Regulation of alkaline metalloprotease promoter by N-acyl homoserine lactone quorum sensing in Pseudomonas fluorescens.
OBJECTIVE
To examine the involvement of N-acyl homoserine lactone (AHL) quorum sensing in alkaline metalloprotease (aprX) promoter regulation in a Pseudomonas fluorescens milk isolate.


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.


CONCLUSIONS
This study contributes to our understanding of the genetic regulation and ecology of P. fluorescens in the economically important system of food spoilage.
Canadian Research Institute for Food Safety, University of Guelph, Guelph, Ontario, Canada.
M
M
Liu
H
H
Wang
M W
MW
Griffiths
D054742:Acyl-Butyrolactones / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D001681:Biological Assay; D002855:Chromatography, Thin Layer; D005516:Food Microbiology; D015964:Gene Expression Regulation, Bacterial; D005818:Genetic Engineering; D008892:Milk / Q000382:microbiology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011551:Pseudomonas fluorescens / Q000378:metabolism*; D053038:Quorum Sensing / Q000502:physiology; D017422:Sequence Analysis, DNA; D012697:Serine Endopeptidases / Q000235:genetics*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
D054742:Acyl-Butyrolactones; D001426:Bacterial Proteins; C402704:AprX protein, bacteria; D012697:Serine Endopeptidases