Description
The bacterial flagellar motor (BFM) is the macromolecular rotary machinery responsible for bacterial motility through flagellar rotation. Its dynamics are tightly regulated by environmental sensing mechanisms, including multiple taxis pathways [1]. In magnetotactic bacteria (MTB), both chemical and magnetic cues modulate BFM behavior, enabling navigation in complex environments [2]. This work aims to establish a quantitative steady-state model of motor dynamics in Magnetospirillum gryphiswaldense (MSR-1) as a foundation for studying how the motor adapts to and integrates chemical stimuli.
Beyond sensory inputs, the BFM is intrinsically mechanosensitive: variations in external load, shear stress, or medium viscosity induce adaptive stator remodeling [3]. While this property is essential for robust motility, it introduces a significant experimental bias in tethered-cell assays, where rotational dynamics are commonly used as a proxy for BFM activity. In particular, even weak fluid flows can alter motor behavior independently of sensory signaling, complicating the interpretation of chemotactic responses.
To minimize flow-induced perturbations while preserving precise chemical control, we developed a PDMS-based microfluidic platform featuring a three-channel architecture interconnected by a porous array of micropillars [4]. This design allows independent perfusion of distinct solutions in the lateral channels, while the central chamber—containing tethered bacteria—remains hydrodynamically isolated. Chemical stimuli are delivered exclusively by diffusion across the micropillar arrays, effectively decoupling chemical gradients from mechanical forces.
This microfluidic system enables unbiased, high-resolution tracking of BFM rotational dynamics under well-defined chemical conditions, providing a robust experimental framework for quantitative chemotaxis studies in magnetotactic bacteria.
[1] Nakamura S, Minamino T. Structure and Dynamics of the Bacterial Flagellar Motor Complex. Biomolecules. 2024 Nov 22;14(12):1488. doi: 10.3390/biom14121488. PMID: 39766194; PMCID: PMC11673145.
[2] Goswami P, He K, Li J, Pan Y, Roberts AP, Lin W. Magnetotactic bacteria and magnetofossils: ecology, evolution and environmental implications. NPJ Biofilms Microbiomes. 2022 Jun 1;8(1):43. doi: 10.1038/s41522-022-00304-0. PMID: 35650214; PMCID: PMC9160268.
[3] Wadhwa N, Tu Y, Berg HC. Mechanosensitive remodeling of the bacterial flagellar motor is independent of direction of rotation. Proc Natl Acad Sci U S A. 2021 Apr 13;118(15):e2024608118. doi: 10.1073/pnas.2024608118. PMID: 33876769; PMCID: PMC8054018.
[4] Liu JS, Zhang YY, Wang Z, Deng JY, Ye X, Xue RY, Ge D, Xu Z. Design and validation of a microfluidic chip with micropillar arrays for three-dimensional cell culture. Chin J Anal Chem. 2017 Aug;45(8):1109–1114. doi: 10.1016/S1872-2040(17)61029-6.