No expression in liquid media?!

Morris Waskar mwaskar at
Sat Oct 20 03:55:30 EST 2001

gerchman at Princeton.EDU (Yoram Gerchman) wrote in message news:<Pine.SOL.4.10.10110161956140.24855-100000 at tucson.Princeton.EDU>...
> Greetings netters
> We are trying to express a fluorescence protein in E. coli. We cloned it
> into the pBad system (Invitrogen) and got nice expression on agar plates
> (although slow- the fluorescence appear only after a few days). When we
> try to expression (e.g. fluorescence) in cells grown in liquid media we
> see nothing We tried varying the arabinose concentration etc but nothing
> worked. Any ideas?
> Thanks Yoram
> ---------------------------------------------------------
> "Support bacteria, it's the only culture some people have."
> Anonymous
> ---

Well, I think that your insert is producing a protein that is toxic to
the cells. On solid media, a few cells producing the protein would
still be able to give a fluorescent colony, even when lysed, while in
liquid media, the protein goes into the medium on cell lysis. you
should try to reduce the induction temperature, probably to 18-25°C so
that the protein is induced slowly, and take samples at different


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