Issue 12, 2019

Confinement and crowding control the morphology and dynamics of a model bacterial chromosome

Abstract

Motivated by recent experiments probing the shape, size and dynamics of bacterial chromosomes in growing cells, we consider a polymer model consisting of a circular backbone to which side-loops are attached, confined to a cylindrical cell. Such a model chromosome spontaneously adopts a helical shape, which is further compacted by molecular crowders to occupy a nucleoid-like sub-volume of the cell. With increasing cell length, the longitudinal size of the chromosome increases in a non-linear fashion until finally saturating, its morphology gradually opening up while displaying a changing number of helical turns. For shorter cells, the chromosome extension varies non-monotonically with cell size, which we show is associated with a radial to longitudinal spatial reordering of the crowders. Confinement and crowders constrain chain dynamics leading to anomalous diffusion. While the scaling exponent for the mean squared displacement of center of mass grows and saturates with cell length, that of individual loci displays a broad distribution with a sharp maximum.

Graphical abstract: Confinement and crowding control the morphology and dynamics of a model bacterial chromosome

Article information

Article type
Paper
Submitted
13 Oct 2018
Accepted
13 Feb 2019
First published
18 Feb 2019

Soft Matter, 2019,15, 2677-2687

Confinement and crowding control the morphology and dynamics of a model bacterial chromosome

P. Swain, B. M. Mulder and D. Chaudhuri, Soft Matter, 2019, 15, 2677 DOI: 10.1039/C8SM02092B

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