Mechanisms of TonB-Dependent Protein Import in Pseudomonas aeruginosa

S-type pyocins are a family of soluble protein antibiotics that are specific for strains of P. aeruginosa. For these proteins to elicit their cytotoxic activity, they must first translocate across the bacterial outer membrane. This process is facilitated by parasitising the Ton system, a bacterial nutrient transport system; comprised of an inner membrane energy-transducing complex and a ligand-specific outer membrane transporter. The mechanism by which pyocin binding to the outer membrane transporter triggers the recruitment of the Ton complex and subsequent protein translocation across the outer membrane is poorly understood. I aim to decipher the molecular and mechanical basis of pyocin translocation by the Ton complex. I will use biochemical and structural techniques to characterise the protein-protein interactions between pyocins with their outer membrane receptors and the Ton complex. I will also design an assay to study the mechanical forces generated by the Ton complex as pyocins are translocated through the outer membrane in vivo, using fluorescence microscopy and force spectroscopy. These studies will determine the mechanism by which P. aeruginosa translocate molecules across the outer membrane; a process of paramount importance for the development of novel antibiotic therapies to target the growing problem of bacterial antibiotic resistance.