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Journal of Bacteriology, January 2008, p. 581-589, Vol. 190, No. 2
0021-9193/08/$08.00+0     doi:10.1128/JB.01307-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

The NtrC Family Regulator AlgB, Which Controls Alginate Biosynthesis in Mucoid Pseudomonas aeruginosa, Binds Directly to the algD Promoter{triangledown} ,{dagger}

Andrew J. Leech,1 April Sprinkle,2 Lynn Wood,1,3 Daniel J. Wozniak,2 and Dennis E. Ohman1,3*

Department of Microbiology and Immunology, Medical College of Virginia Campus of Virginia Commonwealth University, Richmond, Virginia 23298-0678,1 Department of Microbiology and Immunology, Wake Forest University School Medicine, Winston Salem, North Carolina 27157,2 McGuire Veterans Affairs Medical Center, Richmond, Virginia 232493

Received 12 August 2007/ Accepted 24 October 2007

Alginate production in mucoid (MucA-defective) Pseudomonas aeruginosa is dependent upon several transcriptional regulators, including AlgB, a two-component response regulator belonging to the NtrC family. This role of AlgB was apparently independent of its sensor kinase, KinB, and even the N-terminal phosphorylation domain of AlgB was dispensable for alginate biosynthetic gene (i.e., algD operon) activation. However, it remained unclear whether AlgB stimulated algD transcription directly or indirectly. In this study, microarray analyses were used to examine a set of potential AlgB-dependent, KinB-independent genes in a PAO1 mucA background that overlapped with genes induced by D-cycloserine, which is known to activate algD expression. This set contained only the algD operon plus one other gene that was shown to be uninvolved in alginate production. This suggested that AlgB promotes alginate production by directly binding to the algD promoter (PalgD). Chromosome immunoprecipitation revealed that AlgB bound in vivo to PalgD but did not bind when AlgB had an R442E substitution that disrupted the DNA binding domain. AlgB also showed binding to PalgD fragments in an electrophoretic mobility shift assay at pH 4.5 but not at pH 8.0. A direct systematic evolution of ligands by exponential enrichment approach showed AlgB binding to a 50-bp fragment located at bp –224 to –274 relative to the start of PalgD transcription. Thus, AlgB belongs to a subclass of NtrC family proteins that can activate promoters which utilize a sigma factor other than {sigma}54, in this case to stimulate transcription from the {sigma}22-dependent PalgD promoter.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, P.O. Box 980678, Medical College of Virginia Campus of Virginia Commonwealth University, 1101 E. Marshall St., 5-047 Sanger Hall, Richmond, VA 23298-0678. Phone: (804) 828-9728. Fax: (804) 828-9946. E-mail: deohman{at}vcu.edu

{triangledown} Published ahead of print on 2 November 2007.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, January 2008, p. 581-589, Vol. 190, No. 2
0021-9193/08/$08.00+0     doi:10.1128/JB.01307-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Damron, F. H., Napper, J., Teter, M. A., Yu, H. D. (2009). Lipotoxin F of Pseudomonas aeruginosa is an AlgU-dependent and alginate-independent outer membrane protein involved in resistance to oxidative stress and adhesion to A549 human lung epithelia. Microbiology 155: 1028-1038 [Abstract] [Full Text]  
  • Damron, F. H., Qiu, D., Yu, H. D. (2009). The Pseudomonas aeruginosa Sensor Kinase KinB Negatively Controls Alginate Production through AlgW-Dependent MucA Proteolysis. J. Bacteriol. 191: 2285-2295 [Abstract] [Full Text]  


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