Search

Abstract Pseudomonas aeruginosa is a widespread nosocomial pathogen with a significant to cause both severe planktonic acute and biofilm-related chronic infections. Small RNAs (sRNAs) are noncoding regulatory molecules that are stabilized by the RNA chaperone Hfq to trigger various virulence-related signaling pathways. Here, we identified an Hfq-binding sRNA in P. aeruginosa PAO1, PqsS, which promotes bacterial pathogenicity and pseudomonas quinolone signal quorum sensing (pqs QS) system. Specifically, PqsS enhanced acute bacterial infections by inducing host cell death and promoting rhamnolipid-regulated swarming motility. Meanwhile, PqsS reduced chronic infection traits including biofilm formation and antibiotic resistance. Moreover, PqsS repressed pqsL transcript, increasing PQS levels for pqs QS. A PQS-rich environment promoted PqsS expression, thus forming a positive feedback loop. Furthermore, we demonstrated that the PqsS interacts and destabilizes the pqsL mRNA by recruiting RNase E to drive degradation. These findings provide insights for future research on P. aeruginosa pathogenesis and targeted treatment.

The aryl hydrocarbon receptor (AhR) protein senses microbial-secreted metabolites to trigger the host's innate immune system. The Pseudomonas quinolone signal (PQS) and Mycobacterium tuberculosis (MTb) metabolite phthiocol (Pht) are both ligands of AhR with similar chemical structures. As PQS is an essential quorum-sensing molecule that regulates a wide range of virulence factors in Pseudomonas aeruginosa, we hypothesized that Pht and its analogs are potential P. aeruginosa quorum-sensing inhibitors (QSIs) with immune-modulating functions. In this study, we demonstrated that Pht was able to inhibit the P. aeruginosa pqs QS system and reduce both biofilm formation and the production of pyocyanin. Molecular docking analysis suggested that Pht competes with PQS at the binding site of its receptor, PqsR. An electrophoretic mobility shift assay confirmed the Pht-PqsR interaction and showed that Pht attenuated PqsR from binding to the pqsA promoter. Proteomic analysis showed that synthesis of the key pqs QS proteins decreased upon the addition of Pht to the bacterial cultures. Furthermore, Pht analogs vitamins K1 (Phylloquinone), K2 (Menaquinones), and K3 (Menadione) were also showed to inhibit the P. aeruginosa pqs QS system while able to activate the AhR signaling pathways. Our study suggests that the AhR ligands Pht and its vitamin K analogs are promising QSIs for the alternative treatment of P. aeruginosa infections.