Fig. 1. Tracking and classification of bacteria.

(A) Schematic of adhering (blue), diffusing (olive), and swimming (red) bacteria in a capillary. (B) Trajectories tracing the most mobile point on a cell. Straight red lines are fits of the length axis, squares mark anchoring points, and letters mark the type: diffuser (D), swimmer (S), wobbler (W), pivoter (P), and active rotator (R). The image is black/white-inverted and thresholded to be clear in print. Inset: Adhering cell and schematic depicting the anchoring coordinate and most mobile coordinate ∈ [−0.5, 0.5] on its length axis. (C) MSDs as a function of time interval τ from trajectories of swimming (red), diffusing (olive), and adhering (blue) bacteria; thin lines show randomly selected individual trajectories and thick lines represent the average 〈R²(A, τ)〉_i,t of each category. The insets show an example trajectory for each category; squares denote the position in the last frame. (D) Normalized distribution of the translational exponent k_T for WT cells on glass during the first 2 hours of the experiment, showing distinct peaks for adhering (A), diffusing (D), and swimming (S) subpopulations. (E) Normalized distribution of the rotational exponent k_R for adhering cells, showing three peaks for wobblers (W), pivoters (P), and active rotators (R). Data in in panels D and E for the nonflagellated mutant ΔFF are shown in gray. (F) Two-dimensional histogram (logarithmic scaling) of the translational (k_T) and rotational (k_R) exponents for WT cells, showing three peaks for adherers (W, P, and R), one for diffusers (D), and one for swimmers (S). The distributions in panels D to F are based on 139,335 cells for WT and 10,582 cells for ΔFF, and data are weighted for trajectory durations.