Separation Of Antagonistic Microbe And Analysis Of Its Antimicrobial Material

Rice sheath blight and rice blast are the most destructive pathogens for rice, constraining the development of rice. The available means against these two pathogens mainly involve chemical control, resistance breeding and biocontrol. Overuse of chemical pesticides will not only pollute environment but also do harm for animals and human. Biocontrol, especially for microbial control, arises in 1950s and develops fast. Together with resistance breeding, biocontrol appears a new prospect against pathogens.A stain, which has strong antagonistic activity against both of rice sheath blight and rice blast, was isolated and named as Osm-1. According to the morphology, physiological and chemical tests and 16S rDNA sequence, Osm-1 was characterized as Bacillus pumilus with unique physiological and chemical index.Inhibitory ratio of germfree culture broth against rice sheath blight is 97.1%. And inhibitory ratio against rice blast is more than 50%. Culture broth is proved to possess the ability of preventing rice from rice blast by field test. Infectious ratio of rice blast declines by 51.5% after sprayed by culture broth containing Osm-1.Antimicrobial material still worked after treated with 70% acetone and resided in supernatant. It was a relative polar compound, with solubility in water but not in butanol, ethyl acetate and chloroform. Antimicrobial activity was stable after treated by acid and 100℃heat separately. However, it disappeared after treated by basic and both of acid and heat. Purification of antibiotic was achieved by MCI absorption resin and HPLC. After purification, the compound was submitted to LC-TOF/MS and the result of molecular weight was 454.1806. There was no analog in database. Antimicrobial metabolites coming from bacillus genus contain proteins, enzymes, lipopeptides and polypeptides. The molecular weight of them are all over 1000Da. It does exist a few of non-peptide antibiotics such as amicoumacin A (MW:423) with low molecular weight. But they all differ with the compound we found. As a result, the antimicrobial material from Osm-1 is assumed to be a new antibiotic with low molecular weight.Osm-1, belonging to bacillus genus, has the advantages that its spore can sustain high temperature and draught. It is good for industrial production, processing, transportation and reservation. The antibiotic compound, with relative stabilization, high antibiotic activity and low molecular weight, is an ideal antibiotic source and possesses good prospect in development.