Anomalous diffusion of under microfluidic confinement and chemical gradient

• Published in: Soft matter 2023-08, Vol.19 (34), p.6446-6457
• Main Authors: Raza, Md Ramiz, George, Jijo Easo, Kumari, Savita, Mitra, Mithun K, Paul, Debjani
• Format: Article
• ISSN: 1744-683X; 1744-6848
• DOI: 10.1039/d3sm00286a

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 microchannels, with a channel height of 2 μm, to generate quasi-2D conditions. We find that contrary to expectations, bacterial trajectories are superdiffusive even in the absence of a chemical (glucose) gradient. The superdiffusive behaviour becomes more pronounced upon introducing a chemical gradient or strengthening the lateral confinement. Run length distributions for weak lateral confinement in the absence of chemical gradients follow an exponential distribution. Both confinement and chemoattraction induce deviations from this behaviour, with the run length 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. Our findings have implications for understanding how bacteria modulate their motility behaviour in natural habitats. We developed a two-layer microfluidic device to study the motility dynamics of E. coli . We show that both confinement and chemoattractant lead to anomalous diffusion, with power-law distributed run lengths and suppression of large-angle tumbles.