Analysis of Bacteriophage-M 13-DNA Replication in an <em>Escherichia coli</em> Mutant Thermosensitive in DNA Polymerase III.

The various stages of M 13 DNA replication were investigated in an Escherichia coli dnaE mutant thermosensitive in DNA polymerase III after a shift to the restrictive temperature (45 &#176;C). The following results were obtained. (1) DNA polymerase III is not needed for the conversion of the infecting single-stranded phage DNA into the parental replicative form. (2) Semiconservative replicative form replication is completely blocked in the absence of a functional DNA polymerase III. (3) Synthesis of phage-specific DNA continues after a temperature shift late in the infection. However, due to an inherent thermosensitivity of M 13 single-stranded circular DNA production no free single strands are detected. [ABSTRACT FROM AUTHOR]