title: Alginate synthesis in Pseudomonas aeruginosa: environmental regulation of the algC promoter.
abstract: The exopolysaccharide alginate is a major virulence factor of Pseudomonas aeruginosa strains that infect the lungs of cystic fibrosis patients. The synthesis of alginate is almost uniquely associated with the pathogenicity of P. aeruginosa within the environment of the cystic fibrosis lung. The gene algC is one of the essential alginate biosynthetic genes and codes for the enzyme phosphomannomutase. In this report, we present data on the transcriptional regulation of algC expression. The activity of the algC promoter is modulated by the response regulator, AlgR1, a member of the two-component signal transduction protein family, which also regulates other alginate-specific promoters. In both mucoid (alginate-positive) and nonmucoid (alginate-negative) P. aeruginosa strains, transcriptional activation of algC increased with the osmolarity of the culture medium. This osmolarity-induced activation was found to be dependent on AlgR1. AlgR1 was found to interact directly with the algC promoter. Deletion mapping, in conjunction with mobility shift assays, showed that AlgR1 specifically bound with two regions of algC upstream DNA. A fragment spanning nucleotide positions -378 to -73 showed strong specific binding, while a fragment located between positions -73 and +187 interacted relatively weakly with AlgR1. Phosphorylation of the AlgR1 protein resulted in the stimulation of its in vitro ability to bind to the algC promoter region (a fragment spanning nucleotides -378 to -73). Transcription from the algC promoter, which has significant homology with the RNA polymerase sigma-54 (RpoN) recognition sequence, decreased in an rpoN mutant of P. aeruginosa.
authors.affiliation: Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago 60612.
authors.forename: N A
authors.initials: NA
authors.lastname: Zielinski
authors.forename: R
authors.initials: R
authors.lastname: Maharaj
authors.forename: S
authors.initials: S
authors.lastname: Roychoudhury
authors.forename: C E
authors.initials: CE
authors.lastname: Danganan
authors.forename: W
authors.initials: W
authors.lastname: Hendrickson
authors.forename: A M
authors.initials: AM
authors.lastname: Chakrabarty
mesh_terms: D000464:Alginates / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D005809:Genes, Regulator; D005816:Genetic Complementation Test; D007535:Isomerases / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D010442:Peptide Chain Initiation, Translational; D017875:Phosphotransferases (Phosphomutases); D011401:Promoter Regions, Genetic / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000378:metabolism; D051877:RNA Polymerase Sigma 54; D012689:Sequence Homology, Nucleic Acid; D012808:Sigma Factor / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D000464:Alginates; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D012808:Sigma Factor; C067678:AlgR1 protein, Pseudomonas syringae; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54; D007535:Isomerases; D017875:Phosphotransferases (Phosphomutases); C052799:phosphomannomutase