Ampicillin plates

[Ron Caspi]

Hi everybody

Lately we have been having hard time with ampicillin plates in our
lab. I can't figure out what we're doing wrong: we prepare stock
solution of 100 mg/ml ampicillin in water, and add them to LB medium
just before we pour the plates (not too hot) to a concentration of 100
or 150 ug/ml. Alas, there is a major problem of satelite colonies
growing around the resistant colonies when we spread-plate
transformation mixtures. Any idea?

Thanks for any input

PS It would be best if you could cc your reply to my email, so I won't
miss a reply.
________________________________________________________________________
Ron Caspi
Scripps Institution of Oceanography               Phone   (619) 534-0638
La Jolla  CA  92093-0202                          Fax     (619) 534-7313