What are the different kinds of media used for culturing Pichia pastoris and S. cerevisiae?
Following are the rich and minimal media used for culturing Pichia pastoris and S. cerevisiae:
Rich Media:
S. cerevisiae and Pichia pastoris
YPD (YEPD): yeast extract, peptone, and dextrose
YPDS: yeast extract, peptone, dextrose, and sorbitol
Pichia pastoris only
BMGY: buffered glycerol-complex medium
BMMY: buffered methanol-complex medium
Minimal Media (also known as drop-out media):
S. cerevisiae
SC (SD): Synthetic complete (YNB, dextrose (or raffinose or galactose), and amino acids)
Pichia pastoris
MGY: minimal glycerol medium
MD: minimal dextrose
MM: minimal methanol
BMGH: buffered minimal glycerol
BMMH: buffered minimal methanol
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Will the Saccharomyces cerevisiae alpha-factor secretion signal be recognized by Schizosaccharomyces pombe?
S. pombe cannot generate P factor when P factor is replaced for alpha in the alpha factor gene. It can, however, produce alpha factor when alpha is replaced for P in the P factor gene. This is negative evidence that S. pombe can process its own mating factor cleavage sites, but not all the cleavage sites of the S. cerevisiae alpha factor. It is better to use a more generic signal sequence (rather than a pre- pro- signal sequence such as alpha). If it is necessary to go the pre- pro- route, it is better to use the S. pombe P factor leader rather than the S. cerevisiae alpha leader.
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For galactose induction of expression in S. cerevisiae, can I include additional carbon sources in the media to increase yeast growth without repressing expression from the GAL promoter?
Some researchers choose to grow yeast in medium containing 2% galactose as the sole carbon source during induction. However, yeast typically grow more quickly in induction medium containing 2% galactose plus 2% raffinose. Raffinose is a good carbon source for yeast, and unlike glucose, does not repress transcription from the GAL promoter. Raffinose is a trisaccharide of galactose, glucose, and fructose linked in that order. Most yeast can cleave the glucose-fructose bond, but not the galactose-glucose bond. Fructose is then used as a carbon source.
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Which S. cerevisiae yeast strain do your kits contain?
We offer the INVSc1 yeast strain. It is a diploid strain for expression purposes only. It does not sporulate well and is therefore not suited for yeast genetic studies. The genotype and phenotype of the INVSc1 strain are as follows:
Genotype: MATa his3D1 leu2 trp1-289 ura3-52/MATalpha his3D1 leu2 trp1-289 ura3-52
Phenotype: His-, Leu-, Trp-, Ura-
Note that INVSc1 is auxotrophic for histidine, leucine, tryptophan, and uracil. The strain will not grow in SC minimal medium that is deficient in histidine, leucine, tryptophan, and uracil.
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Can old premixed lithium acetate buffers be used for preparing and transforming Saccharomyces cerevisiae?
Stock buffers of TE, lithium acetate, and PEG can be stored. However, the combined solution used to prepare the cells for transformation must be made fresh every time. There is a loss in transformation efficiency if the solutions are not freshly prepared.
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