[Objective] The research aimed to optimize the test condition of PCR-DGGE method to analyze genetic diversity of soil microorganism. [Method] The amplified results of PCR were compared by improving high salt method for extracting soil DNA, improving primer design, changing the annealing temperature and amplification system of PCR reaction process. [Result] The result of extracting soil micro-bial DNA was better by high salt method which was improved. A single band was obtained and operation was easy when choosing 20 μl system for PCR amplification. There was no nonspecific amplification when choosing annealing temperature at 55 ℃, and cycle number of 35 was easy for following DGGE analysis. [Conclusion] The optimized PCR reaction system has high specificity and reliability.
[ Objective ] The paper was to isolate and preliminarily identify the antibacterial active substances of antagonistic actinomyeete strain G19 obtained from the soil highly affected by peach crown gall （Agrobacterium tumefaciens）. [ Method] The antibacterial substances of antagonistic actinomycete strain G19 were ex- tracted using protein precipitation method, then isolated and purified using high performance liquid chromatography and medium-pressure preparative chromatogra- phy. Its molecular weight was determined by MALDI-TOFMS method, and the related functional groups were verified through chemical color reaction. [ Result] Seven peptide portions were produced from the antibacterial substances of antagonistic actinomycete strain G19 with the molecular weights of 900 - 1 300 Da after isolation and purification. It could be also inferred that it contained Cys, and carried with H2O and Na＋. Color reaction of functional groups verified that the sub- stance was polypeptide containing glycosyl. [ Conclusion] The result provided basis for the final definition of the structure of antibacterial substances in antagonistic actinomycete strain G19.
