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  • Title: Regulation of alkaline metalloprotease promoter by N-acyl homoserine lactone quorum sensing in Pseudomonas fluorescens.
    Author: Liu M, Wang H, Griffiths MW.
    Journal: J Appl Microbiol; 2007 Dec; 103(6):2174-84. PubMed ID: 18045400.
    Abstract:
    AIMS: To examine the involvement of N-acyl homoserine lactone (AHL) quorum sensing in alkaline metalloprotease (aprX) promoter regulation in a Pseudomonas fluorescens milk isolate. METHODS AND RESULTS: N-acyl homoserine lactone signals from P. fluorescens strain 395 were separated and detected by thin layer chromatography (TLC). Further analysis of the AHL signals using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) indicated the presence of C4-HSL and 3OC8-HSL. The expression of aprX in P. fluorescens 395 was investigated, using a transcriptional fusion between the aprX promoter and a mutated gfp variant gene (gfp[mut3]). The results demonstrated that the activity of the aprX promoter increased dramatically in the late exponential phase of growth, indicating growth phase-dependent regulation. The activity was repressed in an AHL-deficient environment, in which the signal molecules were hydrolysed by the enzyme AHL lactonase. CONCLUSIONS: N-acyl homoserine lactones produced by P. fluorescens 395 were identified to be C4-HSL and 3OC8-HSL. The protease gene in P. fluorescens is regulated by the AHL-based quorum sensing system at a transcriptional level during the late exponential growth phase. SIGNIFICANCE AND IMPACT OF THE STUDY: This study contributes to our understanding of the genetic regulation and ecology of P. fluorescens in the economically important system of food spoilage.
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