The following protocol is based on our modifications of R. Kraft, J. Tardiff, K. S. Krauter, and L. A. Leinwand. Inoculate 2-5 ml of L broth containing the appropriate antibiotic from a single bacterial colony.
Phenol extract the solution, saving the upper aqueous phase.
Respin the pellets for 1 min and dry under vacuum. Incubate on dry ice for 20 min. Discard the supernatant and dry the pellet under vacuum. Mix and centrifuge to remove any debri. This cooling typically takes 30-45 min.