Dresden 2026 – scientific programme

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BP: Fachverband Biologische Physik

BP 1: Active Matter I (joint session BP/CPP/DY)

BP 1.10: Talk

Monday, March 9, 2026, 12:15–12:30, BAR/SCHÖ

Light-switchable microbial rafts at air-liquid interfaces — •Gustav F. Nolte, Alexandros A. Fragkopoulos, Timo Völkl, Mechthild Rappold, and Oliver Bäumchen — University of Bayreuth, Experimental Physics V, 95447 Bayreuth, Germany

In biological active matter, clustering occurs across a wide range of time and length scales, from molecular assemblies such as actomyosin networks to macroscopic systems like fire ant rafts. Here, we report on a fast, light-switchable, and fully reversible clustering phenotype on the microscale, observed at air-liquid interfaces: the raft formation of the biciliated microalga Chlamydomonas noctigama.

C. noctigama is a relative of the model organism Chlamydomonas reinhardtii, which exhibits light-switchable adhesion and subsequent clustering at solid-liquid interfaces [1,2]. We show how the cluster morphology depends on cell density and discuss potential growth mechanisms by analyzing dynamics of individual clusters. Furthermore, we characterize the dependence of raft formation on the light spectrum and interfacial free energy. Using micropipette force spectroscopy [3], we show that single cells exploit capillary forces for light-switchable ciliary adhesion to the air-liquid interface, enabling raft formation. In their natural habitats, reversible clustering may provide an advantage by allowing cells to accumulate in locations optimal for photosynthesis while increasing resilience to environmental stress.

[1] C. T. Kreis, et al., Nat. Phys. 14, 45 (2018).

[2] S. Till, et al., Phy. Rev. Res. 4, L042046 (2022).

[3] M. Backholm and O. Bäumchen, Nat. Protoc. 14, 594-615 (2019).

Keywords: Chlamydomonas; cell clustering; cell-cell interactions