Characterizing the Formation of Concentric Rings-Pattern by Proteus mirabilis

Many organisms, including bacteria, can form patterns through intricate self-organization processes. Here, we study a concentric rings-pattern formed by Proteus mirabilis. When a small droplet of a Proteus mirabilis culture is inoculated on solid medium, cells grow on the surface for some time. This initial growth phase is followed by periodic cycles of surface-associated group motility (i.e., swarming) and cell multiplication (i.e., consolidation), which eventually leads to a macroscopic concentric rings-pattern. Yet, what regulates the formation of this pattern remains unclear. Our experimental results suggest that both initiation and maintenance of the formation of this pattern depend on cell density. For example, swarming begins only when cells reach a critical cell density, or its period can be tuned by manipulating cell density. In this talk, I will present our data to support this idea of density dependence and discuss its implications.