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SYBS: Symposium Physics of Biological and Synthetic Active Matter

SYBS 1: Physics of Biological and Synthetic Active Matter

SYBS 1.2: Hauptvortrag

Dienstag, 13. März 2018, 10:00–10:30, H 0105

Nonlinear dynamics of beating cilia and flagella: Swimming, steering, and synchronization — •Benjamin M. Friedrich — cfaed, TU Dresden, Dresden, Germany

Cilia and flagella represent a best-seller of nature: their regular bending waves propel cellular swimmers such as sperm cells or green alga in a liquid. In my talk, I will address the physics of flagellar swimming and how mechanical and chemical signals control biological microswimmers. In the first part, I will a present a theory of sperm chemotaxis, i.e. the directed navigation of flagellated sperm cells that follow gradients of signaling molecules released by the egg. Recent experiments revealed that sperm cells of marine invertebrates dynamically switch between two steering modes in a situation-specific manner: steering either fast or slow [1]. We argue that the measurement of a concentration gradient during chemotaxis is corrupted by noise, and compute signal-to-noise ratios below one for physiological conditions. We show that decision making between different steering modes optimally balances the risk of inadvertently steering in the wrong direction by amplifying noise, and the speed of chemotactic re-orientation. Decision making substantially increases the probability to find a target, such as an egg. In a second part, I will discuss flagellar synchronization as an emergent phenomenon in collections of several flagella, which arises from a mutual hydro-mechanical coupling [2,3].

[1] J.F. Jikeli et al. Nature Commun. 6, 2015

[2] G.S. Klindt et al. Phys. Rev. Lett. 117, 2016

[3] R. Ma et al. Phys. Rev. Lett.113, 2014