Beecroft Building, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Dr Maria Tătulea-Codrean, University of Amsterdam
Abstract
Physical interactions between microorganisms and their environments play a central role in the collective dynamics of cilia, flagella, and swimming microorganisms. In the first part of this talk, we will examine the collective swimming and aggregation of Escherichia coli bacteria in anisotropic liquid crystal environments, where confinement and directional order profoundly alter microbial dynamics. In particular, bacterial chains aligned with the nematic director displayed the unexpected trend that swimming speed increased with chain length. To explain this, we combined experiments with agent-based simulations and minimal theoretical models, revealing that statistical variations in swimming speeds naturally lead to aggregation patterns where faster individuals promote the formation of faster, longer chains.
In the second part, we turn to a history-dependent mechanism for the synchronization of rotating bacterial flagella. In our theoretical model, the interplay between hydrodynamic coupling and the dynamic remodelling of the bacterial flagellar motor leads to spontaneous phase locking. While classical models of synchronization rely on elastic compliance or phase-dependent forcing, our theoretical model shows that synchronization can also arise purely from a history-dependent forcing, suggesting a broader class of physical mechanisms for the coordination of biological rotors.
[1] G. Sintès, M. Goral, T. Lopez-Leon, A. Lindner, and M. Tătulea-Codrean. Swimming limited aggregation of E. coli bacteria in liquid crystals. In preparation. (2025)
[2] N. Diederen and M. Tătulea-Codrean. Hydrodynamic synchronization of biological rotors with history-dependent forcing. In preparation. (2025)