Hello,
I am looking for somebody with knowledge about S. cerevisiae yeast and petit colonies.
Cheers,
Estefania
I cryopreserved yeast using a new methodology and then recovered the culture and grew it sucessfully. It has been published that cryopreservation produces less petit colonies than freeze-drying but in this case I did see some petit colonies (although i did not do any tests to identify them, it was just a visual assessment so I am not really sure).
Maybe you can recommend me some way to identify them in a plate culture? So maybe I can see if my methodology preserves healthier yeast cells than the standard way.
Thanks in advance.
Estefania
If I understood you well, your aim is to preserve healthier cells and not petit colonies, right? I saw a paper that describes a way to detect petit colonies in a plate culture: The Jessica A. Hill and Sarah P. Otto, 2007. Role of Pleiotropy in the Maintenance of Sex in Yeast. GENETICS. vol. 175 no. 3 1419-1427. https://doi.org/10.1534/genetics.106.059444
The way that I preserve my S. cerevisiae strain is growing them overnight on 5 mL YPD (on a falcon tube 50 mL) shaking on 180 rpm. On the next day I centrifuge (3000 rpm 5 min), discard the supernatant, resuspend the cells with 500 microliters of fresh YPD media and add the same amount of glycerol 50% to have a stock on glycerol 25% preserved on -80C. I guess the fresh media helps to preserve and therefore keeps the cells healthier.
I hope that I could help somehow.
All the best,
Karen
Dear Estefania,
The simplest way would be to streak out some of those petite-looking colonies on YPG agar (2% peptone, 1% yeast extract, 3% glycerol, 2% agar) and check for growth. Petites cannot utilize non-fermentable carbon sources (e.g. ethanol and glycerol).
Following this, if you want to see if your cryopreservation method results in less petite colonies, you could see how many colonies from old and new preserved stocks grow on YPG agar- either by directly plating serial dilutions directly onto it or replica plating cultures grown on YPD onto YPG plates.
Hope this helps,
Arun
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