Pili are hair like appendages that are found on the outer membrane of bacteria. They are important for bacteria to attach to solid surfaces, are used as an apparatus in transfer of DNA from one cell to another, as well as twitching motility, and cell-cell adhesion.
In 2011 a group of scientist from the Institute of Structural and Molecular Biology identified that pilus biogenesis was initiated by the protein FimD. They also determined that FimD recruited, assembled, and secreted the pilus subunits through an outer membrane pore. Recently, scientist from the same institute have determined that as the pilus is assembled, the first subunit called FimH undergoes a structural change which creates energy to push the pilus through the outer membrane pore as well as prevent the pilus from retreating back into the pore. Additionally these scientists determined that as the pilus passed through the pore it rotates, enabling subsequent pilus subunits to be added to the pilus structure. Understanding this process is important for creating and identifying new therapeutics that could prevent pili biogenesis.