A highly efficient and highly reliable protocol for transformation of Escherichia coli by electroporation

Electroporation is widely adopted for highly efficient transformation of Escherichia coli of different purposes, but its efficiency is highly varied in the range of several orders of magnitude. Here we describe a modified and highly reliable electroporation protocol which combines low temperature growth in the presence of sucrose with a postelectroporation heat pulse, which not only gives rise to an over 250-fold enhancement in transformation compared with conventional protocols, but also alleviates the need for a strict low temperature control at all times of an electroporation-competent cell preparation experiment and highly pure MilliQ grade water which is not readily available in many laboratories. Transformations for a 6-kb E. coli and yeast shuttle vector were always higher than 10⁷ transformants/μg, and more than 10⁸ transformants/μg were sometimes recorded in routine experiments.