# The role of PilU in the surface behaviors of Pseudomonas aeruginosa

## TL;DR

This study explores how PilU affects the surface behaviors of Pseudomonas aeruginosa, revealing its role in cell movement and colony formation.

## Contribution

The study identifies new roles of PilU in both single-cell and multicellular surface behaviors of Pseudomonas aeruginosa.

## Key findings

- ΔpilU cells show increased TFP numbers but reduced movement and delayed microcolony formation.
- ΔpilU cells form thick multilayered colony edges, slowing colony expansion on semi-solid surfaces.
- Cell–cell collision responses shift from touch-turn to touch-upright dominance in ΔpilU mutants.

## Abstract

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 ΔpilU mutants. We found that ΔpilU cells displayed increased TFP numbers but reduced cell movement and delayed microcolony formation. Interestingly, beyond affecting the twitching motility, ΔpilU 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 ΔpilU, 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.

The dynamic function of type IV pilus (TFP) can help cells to search appropriate spatial positions and perceive external environments, and is crucial for a variety of cell behaviors. Beyond the current picture of PilU in generating high retraction forces through a PilT‐dependent manner, this study reveals more roles of PilU in cell surface behaviors including single‐cell behavior like twitching and multicellular behaviors such as microcolony formation and colony expansion. These findings expand our understanding of the physiological roles of PilU in the surface behaviors and provide us insight into developing TFP‐based methods to control the pathogenicity and biofilm formation of Pseudomonas aeruginosa.