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Journal of Bacteriology, May 2009, p. 2993-3002, Vol. 191, No. 9
0021-9193/09/$08.00+0     doi:10.1128/JB.01156-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Pseudomonas aeruginosa AlgR Controls Cyanide Production in an AlgZ-Dependent Manner{triangledown}

William L. Cody,1 Christopher L. Pritchett,1 Adriana K. Jones,2 Alexander J. Carterson,3 Debra Jackson,3,4 Anders Frisk,3 Matthew C. Wolfgang,2,5 and Michael J. Schurr1*

University of Colorado Denver School of Medicine, Department of Microbiology, Aurora, Colorado 80045,1 Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina 27599,2 Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, Louisiana 70112,3 Department of Biology, University of Louisiana at Monroe, Monroe, Louisiana 71209,4 Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina 275995

Received 15 August 2008/ Accepted 17 February 2009

Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic infections in individuals suffering from the genetic disorder cystic fibrosis. In P. aeruginosa, the transcriptional regulator AlgR controls a variety of virulence factors, including alginate production, twitching motility, biofilm formation, quorum sensing, and hydrogen cyanide (HCN) production. In this study, the regulation of HCN production was examined. Strains lacking AlgR or the putative AlgR sensor AlgZ produced significantly less HCN than did a nonmucoid isogenic parent. In contrast, algR and algZ mutants showed increased HCN production in an alginate-producing (mucoid) background. HCN production was optimal in a 5% O2 environment. In addition, cyanide production was elevated in bacteria grown on an agar surface compared to bacteria grown in planktonic culture. A conserved AlgR phosphorylation site (aspartate at amino acid position 54), which is required for surface-dependent twitching motility but not alginate production, was found to be critical for cyanide production. Nuclease protection mapping of the hcnA promoter identified a new transcriptional start site required for HCN production. A subset of clinical isolates that lack this start site produced small amounts of cyanide. Taken together, these data show that the P. aeruginosa hcnA promoter contains three transcriptional start sites and that HCN production is regulated by AlgZ and AlgR and is maximal under microaerobic conditions when the organism is surface attached.

* Corresponding author. Mailing address: University of Colorado Denver, School of Medicine, Department of Microbiology, 12800 E. 19th Avenue, Aurora, CO 80045. Phone: (303) 724-4221. Fax: (303) 724-4226. E-mail: michael.schurr{at}ucdenver.edu

{triangledown} Published ahead of print on 6 March 2009.

Journal of Bacteriology, May 2009, p. 2993-3002, Vol. 191, No. 9
0021-9193/09/$08.00+0     doi:10.1128/JB.01156-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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