The Inhibitory Effect And Mechanism Of Citronella Compounds On Pseudomonas Aeruginosa Quorum Sensing Systems

Quorum sensing(QS)is a kind of communication mechanism between bacteria.Pseudomonas aeruginosa is a common opportunistic pathogen in clinic,which has strong resistance to a variety of antimicrobial agents,and its prevention and control is becoming more and more difficult.The QS systems of P.aeruginosa were involved in the regulation of numerous virulence factors.The inhibition of its quorum sensing systems can effectively attenuate the virulence and pathogenicity of P.aeruginosa.In this study,the QS inhibitory effect and mechanism of citronellal,citronellol,and geraniol from citronella(Cymbopogon nardus)on P.aeruginosa PAO1 were analyzed based on microbiology,molecular biology,transcriptomics,and biochemistry.The main results of this study are as follows:1.Geraniol inhibited three QS systems of the PAO1 strain:las,rhl and pqs.Transcriptomic analysis showed that key genes in the Kyoto Encyclopedia of Genes and Genomes(KEGG)pathways of quorum sensing,biofilm,phenazine biosynthesis,transport,and bacterial chemotaxis of the PAO1 strain were all down regulated by geraniol.The transcription of key genes in P.aeruginosa QS systems were all inhibited by geraniol,including pqsABCDE,phnAB,lasR,and rhlR.The transcription of virulence genes were also inhibited by geraniol,including lasA,lecB,rhlABC,phz,toxA,and chiC.The related virulence factors of PQS signal molecules,pyocyanin,elastase,and biofilm of the PAO1 strain were then inhibited.2.Citronellal significantly inhibited las,rhl and pqs QS systems of the PAO1 strain.Citronellal inhibited the transcription of key genes in the three QS systems of P.aeruginosa,including lasI,lasR,rhll,rhlR,pqsA,and pqsR.Moreover,the transcription of the related virulence genes regulated by the QS systems were also inhibited,including lasA,lasB,pslA,phzM,toxA,chiC,and lecB.In addition,the related virulence factors were decreased,including PQS signal molecules,pyocyanin,elastase,swarming motility,and biofilm.3.Citronellol inhibited the pqs system of the PAO1 strain.Citronellol inhibited the transcription of key genes in the pqs system of P.aeruginosa,such as pqsA and pqsR.Moreover,the transcription levels of the virulence genes regulated by QS systems were inhibited by citronellol,including lasB,phzM,chiC,and pslB;and then the related virulence factors were decreased after citronellol exposed,including PQS signal molecules,pyocyanin,elastase,and biofilm.This study was found that citronellal,citronellol,and geraniol could inhibit the QS systems of P.aeruginosa in varying degrees.Moreover,the inhibitory efficiency of geraniol on the virulence factors regulated by the QS systems of the PAO1 strain was stronger than that of citronellal and citronellol,such as on pyocyanin,LasB,and PQS signal molecules.It laid a theoretical foundation for the prevention and control of virulence and pathogenicity of P.aeruginosa,and provided a reference for the research and development of bacterial QS inhibitors(QSI).