Bacterial Swarms Recruit Cargo Bacteria To Pave the Way in Toxic Environments

Abstract

Swarming bacteria are challenged by the need to invade hostile environments. Swarms of the flagellated bacterium Paenibacillus vortex can collectively transport other microorganisms. Here we show that P.ﾠvortex can invade toxic environments by carrying antibiotic-degrading bacteria; this transport is mediated by a specialized, phenotypic subpopulation utilizing a process not dependent on cargo motility. Swarms of beta-lactam antibiotic (BLA)-sensitive P.ﾠvortex used beta-lactamase-producing, resistant, cargo bacteria to detoxify BLAs in their path. In the presence of BLAs, both transporter and cargo bacteria gained from this temporary cooperation; there was a positive correlation between BLA resistance and dispersal. P.ﾠvortex transported only the most beneficial antibiotic-resistant cargo (including environmental and clinical isolates) in a sustained way. P.ﾠvortex displayed a bet-hedging strategy that promoted the colonization of nontoxic niches by P.ﾠvortex alone; when detoxifying cargo bacteria were not needed, they were lost. This work has relevance for the dispersal of antibiotic-resistant microorganisms and for strategies for asymmetric cooperation with agricultural and medical implications.