I have a plasmid with the P15A origin which apparently has a low copy number (see here). This would explain why my purification yeilds for subsequent digestion are low (gel shows the plasmid after digestion and clean-up with 5µl being loaded). I am currently growing my E. coli containing plasmid up in 5mls overnight before doing a miniprep. My question is should I grow my 5ml cultures up for longer (2 days) or just give it up and do a larger amount for Midiprep.
I am also curious as to what actually controls the plasmid copy number inside cells. An explanation of the regulation of plasmid copy number would be much appreciated.