Bacterial Transformation (Kushner Method)

The principle of this procedure is very similar to that of the standard calcium chloride method, (see Chapter 34 ) i.e., exponential phase cells are harvested and washed with a solution containing divalent cations. This renders the cells competent , which simply means they are now able to take up DNA from the solution. After mixing the competent cells with the DNA, they are subjected to a heat shock to promote the uptake of DNA, presumably by affecting the physical state of the lipids in the membrane.