A new route for polar navigation

Placement of motility structures at the poles of rod-shaped bacteria is a common engineering problem with a variety of potential solutions. While investigating the mechanisms for positioning of the single polar flagellum of Pseudomonas aeruginosa, Cowles and colleagues discovered a new membrane-bound three-component system related to TonB-ExbB-ExbD that they named 'Poc' for polar organelle co-ordinator, which controls polar localization of both the flagellum and type IV pili. The Poc complex itself is not found at the poles, and is required for increased expression of pilus genes upon surface association, suggesting a new paradigm of localization control.