Dresden 2020 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 43: Statistical Physics of Biological Systems II (joint session BP/DY)
DY 43.5: Talk
Wednesday, March 18, 2020, 16:30–16:45, ZEU 250
Sperm chemotaxis in external flows — •Steffen Lange1,2 and Benjamin Friedrich1,2,3 — 1Center for Advancing Electronics Dresden (cfaed) — 2Cluster of Excellence Physics of Life (PoL) — 3Institut Theoretische Physik (ITP), TU Dresden, 01062 Dresden, Germany
Chemotaxis - the navigation of biological cells guided by chemical gradients - is crucial for bacterial foraging, immune responses, and guidance of sperm cells to the egg before fertilization.
Previous work on chemotaxis focused predominantly on idealized conditions of perfect chemical gradients. However, natural gradients are subject to distortions, e.g. by turbulent flows in the ocean.
Recent experiments with bacteria [1] and sperm cells from marine invertebrates [2] have surprisingly revealed the existence of an optimal turbulence strength at which the chemotaxis is more effective than for still water conditions with perfect gradients.
Using sperm chemotaxis in shear flow as a prototypical example, we reproduce an optimal turbulence strength in numerical simulations. We can understand the origin of this optimum and quantify it:
For this we apply a theory of sperm chemotaxis to the concentration filaments, which are typical for scalar turbulence. We explain how external flows distort sperm swimming paths and concentration gradients, but at the same time extend the spatial range of these gradients. Together, these two competing effects set the optimal turbulence strength. We compare our theoretical results to previous experiments and find good agreement.
[1] Taylor, Stocker; Science 2012 [2] Zimmer, Riffell; PNAS 2011