Replication of bacteriophage M13: X. M13 replication in a mutant of Escherichia coli defective in the 5′ → 3′ exonuclease associated with DNA polymerase I

Abstract

The 5′ → 3′ exonuclease associated with DNA polymerase I is required for the growth of bacteriophage M13. Both phage production and the synthesis of progeny single-stranded DNA are temperature-sensitive in Escherichia coli polAex1, a mutant temperature-sensitive in the 5′ → 3′ exonuclease associated with DNA polymerase I. During replicative form to single-stranded DNA synthesis, this strain is defective in making M13 supercoiled DNA and accumulates two classes of abnormal replicative forms; circular replicative form molecules ranging in size from 0.2 to 0.5 times unit-length and structures that sediment at the rate of unit-length replicative form DNA in neutral sucrose gradients but which are partially single-stranded and contain viral strand fragments ranging in size from 0.1 to 0.7 times unit-length.