William B. Melchior, Jr. wmelchior at
Wed Dec 14 14:54:51 EST 1994

In article <452235192wnr at>, Duncan at (Duncan Clark) says:
>In article: <D0KEw2.2uG at>  bipin dalmia <dalmiabk at> writes:
>> >cell lawns appearing on our transformation plates containing amp.  First
>> >the transformants appear and then a few hours later the lawn becomes
>> >visible....
>> the 'satellite' colony effect that you are seeing is due to the
>> ampicillin around the true transformants getting degraded by some
>> secreted b-lactamase and/or inactivated by the lowering of pH when cells
>> grow....

I avoid the problem by putting the plates at 30 deg instead of 37.  Growth of the 
satellite colonies is greatly delayed (ie, none after overnight growth).

Bill M.

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