| Actinomycete B5, isolated from the sea water of Wei-hai and classified as streptomyces, has been studied on strain identification, antimicrobial activity, metabolites stability and purification. The main results are as follows:1. The cultural, physiological and biochemical characteristics demonstrated that the B5 strain are proposed as a close or the similar species to Streptomyces albus 16d-Ⅱ.2. The fungicidal activities against 17 plant pathogens and 4 bacteria were studied by means of mycelium growth rate and diffusion methods, respectively. The results showed that the efficacy of fermentation was above 80 percent against 13 pathogens, the diameters of inhibition zone against 4 bacteria were more than 18mm. The Pet trails results showed that the control efficacy of the fermentation broth of B5 against Pseudoperonospora cubensis and Fulvia fulvum were 70.68% and 64.67%, respectively.3. The results of the stability test indicated that antimicrobial activity of fermentation broth had few variety when strain B5 was cultivated 10 generations respectively the diameters of inhibition zone against 4 bacteria were more than 18mm. The results showed that it was stabile to heat and acid, but unstabile to alkali. At room temperature, when its was treated by pH2 for thirty minutes, the fungicidal activity was equipments with fermentation broth, but treated with six hours above pH12, there was no fungicidal activity.4. Two activity compounds was isolated by HPLC and ion exchange resins and 3#compound was identified as N-Acetylated derivatives of streptonthricin D. The structure of 3# is samilar to AN-201Ⅱ.The value of MIC of 3# compound againsts Bacillus subtilis, Bacillus cereus, Escherichia coli, Staphylococcu aureus is 60μg/mL, 35μg/mL, 40μg/mL, 50μg/mL, but the value of MIC against Pseudomonas aeruginosa is more than 200μg/mL, and the value of EC50 againsts of B sorokiniana, E turcicum, A longipes is 10.2μg/mL, 12.4μg/mL, 8.6μg/mL.
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