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 -