Figure 1. Kinematics of swimming E. coli cells in both Newtonian and viscoelastic fluids.

(A) Trajectories of E. coli cells in buffer (μ = 1.0 mPa · s) and (B) in polymeric solution (CMC MW = 7 × 10⁵, c = 500 ppm, c* = 10⁴, μ = 19 mPa · s). Cells in polymer solution move remarkably straighter compared to cells in buffer. Sample cell trajectories in (C) buffer and (D) polymeric solutions exhibit run-and-tumble i. e. nearly straight lines connected at random angles (tumbles denoted by arrows). (E) The cell body orientation oscillates or ‘wobbles’ in the buffer solution. (F) Wobbles diminish in the polymer solution.