Quorum sensing in Aeromonas salmonicida subsp. achromogenes and the effect of the autoinducer synthase AsaI on bacterial virulence

TY - JOUR

T1 - Quorum sensing in Aeromonas salmonicida subsp. achromogenes and the effect of the autoinducer synthase AsaI on bacterial virulence

AU - Schwenteit, Johanna

AU - Gram, Lone

AU - Nielsen, Kristian F

AU - Fridjonsson, Olafur H

AU - Bornscheuer, Uwe T

AU - Givskov, Michael

AU - Gudmundsdottir, Bjarnheidur K

N1 - Copyright © 2010 Elsevier B.V. All rights reserved.

PY - 2011/1/27

Y1 - 2011/1/27

N2 - The Gram-negative fish pathogenic bacterium Aeromonas salmonicida possesses the LuxIR-type quorum sensing (QS) system, termed AsaIR. In this study the role of QS in A. salmonicida subsp. achromogenes virulence and pigment production was investigated. Five wild-type Asa strains induced the N-acyl-homoserinelactone (AHL) monitor bacteria. HPLC-HR-MS analysis identified only one type of AHL, N-butanoyl-L-homoserine lactone (C4-HSL). A knock out mutant of AsaI, constructed by allelic exchange, did not produce a detectable QS signal and its virulence in fish was significantly impaired, as LD(50) of the AsaI-deficient mutant was 20-fold higher than that of the isogenic wt strain and the mean day to death of the mutant was significantly prolonged. Furthermore, the expression of two virulence factors (a toxic protease, AsaP1, and a cytotoxic factor) and a brown pigment were reduced in the mutant. AsaP1 production was inhibited by synthetic QS inhibitors (N-(propylsulfanylacetyl)-L-homoserine lactone; N-(pentylsulfanylacetyl)-L-homoserine lactone; and N-(heptylsulfanylacetyl)-L-homoserine lactone) at concentrations that did not affect bacterial growth. It is a new finding that the AHL synthase of Aeromonas affects virulence in fish and QS has not previously been associated with A. salmonicida infections in fish. Furthermore, AsaP1 production has not previously been shown to be QS regulated. The simplicity of the A. salmonicida subsp. achromogenes LuxIR-type QS system and the observation that synthetic QSI can inhibit an important virulence factor, AsaP1, without affecting bacterial growth, makes A. salmonicida subsp. achromogenes an interesting target organism to study the effects of QS in disease development and QSI in disease control.

AB - The Gram-negative fish pathogenic bacterium Aeromonas salmonicida possesses the LuxIR-type quorum sensing (QS) system, termed AsaIR. In this study the role of QS in A. salmonicida subsp. achromogenes virulence and pigment production was investigated. Five wild-type Asa strains induced the N-acyl-homoserinelactone (AHL) monitor bacteria. HPLC-HR-MS analysis identified only one type of AHL, N-butanoyl-L-homoserine lactone (C4-HSL). A knock out mutant of AsaI, constructed by allelic exchange, did not produce a detectable QS signal and its virulence in fish was significantly impaired, as LD(50) of the AsaI-deficient mutant was 20-fold higher than that of the isogenic wt strain and the mean day to death of the mutant was significantly prolonged. Furthermore, the expression of two virulence factors (a toxic protease, AsaP1, and a cytotoxic factor) and a brown pigment were reduced in the mutant. AsaP1 production was inhibited by synthetic QS inhibitors (N-(propylsulfanylacetyl)-L-homoserine lactone; N-(pentylsulfanylacetyl)-L-homoserine lactone; and N-(heptylsulfanylacetyl)-L-homoserine lactone) at concentrations that did not affect bacterial growth. It is a new finding that the AHL synthase of Aeromonas affects virulence in fish and QS has not previously been associated with A. salmonicida infections in fish. Furthermore, AsaP1 production has not previously been shown to be QS regulated. The simplicity of the A. salmonicida subsp. achromogenes LuxIR-type QS system and the observation that synthetic QSI can inhibit an important virulence factor, AsaP1, without affecting bacterial growth, makes A. salmonicida subsp. achromogenes an interesting target organism to study the effects of QS in disease development and QSI in disease control.

KW - Aeromonas salmonicida

KW - Animals

KW - Bacterial Proteins

KW - DNA-Binding Proteins

KW - Fish Diseases

KW - Gene Expression Regulation, Bacterial

KW - Gram-Negative Bacterial Infections

KW - Molecular Sequence Data

KW - Mutation

KW - Phenotype

KW - Pigments, Biological

KW - Quorum Sensing

KW - Signal Transduction

KW - Transcription Factors

KW - Trout

KW - Virulence

KW - Virulence Factors

U2 - 10.1016/j.vetmic.2010.07.020

DO - 10.1016/j.vetmic.2010.07.020

M3 - Journal article

C2 - 20708354

SN - 0378-1135

VL - 147

SP - 389

EP - 397

JO - Veterinary Microbiology

JF - Veterinary Microbiology

IS - 3-4

ER -