GC-rich plasmids have a lower copy number than AT-rich plasmids.

Plasmid copy number per bacterial chromosome equivalent was assessed by quantitative real-time PCR of E. coli cultures after 24 h of growth. Shown are copy numbers of AT- (green) and GC-rich (orange) (A) pJet plasmids and (B) pBAV plasmids. Independent-samples t-test: *** P < 0.001, n = 16.