| This study aimed at separating and screening the antagonistic bacteria from rhizosphere soil samples of foxtail millet that Rhizoctonia solani infected, which had a good antagonistic role to Rhizoctonia Solani, then preliminary researches were carried out for fermentative conditions and active productions.Rhizosphere soil samples of R.solani infected foxtail millet were collected from all production areas in China, from which, a total of 1346 microbial strains were separated, including bacteria, streptomyces, fungi, etc. By confrontation culture, antifungal activities to R.solani of these microorganism were determinated, as a result, 16 bacteria, 1 streptomyces and 3 trichoderma that had antagonism to R.solani were screened out. The streptomyces strain"SS56", out of the 20, had shown the highest antifungal activity. At the same time, SS56 had performed higher antifungal activity according to the examination in petri dish and pot culture of fermentation broths. Antifungal spectrum was detected through confrontation culture, the results showed that SS56 had wide antifungal spectrum, which had well inhibition to all R.solani and most soil-borne diseases in crops, it suggested that SS56 had research value in-depth.SS56 strain was preliminarily identified as Glaucum streptomyces according to physiological and biochemical property experiments along with morphologic and cultural characteristics of mycelia and spores, referring to"Classification and Identification of Actinomyces"and"Berger bacterial identification manual"as well.The observation through microscope primarily definitized that SS56 restrained the growth and elongation of R.solani mycelia in foxtail millet by secreting active substances which could cause shortening, branches increasing, bending and metamorphosing, cytoplasmic agglutination of mycelia, topmost growing point expanding and the contents leakage. At the same time, SS56 has obvious inhibition for aerial mycelium of R.solani.The pilot studies of fermentation conditions for SS56, which screened 21 kinds of normal fermentation medium, showed as a result that PD medium was the optimal one. The bacterial age, inoculum doze, rotation speed, temperature and time of fermentation with PD medium were selected, the results demonstrated that the optimal fermentation conditions of SS56 were 4 days of the bacterial age, 10% inoculum doze, 31℃of fermentation temperature, 160rpm of shaking speed and 4 days of cultivation.The preparatory researches made on physical and chemical properties of the active substances existing in fermentation broth for SS56, which suggested that the active substances were stable in weak acid and neutral pH conditions, high temperature-endured, remained stable existence in the 80℃, little decreaced activities in 100℃, activity completely lost in 121℃; The activity still existed in a longer valid period of six month.The preliminary studies on extraction and separation methods of antibacterial active substances for SS56. The outcome showed that active substances existed in both thalli and fermentation broths, which could be separated with extraction by acetic ether and existed mainly in organic phase, it confered that the active substances produced by SS56 was a kind of fat-soluble. Static adsorption experiments revealed macropore polymeric adsorbent NKA-9 with intensive polarity could adsorb the active substance. Concentrated the elutions by subsection and determined their activities, then separated the active components by Thin-Layer Chromatogram and reclaimed preparative bands respectively. The high performance liquid chromatographic analysis showed that it was single peak with the higher activity and purity whose construction could be identified after preparation.
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