E. coli W3110 not accepting two plasmids

Duncan Clark Duncan at genesys.demon.co.uk
Wed Mar 22 12:13:43 EST 1995

In article: <Ralf.Morgenstern-220395101023 at micgt.imm.ki.se>  Ralf.Morgenstern at imm.ki.se (Ralf Morgenstern) writes:
> We have a problem when trying to put multiple plasmids into the E. coli
> host W 3110.

> The amp(r) plasmid is an expression construct similar to the pet series
> vector with both a T7 and lac promoter based on pSPORT.
> The kana(r) plasmid contains a temperature inducible T7 RNA polymerase and
> is based on pBR 322.
> The chl(r) plasmid expresses lysozyme (plys SL).
> It is very puzzling that the double  plasmid containing E. coli can grow on
> the double antibiotic plates but not in the same liquid media (it appears
> that amp(r) is selectively lost).
> The amp(r) and chl(r) resistant plasmids can coexist in other E. coli hosts
> (BL-21 (DE-3)).

> Question: Are different pairs of plasmids incompatible in certain strains
> of bacteria? Has anyone else encountered similar problems and (hopefully)
> solved them.

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