Title: The PomXYZ Proteins Self-Organize on the Bacterial Nucleoid to Stimulate Cell Division,
Abstract: Cell division site positioning is precisely regulated to generate correctly
sized and shaped daughters. We uncover a novel strategy to position the FtsZ
cytokinetic ring at midcell in the social bacterium Myxococcus xanthus. PomX,
PomY and the nucleoid-binding ParA/MinD ATPase PomZ self-assemble forming a
large nucleoid-associated complex that localizes at the division site before
FtsZ to directly guide and stimulate division. PomXYZ localization is generated
through self-organized biased random motion on the nucleoid towards midcell and
constrained motion at midcell. Experiments and theory show that PomXYZ motion
is produced by diffusive PomZ fluxes on the nucleoid into the complex. Flux
differences scale with the intracellular asymmetry of the complex and are
converted into a local PomZ concentration gradient across the complex with
translocation towards the higher PomZ concentration. At midcell, fluxes
equalize resulting in constrained motion. Flux-based mechanisms may represent a
general paradigm for positioning of macromolecular structures in bacteria.