Population dynamics during swarming of Pseudomonas aeruginosa.

Swarming is a group motility behavior exhibited by bacteria that coordinate to spread over surfaces. Swarms of the bacterium Pseudomonas aeruginosa often develop tendril patterns and tendril development requires production of the surfactant rhamnolipid. We recently showed that harder surfaces limit induction of quorum sensing genes including those responsible for rhamnolipid synthesis, but it is not yet clear why similar populations of cells should behave differently on hard surfaces compared with soft (agar) surfaces. Here we explore the population dynamics during P. aeruginosa swarming. We find that the population of P. aeruginosa does not immediately increase as the swarm expands. We also detail three stages of population development during swarming.