High efficiency transformation of E.coli by high voltage electroporation

TLDR

E. coli can be transformed to extremely high efficiencies by subjecting a mixture of cells and DNA to brief but intense electrical fields of exponential decay waveform (electroporation). The study aims to discuss possible mechanisms and provide a simple procedure for practical use of high‑voltage electroporation. High‑voltage electroporation efficiency depends on electric field strength and pulse length, and DNA does not bind to cells before entry.

Abstract

E. coli can be transformed to extremely high efficiencies by subjecting a mixture of cells and DNA to brief but intense electrical fields of exponential decay waveform (electroporation). We have obtained 10(9) to 10(10) transformants/micrograms with strains LE392 and DH5 alpha, and plasmids pUC18 and pBR329. The process is highly dependent on two characteristics of the electrical pulse: the electric field strength and the pulse length (RC time constant). The frequency of transformation is a linear function of the DNA concentration over at least six orders of magnitude; and the efficiency of transformation is a function of the cell concentration. Most of the surviving cells are competent with up to 80% transformed at high DNA concentration. The mechanism does not appear to include binding of the DNA to the cells prior to entry. Possible mechanisms are discussed and a simple procedure for the practical use of this technique is presented.