Researchers Discover Microbes Change Swimming Tactics for Light

Research conducted by a team from the University of Hong Kong and the University of Exeter has revealed that a species of self-propelling microbes, specifically Chlamydomonas reinhardtii, can alter their swimming behavior based on light availability. The findings, published on March 2, 2026, in Physical Review Letters, highlight a unique adaptation that optimizes the microbes’ photosynthesis process.

Microbes like Chlamydomonas reinhardtii propel themselves using hair-like appendages known as flagella. Their swimming strategies are diverse; while some bacteria utilize a “run-and-tumble” technique, others navigate by modifying their swimming paths in response to environmental cues. Despite extensive research on microbial locomotion, the specific biophysical triggers that prompt these changes have remained largely elusive.

In 2021, researchers Kirsty Wan and Dario Cortese from the University of Exeter made significant strides in understanding the swimming mechanics of Chlamydomonas reinhardtii. By observing individual algal cells in three-dimensional space, they discovered that these microorganisms follow corkscrew trajectories through their fluid environment. The direction of these helical paths can be adjusted by changing the frequency, amplitude, and synchronization of their flagella, particularly when influenced by light.

Building on this foundational work, Zhao Wang and his team conducted a more detailed analysis of the swimming dynamics of these algae. Utilizing high-speed imaging techniques, they examined the independent movements of each flagellum under varying light conditions. Their observations revealed that at lower light intensities, the cells swim in counterclockwise circles, with one flagellum dominating propulsion due to its proximity to the cell’s light-sensing structure, known as the eyespot.

As light intensity increases beyond a certain threshold, the behavior shifts dramatically. The balance between the two flagella becomes equal, and the phase relationship of their beats changes, redirecting the cell’s motion toward the light source. This dynamic adjustment not only enhances light absorption but also aids in the optimization of photosynthesis.

The researchers propose that this remarkable ability to alter swimming patterns has evolved in Chlamydomonas reinhardtii to better regulate exposure to light, steering away from unfavorable conditions. Such insights could have broader implications beyond microbial biology.

The findings may inform the development of advanced microscopic swimming robots capable of navigating confined spaces, where traditional methods fall short. These robots could be engineered to perform intricate tasks, including targeted drug delivery within the human body, leveraging the same precise control over trajectory demonstrated by these microscopic organisms.

This research not only enhances our understanding of microbial motion but also opens pathways for innovative applications in technology and medicine, showcasing the potential of nature-inspired design in engineering.

For further details, refer to the study titled “Light-Dependent Switching of Circling Handedness in Microswimmer Navigation” by Zhao Wang et al, available in Physical Review Letters.