Controlling microalgae populations by phototactic memory
Abstract
Understanding how microorganisms navigate in complex environments is a central question in active matter and biological physics. Phototaxis - the ability to use light as a navigation cue - is a widespread strategy in motile microalgae to optimise photosynthesis and avoid light-induced stress. The microalga Chlamydomonas reinhardtii is a model system for studying this behaviour, where navigation is classically attributed to a photosensitive organelle named eyespot. While this mechanism enables cells to sense the direction of incoming light, their response to light intensity gradients remains less understood. Here we show that structured light landscapes can guide microalgae populations and localise them in defined spatial regions. By analysing single-cell trajectories, we find that cells actively steer relative to the local light gradient, and a comparison with a minimal theoretical model shows that a short-time memory of light exposure acting on the transition between positive and negative phototaxis is necessary to reproduce the observed accumulation. At longer times, we observe a gradual decrease in cell number density within the trapping region, consistent with phototactic adaptation. Beyond controlling population dynamics, our results reveal new aspects of phototactic behaviour, highlighting gradient-aligned steering together with temporal integration as central mechanisms for navigation in structured environments.
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BibTeX
@misc{jacucci2026controlling,
title = {{Controlling microalgae populations by phototactic memory}},
author = {Gianni Jacucci and Davide Breoni and Pierre Illien and Luca Tubiana and Jean-François Allemand and Sylvain Gigan and Rapha Ël Jeanneret},
howpublished = {HAL},
year = {2026},
month = nov,
eprint = {2601.07741},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05848410v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Controlling microalgae populations by phototactic memory
AU - Gianni Jacucci
AU - Davide Breoni
AU - Pierre Illien
AU - Luca Tubiana
AU - Jean-François Allemand
AU - Sylvain Gigan
AU - Rapha Ël Jeanneret
PY - 2026
DA - 2026/11/02
PB - HAL
UR - https://hal.science/hal-05848410v1
AB - Understanding how microorganisms navigate in complex environments is a central question in active matter and biological physics. Phototaxis - the ability to use light as a navigation cue - is a widespread strategy in motile microalgae to optimise photosynthesis and avoid light-induced stress. The microalga Chlamydomonas reinhardtii is a model system for studying this behaviour, where navigation is classically attributed to a photosensitive organelle named eyespot. While this mechanism enables cells to sense the direction of incoming light, their response to light intensity gradients remains less understood. Here we show that structured light landscapes can guide microalgae populations and localise them in defined spatial regions. By analysing single-cell trajectories, we find that cells actively steer relative to the local light gradient, and a comparison with a minimal theoretical model shows that a short-time memory of light exposure acting on the transition between positive and negative phototaxis is necessary to reproduce the observed accumulation. At longer times, we observe a gradual decrease in cell number density within the trapping region, consistent with phototactic adaptation. Beyond controlling population dynamics, our results reveal new aspects of phototactic behaviour, highlighting gradient-aligned steering together with temporal integration as central mechanisms for navigation in structured environments.
ER -