Are they true positves?

Deb Britt debbritt at
Mon Apr 8 14:15:52 EST 1996

In article
<Pine.A32.3.92a.960404150516.102753B-100000 at>,
Seng-Lai Tan <sltan at> wrote:

> Hi--
> I've just done a yeast 2-hybrid screen using the Clontech Matchmaker kit.
> I made my own library using Stratagene HybridZap kit.  I had some
> pink colonies that grew on -His plates but they looked weird or different
> from positve control Hf7c strain containing P53 and T Ag.  They also didn't
> smell right.  They, nevertheless, turned blue on beta-gal lift assays.
> Although, I was very careful when plating my cells, I now wonder if my
> colonies are contaminants.  Are there any bacteria or any other bugs that
> can grow on -His plates, look pink and use X-gal as subtrate?
> Please help.  Many thanks in advance.
> Thomas

I don't have any personal experience with this, but there are bacteria that
grow on just about anything.  You can easily tell if it is bacterial
contamination by doing a Gram stain, or even by a wet-mount slide.  Check
with someone who has training in Microbiology.  Good luck.
Deborah Britt, Ph.D.
Medical Oncology
RI Hospital/Brown University

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