Freezing Bacteria-Liquid N2 OK?

[Aaron Pawlyk]

Kimberly Baldwin (kb44+ at andrew.cmu.edu) 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). 

: I appreciate any and all responses-thanks in advance.

: Kimberly Baldwin

: kbal at med.pitt.edu

: -- 
: Kimberly Baldwin
: kb44+ at andrew.cmu.edu

Well, I always store my transformed bacteria in 15% sterile gylcerol.  I
just add .15 mL of glycerol to .85 mL of a saturated LB culture, vortex until
the glycerol is distributed even and then place on dry ice.  This is the
standard way we store bacteria in the lab I work in.  Bacterial stocks that
have been frozen in this manner and stored at -70oC for over 3 years are
still viable.  

To get a new culture started I keep the frozen stock in dry ice and remove
a small amount of the frozen stock with a sterile toothpick and place into
fresh LB/Amp.  Or I streak this small amount of stock on LB/Amp plates.

			-- Aaron