MULTIPLE N-ACYL-L-HOMOSERINE LACTONE SIGNAL MOLECULES REGULATE PRODUCTION OF VIRULENCE DETERMINANTS AND SECONDARY METABOLITES IN PSEUDOMONAS-AERUGINOSA

Pseudomonas aeruginosa produces a spectrum of exoproducts many of whic h have been implicated in the pathogenesis of human infection, Express ion of some of these factors requires cell-cell communication involvin g the interaction of a small diffusible molecule, an ''autoinducer,'' with a positive transcriptional activator, In P. aeruginosa PAO1, LasI directs the synthesis of the autoinducer N-(3-oxododecanoyl)-L-homose rine lactone (OdDHL), which activates the positive transcriptional act ivator, LasR, Recently, we have discovered a second signaling molecule -based modulon in PAO1, termed vsm, which contains the genes vsmR and vsmI. Using HPLC, mass spectrometry, and NMR spectroscopy we now estab lish that in Escherichia coli, VsmI directs the synthesis of N-butanoy l-L-homoserine lactone (BHL) and N-hexanoyl-L-homoserine lactone (WWL) . These compounds are present in the spent culture supernatants of P, aeruginosa in a molar ratio of approximate to 15:1 and their structure s were unequivocally confirmed by chemical synthesis, Addition of eith er BHL or HHL to PAN067, a pleiotropic P, aeruginosa mutant unable to synthesize either of these autoinducers, restored elastase, chitinase, and cyanide production. In E. coli carrying a vsmR/vsmI'::lux transcr iptional fusion, BHL and HHL activated VsmR to a similar extent. Analo gues of these N-acyl-L-homoserine lactones in which the N-acyl side ch ain has been extended and/or oxidized at the C-3 position exhibit subs tantially lower activity (e.g., OdDHL) or no activity (e.g., dDHL) in this fur reporter assay, These data indicate that multiple families of quorum sensing modulons interactively regulate gene expression in P. aeruginosa.