Research On Quorum Sensing Of Specific Spoilage Organisms In Chilled Beef

Quorum sensing is a cell-cell communication mechanism by which bacteria count their own numbers by producing and detecting the accumulation of a signaling molecule that they export into their environment. This review focuses on quorum sensing system about Gram-positive and Gram-negative bacteria,Autoinducers,physiologica functions and correlation with food spoilage,restrain bacteria from growth and the microbiological risk assessment of food based on quorum sensing system.A confirmative method was developed with High Performance Liquid Chromatography-Mass Spectrometry （ HPLC-MS/MS ） to detect AHLs secreted by bacterial quorum sensing.AHLs secreted by bacterial quorum sensing was extracted with ethyl acetate.The sample could be directly analyzed after a simple treatment. Sunfire C18 column （2.1mm×50 mm, 3.5μm）, methanol and water （including 2mM ammonium acetate,0.1% Formic Acid）as the mobile phase were used for separation. The detection method of electrospray ion source with positive ion was used for mass spectrometry analysis.Qualitative and quantitative analysis of 11 kinds of AHLs in were completed within 12 mins. Experimental results showed that:The AHLs showed good linear relationship （r> 0.996） within the concentration of 1（10）～250ng / L. The minimum detection limit was 0.1 ng/L～1 ng/L. The limits of quantification of 0.3ppb～3 ppb. The average recovery was 54.4%¹28.6%. the relative standard deviations of 3.5%～13.9%. this method was used to detect the actual samples to verify the reliability of this method. The results show that, this method was simple, rapid, accurate, and high sensitivity. It was applicable to analyse and detect the AHLs in the bacterial growth environment.Pseudomonas.spp is one of the dominant bacteria that led to meat corruption. In this paper, two standard Pseudomonas spp strains were used: Pseudomonas fluorescens and Pseudomonas aeruginosa. In pure culture conditions by extracting AHLs released by the effect of Pseudomonas aeruginosa quorum sensing. And using HPLC-MS-MS analysis as detection method for amount and types of AHLs released by two Pseudomonas in different culture times. The results showed that: the categories of signal molecules released by Pseudomonas fluorescens were: C₄-HSL,C₆-HSL,C₈-HSL,3-oxo-C₁₀-HSL,3-oxo-C₁₂-HSL,3-oxo-C₁₄-HSL.The categories of signal molecules released by Pseudomonas aeruginosa were as follows: C4-HSL,C6-HSL,C8-HSL,C₁₀-SL,C₁₂-HSL,C₁₄-HSL,3-oxo-C₈-HSL,3-oxo-C₁₀-HSL,3-oxo-C₁₂-HSL,3-oxo-C14-HSL. The signaling molecules released by the two bacteria changed in accordance with the law from the increase to the diminishing. And the content of every types of signaling molecules were quite different. This article provides a theoretical basis in finding the analogue of Pseudomonas signal molecules, interfering with quorum sensing inhibiting the effect of specific gene expression. And it also provides certain research basis for the new strategy for food preservation.Establishment of chilled beef bacterial secreted signaling molecule extraction methods, in the chilled beef at room temperature, The categories of signal molecules released by bacteria in the chilled beef were as follows: C₄-HSL, C₆-HSL ,3-oxo-C₆ -HSL ,3-oxo-C8-HSL and 3-oxo-C₁₂-HSL. the highest content is C4-HSL.