[Dependence of the recA gene for the replication of the bacterial chromosome initiated by the integrated F' plasmid in Escherichia coli].

Mutant strain dnaA46 of Escherichia coli can be integratively suppressed by the F' plasmid. Upon introducing the recA56 mutation through transduction the suppressive integration strain (Sin) becomes unable to grow at 40 degrees C. By means of experiments of marker transfer, acridine orange sensitivity test, F' curing and mini-chromosome transformation it is concluded that the F' plasmid is always in an integrated state in the Sin strains and that the initiation of the replication of the bacterial chromosome is carried on by the integrated F' plasmid. The biosynthesis of DNA and protein of the Sin recA+ and Sin recA- strains at different temperatures were compared. It is concluded from the experimental results that the recA gene functions at the level of DNA replication. The recA gene is known to be the key gene in DNA recombination and SOS repair of DNA damage. The works reported here throw some light on the understanding of the function of the recA gene.