Enhanced chemotaxis efficiency of Escherichia coli in viscoelastic solutions

Bacteria inhabit complex environments rich in macromolecular polymers that exhibit viscoelastic properties. While the influence of viscoelasticity on bacterial swimming is recognized, its impact on chemotaxis-a critical behavior for bacterial survival and colonization-remains elusive. In this study, we employed a microfluidic device to establish attractant gradients and observed the chemotactic behavior of Escherichia coli in both viscoelastic solutions containing carboxymethyl cellulose (CMC) and Newtonian buffers. Our results reveal that E. coli demonstrates markedly enhanced chemotactic efficiency in viscoelastic media. Notably, bacteria achieved faster migration velocities and higher steady-state accumulation in areas with higher attractant concentrations compared to those in Newtonian conditions. Through 3D tracking, we determined that changes in bulk motility parameters alone do not account for the observed enhancements. Further investigations through theoretical analysis and stochastic simulations suggested that the main enhancement mechanisms are mitigation of surface hydrodynamic hindrance resulting from solid surfaces commonly present in bacterial habitats, and the induction of a lifting force in viscoelastic solutions. These findings highlight the significant role of the rheological properties of bacterial habitats in shaping their chemotactic strategies, offering deeper insights into bacterial adaptive mechanisms in both natural and clinical settings.