Mucus viscoelasticity controls bacterial active matter correlations

Active matter is the system of self-propelled particles converting the chemical energy of a nutrient into mechanical motion. Bacteria swimming in biological fluids is a simple representative of active matter. Collective motion and swarming emerge in concentrated bacteria suspension. While the emergence, mechanism, and physical properties of the collective motion of bacteria swarming in Newtonian fluid have been intensively studied, many fundamental questions in the case of complex non-Newtonian fluid, such as viscoelastic mucus, are unexplored. Here, we probe the physical properties of the collective motion of bacteria in viscoelastic mucus. Velocity temporal correlation time and spatial correlation length were studied to characterize the influence of the complex non-Newtonian response of mucus on the collective motion of bacteria. Our study shows that the collective motion's scale increases with the viscoelasticity of the mucus. Our results imply the possibility of manipulation of bacterial active matter through the solution's viscoelasticity.