Bacterial Transformation: The Heat Shock Method

Overview

Transformation is the process that occurs when a cell ingests foreign DNA from its surroundings. Transformation can occur in nature in certain types of bacteria. In molecular biology, transformation is artificially reproduced in the lab via the creation of pores in bacterial cell membranes. Bacterial cells that are able to take up DNA from the environment are called competent cells. In the laboratory, bacterial cells can be made competent and DNA subsequently introduced by a procedure called the heat shock method.

Heat shock transformation uses a calcium rich environment provided by calcium chloride to counteract the electrostatic repulsion between the plasmid DNA and bacterial cellular membrane. A sudden increase in temperature creates pores in the plasma membrane of the bacteria and allows for plasmid DNA to enter the bacterial cell. This video goes through a step-by-step procedure on how to create chemically competent bacteria, perform heat shock transformation, plate the transformed bacteria, and calculate transformation efficiency.

Procedure

Bacterial transformation is a widely used method where foreign DNA is introduced into a bacterium, which can then amplify, or clone the DNA. Cells that have the ability to readily take up this DNA are called competent cells. Although transformation is naturally occurring in many types of bacteria, scientists have found ways to artificially induce and enhance a bacterial cell’s competency. In this video we will talk about one of these ways, heat shock transformation.

Before we ta