Berlin 2018 – wissenschaftliches Programm
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BP: Fachverband Biologische Physik
BP 31: Microswimmers DY II (joint session DY/CPP/BP)
BP 31.5: Vortrag
Donnerstag, 15. März 2018, 11:00–11:15, BH-N 243
Optimal decision making for sperm chemotaxis in the presence of noise — •Justus A. Kromer1, Steffen Märcker2, Steffen Lange3, Christel Baier2, and Benjamin M. Friedrich3 — 1Stanford University, Stanford CA, USA — 2TU Dresden, Dresden, Germany — 3cfaed/TU Dresden, Dresden, Germany
Navigating agents such as biological cells rely on noisy sensory input. In cells performing chemotaxis, such noise arises from the stochastic binding of signaling molecules at low concentrations. We theoretically address the classic problem of chemotaxis towards a single target. As application example, we study chemotaxis of marine sperm towards the egg. Recent experiments revealed that these cells are able to dynamically switch between slow and fast chemotactic steering. The benefit of this decision making remains open.
We reveal an inherent coupling between the speed of chemotactic steering and the strength of directional fluctuations that result from the amplification of noise in the chemical input signal. This implies a trade-off between slow, but reliable, and fast, but less reliable steering. By formulating optimal navigation in the presence of noise as a Markov decision process, we show that dynamic switching between slow and fast steering substantially increases the probability to find the egg. This decision making is most beneficial, if chemical signals are above detection threshold, yet signal-to-noise ratios of gradient measurements are low. This situation generically arises at intermediate distances from the egg, thus defining a 'noise zone' that cells have to cross.