Transformation of Escherichia coli with foreign DNA by electroporation

Abstract

Electroporation has been widely applied in molecular biology in recent years. In this study, successful transformation of plasmid DNA and transfection of phage DNA into E. coli were described by using intense electrical field of exponential decay waveform (electroporation) generated by a Gene Pulsar LN-101 (made in Tianjin, Tianjin Institute of Technology and Nankai University). We have obtained 10(9)-10(10) transformants/micrograms with strain DH5 alpha and plasmid pUC18, by a single voltage pulse at 1.0-2.5 kV (initial electric field strength = 2.8-16 kV/cm) with 5-20 microF capacitor. The efficiency of electroporation depends on various parameters: the electric field strength, capacitance, the pulse length (RC time constant), etc. The frequency of transformation was a linear function of the DNA concentration, as well as the density of recipient cell. The incubation time of before or after electroporation has no significant effect on transformation. The high transfection efficiency was also achieved with strain JM109 and M13mp19RF by electroporation. The method was easier, more time-saving and more efficient than Ca(2+)-dependent transformation (transfection) method. The results obtained by Gene-Pulsar LN-101 was similar to that by the Bio-Rad Gene-Pulsar apparatus.