The long-chain fatty acid sensor, PsrA, modulates the expression of rpoS and the type III secretion exsCEBA operon in Pseudomonas aeruginosa

Mol Microbiol. 2009 Jul;73(1):120-36. doi: 10.1111/j.1365-2958.2009.06757.x. Epub 2009 Jun 8.


The Pseudomonas aeruginosa PsrA autorepressor has dual roles as a repressor of the fadBA5beta-oxidation operon and an activator of the stationary-phase sigma factor rpoS and exsCEBA operon of the type III secretion system (TTSS). Previously, we demonstrated that the repression of the fadBA5 operon by PsrA is relieved by long-chain fatty acids (LCFAs). However, the signal affecting the activation of rpoS and exsC via PsrA is unknown. In this study, microarray and gene fusion data suggested that LCFA (e.g. oleate) affected the expression of rpoS and exsC. DNA binding studies confirmed that PsrA binds to the rpoS and exsC promoter regions. This binding was inhibited by LCFA, indicating that LCFA directly affects the activation of these two genes through PsrA. LCFA decreased rpoS and exsC expression, resulting in increased N-(butyryl)-l-homoserine-lactone quorum sensing signal and decreased ExoS/T production respectively. Based on the crystal structure of PsrA, site-directed mutagenesis of amino acid residues, within the hydrophobic channel thought to accommodate LCFA, created two LCFA-non-responsive PsrA mutants. The binding and activation of rpoS and exsC by these PsrA mutants was no longer inhibited by LCFA. These data support a mechanistic model where LCFAs influence PsrA regulation to control LCFA metabolism and some virulence genes in P. aeruginosa.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Butyrolactone / analogs & derivatives
  • 4-Butyrolactone / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Gene Expression Regulation, Bacterial
  • Mutagenesis, Site-Directed
  • Oleic Acid / metabolism
  • Oligonucleotide Array Sequence Analysis
  • Operon*
  • Protein Binding
  • Protein Structure, Tertiary
  • Pseudomonas aeruginosa / genetics*
  • Pseudomonas aeruginosa / metabolism
  • Quorum Sensing
  • Sigma Factor / genetics
  • Sigma Factor / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*


  • Bacterial Proteins
  • DNA-Binding Proteins
  • N-butyrylhomoserine lactone
  • PsrA protein, Pseudomonas
  • Sigma Factor
  • Transcription Factors
  • sigma factor KatF protein, Bacteria
  • Oleic Acid
  • 4-Butyrolactone