Anomalous diffusion ofE. coliunder microfluidic confinement and chemical gradient

Abstract

We report a two-layer microfluidic device to study the combined effect of confinement and chemical gradient on the motility of wild type E. coli. We track individual E. coli in 50 μm and 10 μm wide channels, with a channel height of 2.5 μm, to generate quasi-2D conditions. We find that contrary to expectations, bacterial trajectories are super-diffusive even in absence of a chemical (glucose) gradient. The superdiffusive behaviour becomes more pronounced on introduction of a chemical gradient or on strengthening the lateral confinement. Runlength distributions for weak confinement in absence of chemical gradients follow an exponential distribution. Both confinement and chemoattraction induce deviations from this behaviour, with the runlength distributions approaching a power-law form under these conditions. Both confinement and chemoattraction suppress large angle tumbles as well. Our results suggest that wild-type E. coli modulates both its runs and tumbles in a similar manner under physical confinement and chemical gradient.

The motion of micro-swimmers over a cavity in a micro-channel

“…This motion behavior shares similarities with the alternating ''sliding'' and ''tumbling'' motion of E. coli in microchannels. 69 However, Mode 2 will flow in the opposite direction within the channel, while Mode 3 will flow in the same direction within the channel. For swimmers with two different propelled modes and swimming directions, the change in cavity size directly affects their movement time inside the cavity and can potentially increase their trapping capability.…”