29G-26 |
The role of quorum sensing in the regulation of protease by pseudomonas fluorescens and its relation to food spoilage |
M. LIU and M. W. Griffiths. Dept. of Food Science, Univ. of Guelph, Food Science Bldg., Guelph, ON N1G 2W1, Canada The production of protease by psychrochophic strains of Pseudomonas fluorescens is of particular significance in the spoilage of food. My research focuses on the role of quorum sensing in the regulation of protease in P. fluorescens, so that new food preservative strategies could be developed to specifically control related food spoilage. The N-acyl-homoserine lactone moieties (quorum sensing signal molecules) from P. fluorescens of dairy origin were detected through bioassays using lux-based reporters. The AHLs were separated and purified by HPLC, and also analyzed by thin layer chromatography (TLC). The production and reception of the signal molecule (acyl-HSL) were monitored by labeling the P. fluorescens culture with [carboxy-C14] methionine.. The relation between cell density and the protease production level with/without AHLs presence were compared. P.fluorescens expressing N-acyl homoserine lactonase gene (aiiA) was inoculated to food sample(milk and ground beef). The AHL level, protease production level and food spoilage time were determined. The results were compared to the P. fluorescens mutants(both protease and AHL production deficient) obtained through transposon mutagenesis. A total of 35 milk-borne P. fluorescens strain produce AHLs with different side-chain lengths. The protease production of the P. fluorescens ATCC strain 15456 were advanced by the addition of the short-chain AHL( C4-HSL). The spoiling ability of P. fluorescens is correlated with its ability to produce AHLs and the extracellular protease. The degrading of the AHLs by AHL-lactonase through introducing aiiA gene into P. fluorescens affected the protease production. Mutants defective in production of AHLs were also defective in the synthesis of protease. Food spoilage process were thus slowed down. The understanding of the role of quorum sensing in the regulation of protease by P. fluorescens has great potential implication for food spoilage and food preservation.
Session 29G, Food Microbiology: General
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