title: PtxR modulates the expression of QS-controlled virulence factors in the Pseudomonas aeruginosa strain PAO1.
abstract: The production of several virulence factors by Pseudomonas aeruginosa is regulated through the hierarchical cell-density dependent quorum sensing (QS) systems las and rhl. A third component of the QS hierarchy, the Pseudomonas quinolone signal PQS, also controls the expression of several genes. We previously described P. aeruginosa PtxR as a transcriptional activator of the exotoxin A gene toxA. Here, we provide evidence that PtxR regulates the production of other virulence factors. Mutation of ptxR in PAO1 increased pyocyanin production. This increase was reduced in the presence of a ptxR plasmid. Throughout the growth cycle, PtxR reduced the expression of the pyocyanin operon phzA1-G1 but not phzA2-G2. As pyocyanin production is stringently controlled by QS, we examined the effect of PtxR on QS-related genes in PAO1. PtxR also reduced the expression of the PQS synthesis operon pqsABCDE. ptxR mutation increased the expression of the rhamnolipid synthesis gene rhlA but decreased lasB expression. The expression of the RhlI synthase gene rhlI and the production of the C(4)-HSL autoinducer were increased in the ptxR mutant, while the expression of the LasI synthase gene lasI and the production of 3OC(12)-HSL were reduced. These results suggest that PtxR negatively regulates the expression of the rhamnolipid and pyocyanin genes through rhlI and the pqsABCDE operon while it positively regulates the expression of lasB through lasI.
authors.affiliation: Department of Microbiology and Immunology, Texas Tech University Health Sciences Center, Lubbock, TX 79430-5907, USA.
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Carty
authors.forename: Nancy
authors.initials: N
authors.lastname: Layland
authors.forename: Jane A
authors.initials: JA
authors.lastname: Colmer-Hamood
authors.forename: M Worth
authors.initials: MW
authors.lastname: Calfee
authors.forename: Everett C
authors.initials: EC
authors.lastname: Pesci
authors.forename: Abdul N
authors.initials: AN
authors.lastname: Hamood
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006017:Glycolipids / Q000235:genetics / Q000378:metabolism; D006714:Homoserine / Q000031:analogs & derivatives / Q000378:metabolism; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009876:Operon; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D011710:Pyocyanine / Q000235:genetics / Q000378:metabolism; D015363:Quinolones / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: C407944:2-heptyl-3-hydroxy-4-quinolone; D001426:Bacterial Proteins; D006017:Glycolipids; C109860:N-(3-oxododecanoyl)homoserine lactone; D015363:Quinolones; D014157:Transcription Factors; D037521:Virulence Factors; C418382:rhamnolipid; D006714:Homoserine; C073470:LysR protein, Bacteria; D011710:Pyocyanine; D008666:Metalloendopeptidases; C043859:pseudolysin, Pseudomonas aeruginosa; D015107:4-Butyrolactone