Cooperative Pattern Formation in Multi-Component Bacterial Systems Through Reciprocal Motility Regulation

Self-organization is a prerequisite of biological complexity. At the population level, it amounts to spontaneously sorting different individuals through space and time. Here, we reveal a simple mechanism by which different populations of motile cells can self-organize through a reciprocal control of their motilities. We first show how the reciprocal activation of motility between two populations of engineered Escherichia coli makes an initially mixed population of cells segregate, leading to out-of-phase population oscillations without the need of any preexisting positional or orientational cues. By redesigning the interaction, the original segregation between the two populations can be turned into co-localization. We account for this self-organization using a theoretical model that shows the reciprocal control of motility to be a robust and versatile self-organization pathway in multi-component systems. We finally show how our theoretical and experimental results can be generalized to three interacting bacterial populations. The authors engineer Escherichia coli into two distinct strains with tunable motility. The induced control of motility leads to the formation of patterns through a self-organizing mechanism that is specific to multi-component active systems.