Alkaline lysis method is the most commonly used method to isolate plasmid DNA. In this method bacterial cells are lysed by treating them with high concentration of alkali along with surfactants. Highly concentrated alkali denatures chromosomal DNA and plasmid DNA. Surfactants are used to remove lipids. After lysis, cell components, proteins, chromosomal DNA, etc. are precipitated by decreasing pH using acetate. The plasmid being small in size does not precipitate out and remains in suspension. This plasmid is then precipitated and separated by using alcohol under chilled conditions. The plasmid samples are then run on Agarose Gel Electrophoresis.
