Synchronization and bundling of anchored bacterial flagella

The synchronization and bundling process of bacterial flagella is investigated by mesoscale hydrodynamic simulations. Systems with two to six flagella are considered, which are anchored at one end, and are driven by a constant torque. A flagellum is modelled as a linear helical structure composed of mass points with their elastic shape maintained by bonds, bending, and torsional potentials. The characteristic times for synchronization and bundling are analyzed in terms of motor torque, separation, and number of flagella. We find that hydrodynamic interactions determine the bundling behavior. The synchronization time is smaller than the bundling time, but their ratio depends strongly on the initial separation. The bundling time decreases with increasing number of flagella at a fixed radius in a circular arrangement due to multi-helix hydrodynamics.