Enzymes

DNase I

Used here to digest naked DNA in lysates prior to quantification of phages by real-time PCR. We use DNase I from Sigma (D4263), which comes in glycerol at a defined concentration. Alternatively, you can use the one in powder form (D4527). Dissolve at least 1 mg/mL in 20 mM Tris-HCl pH 7.5, 1 mM MgCl₂, 50% (w/v) glycerol. Store at -20 °C. Stable for at least 18 months. D4527 contains ≥2000 units per mg. When dissolved at a concentration of 10 mg/mL, 1 mL contains approximately 20 U/µL.