Functional Study Of LuxI And LuxR Genes Related To Quorum Sensing In Hafnia Alvei H4

Quorum sensing is a mechanism of bacterial cell-to-cell signaling and gene regulation that can participate in bacterial infections and food spoilage,as well as regulate bacterial behavior,such as biofilm formation and swimming motility.The substance responsible for signal transmission in quorum sensing system is called signal molecule.Hafnia alvei H4 is a conditional pathogenic,widely found in nature and easily isolated from spoilage foods such as sea food,frozen beef,chicken,raw milk,etc.,which plays an important role in microbial food spoilage.Therefore,this paper mainly studied the spoilage ability of Hafnia alvei H4 in ready-to-eat sea cucumbers,explored the relationship between quorum sensing genes and the ability of spoilage,and verified the functionality of quorum sensing genes.It not only provided a theoretical basis for the next stage of sea food storage and preservation,but also provided new ideas for controlling food spoilage.In this paper,a complementary strain of a quorum sensing gene deletion mutant was constructed by genetic recombination.The deletion mutants(ΔluxI,ΔluxR and ΔluxRI)stored in the laboratory were subjected to ordinary PCR verification,and the construction of the complementary strain was carried out after confirmation.After screening of antibiotics,verification of PCR and alignment of gene sequences,the complementary strains(Com-I,Com-R and Com-RI)were successfully obtained.Lately,the functionality of the quorum sensing gene luxl and luxR was verified.The experimental results showed that the growth of Hafnia alvei H4,the production of biofilm and the ability of swimming were regulated by luxl and luxR genes.The deletion of genes reduces the production of biofilm and the ability of swimming motility.After genes replenishment,all of them will recover obviously,which is similar to wild-type.In addition,the spoilage ability of Hafnia alvei H4 on ready-to-eat sea cucumber was tested.The results showed that after inoculated Hafnia alvei H4 on the ready-to-eat sea cucumber,it can produce common spoilage gases such as hydrogen sulfide and methane.After cultured 120 h,the volatile base nitrogen content reaches spoilage level.It produced a variety of amines in the meanwhile,among them,putrescine and cadaverine were the most significant.These indicated that Hafnia alvei H4 has a spoilage ability,which can lead to the spoilage of sea food and affect the sensory quality,even endangering human health.While studying the spoilage ability of Hafnia alvei H4,it was found that the production of volatile base nitrogen was not regulated by the quorum sensing system,but the production of biogenic amine was related to the quorum sensing system.The deletion of luxl and luxR reduced the production of putrescine and cadaverine.The above experimental results showed that Hafnia alvei H4 can cause spoilage and deterioration of sea food.At the same time,the production of biogenic amines maybe regulated by quorum sensing system.These provided a theoretical basis for the antisepsis and preservation of sea food,and offered a new idea of antisepsis and antibacterial.