Preservation of transformed E. coli

gwallmanning at gwallmanning at
Wed Jun 3 19:59:35 EST 1998

In article <199806020019.UAA11620 at>,
  yersinia at CYBERNEX.NET (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."
Room temp is OK for stab cultures, but I wouldn't regard them as more than a
medium term storage solution (months to a year or two).  I have found sealing
the lid with parafilm to help stop drying out helps extend viability.  For
long term storage freeze-dry or cryofreeze cultures (10-25% glycerol final).
I don't use selection pressure in stabs, but always stab from and plate onto
selective media, and only once had a problem with a large, low-copy plasmid.

Hope this helps,


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