Lac operon curing?

[Doug Pecota]

     I was told that there is a method for selecting cells which lack the 
lac operon by killing cells that contain it?  The person I spoke with was 
unable to give me a reference for how this is done.  If anyone is 
familiar with or has information about this method could they please 
E-mail me (pecota at eng.uci.edu) or post.

P.S.  I know how to grow/detect cells containing the lac operon by 
growing on MacConkey or IPTG/X-Gal agar.

Thanks

Doug Pecota
University of California Irvine