Collective Motion of Proteus mirabilis Swarmer Cells

For surface attached bacteria, it’s all about location, location, location. Cooperative swarming is one strategy that allows cells to work together to expand their colony’s boundary over a surface they could not individually traverse, unlocking new territory and additional nutrients. Proteus mirabilis is a highly effective swarmer, best known for its counterintuitive swarming strategy. Rather than continuously swarming, P. mirabilis colonies alternate between phases of swarming and consolidation, generating a distinctive bullseye pattern. Systems such as chemotaxis or cellular clocks can generate bullseye patterns, but do not explain the swarming cycle of P. mirabilis, so we examine the collective motion of swarmer cells to elucidate the role of physical mechanisms in their pattern formation. Using a “precocious” swarming mutant, which lacks important regulation of the swarming cycle and swarms continuously, we are able to access a steady-state regime of swarming not seen in wild type colonies. We aim to model the collective motion of swarmer cells in the absence of regulation in the precocious mutant in order to understand how wild type regulation of the swarming cycle exploits the collective dynamics of swarmer cells to swarm so effectively.