Identification and Characterization of Type IV Pili as the Cellular Receptor of Broad Host Range Stenotrophomonas maltophilia Bacteriophages DLP1 and DLP2

Bacteriophages DLP1 and DLP2 are capable of infecting both Stenotrophomonas maltophilia and Pseudomonas aeruginosa strains, two highly antibiotic resistant bacterial pathogens, which is unusual for phages that typically exhibit extremely limited host range. To explain their unusual cross-order infectivity and differences in host range, we have identified the type IV pilus as the primary receptor for attachment. Screening of a P. aeruginosa PA01 mutant library, a host that is susceptible to DLP1 but not DLP2, identified DLP1-resistant mutants with disruptions in pilus structural and regulatory components. Subsequent complementation of the disrupted pilin subunit genes in PA01 restored DLP1 infection. Clean deletion of the major pilin subunit, pilA, in S. maltophilia strains D1585 and 280 prevented phage binding and lysis by both DLP1 and DLP2, and complementation restored infection by both. Transmission electron microscopy shows a clear interaction between DLP1 and pili of both D1585 and PA01. These results support the identity of the type IV pilus as the receptor for DLP1 and DLP2 infection across their broad host ranges. This research further characterizes DLP1 and DLP2 as potential “anti-virulence” phage therapy candidates for the treatment of multidrug resistant bacteria from multiple genera.