Bacterial Scattering from Convex Surfaces and its Effects on Motility and Chemotaxis

For many organisms across length scales, self-propulsion is a key mechanism for survival and nutrient acquisition in changing environments. The model microorganism Escherichia coli explores low Reynolds number environments executing ‘run-and-tumble’ chemotaxis in its search for resources. While many studies of chemotaxis and motility take place in open environments, typical real-world environments -- like soils, sediments, or the mammalian gut -- have physical structure across multiple length-scales which can alter or impede cellular trajectories. To understand how physical structure in the environment alters trajectories and attendant persistence lengths, we built microfluidic devices containing arrays of microscopic circular pillars and studied bacterial interactions with these structures through the lens of probabilistic scattering functions. We find that attractive interactions with the pillars and stochastic noise produce a complex set of probability distributions that characterize bacterial motion in structured environments. Thus, understanding how cells navigate chemical gradients and acquire resources in such complex environments is crucial to our understanding of microbial ecology and may enable design of devices for controlling bacterial motility.