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Capillary interactions drive the self-organization of bacterial colonies

Nature Physics volume 21, pages 1444–1450 (2025)Cite this article

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Abstract

Many bacteria inhabit thin water layers on solid surfaces. These thin films occur both naturally—in soils, on hosts and on textiles—and in the laboratory on agar hydrogels. In these environments, cells experience capillary forces, but it is unclear how these forces shape bacterial collective behaviour. Here we show that the water menisci formed around bacteria lead to capillary attraction between cells while still allowing them to slide past one another. We develop an experimental apparatus that allows us to control bacterial collective behaviour by varying the strength and range of capillary forces. Combining three-dimensional imaging and cell tracking with agent-based modelling, we demonstrate that capillary attraction organizes rod-shaped bacteria into densely packed nematic groups and influences their collective dynamics and morphologies. Our results suggest that capillary forces may be a ubiquitous physical ingredient in shaping microbial communities in partially hydrated environments.

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Fig. 1: Water menisci around bacteria and colloidal particles on a hydrated substrate.
Fig. 2: Capillary forces promote mergers and hinder separation of bacterial cells.
Fig. 3: Capillary attraction and cell motility lead to multiple phases of collective cell organization.
Fig. 4: Water availability controls the organization of colonies of M. xanthus.

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Data availability

All data are available from the authors upon request. Source data are provided with this paper.

Code availability

Simulation and analysis codes are available via Zenodo at https://doi.org/10.5281/zenodo.12745141 (ref. 59). Source code of an interactive simulation application is available via GitHub at https://github.com/f-chenyi/water_app.

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Acknowledgements

We thank members of the Shaevitz and Wingreen groups for helpful discussions. We thank M. McBride for the gift of F. johnsoniae strains and for helpful discussions. We thank L. Søgaard-Andersen for the gift of M. xanthus strain SA3985. We thank S. González-LaCorte, S. Jena and J. D. McEnany for their valuable contributions to the early stage of this project. This work was supported in part by the National Science Foundation through the Center for the Physics of Biological Function (PHY-1734030), and awards PHY-1806501 and PHY-2210346, and in part by NIH grant GM082938 (N.S.W.).

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Author notes

  1. These authors contributed equally: Matthew E. Black, Chenyi Fei.

Authors and Affiliations

  1. Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA

    Matthew E. Black, Chenyi Fei, Ned S. Wingreen & Joshua W. Shaevitz

  2. Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

    Ricard Alert

  3. Center for Systems Biology Dresden, Dresden, Germany

    Ricard Alert

  4. Cluster of Excellence Physics of Life, Dresden, Germany

    Ricard Alert

  5. Department of Molecular Biology, Princeton University, Princeton, NJ, USA

    Ned S. Wingreen

  6. Joseph Henry Laboratories of Physics, Princeton University, Princeton, NJ, USA

    Joshua W. Shaevitz

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Contributions

M.E.B., C.F., R.A., N.S.W. and J.W.S. designed research; M.E.B. and J.W.S. designed experiments; M.E.B. conducted experiments; C.F., R.A. and N.S.W. performed modelling; C.F. performed simulation; M.E.B., C.F., R.A., N.S.W. and J.W.S. analysed data; and M.E.B., C.F., R.A., N.S.W. and J.W.S. wrote the paper.

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Correspondence to Ned S. Wingreen or Joshua W. Shaevitz.

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Supplementary information

Supplementary Information

Supplementary Sections I–VII, Tables 1–3 and Figs. 1–27.

Reporting Summary

Supplementary Video 1

Movie for the time series shown in Fig. 2d, showing the merger of non-motile M. xanthus cells due to capillary attraction.

Supplementary Video 2

Movie showing merging and splitting of motile M. xanthus groups. Coloured regions are groups of cells marked as single groups. Overlaid numbers are the detected number of cells in that group.

Supplementary Video 3

Movie showing an example of simulated cells in the gas phase. Simulation parameters are \(\widetilde{l}={10}^{3.5}\), \(\widetilde{F}=10\) and \(\widetilde{\tau }=10\). The colour bar is the same as in Fig. 3.

Supplementary Video 4

Movie showing an example of simulated cells in the droplets phase. Simulation parameters are \(\widetilde{l}={10}^{2}\), \(\widetilde{F}=0.3\) and \(\widetilde{\tau }=3\). The colour bar is the same as in Fig. 3.

Supplementary Video 5

Movie showing an example of simulated cells in the polar clusters phase. Simulation parameters are \(\widetilde{l}={10}^{2.5}\), \(\widetilde{F}=1\) and \(\widetilde{\tau }={10}^{2}\). The colour bar is the same as in Fig. 3.

Supplementary Video 6

Movie showing an example of simulated cells in the “streams” phase. Simulation parameters are \(\widetilde{l}={10}^{2.5}\), \(\widetilde{F}=1\) and \(\widetilde{\tau }=1\). The colour bar is the same as in Fig. 3.

Supplementary Video 7

Movie showing an example of M. xanthus cells in the gas phase.

Supplementary Video 8

Movie showing an example of M. xanthus cells in the droplets phase.

Supplementary Video 9

Movie showing an example of M. xanthus cells in the polar clusters phase.

Supplementary Video 10

Movie showing an example of M. xanthus cells in the streams phase.

Supplementary Video 11

Movie for the time series in Fig. 3f, showing neighbour exchange in the streams phase.

Supplementary Video 12

Movie for the time series shown in Fig. 4a, showing the large-scale morphologies of M. xanthus cells upon changes in water availability.

Supplementary Video 13

Movie showing the large-scale morphologies of F. johnsoniae cells upon changes in water availability.

Supplementary Video 14

Example movie showing how the motility of M. xanthus may be faster in groups compared with individual cells, possibly due to lower normal capillary forces, and thus lower substrate friction, when cells move in groups relative to when they move individually.

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Statistical source data.

Source Data Fig. 3

Statistical source data.

Source Data Fig. 4

Statistical source data.

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Black, M.E., Fei, C., Alert, R. et al. Capillary interactions drive the self-organization of bacterial colonies. Nat. Phys. 21, 1444–1450 (2025). https://doi.org/10.1038/s41567-025-02965-y

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