Regensburg 2025 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 42: Active Matter IV (joint session BP/CPP/DY)
CPP 42.3: Talk
Friday, March 21, 2025, 10:15–10:30, H44
Tumbling E.coli in bulk and close to surfaces — •Pierre Martin1, Tapan Chandra Adhyapak2, and Holger Stark1 — 1Institute of Theoretical Physics, Hardenbergstr. 36, 10623 Berlin, Germany — 2Indian institute of science education and research (IISER), Tirupati, India
Escherichia coli (E. coli) swims by rotating multiple flagella which are connected to the cell body forming a thick bundle. To change direction, E. coli performs tumble events by reversing the rotation of one or more flagella. The involved filaments undergo a series of polymorphic transformations, altering both their helicity and handedness. This complex phenomenon involves the interplay of semiflexible filaments and hydrodynamic flow fields.
Here, we have developed a detailed numerical framework to simulate E. coli, capturing the full dynamics of flexible flagella, including their polymorphism and their hydrodynamic interactions. The filaments and the cell body are embedded in a viscous fluid, which we model using multi-particle collision dynamics. We analyzed a large number of tumble events, with fixed tumble time or taken from a gamma distribution, exploring the roles of hook and flagellar flexibility as well as flagellar polymorphism. We find that they strongly influence the distribution of tumble angles. Finally, we also show that close to a flat surface the mean tumble angle is strongly shifted to smaller values. This indicates that tumble events may not be recognized, which could give the impression of suppressed tumbling near surfaces.
Keywords: Microswimmer; Hydrodynamic; Simulation