The phage-encoded PIT4 protein impacts the Pseudomonas aeruginosa type IV pili by affecting different two-component systems

Two component systems (TCSs) control a large proportion of virulence factors in Pseudomonas aeruginosa. Yet, investigations on inhibitors of regulatory pathways of TCS remain scare, despite their potential in anti-virulence strategies. This work encompasses the working mechanism of PIT4, a protein derived from the lytic P. aeruginosa phage LSL4. This viral protein inhibits bacterial motility and in particular twitching motility, while reducing the virulence of P. aeruginosa towards HeLa cells. Via differential gene expression and a yeast two-hybrid screen, PIT4 was shown to interact with components of different two component systems. In one-on-one interaction assays, it was confirmed that PIT4 interacts with the histidine kinases FleS, PilS and PA2882, through interaction with the histidine kinase domain. As such, this work highlights the potential of previously unknown phage proteins in virulence regulation of multidrug resistant pathogens that might be exploited for anti-virulence strategies and biotechnological applications. Overall design: The transcriptional landscape of cells expressing pit4 was compared to a control, a PAO1 strain harboring an empty construct.