The effect of plasmid DNA sizes and other factors on electrotransformation of Escherichia coli JM109

Abstract

The plasmid size can be an important factor in electrotransformations. We have examined bacterial electroporation with a specific interest in the transformation of plasmids with different sizes of their molecules. We used plasmids pUC19, pBR322 and pPP4. Transformation efficiency drops with increasing size of the DNA. We achieved with plasmid pUC19 a 81% frequency of transformation. The optimal field strength decreases with increasing size of the plasmid. Not only large sized plasmids but also large DNA concentrations lead to a reduced survival rate of the Escherichia coli JM109 cells.