Help! Plaques don't come up.

Andrew Wallace a.wallace at
Thu May 29 03:38:37 EST 1997

Zhong Zhao (BioChem) wrote:
> Hi.
> I am preparing filters for screening Rat Genomic Library. However, I have
> a problem in getting good plaques on plates.
> After overnight in 37C incubator, I see nice plaques but all of them are
> below the surface of topping agarose. The surface of the topping looks
> very shinny. I tried to adjust the topping agarose temp and different
> agarose and all failed.
> Since I do not see plaques on surface, I decide not to make filters since
> there may be nothing there.
> What goes wrong here?
> Please help.
> Thanks much.
> John.

I would also be interested in receiving any advice or information about
this problem, since I am having similar difficulties at the moment using
XL1-Blue transfected with M13 and growing on ordinary LB agar.

Have tried different top agar formulations without success.

Please email any replies directly to me at a.wallace at as there
is usually too much traffic on this group for me to follow by
newsreader. Note also that my reply address has been modified to prevent
spam, so don't just hit "reply".

Thanks for any help,

- note antispam feature in return address. My real address is:
Andrew Wallace,Ph.D., Queens University Belfast,  N. Ireland (UK)   
a.wallace at   

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