| Orychophragmus violaceus(L.)O.E.Schulz belongs to the Orychophragmus genus,Cruciferae family,rich in a variety of nutrients,edible tender leaves,whole grass as medicine,and is a unique herb in China.In this thesis,based on the quorum sensing(QS)screening systems of Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136,Irpex lacteus stand out among 48 endophytic bacteria,43 endophytic fungus,and 7 endophytic actinomycetes isolated from Orychophragmus violaceus,and its chemical composition and biological activity were studied.48 compounds,including 11 new compounds,were obtained by various purification methods such as thin-layer chromatography(TLC),column chromatography,and high performance liquid chromatography(HPLC).The types of compounds mainly involve sesquiterpenes,furans,carbolines,indole,quinolines,and cyclic dipeptides.Among them,norharmane,4-quinolone,irpexlacte C,indole-3carboxaldehyde,and isatin all have QS inhibitory activity.Norharmane could inhibit the QS system of Serratia marcescens NJ01.Combined with its 6 carboline derivatives were studied on the QS inhibitory activity of S.marcescens NJ01 and the evaluation of the potential structure-activity relationships(SARs).The results found that norharmine exhibited the strongest inhibitory activity and could significantly inhibit S.marcescens NJ01 virulence production and biofilm formation.However,the substitution of hydrogens at 1,3,and 7 positions of norharmine led to the weakening of QS inhibitory activity,especially 3 position hydrogen,substituted by a carboxyl group or a carboxymethyl group,resulting in the significant reduction of inhibitory ability in prodigiosin,hemolysin,protease,and biofilms.In addition,combined with ofloxacin resulted in the suppression of the QS system and destruction of the mature biofilm,which released the bacteria out of biofilm,exposure to ofloxacin,inducing the bacteria dead.Therefore,the combination of norharmine and ofloxacin could partially restore its antibiotics.4-Quinolone exhibited the inhibitory effects on proteases,swarming,swimming,and biofilm of Aeromonas caviae SHAe 1,Aeromonas veronii SHAe 101,and Aeromonas hydrophila SHAe 115,as well as the effect on the metabolism of A.veronii SHAe 101.The results showed that 4-quinolone could effectively inhibit the protease production of A.veronii SHAe 101,but almost no inhibition to that of A.hydrophila SHAe 115.Not only that,4-quinolone exhibited inhibitory effects on their swarming,swimming,and biofilm formation of them,and a certain destructive effect on mature biofilm.In addition,4-quinolone(200 μg/mL)caused a metabolic disorder of A.veronii SHAe 101,the content of partial metabolites involved in purine metabolism,pyruvate metabolism,phosphotransferase(PTS)system,tricarboxylic acid(TCA)cycle,and glycolysis/gluconeogenesis was changed,resulted in the interference of QS,the suppression of biofilm formation,and the restriction of sugar transport.Thereby the pathogenicity of A.veronii SHAe 101 was shrunk.In addition,this paper extended the research on the antibacterial activity of the quorum sensing inhibitor(QSI)resveratrol and its 8 derivatives against Xanthomonas oryzae Xoo,as well as metabolomic analysis.The results showed that resveratrol exhibited the strongest inhibitory activity against Xoo’s growth.The SARs indicated that the double bond in resveratrol helps to inhibit the growth of Xoo,and the hydroxyl group is an important active group for the inhibitory effect.Moreover,resveratrol could significantly inhibit Xoo’s flagella,leading to the weakening of Xoo’s chemotaxis and motility,reducing virulence and pathogenicity.In addition,resveratrol could cause oxidative stress and interfere with the metabolism of energy,purines,amino acids,and NAD+to inhibit the growth of Xoo. |
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