Studies On Inhibitive Substance Produced By Antagonistic Strains Of Endophytic Bacteria In Hami Melon Plants

Antagonistic strains from three hundreds and seventy eight endophytic bacteria strains isolated inHami melon plants that strongly showed the ability against Pseuodomonas syringae pv.melonis and Phytophthora drechsler were screened by examining inhibitive activity in vitro.Studied on substances from endophytic bacteria with the type, nature, stability, producing conditions for the period is expected to find new resistance genes resources and provide a scientific basis for antagonistic mechanisms of molecular biology and genetic engineering.The results showed : There are various antagonistic strains in endophytic bacteria in Hami melon plants. By measureing about antibacterial activity of extracellular from the antagonistic strains, antagonistic substance with highter antibacterial activity were selected especially the substance form 194 and 197 strains. The inhibitive substance from 197strain showed growth promoting and strong ability against Pseuodomonas syringae pv.melonis and Phytophthora drechsler . Extracellular have better preventive effect than strain.Chitinase, siderophores and other antimicrobial metabolites were found by analyzing of the antimicrobial substances. The most important antimicrobial mechanism of antagonistic strains is producing antimicrobial substances.It was confirmed that the antagonistic activities came from the protein secreted by the 197 strain. The filtrated from 197 strain was precipitated in grades with the ammonium sulfate to draw the Anti-proteins, The crude proteins drawn with ammonium sulfate at 15%-90% especially at 75% saturation showed strong inhibitive activities. Purification of antagonistic protein with antagonistic activity by PAGE.A purified protein was gained, it was test by SDS-PAGE which shows that it has only one ingredient. The molecular weights is about 45KD.It is a new protein probably.In low temperature condition, the antagonistic protein drawn with ammonium sulfate at 75% could preserve its inhibiting function for more than 7 weeks in alkaline solution (pH=8) , and its inhibitive activity still remained after diluted to 160 times and with hight tempreture treatment。It was sensitive to Protease K and partially sensitive to Protease .Show strong stability of Ultraviolet.The protein have wide antifungal spectrum, which can inhibited spore germination and penetrated hyphae ,dan cause transmogrification of hyphal shape also. Inhibitory effect of Pseuodomonas syringae pv.melonis is cause cell bodies irregular.By means of orthogonal experiment, the optimun fermenting condition of producing antagonistic protein is temperature 40℃, intitial pH value, 7.0; rotational speed,120rpm; fermentation volume, 50ml/150ml; cultured 72 hours.Testing of signature sequences of 16SrDNA, 197 strain may be belonging to the Bacillus cereus.