Polyethylene glycol-mediated bacterial colony transformation.

A moderately efficient and quick method of bacterial colony transformation is described. Plasmid DNA was added to bacteria suspended in a solution of polyethylene glycol/calcium chloride (PEG/CaCl2). After a brief incubation and heat shock, the cells were directly plated. Transformation efficiencies up to 8.6 +/- 1.28 x 10(6) transformants per microgram of pUC18 were obtained. We have found that the reverse of the transformation process could also take place. Suspending a bacterial pellet harboring the plasmid of interest in PEG/CaCl2 results in the release of the plasmid DNA, and thus indirectly lends support to the transformation process.