The spatiotemporal organization of bacterial cells is crucial for the active
segregation of replicating chromosomes. In several species, including
Caulobacter crescentus, the ATPase ParA binds to DNA and forms a gradient along
the long cell axis. The ParB partitioning complex on the newly replicated
chromosome translocates up this ParA gradient, thereby contributing to
chromosome segregation. A DNA-relay mechanism - deriving from the elasticity of
the fluctuating chromosome - has been proposed as the driving force for this
cargo translocation, but a mechanistic theoretical description remains elusive.
Here, we propose a minimal model to describe force generation by the DNA-relay
mechanism over a broad range of operational conditions. Conceptually, we
identify four distinct force-generation regimes characterized by their
dependence on chromosome fluctuations. These relay force regimes arise from an
interplay of the imposed ParA gradient, chromosome fluctuations, and an
emergent friction force due chromosome-cargo interactions.Comment: Formatting issues in the figures and references have been resolve