Break on through to the other side: outer membrane penetration of the nascent flagellum by a stop-polymerization mechanism.

Bacterial cells are equipped with a myriad of organelles or complex protein assemblages that execute specialized functions required for cellular integrity and survival in the ever-changing environment. Of these organelles, the flagellum is renowned for its use as a model system to elucidate the intricate molecular mechanisms that direct and coordinate the precise subcellular placement and step-wise assembly of macromolecular structures (Pandza et al. 2000; Aldridge and Hughes 2002; Macnab 2003; Huitema et al. 2006; Lam et al. 2006; Murray and Kazmierczak 2006). Interrogating the latter process, Chevance et al. (2007) discovered a new conceptual mechanism that underlies flagellar self-assembly and possibly that of other complex protein assemblages.