Replication of the single-stranded DNA of the male-specific bacteriophage M13: Isolation of intracellular forms of phage-specific DNA

Abstract

The intracellular DNA has been isolated from Escherichia coli F + cells infected with the small male-specific bacteriophage M13 and fractionated on a methylated albumin-kieselguhr column. Two infectious forms of phage-specific DNA were isolated and identified as a double-stranded replicative form and single-stranded DNA on the basis of their elution from the methylated albumin-kieselguhr column, infectivity to spheroplasts before and after heating, sedimentation at low ionic strength and buoyant density in CsCl. The replicative DNA was found to be resistant to thermal denaturation, suggesting that it may be a closed ring. It is estimated that there are at least 130 molecules of replicative DNA and 190 molecules of single-stranded DNA per infected bacterium.