title: Anaerobiosis-induced loss of cytotoxicity is due to inactivation of quorum sensing in Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa, an opportunistic pathogen of clinical importance, causes chronic airway infections in patients with cystic fibrosis (CF). Current literature suggests that pockets with reduced oxygen tension exist in the CF airway mucus. However, virulence features of this opportunistic pathogen under such conditions are largely unknown. Cell-free supernatant of the standard laboratory P. aeruginosa strain PAO1 obtained from anaerobic culture, but not aerobic culture, failed to kill A549 human airway epithelial cells. Further investigation revealed that this reduced cytotoxicity upon anaerobiosis was due to the suppressed secretion of elastase, a virulence factor controlled by P. aeruginosa quorum sensing (QS). Both a lacZ-reporter fusion assay and quantitative real-time PCR (RT-PCR) analysis demonstrated that transcription of the elastase-encoding lasB gene was substantially decreased during anaerobic growth compared with aerobic growth. Moreover, transcription of other genes controlled by the LasI/R QS system, such as rhlR, vqsR, mvfR, and rsaL, was also repressed under the same anaerobic growth conditions. Importantly, synthesis of 3-oxo-C(12)-HSL (PAI-1), an autoinducer molecule that mediates induction of the LasI/R QS system, was >22-fold decreased during anaerobic growth while C(4)-HSL (PAI-2), which mediates RhlI/R QS, was nondetectable under the same growth conditions. Transcription of the lasB gene was restored by exogenous supplementation with autoinducers, with PAI-2 more effective than PAI-1 or Pseudomonas quinolone signal (PQS) at restoring transcription of the lasB gene. Together, these results suggest that anaerobiosis deprives P. aeruginosa of the ability to regulate its virulence via QS and this misregulation attenuates the pathogenic potential of this important pathogen.
authors.affiliation: Department of Microbiology, Yonsei University College of Medicine, Seoul 120-752, South Korea.
authors.forename: Kang-Mu
authors.initials: KM
authors.lastname: Lee
authors.forename: Mi Young
authors.initials: MY
authors.lastname: Yoon
authors.forename: Yongjin
authors.initials: Y
authors.lastname: Park
authors.forename: Joon-Hee
authors.initials: JH
authors.lastname: Lee
authors.forename: Sang Sun
authors.initials: SS
authors.lastname: Yoon
mesh_terms: D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D006801:Humans; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D010196:Pancreatic Elastase / Q000235:genetics / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism / Q000494:pharmacology; D017396:Plasminogen Activator Inhibitor 2 / Q000378:metabolism / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011552:Pseudomonas Infections; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D015363:Quinolones / Q000378:metabolism / Q000494:pharmacology; D053038:Quorum Sensing; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C407944:2-heptyl-3-hydroxy-4-quinolone; D001426:Bacterial Proteins; D017395:Plasminogen Activator Inhibitor 1; D017396:Plasminogen Activator Inhibitor 2; D015363:Quinolones; D037521:Virulence Factors; D010196:Pancreatic Elastase; D008666:Metalloendopeptidases; C043859:pseudolysin, Pseudomonas aeruginosa