Sommaire:

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 DNA-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 as seen in-vivo [4]. The evolution of loci positions match the corresponding experimentally reported results for E.coli using FISH [5]. Additionally, the contact map generated using our bead-spring model [4] reproduces the four macro-domains of the experimental Hi-C maps [6]. We modify the architecture by adding just four crosslinks at specific positions along the chain contour in 500 monomer bead-spring ring polymer, which represents the choromosome. After replication of our model-polymer, we obtain two 500-monomer ring polymers, which spontaneously get segregated and organized by virtue of their polymer topology. 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. We also observe quantitative match of FISH data [7] and HiC data [3] for another bacteria C.crescentus where we use another polymer topology [8]. We have extended our studies to investigate chromosome organization in fast growth conditions for E.coli [9]. We have investigated a host of polymer topologies to develop understanding of how polymer topologies effect organization and segregation forces in cylindrical confinement. [1] Jay K. Fisher, Aude Bourniquel, G. Witz, B. Weiner, M. Prentiss, and Nancy Kleckner.


[1] Cell, 153(4):882–895, (2013).
[2] A. Japaridze, C. Gogou, J. W. J. Kerssemakers, H. M. Nguyen, Cees Dekker. Journal : Nature Communications, 11(1), (2020).
[3] Virginia S. Lioy, Ivan Junier, and F. Boccard. Ann. Rev. of Microbiology, 75(1), (2021).
[4] Polymer architecture orchestrates the segregation and spatial organization of replicating E.coli chromosomes in slow growth. D. Mitra, S. Pande, Apratim Chatterji. Soft Matter, 18, 5615-5631 (2022)
[5] J. Cass, N.J. Kuwada, B. Traxler, P.A.Wiggins: Biophys. Journal . 110 (12):2597-260 (2016)
[6] T. B. K. Le, M. V. Imakaev, L. A. Mirny and M. T. Laub, Science, 342, 731–734 (2013).
[7] P.H. Viollier, M. Thanbichler, P.T. McGrath, L.West, M.Meewan, H.H. Mcadams, Lucy Shapiro. Journal: PNAS, 101 (25) 9257 (2004)
[8] Topology-driven spatial organization of ring polymers under confinement Authors: D. Mitra, S. Pande, Apratim Chatterji. Phys. Rev. E, 106, 054502 (2022).
[9] Entropy mediated organization of E.coli chromosome in fast growth conditions. Shreerang Pande, Debarshi Mitra, Apratim Chatterji. arXiv:2304.02275

Pour plus d'informations, merci de contacter Walter J.-C.