Figure 1.

Experimental setup. (a) Sketch of the setup. A bacterium was immobilized on a polystyrene-coated cover glass. When a pilus was bound to the bead in the laser trap and retracted, the bead was displaced by a distance d from the center of the trap. At a predefined distance d corresponding to a force F, a feedback was triggered that moved the piezo table to keep d constant. (b) Typical length change x of a single pilus of MS11_{pilT ind} as a function of time at 60 pN; (c and d) MS11_{pilT oe} at 100 pN. The curves b to d were broken down into retraction intervals (black), elongation intervals (green), and pauses (red).