The Screening And Identification Of Antagonistic Bacterial Strain GXG-2-2 And The Preliminarily Study On Its Antagonistic Metabolites

This research aimed at isolating and screening of antagonistic Bacillus with great activity on take-all disease from the withered grass; identifying the antagonistic strain; optimizing the fermentation medium and conditions; studying the inhibitory substance produced by them preliminarily.(1) In this study, 253 strains of Bacillus were isolated from 5 samples of withered grass which came from Yangling, Shaanxi province. A strain had stronger and stable antagonistic effect against many plant pathogens were selected through agar plate experiment, single-cell isolations, fermented solution plate experiment, and pot experiment.(2) The fermented conditions for the protein yield of strain GXG-2-2 were optimised. when the strain cultured with conditions as following: culture medium temperature 28℃and culture time 48 hours, initial pH 7.0, 180 r/min in shake revolutions with100 mL medium in 250 mL conical flask, in which crude protein, bacterial population and inhibitory activity could reach to the best.(3) GXG-2-2 showed efficiently inhibit to take-all disease of wheat in greenhouse tests, and the shoot height, shoot weight, root length and root weight were much higher than that of diseased control plants. The results showed the soil drench of spore suspension were more significantly control efficiency than seed coating and seed soaking, simultaneous inoculation biocontrol agents with Ggt was better than 1d and 7d post-inoculation, and high concentration of spore suspension was more excellent than low concentration.(4) Through the measure of biological antagonistic activity in plates, the pathogen inhibited table of the crude antifungal protein produced by GXG-2-2 was researched. Results showed that: GXG-2-2 had wide antifungal spectrum, the crude antifungal protein produced by GXG-2-2 had strong inhibitive effect on 20 pathogenic fungus and 3 tested bacteria, especially to Rhizoctonia cerealis and Escherichia coli.(5) In terms of the traditional identification way, according to its morphological, cultural, and physiological biochemical characteristics of GXG-2-2, it was regarded as Bacillus subtilis preliminarily.(6) The antifungal compound produced by B. subtilis GXG-2-2 strain was protein through ammonium sulfate precipitation. The crude protein drawn with ammonium sulfate at 60% saturation showed strong antifungal activity. The protein kept its antifungal activity stable in neutral and alkaline condition, the pH 7.6 was the best. The crude protein produced by GXG-2-2 was resistant to thermostable, ultraviolet and proteinase K, partial sensitive chloroform . The main activity compound of crude protein was detected by PAGE...