Bacterial motility in engineered and natural microscale porous environments

Bacterial motility plays a crucial role in nutrient cycling, bioremediation, and microbial interactions in complex environments such as soil and porous media. Over the past few years, we have been investigating bacterial motion in engineered and natural microscale porous environments, including cylindrical micro-pillars, microsphere-mimicked porous structures, and natural soil samples. We examined how different surface features on cylindrical micro-pillars (e.g., sprockets, gears, spikes, and flowers) influenced bacterial movement, and found that sharp spikes had the most pronounced impact on bacterial motility. In microsphere-mimicked porous structures, we observed that increasing microsphere density led to reduced bacterial velocity and enhanced directional changes, primarily due to collisions with the microspheres. In natural soil samples, we found that bacterial velocity was negatively correlated with soil density. Numerical simulations were performed using the active Brownian motion model. Results from the simulations supported our experimental observations across all conditions, highlighting the role of geometric confinement in shaping bacterial behavior. These findings advance our understanding of bacterial motility in both natural and engineered environments, with implications for soil health, microbial ecology, and biotechnological applications.