Fig. 3

Accumulation profiles of bacteria at the four maze junctions for a monoclonal E. coli population responding to a methylaspartate gradient. Panels show the absolute number of bacteria observed at points along each T-junction (circles, mean ± s.d. from three replicates) in the linear-sensing (a, c, e, g) and log-sensing (b, d, f, h) regimes. Lines show the expected number of bacteria from the simulations. The shaded confidence interval shows the variation in the simulation solution over the time interval of the experiments (40–160 min). Bacteria are introduced at the inlet in the maze at t = 0 min (see Fig. 1) and disperse over time into the maze (see Supplementary Fig. 2 for the accumulation profiles at two different time points). The chemotactic sensitivity in the simulations was fitted to best match the experimental profiles at junction 1. Higher numbers of bacteria are found at later junctions in the maze compared to the simulations performed with a chemotactically homogeneous population of cells, as a consequence of the sorting mechanism