Preparation of Chromosomal DNA from E. coli

This chapter describes a simple and rapid way of extracting and purifying chromosomal DNA from E. coli and many other species of bacteria. This procedure is essentially a simplified version of that described by Marmur in 1961 (1 ). The cells are lysed by treatment with a detergent and the mixture is deproteinized by phenol-chloroform extraction. Further purification can be achieved by treatment with ribonuclease and proteinase K. The resulting DNA, free of protein and RNA contamination, is sufficiently pure to be used for restriction digestion and cloning, e.g., in the preparation of gene libraries.