20100911 232323 Yeast Live.jpg|thumb|''Saccharomyces cerevisiae''<br />Numbered ticks are 11 micrometers apart.]] | [[Image:20100911 232323 Yeast Live.jpg|thumb|''Saccharomyces cerevisiae''<br />Numbered ticks are 11 micrometers apart.]] | ||
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* ''S. cerevisiae'' research is a strong economic driver, at least initially, as a result of its established use in industry. | * ''S. cerevisiae'' research is a strong economic driver, at least initially, as a result of its established use in industry. | ||
==In the Study of Aging== | |||
For more than five decades ''S. cerevisiae'' has been studied as a model organism to better understand aging and has contributed to the identification of more mammalian genes affecting aging than any other model organism.{{pmid|22768836}} Some of the topics studied using yeast are calorie restriction, as well as in genes and cellular pathways involved in senescence. The two most common methods of measuring aging in yeast are Replicative Life Span (RLS), which measures the number of times a cell divides, and Chronological Life Span (CLS), which measures how long a cell can survive in a non-dividing stasis state.{{pmid|22768836}} Limiting the amount of glucose or amino acids in the growth medium has been shown to increase RLS and CLS in yeast as well as other organisms.{{pmid|17530929}} At first, this was thought to increase RLS by up-regulating the sir2 enzyme, however it was later discovered that this effect is independent of sir2. Over-expression of the genes sir2 and fob1 has been shown to increase RLS by preventing the accumulation of extrachromosomal rDNA circles, which are thought to be one of the causes of senescence in yeast.{{pmid|17530929}} The effects of dietary restriction may be the result of a decreased signaling in the TOR cellular pathway.{{pmid|22768836}} This pathway modulates the cell's response to nutrients, and mutations that decrease TOR activity were found to increase CLS and RLS.{{pmid|22768836}}{{pmid|17530929}} This has also been shown to be the case in other animals.{{pmid|22768836}}{{pmid|17530929}} A yeast mutant lacking the genes Sch9 and Ras2 has recently been shown to have a tenfold increase in chronological lifespan under conditions of calorie restriction and is the largest increase achieved in any organism.{{pmid|18225956}} | For more than five decades ''S. cerevisiae'' has been studied as a model organism to better understand aging and has contributed to the identification of more mammalian genes affecting aging than any other model organism.{{pmid|22768836}} Some of the topics studied using yeast are [[Caloric Restriction|calorie restriction]], as well as in genes and cellular pathways involved in [[Senecent Cells|senescence]]. The two most common methods of measuring aging in yeast are Replicative Life Span (RLS), which measures the number of times a cell divides, and Chronological Life Span (CLS), which measures how long a cell can survive in a non-dividing stasis state.{{pmid|22768836}} Limiting the amount of glucose or amino acids in the growth medium has been shown to increase RLS and CLS in yeast as well as other organisms.{{pmid|17530929}} At first, this was thought to increase RLS by up-regulating the [[SIRT2|sir2]] enzyme, however it was later discovered that this effect is independent of sir2. Over-expression of the genes sir2 and fob1 has been shown to increase RLS by preventing the accumulation of extrachromosomal rDNA circles, which are thought to be one of the causes of senescence in yeast.{{pmid|17530929}} The effects of dietary restriction may be the result of a decreased signaling in the TOR cellular pathway.{{pmid|22768836}} This pathway modulates the cell's response to nutrients, and mutations that decrease TOR activity were found to increase CLS and RLS.{{pmid|22768836}}{{pmid|17530929}} This has also been shown to be the case in other animals.{{pmid|22768836}}{{pmid|17530929}} A yeast mutant lacking the genes Sch9 and Ras2 has recently been shown to have a tenfold increase in chronological lifespan under conditions of calorie restriction and is the largest increase achieved in any organism.{{pmid|18225956}} | ||
Mother cells give rise to progeny buds by mitotic divisions, but undergo replicative aging over successive generations and ultimately die. However, when a mother cell undergoes meiosis and gametogenesis, lifespan is reset.{{pmid|21700873}} The replicative potential of gametes (spores) formed by aged cells is the same as gametes formed by young cells, indicating that age-associated damage is removed by meiosis from aged mother cells. This observation suggests that during meiosis removal of age-associated damages leads to rejuvenation. However, the nature of these damages remains to be established. | Mother cells give rise to progeny buds by mitotic divisions, but undergo replicative aging over successive generations and ultimately die. However, when a mother cell undergoes meiosis and gametogenesis, lifespan is reset.{{pmid|21700873}} The replicative potential of gametes (spores) formed by aged cells is the same as gametes formed by young cells, indicating that age-associated damage is removed by meiosis from aged mother cells. This observation suggests that during meiosis removal of age-associated damages leads to rejuvenation. However, the nature of these damages remains to be established. | ||