The AHLs Secretion Regularity And The Screen Of Quorum Sensing Inhibitor Of Hafnia Alvei

China is a big country of production and consumption of aquatic products, and the total output of aquatic products has been number one for more than 20 years in the world. But at the same time, it is quite shocked that aquatic products become corrupt because of spoilage organisms. The loss rate of aquatic products in our country caused by spoilage organisms is about 15%, resulting in huge economic losses and serious public health problem. In recent years, research has shown that the decaying of aquatic products is closely related to the phenomenon of spoilage organisms quorum sensing. So this thesis mainly studies the law of signaling molecules(AHLs) secreted by spoilage organism Hafnia alvei isolated from ready-to-eat sea cucumber and the screen of quorum sensing inhibitor, aims at providing theoretical basis for the preservative of Hafnia alvei and aquatic product freshness and developing new ideas to inhibit food spoilage and study preservative.This article explored the law of AHLs secreted by spoilage organism Hafnia alvei isolated from ready-to-eat sea cucumber. The results showed that Hafnia alvei began to produce AHLs at the beginning of the logarithm, and reached maximum in the late logarithmic, then decreased in stable phase but still maintained a relatively long time, and the content of AHLs was density-dependent. In early growing season, the pH of culture solution of Hafnia alvei had no significant change, then obviously decreased at logarithmic phase,however, it was only 5.71 in the late logarithmic. Later, it re-grew gradually, and finally tended to be stable when entered into stable phase.This article also explored the effects of common environmental factors on AHLs secreted by Hafnia alvei. The results showed that the ability of Hafnia alvei secreting AHLs was regulated by environmental factors. The optimum temperature of Hafnia alvei secreting AHLs was 30℃, and the optimum pH was 7.0, besides, the final concentration of 0.5%~3%NaCl stimulated the secretion of AHLs. The ability of Hafnia alvei secreting AHLs was higher than others when fructose and ammonium sulfate was used respectively.In addition, this article also used Chromobacterium violaceum CV026 to screen quorum sensing inhibitors from natural products, and studied the effect of inhibitor on Hafnia alvei quorum sensing system. The results showed that resveratrol had significant effect oninhibiting the production of purple pigment in selected natural products and it could inhibit quorum sensing. Resveratrol could inhibit swimming ability of Hafnia alvei when it had no effect on cell growth, and swimming ability was concentration-dependent. However, there was no clear effect on the secretion of AHLs by resveratrol.The above experimental results showed that there was some law in Hafnia alvei secreting AHLs, and resveratrol could inhibit quorum sensing system of Hafnia alvei. This article laid the foundation for new strategies of food preservation based on interfering in quorum sensing of spoilage bacteria. And this also accumulated basic data for the research of gram negative bacterial quorum sensing system.