Swimming speeds of E. coli in buffer and polymeric solutions.
(A) Velocity , average cell orientation and instantaneous cell body orientation θ are defined as shown. (B) Temporal variations in the cell body speeds in buffer and polymeric solutions (c = 500 ppm) reveal tumbles (arrows) via sudden drops in. The cell in buffer swims at a lower velocity and tumbles more frequently compared to the cell in the polymer solution. (C) The mean cell velocity increases from 8.3 to 12.4 μm/s with increasing polymer concentration.