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Journal of Bacteriology, May 2002, p. 2576-2586, Vol. 184, No. 10
0021-9193/02/$04.00+0     DOI: 10.1128/JB.184.10.2576-2586.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Advancing the Quorum in Pseudomonas aeruginosa: MvaT and the Regulation of N-Acylhomoserine Lactone Production and Virulence Gene Expression{dagger}

Stephen P. Diggle,1 Klaus Winzer,2 Andrée Lazdunski,3 Paul Williams,1,2 and Miguel Cámara1*

School of Pharmaceutical Sciences,1 Institute of Infections and Immunity, University Park, University of Nottingham, Nottingham NG7 2RD, United Kingdom,2 Laboratoire d’Ingénierie des Systèmes Moléculaires, Centre National de la Recherche Scientifique, 13402 Marseille Cedex 20, France3

Received 4 September 2001/ Accepted 26 January 2002

Pseudomonas aeruginosa regulates the production of many exoproteins and secondary metabolites via a hierarchical quorum-sensing cascade through LasR and RhlR and their cognate signal molecules N-(3-oxododecanoyl)-L-homoserine lactone (3O-C12-HSL) and N-(butanoyl)-L-homoserine lactone (C4-HSL). In this study, we found that transcription of the quorum sensing-regulated genes lecA (coding for PA-IL lectin), lasB (coding for elastase), and rpoS appeared to be growth phase dependent and their expression could not be advanced to the logarithmic phase in cells growing in batch culture by the addition of exogenous C4-HSL and 3O-C12-HSL. To identify novel regulators responsible for this growth phase dependency, a P. aeruginosa lecA::lux reporter strain was subjected to random transposon mutagenesis. A number of mutants affected in lecA expression were found that exhibited altered production of multiple quorum sensing-dependent phenotypes. While some mutations were mapped to new loci such as clpA and mvaT and a putative efflux system, a number of mutations were also mapped to known regulators such as lasR, rhlR, and rpoS. MvaT was identified as a novel global regulator of virulence gene expression, as a mutation in mvaT resulted in enhanced lecA expression and pyocyanin production. This mutant also showed altered swarming ability and production of the LasB and LasA proteases, 3O-C12-HSL, and C4-HSL. Furthermore, addition of exogenous 3O-C12-HSL and C4-HSL to the mvaT mutant significantly advanced lecA expression, suggesting that MvaT is involved in the growth phase-dependent regulation of the lecA gene.

* Corresponding author. Mailing address: School of Pharmaceutical Sciences, University Park, University of Nottingham, Nottingham NG7 2RD, United Kingdom. Phone: 44 (0)115 9515036. Fax: 44 (0)115 9515102. E-mail: miguel.camara{at}nottingham.ac.uk.

{dagger} For a commentary on this article, see page 2569 in this issue

Journal of Bacteriology, May 2002, p. 2576-2586, Vol. 184, No. 10
0021-9193/02/$04.00+0     DOI: 10.1128/JB.184.10.2576-2586.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



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