8 research outputs found
Regulation of Pom cluster dynamics in Myxococcus xanthus
Precise positioning of the cell division site is essential for the correct
segregation of the genetic material into the two daughter cells. In the
bacterium Myxococcus xanthus, the proteins PomX and PomY form a cluster on the
chromosome that performs a biased random walk to midcell and positively
regulates cell division there. PomZ, an ATPase, is necessary for tethering of
the cluster to the nucleoid and regulates its movement towards midcell. It has
remained unclear how the cluster dynamics change when the biochemical
parameters, such as the attachment rates of PomZ to the nucleoid and the
cluster, the ATP hydrolysis rate of PomZ or the mobility of PomZ dimers
interacting with the nucleoid and cluster, are varied. To answer these
questions, we investigate a one-dimensional model that includes the nucleoid,
the Pom cluster and the PomZ protein. We find that a mechanism based on the
diffusive PomZ fluxes on the nucleoid into the cluster can explain the latter's
midnucleoid localization for a broad parameter range. Furthermore, there is an
ATP hydrolysis rate that minimizes the time the cluster needs to reach
midnucleoid. If the dynamics of PomZ dimers on the nucleoid is slow relative to
the cluster's velocity, we observe oscillatory cluster movements around
midnucleoid. To understand midnucleoid localization, we developed a
semi-analytical approach that dissects the net movement of the cluster into its
components: the difference in PomZ fluxes into the cluster from either side,
the force exerted by a single PomZ dimer on the cluster and the effective
friction coefficient of the cluster. Importantly, we predict that the Pom
cluster oscillates around midnucleoid if the diffusivity of PomZ on the
nucleoid is reduced. A similar approach to that applied here may also prove
useful for cargo localization in ParABS systems.Comment: 17 pages, 6 figures, 10 pages supplemental material (including 12
figures and 1 table
Theory of Active Intracellular Transport by DNA-relaying
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
Data for "Cerebellar contributions to a brainwide network for flexible behavior"
Download the README.txt file for a detailed description of this dataset's conten