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Modeling of surfactant-driven front instabilities in spreading bacterial colonies

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The spreading of bacterial colonies at solid-air interfaces is determined by the physico-chemical properties of the involved interfaces. A widespread strategy for an efficient surface colonization is the production of surfactants.

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 flowsmay cause an instability of the circular colony shape and the subsequent formation of fingers.

In this work, which has been published in Soft Matter, the effect of bacterial surfactant production and substrate wettability on colony growth and shape is studied within the framework of a hydrodynamic thin film model. It is shown 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.

Voir en ligne : Modelling of surfactant-driven front instabilities in spreading bacterial colonie, Sarah Trinschek, Karin John & Uwe Thiele