LAUSR

Active dispersal of microorganisms is often attributed to the cells’ motile organelles. However, much less is known about whether sessile cells can access such motility through aggregation with motile counterparts. Here, we show that the rosette aggregates of the bacterium Caulobacter crescentus , although predominantly sessile, can actively disperse through the flagellar motors of motile members. Comparisons in kinematics between the motile rosettes and solitary swimming cells indicate that the rosettes can be powered by as few as a single motor. We further reconstructed the 3D movements of the rosettes to reveal that their proximity to a solid-liquid interface promotes a wheel-like rolling, as powered by the flagellar torque. This rolling movement also features a sequence of sharp turns, a reorientation mechanism distinct from that of swimming cells. Overall, our study elucidates an unexplored regime of aggregation-based motility that can be widely applied to sessile-motile composites. Yu Zeng and Bin Liu investigate the potential biological function of aggregate formations, called rosettes, of the motile and sessile forms of the aquatic bacteria Caulobacter crescentus. Through microscopy studies and computational simulations, they show that rosettes actively traverse long distances through the flagellar motors of very few motile cells by inducing a wheel-like rolling when adjacent to a solid-liquid interface.