Multispecies Swarms of Social Microorganisms as Moving Ecosystems

Microorganisms use collective migration to cross barriers and reach new habitats, and the ability to form motile swarms offers a competitive advantage. Traditionally, dispersal by microbial swarm propagation has been studied in monoculture. Microorganisms can facilitate other species' dispersal by forming multispecies swarms, with mutual benefits. One party (the transporter) moves a sessile partner (the cargo). This results in asymmetric associations ranging from temporary marriages of convenience to long-term fellow travellers. In the context of the 'microbial market', the parties offer very different services in exchange. We discuss bacteria transporting bacteria, eukaryotic microorganisms moving bacteria, and bacteria facilitating the spread of eukaryotes - and ask what the benefits are, the methods of study, and the consequences of multispecies, swarming logistics networks. Increasingly, microorganisms are studied in relation to other microorganisms.Many microorganisms can collectively migrate over surfaces to new ecological niches as a swarm.In recent years, some swarms have been shown to transport other microorganisms as cargo. This leads to interesting, asymmetric relationships whilst 'on the move' - which can be considered a mobile ecosystem.