The role of PilU in the surface behaviors of Pseudomonas aeruginosa

In Pseudomonas aeruginosa, the dynamic activity of type IV pilus (TFP) is essential for various bacterial behaviors. While PilU is considered a homolog of the TFP disassembling motor PilT, its specific roles remain unclear. Using pilus visualization and single-cell tracking techniques, we characterized TFP dynamics and surface behaviors in wild-type and DeltapilU mutants. We found that DeltapilU cells displayed increased TFP numbers but reduced cell movement and delayed microcolony formation. Interestingly, beyond affecting the twitching motility, DeltapilU cells formed a thick multilayered colony edge on semi-solid surfaces, slowing colony expansion. Cell-cell collision responses changed from touch-turn dominance in wild-type to touch-upright dominance in DeltapilU, affecting colony morphology and expansion. These findings expand our understanding of PilU's physiological roles and provide potential targets for developing strategies to control P. aeruginosa biofilm formation and virulence.