Article

The phenazine pyocyanin is a terminal signalling factor in the quorum sensing network of Pseudomonas aeruginosa

Divisions of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
Molecular Microbiology (Impact Factor: 5.03). 10/2006; 61(5):1308-21. DOI: 10.1111/j.1365-2958.2006.05306.x
Source: PubMed

ABSTRACT Certain members of the fluorescent pseudomonads produce and secrete phenazines. These heterocyclic, redox-active compounds are toxic to competing organisms, and the cause of these antibiotic effects has been the focus of intense research efforts. It is largely unknown, however, how pseudomonads themselves respond to - and survive in the presence of - these compounds. Using Pseudomonas aeruginosa DNA microarrays and quantitative RT-PCR, we demonstrate that the phenazine pyocyanin elicits the upregulation of genes/operons that function in transport [such as the resistance-nodulation-cell division (RND) efflux pump MexGHI-OpmD] and possibly in redox control (such as PA2274, a putative flavin-dependant monooxygenase), and downregulates genes involved in ferric iron acquisition. Strikingly, mexGHI-opmD and PA2274 were previously shown to be regulated by the PA14 quorum sensing network that controls the production of virulence factors (including phenazines). Through mutational analysis, we show that pyocyanin is the physiological signal for the upregulation of these quorum sensing-controlled genes during stationary phase and that the response is mediated by the transcription factor SoxR. Our results implicate phenazines as signalling molecules in both P. aeruginosa PA14 and PAO1.

Download full-text

Full-text

Available from: Lars E. Dietrich, Jun 18, 2015
0 Followers
 · 
136 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pyocyanin acts as a virulence factor in Pseudomonas aeruginosa, a plant and animal pathogen. In this study we evaluated the effect of pyocyanin on growth and development of Arabidopsis seedlings. Root inoculation with P. aeruginosa PAO1 strain inhibited primary root growth in WT Arabidopsis seedlings. In contrast, single lasI- and double rhlI-/lasI- mutants of P. aeruginosa defective in pyocyanin production showed decreased root growth inhibition concomitant with an increased phytostimulation. Treatment with pyocyanin modulates root system architecture inhibiting primary root growth and promoting lateral root and root hair formation without affecting meristem viability or causing cell death. These effects correlated with altered proportions of hydrogen peroxide and superoxide in root tips and with an inhibition of cell division and elongation. Mutant analyses showed that pyocyanin modulation of root growth was likely independent of auxin, cytokinin and abscisic acid, but required ethylene signaling as the Arabidopsis etr1-1, ein2-1 and ein3-1 ethylene-related mutants were less sensitive to pyocyanin-induced root stoppage and reactive oxygen species (ROS) distribution. Our findings suggest that pyocyanin is an important factor modulating the interplay between ROS production and root system architecture by an ethylene dependent signaling.
    Molecular Plant-Microbe Interactions 11/2013; DOI:10.1094/MPMI-08-13-0219-R · 4.46 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: SoxR from E. coli and related enterobacteria is activated by a broad range of redox-active compounds through oxidation or nitrosylation of its [2Fe-2S] cluster. Activated SoxR then induces SoxS, which subsequently activates more than 100 genes in response. In contrast, non-enteric SoxRs directly activate their target genes in response to redox-active compounds that include endogenously produced metabolites. We compared the responsiveness of SoxRs from Streptomyces coelicolor (ScSoxR), Pseudomonas aeruginosa (PaSoxR) and E. coli (EcSoxR), all expressed in S. coelicolor, toward natural or synthetic redox-active compounds. EcSoxR responded to all compounds examined, whereas ScSoxR was insensitive to oxidants such as paraquat (Eh -440 mV) and menadione sodium bisulfite (Eh -45 mV) and to NO generators. PaSoxR was insensitive only to some NO generators. Whole cell EPR analysis of SoxRs expressed in E. coli revealed that the [2Fe-2S](1+) of ScSoxR was not oxidizable by paraquat, differing from EcSoxR and PaSoxR. The mid-point redox potential of purified ScSoxR was determined to be -185 ± 10 mV, higher by ∼100 mV than those of EcSoxR and PaSoxR, supporting its limited response to paraquat. The overall sensitivity profile indicates that both redox potential and kinetic reactivity determine the differential responses of SoxRs toward various oxidants.
    Molecular Microbiology 09/2013; 90(5). DOI:10.1111/mmi.12410 · 5.03 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: AIMS: The study aimed to discover Quorum Sensing (QS) inhibitors from marine sponge derived actinomycetes and analyse its inhibitory activities against QS mediated virulence factors in Pseudomonas aeruginosa. METHODS AND RESULTS: 72 actinomycetes isolated from marine invertebrates collected from the western coast of India were screened against the QS indicator strain Chromobacterium violaceum CV12472. Methanol extracts of 12 actinomycetes showing inhibition of violacein production were accessed for down regulation of QS mediated virulence factors like swarming, biofilm formation, pyocyanin, rhamnolipid and LasA production in Pseudomonas aeruginosa ATCC 27853. The isolates NIO-10068, NIO-10058, and NIO-10090 exhibited very good anti-QS activity, with NIO 10068 being the most promising one. Mass spectrometric analysis of NIO 10068 methanol extract revealed the presence of cinnamic acid and linear dipeptides, proline-glycine and N-amido-α-proline in the active extract. Detailed investigation suggested that though linear dipeptide, Pro-Gly is to some extent responsible for the observed biological activity cinnamic acid seems to be the main compound responsible for it . CONCLUSION: Marine derived actinomycetes are a potential storehouse for QS inhibitors. © 2012 The Authors Letters in Applied Microbiology © 2012 The Society for Applied Microbiology.
    Letters in Applied Microbiology 12/2012; DOI:10.1111/lam.12034 · 1.75 Impact Factor