title: Surfactin from Bacillus subtilis displays an unexpected anti-Legionella activity.
abstract: A contaminant bacterial strain was found to exhibit an antagonistic activity against Legionella pneumophila, the causative agent of Legionnaires' disease. The bacterial strain was identified as a Bacillus subtilis and named B. subtilis AM1. PCR analysis revealed the presence of the sfp gene, involved in the biosynthesis of surfactin, a lipopeptide with versatile bioactive properties. The bioactive substances were extracted from AM1 cell-free supernatant with ethyl acetate and purified using reversed phase HPLC (RP-HPLC). Subsequent ESI-MS analyses indicated the presence of two active substances with protonated molecular ions at m/z 1008 and 1036 Da, corresponding to surfactin isoforms. Structures of lipopeptides were further determined by tandem mass spectrometry and compared to the spectra of a commercially available surfactin mixture. Surfactin displays an antibacterial spectrum almost restricted to the Legionella genus (MICs range 1-4 μg/mL) and also exhibits a weak activity toward the amoeba Acanthamoeba castellanii, known to be the natural reservoir of L. pneumophila. Anti-biofilm assays demonstrated that 66 μg/mL of surfactin successfully eliminated 90 % of a 6-day-old biofilm. In conclusion, this study reveals for the first time the potent activity of surfactin against Legionella sp. and preformed biofilms thus providing new directions toward the use and the development of lipopeptides for the control of Legionella spread in the environment.
authors.affiliation: Equipe Microbiologie de l'Eau, Université de Poitiers, Ecologie & Biologie des Interactions, UMR CNRS 7267, 1 Rue Georges Bonnet, TSA 51106, 86073, Poitiers Cedex 9, France.
authors.forename: Clémence
authors.initials: C
authors.lastname: Loiseau
authors.forename: Margot
authors.initials: M
authors.lastname: Schlusselhuber
authors.forename: Renaud
authors.initials: R
authors.lastname: Bigot
authors.forename: Joanne
authors.initials: J
authors.lastname: Bertaux
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Berjeaud
authors.forename: Julien
authors.initials: J
authors.lastname: Verdon
mesh_terms: D000656:Amoeba / Q000187:drug effects / Q000502:physiology; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000187:drug effects; D007875:Legionella / Q000187:drug effects* / Q000502:physiology; D055666:Lipopeptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data
chemical_list: D000900:Anti-Bacterial Agents; D055666:Lipopeptides