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The regulation of type III secretion system of Pseudomonas aeruginosa

Abstract : Pseudomonas aeruginosa is an opportunistic pathogen that causes acute and chronic infections in hospitalized individuals, burn victims, and cystic fibrosis patients. One of the virulence factors most strongly correlated with severe infection both in animal models and in human patients is the type III secretion system (TTSS).We have observed a previously identified protein, PsrA, necessary for full activation of TTSS gene expression in P. aeruginosa. Electrophoretic mobility shift assays showed that recombinant PsrA could bind to the exsCEBA promoter region. Mutant with a deletion in the psrA gene showed a marked decrease in the secretion of the type III effectors and weak resistance to phagocyte-like PLB-985 cells. Taken altogether, these results suggest that PsrA is a newly identified activator that is involved in the expression of the TTSS by enhancing the exsCEBA transcriptional level.In the second time, we found that an inhibitory signal, which is similar but not known quorum sensing signal, produced in the stationary phase culture supernatant, can repress in vitro the expression of TTSS. The analysis of thousands of transposon insertion mutants showed that the production of this signal might depend on the tryptophan, which is the precursor of many metabolites, such as indole-3-acetic acid (IAA). IAA sodium salt (IAA-Na) and one of IAA-like compound, 1-naphthaleneacetic acid potassium salt (NAA-K) can indeed inhibit the expression and the secretion of the TTSS at millimolar concentrations. The precise identification of this signal requires more investigations.
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Contributor : Dakang Shen <>
Submitted on : Tuesday, November 28, 2006 - 12:28:21 PM
Last modification on : Friday, November 6, 2020 - 4:14:18 AM
Long-term archiving on: : Saturday, May 14, 2011 - 12:54:18 AM


  • HAL Id : tel-00116844, version 1




Dakang Shen. The regulation of type III secretion system of Pseudomonas aeruginosa. Life Sciences [q-bio]. Université Joseph-Fourier - Grenoble I, 2006. English. ⟨tel-00116844⟩



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