Study On Secondary Metabolites Produced By Two Soil Bacteria

Microbial natural products play an important role in the drug discovery process.In the thesis,two bacterial strains,designated as TJU02-43 and BD06-03,were isolated from soil samples collected in China.After identification by 16 S r DNA sequence analysis,they were identified as Streptomyces venezuelae and Pseudomonas aeruginosa,respectively.Optimization of culture conditions was conducted to increase the variety and production of secondary metabolites.Based on the optimization results,large scale culture was carried out.As a result,several pure compounds were obtained from these two strains,using a series of fractionation techniques including solvent extraction,HP-20 column,silica gel column,and preparative HPLC separation.The structure elucidations of pure compounds were carried out based on ESI-MS and NMR spectrum.As a result,two major components,named kromycin and 10-deoxymethynolide,were isolated from ethylacetate extract of Streptomyces venezuelae TJU02-43.Both of them are known macrolides,and did not show any antimicrobial activities against a panel of test strains.For Pseudomonas aeruginosa BD06-03,two new 4-quinolone derivatives,together with eight known compounds,were isolated from the dichloromethane(DCM)extract.The eight known compounds were N-(2-hydroxyphenyl)-acetamide,Phenazine-1-carboxamide,1-hydroxyphenazine,3-heptyl-3-hydroxy-1,2,3,4-tetrahydro quinoline-2,4-dione,2-heptyl-1-hydroxyl-4-quinolone,2-nonyl-1-hydroxyl-4-quinolone,2-((2)-undec-4′-enyl)-1-hydroxyl-4-quinolone,2-heptyl-4-quinolone,while the two new metabolites were 2-(2′-hydroxyl)nonyl-4-quinolone and the 2-(E-2′-(methylthio)vinyl)-4-quinolone.Their antimicrobial activities were tested by agar well diffusion methods.Phenazine-1-carboxamide and 1-hydroxyphenazine exhibited inhibitory activities against Bacillus subtillis subsp.spizizenii(ATCC? 6633?),and Moraxella(Branhamella)catarrhalis(ATCC? 25238?).2-heptyl-1-hydroxyl-4-quinolone and 2-nonyl-1-hydroxyl-4-quinolone showed antibacterial activities against Bacillus subtillis subsp.spizizenii(ATCC? 6633?)and Staphylococcus aureus(ATCC? 12600?),and their MIC values were obtained by micro-broth dilution method.