Regensburg 2022 – scientific programme

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SYSM: Interplay of Substrate Adaptivity and Wetting Dynamics from Soft Matter to Biology

SYSM 1: Interplay of Substrate Adaptivity and Wetting Dynamics from Soft Matter to Biology

SYSM 1.5: Invited Talk

Wednesday, September 7, 2022, 17:15–17:45, H1

Active contact line depinning by micro-organisms spreading on hydrogels — Marc Hennes^1,2, Julien Tailleur^1,3, Gaëlle Charron¹, and •Adrian Daerr¹ — ¹Université Paris Cité, UMR 7057 Matière et Systèmes Complexes, Frankreich — ²Universität zu Köln, Institut für Biologische Physik — ³CNRS, Frankreich

Capillary forces, capable of pinning millimetre-sized water droplets on inclined surfaces, become enormous at the bacterial scale, exceeding typical propulsion forces of microbes by several orders of magnitude. It is thus fascinating to explore the tricks that micro-organisms have evolved to overcome contact line pinning and spread across substrates. I will discuss specifically the spreading of bacteria (Bacillus subtilis) across agar hydrogels.

Recently we discovered a mode of collective bacterial motility in humid environment through the depinning of bacterial droplets[1]. Bacteria harness a variety of phenomena, drawing both on the porosity and the softness of the substrate, that result in unpinning the contact line, hence inducing a collective slipping of the colony across surfaces at slopes that can be as small as 0.5^∘. The exploited microscopic mechanisms could play a role in other contexts, including biofilm formation and flagella dependent migration modes like swarming, and highlight the possibilties of tuning the wetting dynamics on soft porous substrates.

[1] M. Hennes, J. Tailleur, G. Charron, A. Daerr, Proc. Nat. Acad. Sc. USA 114, 5958–5963, (2017), doi: 10.1073/pnas.1703997114