Preservation of transformed E. coli

Robert Negm rnegm at
Wed Jun 3 09:37:08 EST 1998

Dear Yersinia,

In response to your question regarding cyropreservation of E. coli. I
typically prepare a 50% solution of glycerol, autoclave it, and when my
cultures containing the appropriate antibiotic reach post-exponential growth
I add 1.0 ml of culture to 1.0 ml of glycrol  (1:1, final 25% glycerol)
solution directly to a sterile cryovial. Mix then freeze at -80°C. Its
important to maintain the microogranism in the presence of the antibiotic,
especially if the strain harbors a plasmid or transposon conferring the
resistance to the antimicrobial. In our lab, we use StrainMan 1.0 from
Caesar Software to manage all of our strain information  for our frozen
stock cultures. The software helps us find strains that were frozen, how
they were frozen, and when. Check it out at


Robert Negm

Yersinia wrote:

> Hello all,
> A  correspondent of mine who's a graduate student asked me a question,
> but some of it's slightly over my head, so I thought I'd pass it along to
> you knowledgeable people:
> <What's the best temperature at which to keep agar stab cultures?  (I'm
> growing pUC19-transformed E. coli in 2XYT agar with a trace of
> ampicillin).  My lab protocol says to keep 'em at room temperature, but
> I'm worried about the ampicillin stability.  My lab advisor says to stick
> 'em in the -20 freezer, but they don't have any cryoprotectants like
> glycerol in them.  At present, I've got them in the fridge at 4 degrees.>
> Thank you for your help.
> Infectionately,
> Yersinia.
> __________________________________________
> "The lab called. Your brain is ready."

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