Berlin 2018 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 15: Postersession III

BP 15.97: Poster

Dienstag, 13. März 2018, 14:00–16:00, Poster B

Collective Behaviour of Microalgae Beyond Phototaxis — •Johannes Frey, Alexandros Fragkopoulos, and Oliver Bäumchen — Max Planck Institute for Dynamics and Self-organization (MPIDS), Am Faßberg 17, D-37077 Göttingen

Chlamydomonas reinhardtii is a unicellular, eukaryotic microalga that has two flagella allowing the cell to propel itself in its surrounding fluid. This microalga is photoactive since, among else, it can perform photosynthesis and phototaxis. Here, we present the discovery of a light-sensitive collective behaviour within a population of planktonic Chlamydomonas cells. At low light intensities, we observe the cells to form inhomogeneous patterns within the confinement, while above a threshold the distribution of cells becomes homogenous. All experiments are performed under red light indicating that this phenomenon is not related to phototaxis. The swimming behaviour is fully reversible and time-resolved experiments show a dependence of its appearance on the geometry and size of the compartment as well as on the cell density. For circular chambers, we quantify the dynamics of the spatial distribution of cells as a function of the radius and height of the compartment and the cell density. The light intensity dependence and a color discrimination of the effect suggest, that the change in the cell motility is related to photosynthesis, but the exact biological mechanism remains to be explored.