Question about Glycerol freezing - (Apr/22/2020 )

Hi all,

I recently moved into a new lab that has a -80 C freezer, up untill now I used to freeze my cells in a standard -20 C freezer. the freezing  protocol I'm using consists of a 1-step Glycerol:PBS 50:50 freeze.

I'm thinking about moving my stocks to the -80 C freezer, and would love to hear thoughts on why it would be better for them. Also, in case I'm deciding to move my currently -20 C frozen tubes into -80 C, is there any intermediate step I should be aware of?

My stock currently consists of:

E.Coli ATCC/ Listeria Mono ATCC/ Salmonella Thypi/ Candida Albicans ATCC/ Penicilum Rubens ATCC

And several more gram negative Bacteria.

Thanks!

Ziv

Storage at -80C is more stable than at -20C. Degradation is slowed further by the lower temperature.

50:50 glycerol should be fine at -80C although the solution will freeze. The glycerol will reduce ice crystal formation so more cells will remain viable when defrosted than without the glycerol.

Thank you! So I can just go ahead and move my tubes to the -80 freezer? no intermediate step?(for example dry Nitrogen treatment) 

You should be able to just transfer them. If, however, you have doubts, then transfer one of each strain to the -80C, holding the rest at -20C during this test. After a few days plate some to compare viability.

-80C is generally used for long term storage of aliquots.

Thanks again!