MatP local enrichment delays segregation independently of tetramer formation and septal anchoring inVibrio cholerae

Abstract

The cellular arrangement and segregation choreography of the genetic material is involved in the timing of assembly and cellular positioning of the cell division apparatus in bacteria. Key to this mode of regulation is the positioning of sister copies of the replication terminus zone (ter) of the chromosomes at the end of the replication cycle. The Vibrio cholerae genome is distributed on two chromosomes, ChrI and ChrII. ChrI is derived from the ancestor of the Vibrionales and Enterobacterales. ChrII is derived from a megaplasmid. ChrI encodes for a homologue of MatP, a protein that tethers sister copies of the ter of the Escherichia coli chromosome together at mid-cell at the time of cell division. MatP structures the ter by binding to a ter-specific DNA motif, matS. It forms tetramers that can bridge DNA segments together and it connects sister ter copies to the divisome via an interaction with a cell division protein, ZapB. We find that MatP structures the ter of ChrI and ChrII, ter1 and ter2, and ensures the cohesion and mid-cell position of sister ter1 and ter2 copies at the time of cell division, demonstrating that ChrII is organised and behaves as a bona fide chromosome. We show that cohesion and positioning are independent of cell division and tetramer formation, but are linked to the local density of matS sites, with sister ter2 separating earlier than sister ter1 because of a lower number of matS sites. Overall, our results suggest that the primary mechanism of action of MatP is to slow down the decatenation of newly replicated molecules.