The role of quorum sensing in the regulation of extracellular enzymes by Pseudomonas fluorescens



McPhee, John Douglas

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University of Guelph


Research on bacteria has recently shown that they coordinate group behaviour by sensing their cellular density. Termed quorum sensing, this discovery has given researchers new direction to study and control bacteria. It was found in the present study that current quorum sensing detection methods (petri dish assay using biosensors) were prone to limitations. Problems associated with the method included: poor reproducibility; interference from compounds in different media; interference from test microorganisms; background noise; and restriction to qualitative results. A novel 96-well microtitre plate assay was developed that offered many improvements. Using these methods, ' Pseudomonas fluorescens' was found to synthesize the molecule responsible for cellular communication, acythomoserine lactone (AHL). The medium employed to support 'Pseudomonas' growth was found to influence AHL production. Milk was found to increase AHL synthesis. It was determined that quorum sensing systems in 'Pseudomonas fluorescens' may be used to regulate extracellular enzyme synthesis. Because current practices to control for growth or enzyme production adversely affect the quality of dairy products, alternatives are widely sought. The discovery that ' Pseudomonas fluorescens' uses quorum sensing to regulate enzyme synthesis offers a new approach to control dairy product spoilage.



Pseudomonas fluorescens, Quorum sensing, Extracellular enzymes, Regulation, Dairy products