BL21 problem

Rafael Maldonado rmaldonado at
Mon Feb 17 14:47:32 EST 2003

Philipp Wechner wrote:

> why do i only get these big colonies with BL21?

It is a fairly common thing, in many different bacterial strains, and 
depending of the antibiotic used in the selection. I also have observed 
it in DH5alpha and HB101. Tetracycline is specially active in making 
different size colonies. My guess is that copy number plasmid is 
different, for some reason, in those plates. I would not bother about this.


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