DAO 78:105-113 (2007)  -  DOI: https://doi.org/10.3354/dao01865

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

Maria Rasch1, Vicky Gaedt Kastbjerg1, Jesper Bartholin Bruhn1, Inger Dalsgaard2, Michael Givskov3, Lone Gram1,*

1Danish Institute for Fisheries Research, Department of Seafood Research, Technical University of Denmark, Søltofts Plads bldg. 221, 2800 Kgs. Lyngby, Denmark
2Danish Institute for Fisheries Research, Fish Disease Laboratory, Technical University of Denmark, Stigbøjlen 4, 1870 Frederiksberg C, Denmark
3Center for Biomedical Microbiology, BioCentrum, Technical University of Denmark bldg. 301, 2800 Kgs. Lyngby, Denmark
*Corresponding author. Email:

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.


KEY WORDS: Acylated homoserine lactones · Aeromonas salmonicida · Pigment · Protease · Quorum sensing inhibitors


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Cite this article as: Rasch M, Kastbjerg VG, Bruhn JB, Dalsgaard I, Givskov M, Gram L (2007) Quorum sensing signals are produced by Aeromonas salmonicida and quorum sensing inhibitors can reduce production of a potential virulence factor. Dis Aquat Org 78:105-113. https://doi.org/10.3354/dao01865

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