Isolation And Characterization Of Two Marine-derived Actinomycetes And Studies On Their Bioactive Secondary Metabolites

The complex marine environment contributed to the unique way of life and metabolic pathway for the marine microorganisms and given them an obvious advantage in synthesizing of novel biologically active compounds.Marine-derived actinomycete have become an important source of bioactive natural products and the main force of new drug due to its ability to synthesizing of functional diversity of secondary metabolites.In this thesis,six different media were used to isolate the phylogenetic diversity of cultivable actinomycete associated with marine sediments collected from the Jiaozhou Bay and 63 actinomycetes were obtained.The cylinder-plate method was used to examine antimicrobial activities against Bacillus subtilis,Micrococcus luteus,Escherichia coli,Pseudomonas.Aeruginosa,Candida albicans and Saccharomyces cerevisiae,and 36 strains showed antimicrobial activity.On the basis of stable resistibility and broad antibacterial spectrum,two marinederived actinomycete U-19-3 and S-19-3 was selected and further studied focusing on the classification and identification of strains,screening of functional genes,optimization of fermentation conditions,separation and purification of the active product.The main conclusions were shown as follows:By studying the morphological characteristics,physiological and biochemica l properties,16 S rDNA and phylogenetic tree,U-19-3 was preliminary identified as Streptomyces roseoverticillatus and S-19-3 as Micromonospora lupine.Meanwhile,PKS,NRPS and halogenases genes screened by PCR showed that the type I and type II PKS genetic fragments were amplified from strain U-19-3 while type I genetic fragments was amplified from strain S-19-3.The fermentation conditions including the culture medium composition and NaCl concentration in shake flask and fermentation period in 5L fermenter were determined with the aim of production of antimicrobial active substanceBy silica gel chromatography,macroporous resin,thin-layer chromatograp hy,Sephadex LH20 gel chromatography,high performance liquid chromatography and bioactivity-guiding methods,the crude extract of antimicrobial active substance was separated and purified.It is speculated that the antimicrobial active substance produced by U-19-3 was terpene and produced by S-19-3 was aminoglycoside antibiotics.