DH5a w/o plasmid growing on Amp?

Ted M. tedm at darkwing.uoregon.edu
Wed Feb 28 01:24:11 EST 1996

Perhaps a quick trip to a microscope (there's probably one down the hall)
will shed some light on this mystery. It is possible to have a plasmid
integrate into the bacterial chromasome, since the beta lactamase gene is
probably coating all of our benches...but unlikely!

Ted Michelini

In article <4gkv0d$1ff at nntp3.u.washington.edu>, Karen Peck-Miller
<kpeck-miller at sci.nwfsc.noaa.gov> wrote:

> I have a one year old frozen glycerol stock of DH5a which is showing 
> some growth on Lb-Amp plates.  I've ruled out any problem with the 
> plates themselves, and the cultures from this stock have previously 
> behaved as expected (that is, unable to grow on ampicillin).
> I was so surprised by this that I thought I'd ask if anyone else has 
> seen this happen.
> Karen

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