Active depinning of bacterial droplets: The collective surfing of Bacillus subtilis
Résumé
Significance How bacteria propagate and colonize new environments is of paramount importance, e.g., to food processing, transport, and storage. In this article, we show that Bacillus subtilis can turn millimetric water droplets into vehicles to quickly cover large distances. To this end, they overcome the enormous capillary forces that prevent the sliding of water droplets even on vertical surfaces such as refrigerator walls. B. subtilis does so by actively unpinning the surrounding liquid to cause the collective surfing of the entire community on slopes as small as 0.1°. We show this depinning to rely on a variety of mechanisms, which could each be relevant to the motility of microorganisms in partially humid environments such as unsaturated soils.