In article <cdsouza-2611971812320001 at adams-centris660av.tamu.edu>
cdsouza at bio.tamu.edu (Biology) writes:
> Does anybody know of a nifty way to select for lac- E.coli on LB media. I
> am aware of positive selection vectors but is there a substrate that's
> converted to a toxic product? Thanks. Cletus
>cdsouza at bio.tamu.edu
Two classic selections for lac- are TONPG which is a toxic compound
that is accumulated by lac permease. This selection gives lacY- mutants
some of which are also deletions of Z or polar mutations in Z.
selection on lactose using a galE mutant strain. lacZ converts Lac to
glu and gal, and growth on gal with a galE mutant is toxic.
I would suggest looking at either volume of Miller (CSH 1972 Expts in
Molecular Genetics, or CSH 1992, A short course in bacterial genetics.)
The older volume discusses more compounds, the newer volume describes
the above 2 in a bit more detail.
P.S. Give Ry Young a call for more info.
Michael Benedik
Department of Biochemical Sciences
University of Houston
benedik at uh.edu
