Construction Of SPA7074-deficient Mutant Of Biocontrol Streptomyces Act12 And Characterization Of Its Secondary Metabolites

Streptomyces pactum Act12 is a multifunctional actinobacteria which was isolated from Qinghai Tibet Plateau.Streptomyces pactum Act12 is a multifunctional actinobacteria which has excellent bio-control activity,such as growth promoting for strawberry, and a higher production for tanshinone.The Act12 bio-control agents has been applied to agricultural production. There is not abundant of metabolites in previous study in laboratory. Whereas,Act12 has abundant of biosynthetic gene clusters which indicates the most of the clusters in it is silent. So we disrupt the gene spa7074(accession number: KU955325),which encodes a member of the TetR family transcriptional factors in biocontrol strain Act12 and characterize the secondary metabolites in the mutant strain by homologous recombination. The fermentation extract of the mutant has a better antimicrobial activity for several pathogenic bacteria than the Act12 by bacteriostasis text. The secondary metabolites of the mutant strain Δspa7074 and Act12 was detected via HPLC and there are several other different peaks in the mutan. The structure of one different peak was analyzed by MS and NMR. Compared to the wild-typestrain, the production of some unknown compounds in the mutant strain Δspa7074 increased obviously. One of the compounds was purified and identified as oligomycin D by MS and NMR analysis. A high-yield oligomycin D-producing strain Δspa7074 was derived via genetic engineering in this study. The antimicrobial activity of the mutant strain Δspa7074 increased obviously.There are abuntant of bioactive natural products such as antibiotics in actinomycetes.This study obtains 66 strains which has different morphological characteristics and has a determination of the bacteriostatic activity from stone forest in Yunnan province. Then, we screened 10 bioactive strains which were identified as actinomycetes by 16 S rDNA. At last, we have a metabolite analysis for three strains among them: sh1-26,shl-34,shl-50 which have suppression biactivities for G+ bacteria and fungus which providing candidate strains for new antibiotic finding.