The Pseudomonas aeruginosa lectins PA-IL and PA-IIL are controlled by quorum sensing and by RpoS

J Bacteriol. 2000 Nov;182(22):6401-11. doi: 10.1128/JB.182.22.6401-6411.2000.


In Pseudomonas aeruginosa, many exoproduct virulence determinants are regulated via a hierarchical quorum-sensing cascade involving the transcriptional regulators LasR and RhlR and their cognate activators, N-(3-oxododecanoyl)-L-homoserine lactone (3O-C12-HSL) and N-butanoyl-L-homoserine lactone (C4-HSL). In this paper, we demonstrate that the cytotoxic lectins PA-IL and PA-IIL are regulated via quorum sensing. Using immunoblot analysis, the production of both lectins was found to be directly dependent on the rhl locus while, in a lasR mutant, the onset of lectin synthesis was delayed but not abolished. The PA-IL structural gene, lecA, was cloned and sequenced. Transcript analysis indicated a monocistronic organization with a transcriptional start site 70 bp upstream of the lecA translational start codon. A lux box-type element together with RpoS (sigma(S)) consensus sequences was identified upstream of the putative promoter region. In Escherichia coli, expression of a lecA::lux reporter fusion was activated by RhlR/C4-HSL, but not by LasR/3O-C12-HSL, confirming direct regulation by RhlR/C4-HSL. Similarly, in P. aeruginosa PAO1, the expression of a chromosomal lecA::lux fusion was enhanced but not advanced by the addition of exogenous C4-HSL but not 3O-C12-HSL. Furthermore, mutation of rpoS abolished lectin synthesis in P. aeruginosa, demonstrating that both RpoS and RhlR/C4-HSL are required. Although the C4-HSL-dependent expression of the lecA::lux reporter in E. coli could be inhibited by the presence of 3O-C12-HSL, this did not occur in P. aeruginosa. This suggests that, in the homologous genetic background, 3O-C12-HSL does not function as a posttranslational regulator of the RhlR/C4-HSL-dependent activation of lecA expression.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesins, Bacterial / genetics
  • Adhesins, Bacterial / metabolism
  • Amino Acid Sequence
  • Bacterial Proteins / genetics*
  • DNA-Binding Proteins / genetics
  • Gene Expression Regulation, Bacterial*
  • Homeodomain Proteins / genetics
  • Lactones / pharmacology
  • Lectins / genetics*
  • Lectins / metabolism
  • Molecular Sequence Data
  • Mutation
  • Pseudomonas aeruginosa / genetics*
  • Pseudomonas aeruginosa / metabolism
  • Repressor Proteins / genetics*
  • Sigma Factor / genetics*
  • Trans-Activators / genetics
  • Transcription, Genetic


  • Adhesins, Bacterial
  • Bacterial Proteins
  • DNA-Binding Proteins
  • Homeodomain Proteins
  • Lactones
  • LasR protein, Pseudomonas aeruginosa
  • LecA protein, bacteria
  • Lectins
  • Repressor Proteins
  • Sigma Factor
  • Trans-Activators
  • sigma factor KatF protein, Bacteria

Associated data

  • GENBANK/AF229814