Regensburg 2013 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 18: Poster: Polymer Dynamics

CPP 18.7: Poster

Dienstag, 12. März 2013, 18:15–20:15, Poster C

Entropic DNA segregation in bacteria — •Elena Minina and Axel Arnold — Institute for Computational Physics, University of Stuttgart, Allmandring 3, 70569, Stuttgart, Germany

Cell division is a complex process consisting of two main parts - DNA replication and segregation. In all higher organisms, both parts involve active mechanisms. In particular, the mechanism for segregation is too complex to be employed by primitive bacteria like Escherichia coli. During replication DNA of the mother cell is copied into two daughter strands, which segregate, i.e. move towards opposite sides of the rod-shaped cell. It was previously shown that the segregation can be driven by entropy only, without need for an active mechanism [A. Arnold and S. Jun, Phys. Rev. E 76 (2007)]. The time scale for this entropic segregation is much faster than simple diffusion, and sufficient to explain DNA segregation in primitive bacteria. However, there is barrier towards entropic segregation, which has to be overcome by diffusion and would be a major obstacle towards purely entropic segregation.

In the present study we use MD simulations in order to investigate the influence of finite replication speed on the segregation. We model the replication by unzipping of two initially cross-linked, ladder-like strands, and compare to a more realistic model, where a second strand is added gradually. Our results show that the finite replication speed allows to overcome the induction time, which is only an artifact of spontaneous segregation. Without the need for induction, entropic segregation is indeed a promising candidate to explain bacterial DNA segregation without active mechanisms.