Cells are typically made electrocompetent by incubating them in a buffered solution at pH 6-8 containing a reducing agent, such as dithiothreitol (DTT) or ??-mercaptoethanol (BME), to reduce cell wall proteins to facilitate subsequent uptake of DNA. A preferred incubation buffer in this regard is a fresh solution of 50 mM potassium phosphate buffer, pH 7.5, containing 25 mM DTT. The cells are incu