Freezing Bacteria-Liquid N2 OK?
rafael at corona.med.utah.edu
Fri Mar 17 21:44:30 EST 1995
On Fri, 17 Mar 1995, Kimberly Baldwin wrote:
> Hello All,
> I was wondering about the feasability of storing frozen bacterial stocks
> under liquid nitrogen vs. storing at -80oC. Are the cells viable? Should
> they first be frozen slowly prior to storing under liquid nitrogen? Or is
> snap freezing them okay? Should they be frozen as glycerol stocks-or is
> DMSO or DMF okay to use instead? I have always in the past stored them at
> -80oC (in glycerol or with DMSO).
You can keep bacterial cells under N2 if you want. -80 is enough to keep
them during years; I suppose in N2 (-120, I think) they will be viable
DMSO is more convenient: it's easy to handle, it don't need autoclaving
and the cells are viable longer; just add at 7% v/v and freeze. I never
used DMF, it's new to me. I'm surprised of seeing in storage cells medium.
Always freeze the cells as faster as you can. The faster way is N2;
a slow feezing process will kill more cells than a fast one. EtOH-dry ice
baths are pretty fast too.
Anyway, putting the tube directly at -80 works fine for most purposes. If
the viabilty decresase 10% doing that, you still have 10^6 cells in 1 ml
vial. That is enough for 20 years of keeping at -80, using DMSO. The limit
with glycerol is around 10 years.
Those data are for E. coli and S. typhimurium.
Rafael Maldonado "You gave to a boy the job
Department of Human Genetics of a man. He's dead."
University of Utah
Salt Lake City, Utah 84112. USA. John Wayne
Rafael at genetics.med.utah.edu
Rafael at corona.med.utah.edu "No por mucho madrugar, amanece
Tlf: 801-581-4429 mas temprano"
More information about the Methods