MS2 phage stock preparation

MS2 phage (from ATCC 15597-B1) and log-phase donor E. coli c-3000 were cultured in LB medium at 37°C with shaking overnight. Cells were removed by centrifugation at 4000 rpm for 20 min at 25°C. The supernatant was filtered with a 0.22-μm filter (Stericup Filter, EMD Millipore) to remove any remaining residues. The phage was then stored at 4°C. Typically, a stock concentration of 10¹¹ to 10¹² PFU/ml was obtained. A single plaque of MS2 (grown on the host E. coli c-3000) was picked into an Eppendorf tube containing 1 ml of NaCl (0.85%) using a sterile Pasteur pipette. The tube was stored overnight at 4°C to allow the release of the viral particles from the agarose. Ten microliters of chloroform were then added to the sample; the tube was vortexed and centrifuged for 3 min at 13,000 rpm at room temperature. The supernatant was filtered with a 0.22-μm Minisart syringe filter (Sartorius) to remove any residues.