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In recent times, researchers are using statistical physics to understand the emergent dynamics
and organization in living systems, such as organization of the DNA within the living cell.
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 [1,2,3]. Using principles of entropic repulsion
between polymer loops confined in a cylinder, we use Monte carlo simulations to show that the segregation
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 segments (loci) get spatially localized. The evolution of loci positions match
the corresponding experimentally reported results. Additionally, the contact map generated using our bead-spring
model reproduces the four macro-domains of the experimental Hi-C maps.
Thus we have proposed a framework which reconciles many spatial organizational aspects of E. coli
chromosome as seen in-vivo, and provides a consistent mechanistic understanding of the process underlying
segregation. Certain Proteins are expected to contribute to change the DNA-polymer architecture.
[1] Jay K. Fisher, Aude Bourniquel, G. Witz, B. Weiner, M. Prentiss, and Nancy Kleckner.
Four-dimensional imaging of e. coli nucleoid organization and dynamics in living cells.
Journal Cell, 153(4):882–895, 2013.
[2] A. Japaridze, Christos Gogou, Jacob W. J. Kerssemakers, Huyen My Nguyen, and Cees Dekker. Di-rect observation of independently moving replisomes in Escherichia coli.
Journal : Nature Communications, 11(1), June 2020.
[3] Virginia S. Lioy, Ivan Junier, and Frédéric Boccard.
Multiscale dynamic structuring of bacterial chromosomes.
Journal : Annual Review of Microbiology, 75(1), August 2021. |