Phage-Mediated Iron Acquisition by <i>Pseudomonas aeruginosa</i>

Iron acquisition is critical to bacterial growth and pathogenesis. Here, we describe a previously unrecognized mechanism by which the major human pathogen <i>Pseudomonas aeruginosa</i> acquires iron through a unique partnership with bacteriophages (phages). Pf is a filamentous phage that infects <i>P. aeruginosa</i> and is associated with chronic infections. We reveal that Pf contributes to <i>P. aeruginosa</i> pathogenesis by promoting iron uptake. We demonstrate that Pf phage is highly induced under iron-deplete growth conditions and that once induced, Pf virions directly bind and locally concentrate free iron. Pf-bound iron is more efficiently utilized by <i>P. aeruginosa</i> than unbound iron, enhancing bacterial growth. We further demonstrate that Pf-mediated iron acquisition depends on type IV pili, which facilitate Pf attachment and confers strain selective uptake of phage-bound iron, providing a competitive fitness advantage in polymicrobial settings. Together, these findings identify an unrecognized role for filamentous phages in mediating iron acquisition and reveal a novel phage-bacterium partnership that operates through selective kin cooperation.