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Abstract

The chromosomal replication origin region (ori) of characterised
bacteria is dynamically positioned throughout the cell cycle. In slowly
growing Escherichia coli, ori is maintained at mid-cell from birth until
its replication, after which newly replicated sister oris move to
opposite quarter positions. Here, we provide an explanation for on
positioning based on the self-organisation of the Structural Maintenance
of Chromosomes complex, MukBEF, which forms dynamically positioned
clusters on the chromosome. We propose that a non-trivial feedback
between the self-organising gradient of MukBEF complexes and the oris
leads to accurate on positioning. We find excellent agreement with
quantitative experimental measurements and confirm key predictions.
Specifically, we show that oris exhibit biased motion towards MukBEF
clusters, rather than mid-cell. Our findings suggest that MukBEF and
oris act together as a self-organising system in chromosome
organisation-segregation and introduces protein self-organisation as an
important consideration for future studies of chromosome dynamics.