Copy Number Mutations (Cop ⁻ ) of the Plasmid Containing the Replication Origin ( <i>oriC</i> ) of the <i>Escherichia coli</i> Chromosome: Lethal Effect of the Cop Region Cloned onto a High-Copy-Number Vector on Host Cells

Abstract

High-copy-number mutants were isolated from an oriC plasmid. They carried insertion mutations within a region (about 470 base pairs) near the uncB gene. When a segment containing this region was cloned onto a high-copy-number plasmid, such a plasmid could be maintained as an intact form only when it was present in a lower copy number.