E. Coli Transformation

[Stephen J. Palmieri]

      I've got the weirdest problem known to mankind concerning my
transformation.  I've got some sort of bacterial contamination that will
not go away.  If  I plate untransformed cells(doesnot matter which strain)
on an LB/Amp plate, nothing grows. But if I transform a ligation reaction
I get these colonies containing no plasmid DNA and have a really bizzare
odor and look in liquid culture.  If I transform a covalently closed
plasmid about 80-90% of the colonies contain plasmid DNA so it is not a
matter of degredation in my minipreps.  I've been using XL1-Blue and SURE
cells because they grow very slow and I can tell a true transformant from
a contaminating colony.  I've sterilized everything I could think of
including changing my source of ddH2O  and increasing the Amp
concentration to 100ug/ml.  Can someone out there please tell me what the
hell is going on?  Anything would be much appreciated.

                           Steve Palmieri