Quorum Sensing-Dependent Regulation and Blockade of Exoprotease Production in Aeromonas hydrophila

Abstract

In Aeromonas hydrophila, the ahyI gene encodes a protein responsible for the synthesis of the quorum sensing signal N-butanoyl-l-homoserine lactone (C4-HSL). Inactivation of the ahyI gene on the A. hydrophila chromosome abolishes C4-HSL production. The exoprotease activity of A. hydrophila consists of both serine protease and metalloprotease activities; in theahyI-negative strain, both are substantially reduced but can be restored by the addition of exogenous C4-HSL. In contrast, mutation of the LuxR homolog AhyR results in the loss of both exoprotease activities, which cannot be restored by exogenous C4-HSL. Furthermore, a substantial reduction in the production of exoprotease by the ahyI + parent strain is obtained by the addition of N-acylhomoserine lactone analogs that have acyl side chains of 10, 12, or 14 carbons. The inclusion ofN-(3-oxododecanoyl)-l-homoserine lactone orN-(3-oxotetradecanoyl)-l-homoserine lactone at 10 μM in overnight cultures of A. hydrophila abolishes exoprotease production in azocasein assays and reduces the activity of all the exoprotease species seen in zymograms.

Potential virulence and antimicrobial susceptibility of Aeromonas popoffii recovered from freshwater and seawater

“…The associated phenotypic activities investigated were: L-hemolysis, assayed on TSA agar (Difco) containing 5% sheep or human blood agar, at 20 and 37³C ; DNase activity, assessed at 37³C on DNase agar; lipase activity, tested at 37³C on TSA plates containing 0.5% tributyrin emulsi¢ed in the presence of 0.2% Triton X-100; and the serine protease activity, detected at 30³C by the azocasein method as previously described [24].…”

Isolation and characterization of new potential probiotic bacteria based on quorum-sensing system

“…violaceum CV026-overlaid bioassay agar plates. The extracellular proteases activity was determined by loading the supernatant of the culture into the wells on LB agar plates supplemented with 10% (v ⁄ v) sterile skim milk as described previously (Swift et al 1999).…”

The impact of mutations in the quorum sensing systems of Aeromonas hydrophila, Vibrio anguillarum and Vibrio harveyi on their virulence towards gnotobiotically cultured Artemia franciscana

“…LVS3isolate that enhances growth and survival of ArtemiaVerschuere et al (1999) in ahyI (AHL synthase that produces BHL a )Swift et al (1999) AH-1NahyR mutation in ahyR (AHL receptor that detects the AHL produced by AhyI)Swift et al (1999) Vibrio anguillarum strains NB10 wild type from which strains DM21, DM25, DM27, DM64, DM63 and AC11 are derivedMilton et al (1997) DM21 mutation in vanI (AHL synthase that produces ODHL b and to a lesser extend OHL c and OOHL d ) Milton et al (1997) DM25 mutation in vanR (AHL receptor that detects the AHLs produced by VanI) Milton et al (1997) DM27 mutation in vanM (AHL synthase that produces OHHHL e and HHL f ) Milton et al (2001) DM64 mutation in vanN (AHL receptor that detects the AHLs produced by VanM) Croxatto et al (2004) DM63 mutation in vanQ (AI-2 receptor) Croxatto et al (2004) AC11 mutation in vanO (encoding VanO, a protein in the AHL and AI-2 signal transduction chain) Croxatto et al (2004) Vibrio campbellii PN9801 pathogen for Artemia Soto-Rodriguez et al (2003) Vibrio harveyi strains BB120 wild type from which strains BB152, BB170, MM30, BB886, MM77 and JAF548 are derived Bassler et al (1997) BB152 mutation in luxM (AHL synthase that produces OHBHL g ) Bassler et al (1994) BB170 mutation in luxN (AHL receptor that detects the AHL produced by LuxM) Bassler et al (1993) MM30 mutation in luxS (AI-2 synthase) Surette et al (1999) BB886 mutation in luxP (AI-2 receptor) Bassler et al (1994) MM77 mutation in luxM and luxS Mok et al (2003) JAF548 mutation in luxO (encoding LuxO, a protein in the AHL and AI-2 signal transduction chain) Freeman and Bassler (1999) a. N-butanoyl-L-homoserine lactone. b. N-(3-oxodecanoyl)-L-homoserine lactone.…”