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The distinct quorum sensing hierarchy of las and rhl in Pseudomonas sp. M18

Jishun Lu1, Xianqing Huang, Mingyue Zhang

  • 1College of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China. jishunlu@gmail.com

Current Microbiology
|September 4, 2009
PubMed

Insights

Pseudomonas sp. M18 exhibits a unique quorum sensing (QS) hierarchy. The LasR/LasI system negatively controls rhlI expression, influencing antifungal agent production.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Pseudomonas sp. M18 produces antifungal agents phenazine-1-carboxylic acid (PCA) and pyoluteorin.
  • The well-characterized Pseudomonas aeruginosa quorum sensing (QS) systems, LasR/LasI and RhlR/RhlI, are present in Pseudomonas sp. M18.

Purpose of the Study:

  • To elucidate the complex regulatory hierarchy of the Las and Rhl QS systems in Pseudomonas sp. M18.
  • To investigate the interrelationships between QS systems and their impact on antifungal compound production.

Main Methods:

  • LacZ translational fusion expression analysis to study gene expression.
  • Acyl-homoserine lactone thin-layer chromatography (TLC) bioassays to detect QS signals.
  • Investigating the regulatory roles of LasR, LasI, RhlR, and RhlI.

Main Results:

  • A distinct QS cascade was identified in strain M18, differing from P. aeruginosa.
  • LasR/LasI negatively controlled rhlI expression, while LasR positively influenced rhlR expression during log-phase.
  • Response regulators (LasR, RhlR) expression was independent of cognate synthases (LasI, RhlI).
  • The Las system modulated the timing and magnitude of rhlI and rhlR expression.
  • LasR negatively controlled PCA production by modulating rhlI expression.

Conclusions:

  • The QS systems in Pseudomonas sp. M18 display a unique and complex regulatory hierarchy.
  • Interactions between QS systems are strain-specific, impacting antifungal metabolite biosynthesis.
  • Understanding these QS networks is crucial for controlling microbial communities and metabolite production.

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