Remodeling of Chemotaxis is a Cornerstone of Bacterial Swarming

Many bacteria use flagella-driven motility to swarm or move collectively over a surface terrain. Bacterial adaptations for swarming can include cell elongation, hyper-flagellation, recruitment of special stator proteins and surfactant secretion, among others. We recently demonstrated another swarming adaptation in Escherichia coli, wherein the chemotaxis pathway is remodeled to increase run durations (decrease tumble bias), with running speeds increased as well. We show here that the modification of motility parameters during swarming is not unique to E. coli, but shared by a diverse group of bacteria we examined - Proteus mirabilis, Serratia marcescens, Salmonella enterica, Bacillus subtilis, and Pseudomonas aeruginosa - suggesting that altering the chemosensory physiology is a cornerstone of swarming. ImportanceBacteria within a swarm move characteristically in packs, displaying an intricate swirling motion where hundreds of dynamic packs continuously form and dissociate as the swarm colonizes increasing expanse of territory. The demonstrated property of E. coli to reduce its tumble bias and hence increase its run duration during swarming is expected to maintain/promote side-by-side alignment and cohesion within the bacterial packs. Here we observe a similar low tumble bias in five different bacterial species, both Gram positive and Gram negative, each inhabiting a unique habitat and posing unique problems to our health. The unanimous display of an altered run-tumble bias in swarms of all species examined here suggests that this behavioral adaptation is crucial for swarming.