In my PhD, I investigate the quality control in assembly of type III secretion system export apparatus. At the core of the T3SS lies the export apparatus. In Salmonella pathogenicity island-1 encoded T3SS, the export apparatus is composed of 5 highly conserved proteins, SpaP, SpaQ, SpaR, SpaS and InvA, with a stoichiometry of 5:4:1:1:9. However, how this protein complex assembles is unclear. I am interested in gaining mechanistical understanding of the export apparatus assembly process. How is the stoichiometry achieved? Is the assembly process translationally regulated? Does the genetic organization affect the assembly process? How are the subunits inserted and folded in the membrane?