The Mechanism Of Biofilm Quorum Sensing Regulation On The Antibiotic Resistance Genes Transfer And Virulence Factors Expression

In recent years,the antibiotic resistance dissemination and pathogenicity of bacterial has become one of the public health problems.Pseudomonas aeruginosa is a common conditional pathogen in the environment,which usually exists in the form of biofilm,can secrete a variety of virulence factors,and can obtain antibiotic resistance in many ways,which brings more serious threats to clinical treatment and ecological environmentPlasmid-mediated conjugative transfer is one of the important ways for the dissemination of bacterial antibiotic resistance.On the one hand,the formation of biofilm can protect bacteria from antimicrobial agents and enhance the antibiotic resistance of bacterial.On the other hand,due to the high abundance of bacteria in the biofilm,it creates good conditions for the conjugative transfer of drug resistance genes.The pathogenicity of Pseudomonas aeruginosa is mainly attributed to the secretion of virulence factors,and the secretion of virulence factors is also closely related to the formation of biofilm.Therefore,the regulation of biofilm is one of the keys to control bacterial antibiotic resistance and pathogenicity.Some studies have shown that quorum sensing plays an important role in controlling the formation of bacterial biofilm and the production of virulence factors.Therefore,the regulation of bacterial biofilm and virulence factor secretion by quorum quenching may become an effective way to control bacterial antibiotic resistance pollution and pathogenicity.Some studies have shown that vanillin,a plant extract,can be used as a natural quorum sensing inhibitor to regulate the bacterial quorum sensing systemIn this paper,the effects of quorum sensing on the formation of biofilm and the conjugative transfer of antibiotic resistance genes in Pseudomonas aeruginosa were investigated,and the effects of vanillin on the secretion of virulence factors and the expression of related genes in antibiotic resistant bacteria were explored.The main research contents and conclusions are as follows:(1)the conjugate system of E.coli DH5α containing RP4 plasmid and PAO1 was used as the research object to explore the effect of quorum sensing inhibitor on the transfer of antibiotic resistance of bacteria in the biofilm.The effects of vanillin on the expression of quorum sensing related genes,the concentration of AHLs signal molecules in the system,the content of biofilm formation and the conjugative transfer frequency were determined.The results showed that the sub-inhibitory concentration of vanillin down-regulated the expression of related genes in Las and Rhl system without affecting the growth of bacteria,and then inhibited the synthesis of 3-oxo-C 12-HSL and C4-HSL.At the same time,with the increase of vanillin concentration,the biofilm forming ability of the two kinds of drug-resistant bacteria decreased,and the conjugative transfer frequency decreased in a concentration-dependent manner.Therefore,it is considered that the sub-inhibitory concentration of vanillin can regulate the formation of biofilm and inhibit the horizontal transfer of antibiotic resistance genes among cross-genus bacteria by affecting the bacterial quorum sensing system.(2)To explore the effect of quorum sensing inhibitor vanillin on the expression of virulence factors in Pseudomonas aeruginosa.Vanillin effectively inhibited the production of pyocyanin in PAO1 by inhibiting quorum sensing system,and the content of pyocyanin decreased with the increase of vanillin concentration.Sub-MIC of vanillin effectively inhibited the motility of PAO1,and inhibited the flagellum-mediated swimming ability of bacteria by inhibiting the expression of motA gene.