title: Quorum sensing signals are produced by Aeromonas salmonicida and quorum sensing inhibitors can reduce production of a potential virulence factor.
abstract: Many pathogens control production of virulence factors by self-produced signals in a process called quorum sensing (QS). We demonstrate that acyl homoserine lactone (AHL) signals, which enable bacteria to express certain phenotypes in relation to cell density, are produced by a wide spectrum of Aeromonas salmonicida strains. All 31 typical strains were AHL producers as were 21 of 26 atypical strains, but on a strain population basis, production of virulence factors such as protease, lipase, A-layer or pigment did not correlate with the production and accumulation of AHLs in the growth medium. Pigment production was only observed in broth under highly aerated conditions. Quorum sensing inhibitors (QSIs) are compounds that specifically block QS systems without affecting bacterial growth and 2 such compounds, sulphur-containing AHL-analogues, reduced production of protease in a typical strain of Aeromonas salmonicida. The most efficient compound N-(heptylsulfanylacetyl)-L-homoserine lactone (HepS-AHL), reduced protease production by a factor of 10. Five extracellular proteases were detected on gelatin-containing sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) gels and 3 of these were completely down regulated by HepS-AHL. Hence, QSIs can curb virulence in some strains and could potentially be pursued as bacterial disease control measures in aquaculture.
authors.affiliation: Danish Institute for Fisheries Research, Department of Seafood Research, Technical University of Denmark, Søltofts Plads bldg. 221, 2800 Kgs. Lyngby, Denmark.
authors.forename: Maria
authors.initials: M
authors.lastname: Rasch
authors.forename: Vicky Gaedt
authors.initials: VG
authors.lastname: Kastbjerg
authors.forename: Jesper Bartholin
authors.initials: JB
authors.lastname: Bruhn
authors.forename: Inger
authors.initials: I
authors.lastname: Dalsgaard
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Lone
authors.initials: L
authors.lastname: Gram
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives; D054742:Acyl-Butyrolactones / Q000494:pharmacology*; D048409:Aeromonas salmonicida / Q000187:drug effects* / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology*; D000818:Animals; D005393:Fish Diseases / Q000382:microbiology; D005399:Fishes / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology / Q000662:veterinary; D010447:Peptide Hydrolases / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism; D010860:Pigments, Biological / Q000032:analysis / Q000096:biosynthesis; D053038:Quorum Sensing / Q000187:drug effects; D013997:Time Factors; D037521:Virulence Factors / Q000096:biosynthesis
chemical_list: D054742:Acyl-Butyrolactones; C092312:N-butyrylhomoserine lactone; D010860:Pigments, Biological; D037521:Virulence Factors; D010447:Peptide Hydrolases; D015107:4-Butyrolactone