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Physics Colloquium: Sticky Microbes – Microalgae Switch their Adhesiveness by Light

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Sprecher: Dr. Olivier Bäumchen
Veranstaltung: Mittwoch, den 20. September 2017, 16:00 - 17:00
Ort: Campus Limpertsberg, room BSC 1.04
162a, Avenue de la Faiencerie
L-1511 Luxembourg

Optimization through adaptation to the natural habitat represents a general theme in the evolution of life that can be readily observed for cells, microorganisms and even higher-level animals. For microbial life, the ability to adhere to surfaces is ultimately linked to the formation of dense populations called biofilms, which may help to protect the community of cells against external stimuli. In many physiological and technological settings, however, such biofilms are harmful and thus undesired. In contrast to marine phytoplankton, many photoactive microalgae live in complex environments, such as liquid-infused soil and moist rocks, where they encounter and colonize a plethora of surfaces.
We discovered that the adhesion of green microalgae to surfaces can be reversibly switched on and off by light [1]. Using a novel micropipette force spectroscopy technique, we measured in vivo single-cell adhesion forces and show that the microalga's flagella provide light-switchable adhesive contacts with the surface. This light-induced adhesion to surfaces is an active and completely reversible process that occurs on a timescale of seconds, mediated by flagella membrane proteins and triggered by a blue-light photoreceptor. Our results suggest that light-switchable adhesiveness is a natural functionality and general trait of soil-dwelling microalgae to regulate the transition between planktonic and surface-associated state. This mechanism yields an adhesive adaptation to optimize the photosynthetic efficiency and has abundant implications in ecological, environmental and technological scenarios, such as water purification, bioremediation, and photo-bioreactors for the sustainable production of biofuels.
The research group studies the physics of living matter at interfaces and combines concepts from statistical physics, soft matter physics, biological physics and fluid dynamics. In the final part of the talk, I will briefly summarize related research activities, such as the motility of microbes in confinement, the emergence of collective effects in active suspensions and the cooperative transport of molecular motor assemblies.

[1] C. Kreis, M. Le Blay, C. Linne, M. Makowski, and O. Bäumchen, “Adhesion of Chlamydomonas Microalgae to Surfaces is Switchable by Light”, Nature Physics (2017).

Daten: 2017_09_20_Olivier Baumchen_PC.pdf 37,85 kB