Role of XerCD in release of over-replicated DNA through Outer Membrane Vesicles in Escherichia coli

Abstract

Outer membrane vesicles (OMVs) are universally produced by prokaryotes and play important roles in symbiotic and pathogenic interactions. Here we show that the Gammaproteobacterium Escherichia coli produces OMVs that contain DNA enriched for the region around the terminus of replication ter, and specifically for the recognition sequence dif of the two site-specific recombinases XerCD, similar to OMVs from the Alphaproteobacterium Dinoroseobacter shibae. In deletion mutants of xerC or xerD, the enriched region around ter becomes broader while the peak directly at the dif sequence itself is reduced. ImportanceImprecise termination of replication can lead to over-replicated parts of bacterial chromosomes that have to be excised and removed from the dividing cell. The underlying mechanism is so far poorly understood. Our data suggest a conserved mechanism for repair and removal of over-replicated DNA through outer membrane vesicles and an active role of the site-specific XerCD recombinase complex therein.