Plasmid copy number per cell as determined by qPCR.

<p>Plasmid copy numbers were determined in <i>E. coli</i> DH5α harboring one or two vectors. In pink is the copy number of all vectors with the p15A <i>ori</i>; in blue is the copy number of pGEX-6p-1, which is controlled by the pBR322 <i>ori</i>. Plasmids pSAM and pGEX-6p-1 retained their copy numbers both individually and when cells were doubly transformed. This trend for pSAM was similar to that observed with pACYCDuet (a member of the p15A family) both individually and when doubly transformed with pGEX-6p-1. Plasmid pSAMRNAI causes a decrease in the copy number of pGEX-6p-1 when cells were doubly transformed due to the presence of the pET-28a(+)-derived RNAI retained by pSAMRNAI.