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Light-Dependent Switching of Circling Handedness in Microswimmer Navigation
Phys. Rev. Lett. 136, 078301 – Published 20 February, 2026
DOI: https://doi.org/10.1103/6cdq-1nvv
Abstract
Many swimming microorganisms navigate their environment by modulating the curvature of their swimming trajectories in response to external cues. Here, we show that the biflagellate alga Chlamydomonas reinhardtii swims in circles and actively switches its trajectory handedness in response to orthogonal illumination: the cell swims counterclockwise at low light intensities yet clockwise at high light intensities. This handedness switching arises from light-dependent modulation of flagellar beating, including rapid and reversible changes in beat extension, phase, and—crucially—beat plane orientation. Using high-speed imaging and hydrodynamic modeling, we reveal that this beat plane reorientation is critical for Chlamydomonas to swim orthogonally to light as well as to dynamically modulate its trajectory curvature, enabling transitions between global exploration and localized searching in spatially structured light fields. Our results establish beat plane reorientation as a novel mechanism for curvature control in microswimmer navigation.
Physics Subject Headings (PhySH)
Focus
Algal Swimming Patterns Change with Light Intensity
In response to changes in illumination, a swimming microorganism reverses the direction of its circular trajectory by tilting its flagella’s planes of motion.
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