Life has evolved diverse protein machines and bacteria provide many fascinating examples.

Flagella are the primary organelles of motility in bacteria and enable movement towards nutrients and away from harmful substances, a process known as chemotaxis. Flagella-mediated motility is also important for many pathogens – including Salmonella enterica – and allows the bacteria to reach the site of infection, facilitate host-pathogen interactions, and promote biofilm formation. The bacterial flagellum is by far the most prominent extracellular structure known in bacteria and made through self-assembly of several tens of thousand individual building blocks. However, many questions concerning the regulation, organization and assembly of this remarkably complex motility organelle remain poorly understood. We use a combination of genetic engineering, biochemistry and fluorescent microscopy techniques to understand the genetic regulation, self-assembly and protein export mechanisms of this fascinating nanomachine.