Cloning an antimicrobial peptide that may kill the host - (Jul/29/2014 )

I would like to clone into a plasmid an antimicrobial peptide driven by an acetamide promoter that kills gram positive bacteria with a MIC bellow 1.5 uM. I would like to clone it in a plasmid that replicates quite well in gram negative cells. Unfortunately, I found later that it can be toxic for gram negative bacteria (e. coli Dh5, top 10 and etc) in concentrations over 5.9 uM. Is there any trick I could do to increase the amount of cells hosting the new plasmid?

Clone it into a low copy-number plasmid such as pBR322 or any of its derivatives.