Speaker
Description
Liquid crystals serve as model systems for structured environments and represent a broader class of anisotropic, non-Newtonian fluids encountered by bacteria, such as host mucus \cite{1} and extracellular polymeric substances involved in biofilm formation \cite{2}. In this study, we investigated the collective swimming of fluorescently labelled Escherichia coli in nematic liquid crystals and observed the emergence of long-lived chains of bacteria swimming along the nematic director, similar to those observed for Proteus mirabilis by Mushenheim et al. \cite{3}. Remarkably, we found that longer chains swim faster, contrary to predictions from fundamental force-balance models and observations of merging bacterial pairs. To explain this counterintuitive behaviour and identify the physical mechanism driving bacterial aggregation in liquid crystals, we combined experiments with agent-based simulations and minimal theoretical modeling. By incorporating the intrinsic speed distribution of individual bacteria, our simulations revealed a positive correlation between chain length and swimming speed, consistent with experimental observations. A minimal aggregation model, based on encounter probabilities between a bacterium and its two nearest neighbours, further supports our interpretation that longer chains swim faster because they are more likely to contain faster-swimming individuals, which meet and merge with their neighbours in less time.
Bibliography
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pages={e2200930119},
year={2022},
publisher={National Academy of Sciences}
}
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title={Dynamic self-assembly of motile bacteria in liquid crystals},
author={Mushenheim, Peter C and Trivedi, Rishi R and Tuson, Hannah H and Weibel, Douglas B and Abbott, Nicholas L},
journal={Soft Matter},
volume={10},
number={1},
pages={88--95},
year={2014},
publisher={Royal Society of Chemistry}
}
@misc{4,
title={Swimming-limited aggregation of bacteria in liquid crystals},
author={Guillaume Sintès and Martyna Goral and Teresa López-León and Anke Lindner and Maria Tătulea-Codrean},
year={2026},
eprint={2607.05239},
archivePrefix={arXiv},
primaryClass={cond-mat.soft},
url={https://arxiv.org/abs/2607.05239},
}
