The Screening And Effects Of QSIs On The AHLs Secretion And The QS-genes Expressions In Hafnia Alvei

Quorum sensing is a communication mechanism of information exchange between bacterial cells,coordinating group behaviors and regulating gene expressions,which can cause food corruption and deterioration.Quorum sensing inhibitors(QSIs)interfere with the quorum sensing system of bacterias,inhibit the expressions of quorum sensing phenotype,and achieve the purpose of antibacterial and anti-corrosion.Hafnia alvei is a specific spoilage bacteria and leads to the spoilage of Marine products,meat products and dairy products under certain conditions.Food corruption and biofilm formation have caused serious hazard to the food industry and human health.Therefore,this study mainly aims to screen for quorum sensing inhibitors,and research for the effect on the production of AHLs secreted by Hafnia alvei from the instant sea cucumber,the biofilm formation and motility,the regulation of QS-genes expressions.QSIs provide a new strategy for food preservation and preservation,and give full play to the preservative effect of sulfide flavors.Quorum sensing inhibitors were screened by Chromobacterium violaceum 026(CV026)biosensor detection system.Results show that the selected 10 kinds of sulfide flavors,diallyl disulfide(DADS)and methyl 2-methyl-3-furyl disulfide(MMFDS)have an more significant effect than the others,which indicated that the inhibition ability were better than other kinds of sulfide flavors.In this paper,the AHL crude extraction were tested by high performance liquid chromatography(HPLC)analysis,the results show that Hafnia alvei cultivated 12 h mainly produces C6-HSL,and after adding DADS and MMFDS the production of C6-HSL were decreased.Agar difusion wells method is used to determine the effect of DADS and MMFDS to H.alvei after the different incubation time on the secretion signal molecule yield,the results show that the DADS had obvious inhibition effect on the AHL production in 4 h,8 h and 12 h.MMFDS was able to inhibit AHLs' secretion significantly at 4h,but which did not show obvious differences at 8 h and 12 h?In addition,this paper studied the inhibitory effect of quorum sensing inhibitors on the biofilm formation and swimming ability of Hafnia alvei.The results showed that the two kinds of QSIs can inhibit the biofilm formation and swimming ability of H.alvei.By using the scanning electron microscopy(SEM),DADS and MMFDS could significantly damage the biofilm structure of Hafnia alvei and reduce the biofilm density.This work used the two Hafnia alvei mutants strains,one was lacking-luxR gene called ?R mutant,the other was lacking-luxI gene called ?I mutant,which were built through the knockout technology.After adding DADS and MMFDS to Hafnia alvei wild-type strains and two mutant strains cultivated 12 h,then the luxI/R genes relation expressions were calculated.At the end,luxI gene of Hafnia alvei was found is the principal factor in adjustment of Hafnia alvei QS system.DADS and MMFDS not only add the aroma to the food,but also have QS inhibition activity,which can inhibit the food spoilage due to AHLs of Hafnia alvei.The above results laid the foundation for food processing interfered with QS,and provide a new way of regulating the development and utilization of sulfide flavors as food additive.