The YebC Family Protein PA0964 Negatively Regulates thePseudomonas aeruginosaQuinolone Signal System and Pyocyanin Production
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ABSTRACTBacterial pathogenicity is often manifested by the expression of various cell-associated and secreted virulence factors, such as exoenzymes, protease, and toxins. InPseudomonas aeruginosa, the expression of virulence genes is coordinately controlled by the global regulatory quorum-sensing systems, which includes thelasandrhlsystems as well as thePseudomonasquinolone signal (PQS) system. Phenazine compounds are among the virulence factors under the control of both therhland PQS systems. In this study, regulation of thephzA1B1C1D1E1(phzA1) operon, which is involved in phenazine synthesis, was investigated. In an initial study of inducing conditions, we observed thatphzA1was induced by subinhibitory concentrations of tetracycline. Screening of 13,000 mutants revealed 32 genes that alteredphzA1expression in the presence of subinhibitory tetracycline concentrations. Among them, the gene PA0964, designatedpmpR(pqsR-mediatedPQSregulator), has been identified as a novel regulator of the PQS system. It belongs to a large group of widespread conserved hypothetical proteins with unknown function, the YebC protein family (Pfam family DUF28). It negatively regulates the quorum-sensing response regulatorpqsRof the PQS system by binding at its promoter region. AlongsidephzA1expression and phenazine and pyocyanin production, a set of virulence factors genes controlled by bothrhland the PQS were shown to be modulated by PmpR. Swarming motility and biofilm formation were also significantly affected. The results added another layer of regulation in the rather complex quorum-sensing systems inP. aeruginosaand demonstrated a clear functional clue for the YebC family proteins.
