no plasmid extracted - low copy number - (Dec/07/2007 )

hi,
i extracted pACYC-derived plasmids but no DNA was detected on gel. the final concentration of Chloromycetin i used was 25ug/ml, i tried 2ml and 15ml respectively, but failed to extract any plasmid DNA. what's the reason?
thanks.

I think you were growing cultures that lost the plasmid.
Try starting a culture from a fresh colony