Quorum sensing signals are produced by Aeromonas salmonicida and quorum sensing inhibitors can reduce production of a potential virulence factor

• Published in: Diseases of aquatic organisms 2007-12, Vol.78 (2), p.105-113
• Main Authors: RASCH, Maria, KASTBJERG, Vicky Gaedt, BRUHN, Jesper Bartholin, DALSGAARD, Inger, GIVSKOV, Michael, GRAM, Lone
• Format: Article
• Language: English
• Subjects: 4-Butyrolactone - analogs & derivatives; Acyl-Butyrolactones - pharmacology; Aeromonas salmonicida; Aeromonas salmonicida - drug effects; Aeromonas salmonicida - growth & development; Aeromonas salmonicida - pathogenicity; Aeromonas salmonicida - physiology; Animal aquaculture; Animal productions; Animals; Biological and medical sciences; Brackish; Fish Diseases - microbiology; Fishes - microbiology; Freshwater; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial - drug effects; Gram-Negative Bacterial Infections - microbiology; Gram-Negative Bacterial Infections - veterinary; Marine; Peptide Hydrolases - analysis; Peptide Hydrolases - biosynthesis; Peptide Hydrolases - metabolism; Pigments, Biological - analysis; Pigments, Biological - biosynthesis; Pisciculture; Quorum Sensing - drug effects; Time Factors; Vertebrate aquaculture; Virulence Factors - biosynthesis
• ISSN: 0177-5103; 1616-1580
• DOI: 10.3354/dao01865

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.