Towards a molecular understanding of bacterial Type IV filament systems

Type IV filament systems (T4FS) are multi-component nanomachines spanning the cell envelope of most bacteria and archaea. They have diverse function including motility, bacterial predation and virulence, all of which rely on a shared mechanism involving T4FS-derived pilus filaments. While the principles governing pilus assembly are likely conserved across most T4FS, they remain poorly understood. This proposal addresses this knowledge gap by investigating two archetypal T4FS: the Type IV pilus system (T4PS) and Tad pilus system (TadPS). Key aims include understanding how these systems assemble, how their ultrastructure facilitates pilus extension/retraction, and how the ATPase motors couple nucleotide hydrolysis to the physical processing of pilins. To achieve these aims a multidisciplinary approach is undertaken combining in- vitro and in-cell structural biology, light microscopy, and advanced single- molecule imaging. By comparing the T4PS and TadPS, we uncover fundamental T4FS mechanistic principles that predate the evolutionary divergence of archaea and bacteria. Knowledge learnt will direct bottom-up reconstitution strategies aiming to recreate twitching motility and ultimately directed motion in synthetic cellular systems. This ambitious program seeks a molecular understanding of the TadPS and T4PS. It describes how these systems promote bacterial pathogenesis and facilitates development of targeted anti-virulence therapeutics.