The phage-encoded PIT4 protein affects multiple two-component systems of Pseudomonas aeruginosa

ABSTRACT Two-component systems (TCSs) control a large proportion of virulence factors in Pseudomonas aeruginosa. Yet, investigations on inhibitors of regulatory pathways of TCSs remain scarce, despite their potential in anti-virulence strategies. This work elucidates the molecular mechanism of PIT4, a protein encoded by the lytic P. aeruginosa phage LSL4. Single-copy expression of this early phage gene inhibits bacterial motility, in particular twitching motility, and reduces the virulence of P. aeruginosa in HeLa cells. Differential gene expression and a yeast two-hybrid screen showed that PIT4 interacts with components of different two-component systems. In one-on-one interaction assays, it was confirmed that PIT4 specifically interacts with the histidine kinase domains of FleS, PilS, and PA2882. This identified phage mechanism therefore demonstrates the ability of phage proteins to simultaneously target and impact multiple pathways and hints toward a biological function as an infection-exclusion mechanism. This work highlights the potential of previously unknown phage proteins in virulence regulation of multidrug resistant pathogens that could in future be exploited for anti-virulence strategies and biotechnological applications. IMPORTANCE More and more Pseudomonas aeruginosa isolates have become resistant to antibiotics like carbapenem. As a consequence, P. aeruginosa ranks in the top three of pathogens for which the development of novel antibiotics is the most crucial. The pathogen causes both acute and chronic infections, especially in patients who are the most vulnerable. Therefore, efforts are urgently needed to develop alternative therapies. One path explored in this article is the use of bacteriophages and, more specifically, phage-derived proteins. In this study, a phage-derived protein was studied that impacts key virulence factors of the pathogen via interaction with multiple histidine kinases of TCSs. The fundamental insights gained for this protein can therefore serve as inspiration for the development of an anti-virulence compound that targets the bacterial TCS.