Rotational dynamics of bound pairs of bacteria-induced membrane tubes

Abstract

We present experiments demonstrating tube formation in giant unilamellar vesicles that are suspended in a bath of swimming E. coli bacteria. The tubes are generated by the pushing force exerted by the bacteria on the membrane of the vesicles. Once generated, the bacteria are confined within the tubes, resulting in long-lived tubes that protrude into the vesicle. We show that such tubes interact to form stable bound pairs that orbit each other. We speculate that the tubes are maintained by the persistent pushing force generated by the bacterium, and the rotating pairs are stabilized by a combination of curvature mediated interaction and vorticity generated in the membrane by the rotation of the flagella.