Extraction and analysis of plasmid DNA from Listeria monocytogenes

A plasmid preparation is a method used to extract and purify plasmid DNA. Methods developed to purify plasmid DNA from bacteria generally involve harvesting and alkaline lysis of the bacteria and precipitation of chromosomal DNA and protein, followed by purification of the plasmid DNA. Here, we describe the mini-preparation of plasmid DNA by a rapid small-scale method, adapted for Listeria monocytogenes. The quality of plasmid DNA isolated using this method is sufficient for analytical purposes but may be upscaled for further downstream analysis. Electrophoretic separation of the resultant lysate allows conclusions to be made on the presence, number, copy number, and size of the plasmids in the analyzed bacterial strains.