William Durham

The secret lives of bacteria: from single-cell sensing to universal patterns of collective movement

Bacterial motility shapes everything from the spread of infections to the structure of microbial communities, yet little is known about how bacteria attached to surfaces regulate their movement. In this talk I will present four recent discoveries about how the pathogen Pseudomonas aeruginosa crawls across surfaces using grappling hook-like appendages called pili. First, individual cells can sense chemical gradients directly across their own body length — overturning a 50-year-old paradigm and revealing a fundamentally new way that bacteria navigate their environment. Second, when moving collectively, cells selectively reverse direction to align their movement with their neighbours, generating large-scale coordinated flows that drive colony expansion. Third, these flow patterns are strikingly similar to those produced by collectively moving dog kidney cells and human breast cancer cells, suggesting universal patterns of collective movement are conserved across very different cell types. Fourth, when bacteria that move at different speeds are mixed together, they spontaneously sort themselves into distinct patches at singularities in cell orientation known as topological defects — a finding with potential implications for how microbial communities are structured. Together, these findings improve our understanding of how bacteria colonise surfaces and form the biofilms responsible for many difficult-to-treat infections.