Figure 3: Statistics of cell displacements.
Analysis of trajectories using the low magnification. (a) The distribution of cell displacements along each axis between a fixed number of frames. Following a scaling of Δt1/1.33, all distributions approximately fit a Lévy stable distribution with parameter 1.33. (b) The probability density function (PDF) of cell directions (with respect to an arbitrary lateral axis of the frame) is uniform for all time intervals. Data were taken at high magnification. (c) Persistence in the direction of motion. The direction of motion remains fairly constant for times that are significantly longer than the characteristic run times in bacteria (∼1 s). Experiments with S. marcescens yield similar results (data not shown). (d) The velocity auto-correlation function decays algebraically with slope of −0.41, in agreement with the theory of LWs.
