No Blue Colonies...I'm not that good.

JSUPolek jsupolek at
Tue Feb 19 01:09:05 EST 2002

I'm trying to shotgun clone in chromosomal fragments of a cellulolytic anaerobe
into pUC19.  Everthing has gone well, and I'm using a Rec- strain of E. coli
for transformation. But all I get are white colonies.  NO blue colonies at all,
not even on the control bacteria with unligated plasmid.  Some plates had
X-gal, and some had Bluo-gal.  Some had IPTG and some did not.  Amp
concentration was 10mg/ml, and I did 1:1, 1:10, 1:100, and even 1:1000
dilutions.  Colonies were in numbers in proportion to the dilutions, so they
were my E. coli.  Why didn't any of them turn blue??  I don't necessarily need
the b/w colony selection for what I'm screening for, but it would be helpful. 
I would appreciate any help.  Thank you, S. Polek

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