Long range self-organization in bacterial swarms

When grown on air-semisolid interface, many bacteria are able to move in groups and expand rapidly, in a manner called swarming. Bacteria swarming displays rich collective behavior. In this work, we focus on the interaction between swarm cells of E. coli and their fluid environment. Using novel tracers, we discovered large scale self-organization in E. coli swarming colonies that spans a distance of milimeters. This long range self-organization most likely results from local interactions. The results provide new insights into the collective behavior in active matter systems.