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Spreading strategies and morphology of bacterial colonies: interplay between passive physico-chemical effects and bioactive growth

Banff International Research Station for Mathematical Innovation and Discovery

The spreading of bacterial colonies at solidâ air interfaces is determined by the physico-chemical properties of the involved interfaces and bioactive growth processes. The production of surfactant molecules by bacteria is a widespread strategy that allows the colony to efficiently expand over the substrate. On the one hand, surfactant molecules lower the surface tension of the colony, effectively increasing the wettability of the substrate, which facilitates spreading. On the other hand, gradients in the surface concentration of surfactant molecules result in Marangoni flows that drive spreading. These flows may cause an instability of the circular colony shape and the subsequent formation of fingers. In this work, we study the effect of bacterial surfactant production and substrate wettability on colony growth and shape within the framework of a hydrodynamic thin film model. We show that variations in the wettability and surfactant production are sufficient to reproduce four different types of colony growth, which have been described in the literature, namely, arrested and continuous spreading of circular colonies, slightly modulated front lines and the formation of pronounced fingers.

Mathematics; Fluid mechanics; Approximations and expansions; Fluid dynamics

video/mp4

Author affiliation: Université Grenoble-Alpes

2019-10-27

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/72075

Unreviewed

http://creativecommons.org/licenses/by-nc-nd/4.0/