Article: article from journal or magazin.
Negative control of quorum sensing by RpoN (sigma54) in Pseudomonas aeruginosa PAO1.
Journal of Bacteriology
In Pseudomonas aeruginosa PAO1, the expression of several virulence factors such as elastase, rhamnolipids, and hydrogen cyanide depends on quorum-sensing regulation, which involves the lasRI and rhlRI systems controlled by N-(3-oxododecanoyl)-L-homoserine lactone and N-butyryl-L-homoserine lactone, respectively, as signal molecules. In rpoN mutants lacking the transcription factor sigma(54), the expression of the lasR and lasI genes was elevated at low cell densities, whereas expression of the rhlR and rhlI genes was markedly enhanced throughout growth by comparison with the wild type and the complemented mutant strains. As a consequence, the rpoN mutants had elevated levels of both signal molecules and overexpressed the biosynthetic genes for elastase, rhamnolipids, and hydrogen cyanide. The quorum-sensing regulatory protein QscR was not involved in the negative control exerted by RpoN. By contrast, in an rpoN mutant, the expression of the gacA global regulatory gene was significantly increased during the entire growth cycle, whereas another global regulatory gene, vfr, was downregulated at high cell densities. In conclusion, it appears that GacA levels play an important role, probably indirectly, in the RpoN-dependent modulation of the quorum-sensing machinery of P. aeruginosa.
4-Butyrolactone/analogs & derivatives, 4-Butyrolactone/metabolism, Bacterial Proteins/genetics, Bacterial Proteins/metabolism, Cell Division/genetics, Cyclic AMP Receptor Protein/genetics, Cyclic AMP Receptor Protein/metabolism, DNA-Binding Proteins/genetics, DNA-Binding Proteins/metabolism, DNA-Directed RNA Polymerases/genetics, DNA-Directed RNA Polymerases/metabolism, Gene Expression Regulation, Bacterial, Genetic Complementation Test, Ligases, Mutagenesis, Site-Directed, Pseudomonas aeruginosa/physiology, RNA Polymerase Sigma 54, Repressor Proteins/genetics, Repressor Proteins/metabolism, Sigma Factor/genetics, Sigma Factor/metabolism, Trans-Activators/genetics, Trans-Activators/metabolism, Transcription Factors/genetics, Transcription Factors/metabolism
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