Mechanosensing-driven collision reversal governs bacterial locomotion and collective dynamics

How bacterial cells navigate complex environments holds significant importance for biological processes such as biofilm formation and bacterial infection. The opportunistic pathogen Pseudomonas aeruginosa employs twitching motility on the substrate driven by type IV pili, which not only enable propulsion but also serve a mechanosensory role by reversing cell polarity upon collision with obstacles. While collision-induced reversals have been studied at the single-cell level, their collective effects on bacterial populations are still lacking. Here, we investigate these collective dynamics using a self-propelled spherocylinder model with tunable collision reversal probabilities. We find that collision reversal significantly influences persistence of cell motion in a density-dependent manner, modulating the timescales of ballistic-to-diffusive transitions. Suppressing collision reversal leads to a qualitative shift from isotropic diffusive motion to phase separation and collective dynamics. Surprisingly, an intermediate reversal rate optimizes exploration efficiency in both invasion front and maze-like environments, and quantitative measurements on the structure and dynamics of P. aeruginosa across varying packing densities and collision reversal rates validate our model. Our results highlight that mechanosensing through collision reversal is not only critical for collective locomotion but also enhances adaptability in complex environments.