Need ideas for Lac+/- screening in Neisseria

Stephen Mamber mamber at
Mon Jul 31 18:34:49 EST 1995

In article <3v8cfs$8al at>, h-seifert at (Hank Seifert) says:

>We presume the indole derivative cleaved from the Xgal by betea-gal 
>is toxic for the bugs.
>Does anyone have other screens for beta-gal activity that can be done on
>a solid medium? 
Solution 1:  Try bluo-gal, Gibco/BRL #15519-028, an expensive $200/g.  
This is also a halogenated indolyl derivative, but you may be luckier
with this.  

Solution 2:  Make master-plates on X-gal-less agar and replica-plate to
X-gal-containing media.  At least that way, you can identify the lethals
as your putative fusion strains and then perform liquid B-gal assays using
something less toxic, like ONPG.

Solution 3:  Good old MacConkey agar, if your Neisseria can stand it, or
a formulation without crystal violet and/or bile salt (see a Difco Manual,
or make your own formulation).  As long as the neutral red isn't toxic.

Solution 4:  4-Methylumbelliferyl-B-D-gal, Sigma#M1633, a cheap $25.35/g.
But you may kill your cells visualizing it under UV fluorescence (so you
may need to replica-plate).  Also, I don't have any personal experience 
with MUGal.  Try one of these refs:  Appl. Environ. Microbiol. 59:3534,
1993; J. Bacteriol. 175:6902, 1993.

I'm sure I can think of other tricks - email me if you need more advice.


mamber at  

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