Need ideas for Lac+/- screening in Neisseria

Mark D. Garfinkel mg16 at
Fri Jul 28 10:04:08 EST 1995

In article <3v8cfs$8al at>,
Hank Seifert <h-seifert at> wrote:
>We are attempting a screen for constiutive regulatory mutants that allow 
>expression of a gene fused to a LacZ reporter in the genome of the 
>gonococcus.  The bacterial colonies grow fine on Xgal unless they express
>the LacZ. Then they growth slowly and are hard to recover.
>We presume the indole derivative cleaved from the Xgal by betea-gal 
>is toxic for the bugs.
	Growth of the lacZ reporter on media lacking Xgal is OK, then?
Are they able to grow with lactose as sole carbon source? In other words,
is the lacZ reporter deleterious only when Xgal is around? If so, here's
a wild-ass idea: the Br-Cl-indole derivative is screwing around with host
tryptophan biosynthesis. Try supplementing with extra trp.

Mark D. Garfinkel (e-mail: mg16 at
(c) 1995; all rights reserved. Permission granted for Usenet quotation
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