Curing plasmids from a strain

K N and P J Harris ecoli at cix.compulink.co.uk
Wed Jun 11 11:38:36 EST 1997

> ==========
> bionet/microbiology #6086, from chris.michiels at agr.kuleuven.ac.be, 
1876 chars, Wed  04 Jun 1997 14:03:21 -0
> Comment to 6078.
> ----------
> Article: 7138 of bionet.microbiology
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> From: Chris Michiels <chris.michiels at agr.kuleuven.ac.be>
> Newsgroups: bionet.microbiology
> Subject: Re: Curing plasmids from a strain
> Date: Wed, 04 Jun 1997 14:03:21 -0700
> Organization: K.U.Leuven
> Message-ID: <3395D819.7CB at agr.kuleuven.ac.be>
> References: <916D87B9F at rose.le.ac.uk>
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> Dr Martin Goldberg wrote:
> > 
> > I have a strain with a pBR322-based plasmid and I want to cure the
> > strain of this plasmid. Is there any way of achieving this without
> > using agents such as ethidium bromide? I am considering 
> > the plasmid by transforming the strain with pBR322 or one of its
> > other derivatives and selecting for this latter plasmid. Has anybody 
got an
> > opinion on this approach or are there any more elegant methods?
> > If your pBR322-derivative still confers tetracyclin resistance on 
the host (E. coli?), 
> you could try with a positive selection procedure for loss of 
tetracyclin resistance. 
> This has been described for E. coli, and is based on the fact that 
(pBR-based) Tc 
> resistance results in sensitivity to fusaric acid. Loss of TC 
resistance can be 
> selected by resistance to fusaric acid. This allows you to select for 
spontaneous loss 
> of the plasmid. If you don't find a reference, I'm sure I can find it. 
> Best regards,
> Chris Michiels
> K.U.Leuven
> Lab Food Microbiology
> Leuven, Belgium
A standard way of "accidentally" curing Rhizobium of plasmids is to keep 
them at elevated temperatures that are not "lethal". This is the least 
invasive way of losing plasmids.
Peter Harris,
University of Reading, UK.

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