Screening And Separation Of Bacterial Quorum Sensing Inhibitors And Preliminary Study On The Mechanism Of QSI

Most of the diseases caused by Staphylococcus epidermidis are difficult to cure and repeated episodes,which is because S.epidermidis is easy to form biofilm.Bacteria can increase the antibiotic resistance in the biofilm state by 10 to 1000 times than in the floating state,and the bacteria biofilm formation are more resistant to antibiotics.The formation of S.epidermidis biofilm is regulated by quorum sensing,which can directly control the formation or dissociation of biofilm.The quorum sensing inhibitor is non-bacterial inhibition,so the bacteria will not develop resistance to antibiotics,which has become the trend of antibiotic drug development.At the beginning of the experiment,different medium fermentation actinomycetes were found to have a great effect on inhibiting the biofilm formation of S.epidermidis and quorum sensing of Chromobacterium violaceum.In the preliminary work,it was found that Streptomyces griseus TRM10325 well inhibited the quorum sensing of C.violaceum and biofilm formation of S.epidermidis.Therefore,17 kinds of synthetic medium and 26 kinds of natural medium fermenting actinomycetes TRM10325 were selected,and the inhibitory effect on the quorum sensing of C.violaceum and the biofilm formation of S.epidermidis was detected by microplate method.The experimental results showed that the different formulations of the medium had different effects on the quorum sensing.Different media have obvious effects on the production of different secondary metabolites of actinomycetes.Provide experimental basis for screening optimal fermentation medium.From Xinjiang's abundant biological resources,microplates method were used for screening,actinomycetes and plant-derived quorum sensing inhibitors of S.epidermidis biofilm formation and C.violaceum quorum sensing.A total of 170 actinomycetes and 15 species of plants were screened from southern Xinjiang.The Streptomyces griseus TRM10325 and Coreopsis tinctoria Nutt were able to inhibit quorum sensing of C.violaceum ATCC12472 and the biofilm formation of S.epidermidis ATCC35984.Therefore,This study intends to screen and isolate QSI from the fermentation broth of TRM10325 and Coreopsis tinctoria Nutt,providing experimental basis for the development of new antibacterial drugs.Multiple separation techniques such as macroporous resin column chromatography and high performance liquid chromatography are used,and the analytical data of spectroscopy experiments such as IR,UV,1D & 2D NMR are integrated to isolation and identification of quorum sensing inhibitors of actinomycetes and plant sources.Plant-derived QSI isolated eight monomeric compounds from Coreopsis tinctoria Nutt,of which seven were flavonoids and one enyne compound.The activity of these 8 compounds in inhibiting the biofilm formation of S.epidermidis and the quorum sensing of C.violaceum was detected.It was found that the inhibition of the biofilm formation of S.epidermidis ATCC35984 was weaked,and the inhibition of C.violaceum ATCC12472 quorum sensing was wonderful.Actinomycete D and quercetin were selected to study the mechanism of the biofilm formation of S.epidermidis ATCC35984.It was found that actinomycin D and quercetin can greatly reduce the cell surface hydrophobicity of S.epidermidis,the initial adhesion phase of biofilm formation exerts a significant inhibitory effect,and is more effective than the aggregation period.Actinomycin D and quercetin can also change the species and content of extracellular polysaccharides of S.epidermidis,thereby reducing the ability on biofilm formation.However,actinomycin D and quercetin did not effect on the extracellular protein and DNA.The purpose of this study is to make full use of Xinjiang's rich biological resources,to screen QSI from it,and to provide experimental basis for the development of new antibacterial drugs.