Figure 2.

Swimming parameters vs. cell length. Run times (a), mean run speeds (b), tumble times (c), and absolute values of the cosines of tumble angles (d) for all tracks in each treatment were binned into logarithmically distributed size classes, and then mean values were obtained for each class. Blue circles represent control cells, and red squares represent cephalexin treated cells. Error bars represent the standard error of the means in each size class. Vertical grey dotted lines in all plots mark the average length of untreated E. coli. Horizontal grey dotted line in d marks the value corresponding to a uniform distribution of angles. Black lines in b and d represent the power density models (solid line, equations (6) and (8) respectively), the constant power models (dashed line, equations (7) and (9)) and the RFT model (dotted line, equation (3)). Dash-dot line in c is the best least-squares regression model between the logarithm of the tumble angle and the tumble time, after forcing the model to cross the value for normal-size cell: t = t _n + b log₁₀(l/l _n), where t is tumble time, l the length of the cell, and subscript n refers to normal-size cells estimates [b ± s.e. = 0.37 ± 0.02; R ² = 0.82; d.f. = 27]. Note the base-2 logarithmic axes for cell length.