Curing plasmids from a strain

Chris Michiels chris.michiels at agr.kuleuven.ac.be
Wed Jun 4 16:03:21 EST 1997

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 competing-out
> 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. Somewhere...
Best regards,

Chris Michiels
Lab Food Microbiology
Leuven, Belgium

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