Chapter 10 : Extraction of Bacterial DNA

Abstract:

This chapter discusses the procedure for extraction of bacterial DNA. The preparation of DNA from any cell type involves the same general steps: (i) breaking open the cell (and the nuclear membrane, if applicable), (ii) removing proteins and other cell debris from the nucleic acid, and (iii) final purification. Cell membranes are made of proteins and fats. Just as detergent dissolves fats in a frying pan, a little detergent dissolves cell membranes. After cell lysis, the next step in DNA preparation usually involves purification by removing proteins from the nucleic acid. Furthermore, phenol and water, like oil and water, do not mix but instead form separate layers. Adding phenol to an aqueous (water-based) DNA-protein mixture, like a cell lysate, and mixing them well, makes the protein to dissolve in the phenol. To remove the protein, the phenol layer is removed. Following the removal of the protein, the DNA is usually subjected to additional purification.