Expression of a Phage-Encoded Gp21 Protein Protects Pseudomonas aeruginosa against Phage Infection
Guanhua Xuan, Hong Lin, Jingxue Wang
Abstract
The majority of the annotated phage genes are currently deposited as "hypothetical protein" with unknown function. Research has revealed that some phage proteins serve to inhibit or redirect the host intracellular processes for phage infection. Conversely, we report a phage encoded protein Gp21 that protects the host against phage infection. The pathways that Gp21 involved in antiphage defense in Pseudomonas aeruginosa PAO1 interfere with quorum sensing and decrease type IV pilus-mediated phage adsorption. Gp21 is a novel protein with a low sequence homology with other reported twitching inhibitory proteins. As a lytic phage-derived protein, Gp21 expression protects P. aeruginosa PAO1 from reinfection by phage vB_Pae_QDWS, which may explain the well-known pseudolysogeny caused by virulent phages. Our discoveries provide valuable new insight into phage-host evolutionary dynamics.