Study On The Effect Of EGCG On The Synthesis Of Biofilm And Colanic Acid In Escherichia Coli

Colanic acid(CA),as the component of biofilm matrix,is a major extracellular polysaccharide secreted into the environment by Escherichia coli(E.coli)in response to stress.Epigallocatechin gallate(EGCG)is the main functional component of tea polyphenols with significant antibacterial effects.In recent years,the focus of EGCG research on bacterial biofilm inhibition has been on high dose.Therefore,this paper focuses on the effects of different EGCG concentrations on E.coli growth conditions,bacterial biofilm,and CA formation,as well as exploring the mechanism of EGCG on E.coli biofilm formation.The main findings are as follows:(1)EGCG(0-100 μ M)treated wild-type E.coli strain BW25113 was analysed for growth status,biofilm and CA formation of the strain were analyzed.The results showed that EGCG inhibited the growth of wild-type BW25113 strain in a dose-dependent manner under normal conditions(LB medium,37°C);under nutrient limited and low temperature conditions(M9 medium 25°C),low doses of EGCG(5 μM,10 μM)promoted the growth of wild-type BW25113 strain and high doses(50 μM,100 μM)inhibited it.Under low temperature conditions,the biofilm and CA of wild-type BW25113 strain were analyzed by crystal violet and mordant staining,and it was found that low dosages of EGCG promoted biofilm and CA production while high doses inhibited both.(2)CpxA and CpxR gene deletion strains were used to explore the mechanism of different EGCG concentrations on growth status,biofilm formation and CA formation.The results showed that the effects of EGCG on the growth and biofilm formation of ΔCpxA andΔCpxR strains were consistent with wild-type BW25113 strain.Analysis of the expression levels of 20 gene clusters for CA synthesis by q PCR fluorescence quantification revealed that low-dose EGCG promoted the expression of CA synthesized polymerase related gene wca D and outer membrane protein wza in wild-type BW25113 strain and ΔCpxA strain,while high-dose inhibited its.However,EGCG up-regulated the expression of wca D and wza in the ΔCpxR strain at all concentrations(1-100μM).The above results indicated that the CpxA/R system was not involved in the effect of EGGC on the growth and biofilm of wild-type BW25113 strain,but there is a possibility that EGCG indirectly affects the regulatory pathway of CA polymerization and extracellular transport,which is through activating the response regulator CpxR.