Modulation of Bacterial Flagellar Dynamics Near Surfaces in Biofilm Initiation

Biofilm formation is a critical process in bacterial pathogenesis and environmental persistence, initiated when bacteria transition from planktonic to surface-associated states. This transition involves complex motility dynamics as bacteria approach surfaces, modulated by flagellar rotation and chemotactic signaling. Recent studies highlight the role of flagella in surface sensing and adhesion, with CheY-CheZ regulating chemotaxis and c-di-GMP controlling the switch from motility to sessility (Guttenplan & Kearns, 2013, Mol. Microbiol.; Belas, 2014, Trends Microbiol.). High-resolution tracking has revealed that bacteria adjust flagellar rotation near surfaces, exhibiting behaviors like “run-and-tumble” suppression or circular trajectories (Molaei et al., 2014, Phys. Rev. Lett.). However, the precise mechanisms by which bacteria tune flagellar dynamics in response to surface proximity, and how CheY-CheZ and c-di-GMP signaling pathways couple to these physical interactions, remain poorly understood.

Cutting-Edge Advances: Optical tweezers and holographic microscopy enable 6-DoF (degrees of freedom) tracking of bacterial trajectories, revealing flagellar synchronization and surface-induced reorientation (Taute et al., 2018, Nat. Commun.).

• Signaling Pathways: CheY phosphorylation modulates flagellar switching, while c-di-GMP regulates motor torque and adhesion protein expression (Boehm et al., 2010, Cell).

• Surface Interactions: Hydrodynamic models show wall-induced drag alters flagellar rotation, but experimental validation of signaling-driven modulation is limited (Lauga & Powers, 2009, Rep. Prog. Phys.).

Our Questions:

– How do bacteria dynamically adjust flagellar rotation in response to surface proximity, and what is the role of CheY-CheZ signaling in this process?

– How does c-di-GMP signaling influence flagellar dynamics and the transition to surface adhesion during biofilm initiation?

– Can we quantify the coupling between physical (hydrodynamic) and biochemical (signaling) mechanisms in near-surface bacterial motility?