This Article Full Text Full Text (PDF) Supplemental material Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tart, A. H. Articles by Wozniak, D. J. Search for Related Content PubMed PubMed Citation Articles by Tart, A. H. Articles by Wozniak, D. J.

The Alternative Sigma Factor AlgT Represses Pseudomonas aeruginosa Flagellum Biosynthesis by Inhibiting Expression of fleQ

Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157,¹ Department of Microbiology and Immunology and Cystic Fibrosis/Pulmonary Research and Treatment Center, University of North Carolina, Chapel Hill, North Carolina 27599²

Received 30 June 2005/ Accepted 29 August 2005

Pseudomonas aeruginosa poses a serious risk in individuals suffering from cystic fibrosis (CF). Strains colonizing the CF lung are generally motile but frequently convert to a nonmotile phenotype as the disease progresses. In many cases, this is coordinately regulated with the overproduction of the exopolysaccharide alginate. Both the expression of alginate (mucoidy) and the loss of flagellum synthesis may provide the bacterium with a selective advantage in the CF lung. Previously published data showed that the regulation of alginate production and flagellum biosynthesis in the CF isolate FRD1 is inversely controlled by the alternative sigma factor AlgT. In this study, we observed that in CF isolates, the mucoid and the nonmotile phenotypes occur predominantly together. Using microarrays, we compared the transcriptomes of isogenic AlgT⁺ and AlgT^– P. aeruginosa and discovered that AlgT significantly downregulated the majority of flagellar genes. A pronounced inhibitory effect was observed in several genes essential for proper flagellum expression, including fleQ, which encodes an essential flagellar regulator. The microarray data were confirmed by reverse transcriptase PCR analysis and promoter fusion assays in isogenic AlgT⁺ and AlgT^– strains. Transmission electron microscopy, motility assays, and Western blots showed that ectopic expression of FleQ in mucoid, nonmotile CF isolates restored flagellum biosynthesis and motility. Together, these data show that AlgT mediates the negative control of flagellum expression by inhibiting the expression of the flagellar regulator fleQ.

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

This article has been cited by other articles:

• Qiu, D., Eisinger, V. M., Head, N. E., Pier, G. B., Yu, H. D. (2008). ClpXP proteases positively regulate alginate overexpression and mucoid conversion in Pseudomonas aeruginosa. Microbiology 154: 2119-2130 [Abstract] [Full Text]  
• Leon, R., Espin, G. (2008). flhDC, but not fleQ, regulates flagella biogenesis in Azotobacter vinelandii, and is under AlgU and CydR negative control. Microbiology 154: 1719-1728 [Abstract] [Full Text]  
• Schenk, A., Weingart, H., Ullrich, M. S. (2008). The alternative sigma factor AlgT, but not alginate synthesis, promotes in planta multiplication of Pseudomonas syringae pv. glycinea. Microbiology 154: 413-421 [Abstract] [Full Text]  
• Augustin, D. K., Song, Y., Baek, M. S., Sawa, Y., Singh, G., Taylor, B., Rubio-Mills, A., Flanagan, J. L., Wiener-Kronish, J. P., Lynch, S. V. (2007). Presence or Absence of Lipopolysaccharide O Antigens Affects Type III Secretion by Pseudomonas aeruginosa. J. Bacteriol. 189: 2203-2209 [Abstract] [Full Text]  
• Duque, E., Rodriguez-Herva, J.-J., de la Torre, J., Dominguez-Cuevas, P., Munoz-Rojas, J., Ramos, J.-L. (2007). The RpoT Regulon of Pseudomonas putida DOT-T1E and Its Role in Stress Endurance against Solvents. J. Bacteriol. 189: 207-219 [Abstract] [Full Text]  
• Murray, T. S., Kazmierczak, B. I. (2006). FlhF Is Required for Swimming and Swarming in Pseudomonas aeruginosa.. J. Bacteriol. 188: 6995-7004 [Abstract] [Full Text]  
• Tart, A. H., Blanks, M. J., Wozniak, D. J. (2006). The AlgT-Dependent Transcriptional Regulator AmrZ (AlgZ) Inhibits Flagellum Biosynthesis in Mucoid, Nonmotile Pseudomonas aeruginosa Cystic Fibrosis Isolates.. J. Bacteriol. 188: 6483-6489 [Abstract] [Full Text]