Outer membrane proteins are essential for Gram-negative bacteria to rapidly adapt to changes in their environment. Intricate remodelling of the outer membrane proteome is critical for bacteria lpathogens to survive environmental changes, such asentry into host tissues 1–3. Fimbriae (also known as pili) are appendages that extend up to 2 μm beyond the cell surface to function in adhesion for bacterial pathogens, and are critical for virulence. The best-studied examples of fimbriae are the type 1 and P fimbriae of uropathogenic Escherichia coli, the major causative agent of urinary tract infections in humans. Fimbriae share a common mode of biogenesis, orchestratedby a molecular assembly platform called ‘the usher’ located in the outer membrane. Although the mechanism of pilus biogenesisis well characterized, how the usher itself is assembled at the outer membrane is unclear. Here, we report that a rapid response in usher assembly is crucially dependent on the translocation assembly module. We assayed the assembly reaction for a range of ushers and provide mechanistic insight into theβ-barrel assembly pathway that enables the rapid deployment of bacterial fimbriae.