Introduction of plasmid DNA into cells.

Transformation of E. coli can be achieved using any of the four protocols in this unit. The first method using calcium chloride gives good transformation efficiencies, is simple to complete, requires no special equipment, and allows storage of competent cells. The alternate one-step method is considerably faster and also gives good transformation efficiencies (although they are somewhat lower). If considerably higher transformation efficiencies are needed, the third method using electroporation is simple, fast, and reliable. As in the calcium chloride protocol, prepared cells can be stored. The final method described is an adaptation of the electroporation protocol that allows direct transfer of vector DNA from yeast into E. coli.