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Association of hemolytic activity of Pseudomonas entomophila, a versatile soil bacterium, with cyclic lipopeptide

Isabelle Vallet-Gely1, Alexey Novikov, Luis Augusto

  • 1Centre de Génétique Moléculaire, CNRS, 91198 Gif-sur-Yvette, France. vallet@cgm.cnrs-gif.fr

Applied and Environmental Microbiology
|December 22, 2009
PubMed

Insights

Pseudomonas entomophila produces a novel cyclic lipopeptide, entolysin, essential for swarming motility but not virulence in Drosophila. This study also reveals entolysin

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Pseudomonas entomophila is an insect pathogen closely related to Pseudomonas putida.
  • The GacS/GacA system regulates virulence factors, including AprA protease, in P. entomophila.
  • P. entomophila exhibits significant hemolytic activity, suggesting the presence of potent secreted molecules.

Purpose of the Study:

  • To identify the molecule responsible for the hemolytic activity in P. entomophila.
  • To elucidate the genetic basis and regulation of entolysin biosynthesis and secretion.
  • To determine the physiological role of entolysin in P. entomophila, including its contribution to virulence and motility.

Main Methods:

  • Genetic analysis to identify genes involved in entolysin production (EtlA, EtlB, EtlC, EtlR, MacAB).
  • Biochemical characterization of the hemolytic activity and the novel cyclic lipopeptide, entolysin.
  • Investigation of regulatory mechanisms involving the GacS/GacA system, small RNAs, and RsmA-like proteins.
  • Virulence assays in Drosophila melanogaster and swarming motility tests.

Main Results:

  • A new cyclic lipopeptide, entolysin, composed of 14 amino acids and a 3-hydroxy fatty acid, was identified as the source of hemolytic activity.
  • Three nonribosomal peptide synthetases (EtlA-C) and accessory factors (EtlR, MacAB) are essential for entolysin biosynthesis and secretion.
  • Entolysin production is regulated by the GacS/GacA two-component system, involving small RNAs and RsmA-like proteins.
  • Entolysin is crucial for swarming motility but dispensable for P. entomophila virulence in Drosophila.
  • P. entomophila demonstrated strong biocontrol capabilities.

Conclusions:

  • Entolysin is a novel cyclic lipopeptide produced by Pseudomonas entomophila, playing a key role in swarming motility.
  • The biosynthesis and secretion of entolysin are complex processes regulated by the GacS/GacA system.
  • Despite its hemolytic activity, entolysin does not contribute to the pathogenicity of P. entomophila towards Drosophila.
  • The study uncovers new insights into Pseudomonas entomophila physiology, including its biocontrol potential.

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