Polymer architecture orchestrates the segregation and spatio-temporal organization of replicating E. coli chromosomes in slow growth.

The mechanism and driving forces of chromosome segregation in the bacterial cell cycle of E. coli is one of the least understood events in its life cycle. Using principles of  entropic repulsion between polymer loops confined in a cylinder, we use Monte carlo simulations to show that the  segregation dynamics is spontaneously enhanced by the  adoption of a certain DNA-polymer architecture  as replication  progresses. Secondly, the chosen polymer-topology ensures  its self-organization along  the cell axis while segregation is in progress, such that various chromosomal loci get spatially localized. The  time evolution of loci positions quantitatively match the corresponding experimentally reported results, including observation of the cohesion time and  the ter-transition.  Additionally,  the contact map generated using our bead-spring   model reproduces the  four macro-domains of the experimental Hi-C  maps. Lastly, the proposed mechanism  reproduces the observed universal dynamics as the sister loci separate during segregation. We propose that cross-links (plausibly induced by SMC proteins) at crucial positions along the contour is  enough to provide sufficient entropic forces for segregation within experimentally observed time scales.