Dresden 2026 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 57: Statistical Physics of Biological Systems IV (joint session BP/DY)

DY 57.4: Vortrag

Freitag, 13. März 2026, 10:30–10:45, BAR/SCHÖ

Modeling Cooperative Remodeling and Energy Landscapes in the Bacterial Flagellar Motor — •Nils-Ole Walliser — Laboratoire Charles Coulomb, University of Montpellier, Montpellier, France

Bacteria use the flagellar motor to adapt their motility to changing mechanical conditions. This rotary motor tunes its torque by recruiting and releasing torque-generating stator units. I will present statistical-physics-based models that use single-motor measurements to infer interaction potentials and energy landscapes in the bacterial flagellar motor. First, using single-motor bead assays that resolve stepwise changes in rotation speed and thus stator occupancy, we model stator recruitment as a finite-size lattice gas and infer stator-stator cooperativity from occupancy fluctuations. This reveals moderate attractive interactions and shows that the motor operates in a regime that balances responsiveness to load changes with noise in stator number. Second, I will discuss experiments where the motor load is actively perturbed, uncovering a strong asymmetry in the relaxation to the steady state when starting from higher versus lower stator occupancy. A two-state catch-bond model quantitatively explains this stoichiometry-dependent asymmetry and captures the mechanosensitive nature of stator anchoring to the cell wall. Finally, I will show how high-temporal-resolution rotation traces can be used to reconstruct, in a model-independent way, the tilted periodic energy landscape of the rotor/LP ring within a Smoluchowski framework, yielding barrier heights, torque and internal friction.

Keywords: Bacterial flagellar motor; Motor remodeling (stator recruitment); Cooperativity in lattice-gas models; Catch-bond kinetics; Energy landscape reconstruction