Confinement and crowding control the morphology and dynamics of a model bacterial chromosome. Issue 12 (4th March 2019)

• Record Type: Journal Article
• Authors: Swain, Pinaki; Mulder, Bela M.; Chaudhuri, Debasish
• Is Part Of: Soft matter. Volume 15:Issue 12(2019)
• Page Start: 2677
• Page End: 2687
• Publication Date: 2019-03-04
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/c8sm02092b
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : Motivated by recent experiments probing the shape, size and dynamics of bacterial chromosomes in growing cells, we consider a circular polymer attached to side-loops to model the chromosome confined to a cylindrical cell, in the presence of cytoplasmic crowders. 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.