Molecular mechanics of type-IV pili driven migration of P. aeruginosa

Bacteria can generate mechanical forces that are important for the colonization of surfaces, formation of biofilms, and infection of host cells. In Gram-negative bacterial pathogens, such as Pseudomonas aeruginosa, forces result from ATP-hydrolysis-driven extension-retraction cycles of extracellular filaments called type-IV pili. How bacteria adapt their pilus-based behavior to the mechanical environment is not known. Here, we show that the early stage of surface colonization by P. aeruginosa is modulated by substrate-dependent pilus activity. Our experimental data reveals a complex response of the bacterial migration machinery to substrate properties, including adaptation of the dynamics of pili, their spatial arrangement, and their number. The combination of experimental data with mathematical modeling reveals a comprehensive picture of the interplay of active and passive molecular mechanisms during migration of P. aeruginosa on solid substrates.