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

Description

Vibrio cholerae harbours a primary chromosome derived from the monochromosomal ancestor of the Vibrionales (ChrI) and a secondary chromosome derived from a megaplasmid (ChrII). The choreography of segregation of the replication terminus of ChrI and ChrII, TerI and TerII, determines when and where cell division occurs. ChrI encodes for a homolog of Escherichia coli MatP. Using a combination of deep sequencing and fluorescence microscopy techniques, we show that MatP structures TerI and TerII into macrodomains, targets them to mid-cell in the course of replication and delays their segregation, demonstrating that ChrII behaves as a bona fide chromosome. We further show that the extent of the segregation delay mediated by MatP depends on the number and local density of matS sites, and is independent of its assembly into tetramers and any interaction with a cell division protein, in contrast to what has been observed in E. coli.

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Cells were grown in M9 minimal medium supplemented with 0.2% fructose and 1 μg/ml thiamine to exponential phase and spread on a 1% (w/v) agar pad (ultrapure agarose, Invitrogen) for analysis. For time-lapse movies the slides were incubated at 30°C and images acquired using an Evolve 512 EMCCD camera (Roper Scientific) attached to an Axio Observe spinning disk (Zeiss). For snapshot images and their metadata cell images were acquired using a DM6000-B (Leica) microscope and analysed using MicrobeTracker..

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