How to cure E. coli from a plasmid?

Duke Groebe drg at
Wed Dec 8 10:13:26 EST 1993

In article <16789.jdboer at>, jdboer at SOL.UVIC.CA ("Johan de Boer")
> Hi,
> I have to remove a plasmid with amp resistance from a bacterial strain. I 
> have heard about using acridine orange to cure the strain, but does someone 
> know how to really do it?
> Johan de Boer
> jdboer at
> Victoria, Canada

I got the following protocol from an old bacteriologist and it seemed to
work for me (I only did it once, though):

1.  Grow bug with plasmid overnight (approx. 2e09 cells/ml).

2.  Dilute to 1e04 cells/ml in LB, 0.1M Tris, pH 7.6, 20ug/ml acridine

3.  Grow o/n in dark.

4.  Replica plate to find "cured" bug.

Good luck,


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