Bacterial trapping near topographic surfaces under shear flow

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Motile bacteria, such as Escherichia coli (E. coli), colonize surfaces, where they form hazardous biofilms and cause biofouling. When reaching the surface, they first need to be trapped by physical mechanisms, which then promotes their irreversible attachment to the surface through chemical bonding. Despite much insight, near-surface trapping of E. coli is still a poorly understood complex process, which is determined by E. coli’s run-and-tumble motility and physical conditions, such as shear flow and the surface topography. However, controlling near-surface trapping is essential for medical and biotechnological applications, for example, for preventing biofilms and biofouling but also for using bacteria as drug carriers to target disease sites such as malignant tumors. Therefore, the Indian and German groups join forces and use their complementary expertises to carry out a comprehensive simulation analysis in order to explore how physical conditions can be used to control the trapping of E. coli in shear flow near surfaces with different topography.We will perform a step-by-step analysis of the complex problem and heavily rely on a realistic model E. coli developed earlier by the Indian project leader. It will be used for a thorough preparatory analysis of the run-and-tumble motion in the bulk. In parallel, the German group will implement the model E. coli in a code based on the method of Multi-Particle Collision Dynamics, which will enable us to simulate fluid flows around the bacterium near surfaces with varying topography. Sharing the code between both groups, we will thoroughly analyze how a motile E. coli becomes trapped near a surface either in a quiescent fluid or under shear flow and thereby clarify contradicting observations. Our foci will be on the role of flagellar dynamics during runs and tumbles including polymorphism, which has so far been not resolved in any of the reported experimental studies on surface trapping, and also on the role of rheotaxis and Jeffery orbits for the bacterial dynamics. Finally, we will model surfaces with non-planar topography and investigate situations related to the control of biofouling and targeted drug deposition.