The Effects Of Quorum Sensing Inhibitors On The Biofilm Formation Of Hafnia Alvei H4

Quorum sensing(QS)is an intercellular signaling and gene regulatory mechanism,which is implicated in bacterial pathogenicity and food spoilage.Therefore,blocking bacterial QS system may prevent QS-controlled phenotypes responsible for food spoilage.Hafnia alvei is an opportunistic pathogen,and it is mainly found in spoilage food,such as frozen beef,chicken,milk and surimi products,which is also known to play a role in microbial food spoilage.Food spoilage and biofilm formation caused by food-related bacteria have posed a significant problem for the food industry.Thus,the main purpose of this study is to screen quorum sensing inhibitors and to study the anti-biofilm activity of them towards H.alvei H4 isolated from ready-to-eat sea cucumber,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 study detected biofilm formation ability of three specific spoilage bacteria isolated from ready-to-eat sea cucumber by the methods of and crystal violet assay,we found that the biofilm formation ability of H.alvei H4 was the strongest between H.alvei H4 and Pseudomonas and Serralia,The relationship between biofilm formation and AHLs were research in this study,the results showed that AHLs could promoted biofilm formation of H.alvei at different concentrations.The three mutant strains of Hafnia alvei H4 were detected and we found that luxR and/or luxl genes have knocked out.And this study compared biofilm formation ability of the wild-type strain and its three mutant strains of H.alvei H4,we found the regulation effect of luxl gene on H.alvei H4 biofilm is the largest.The quorum-sensing inhibitory activities of the several bioactive substances were screened by Chromohacteriunr viokaceum 026 biosensor detecting system.Research indicated that four bioactive substances having quorum sensing inhibitory activities,includingy resveratrol.dihydrocoumarin,benzyl isothiocyanate and 3-(Methylthio)Propyl isothiocyanate.In addition,the effects of quorum-sensing inhibitors on the biofilm formation and swimming abilities of H.alvei H4 were investigated in this study.The results found that four quorum-sensing inhibitors could inhibited biofilm formation and swimming abilities of H.alvei H4 using at the sub-inhibitory concentrations in a dose-dependent manner.Scanning electron microscopy showed that dihydrocoumarin could effectively destroy the biofilm structure of H.alvei H4,and decrease biofilm density.The above results indicated that,the spoilage of ready-to-eat sea cucumber had been quite related with biofilm formation mediated by quorum sensing of bacteria.This study 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.