Generalized receptor law governs phototaxis in the phytoplankton Euglena gracilis
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Giometto-2015-Generalized receptor.pdf
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Author(s)
Giometto, Andrea
Altermatt, Florian
Maritan, Amos
Stocker, Roman
Rinaldo, Andrea
Date Issued
June 2015
Journal
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences (U.S.)
Citation
Giometto, Andrea, Florian Altermatt, Amos Maritan, Roman Stocker, and Andrea Rinaldo. “Generalized Receptor Law Governs Phototaxis in the Phytoplankton Euglena Gracilis.” Proc Natl Acad Sci USA 112, no. 22 (May 11, 2015): 7045–7050.
Version
Final published version
Abstract
Phototaxis, the process through which motile organisms direct their swimming toward or away from light, is implicated in key ecological phenomena (including algal blooms and diel vertical migration) that shape the distribution, diversity, and productivity of phytoplankton and thus energy transfer to higher trophic levels in aquatic ecosystems. Phototaxis also finds important applications in biofuel reactors and microbiopropellers and is argued to serve as a benchmark for the study of biological invasions in heterogeneous environments owing to the ease of generating stochastic light fields. Despite its ecological and technological relevance, an experimentally tested, general theoretical model of phototaxis seems unavailable to date. Here, we present accurate measurements of the behavior of the alga Euglena gracilis when exposed to controlled light fields. Analysis of E. gracilis’ phototactic accumulation dynamics over a broad range of light intensities proves that the classic Keller–Segel mathematical framework for taxis provides an accurate description of both positive and negative phototaxis only when phototactic sensitivity is modeled by a generalized “receptor law,” a specific nonlinear response function to light intensity that drives algae toward beneficial light conditions and away from harmful ones. The proposed phototactic model captures the temporal dynamics of both cells’ accumulation toward light sources and their dispersion upon light cessation. The model could thus be of use in integrating models of vertical phytoplankton migrations in marine and freshwater ecosystems, and in the design of bioreactors.
MIT Department
Massachusetts Institute of Technology. Department of Civil and Environmental Engineering
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DOI of Published Version
https://doi.org/10.1073/pnas.1422922112
