MatP local enrichment delays segregation independently of tetramer formation and septal anchoring in Vibrio cholerae [HiSC2]

Vibrio cholerae harbours a primary chromosome derived from the monochromosomal ancestor of the Vibrionales (ChrI) and a secondary chromosome derived from a megaplasmid (ChrII). Both carry a single origin of replication with replication terminating in a diametrically opposite zone, TerI and TerII, respectively. The choreography of TerI and TerII segregation determines when and where cell division occurs. Using a combination of deep sequencing and fluorescence microscopy techniques, we show that TerI and TerII both carry a very high density of MatP binding sites, are both structured into macrodomains, and are both targeted to mid-cell during replication by MatP, demonstrating that ChrII behaves as a bona fide chromosome. We further show that MatP-mediated cohesion and cellular positioning are independent of cell division and tetramer formation, but are linked to the local density of matS sites, in apparent contradiction to the mechanism of action of MatP in Escherichia coli. Overall design: HiSC2 was used to monitor the frequency of sister chromosomes contacts after replication (Cre-loxP) or before cell division (XerCD-dif) in wt and matP mutants in V. cholerae