Rolling motion of uni-flagellated bacteria near a solid surface

Bacterial interaction with surfaces is ubiquitous in nature and is essential to many biological processes such as infection and biofilm formation. Here we study the tethering of uni-flagellated Caulobacter crescentus to a solid surface. In particular, we focus on weak reversible adhesion, which allows subsequent detachment. By applying an electrical field parallel to the surface, we observe that some initially tethered bacteria detach from the surface, but remain close to it. The detached cells perform rolling motion, a mixture of translation and rotation, different from the almost exclusive translation observed for nonmotile bacteria or swimming cells that are not previously attached. Our analysis of the rolling motion accounts for electrophoretic force, flagellar rotation, and the cell’s close proximity to the solid surface.