Rapid isolation and sequencing of purified plasmid DNA from Bacillus subtilis

We report two methods for isolation of plasmid DNA from the gram-positive bacterium Bacillus subtilis. The protoplast alkaline lysis procedure was developed for general use, and the protoplast alkaline lysis magic procedure was developed for isolation of DNA for sequencing. Both procedures yielded large amounts of high-quality DNA in less than 1 h, while current protocols require 4 to 7 h to perform and give lower yields and quality. Plasmid DNA was obtained from strains containing either high- or low-copy-number plasmids. In addition, the procedures were easily adapted to yield large amounts of plasmid DNA suitable for sequencing from another gram-positive organism, Staphylococcus aureus. Further, we demonstrated that neither chloramphenicol, used for plasmid selection, nor the mutation recE4 reduced plasmid DNA yield from the strains we examined.