Isolation And Composition Analysis Of Secondary Metabolites From A Strain Of Bacillus Amyloliquefaciens Which Inhibitrice Blast Fungus

Rice blast is one of the three major diseases affecting rice production,which seriously affects the yield and quality of rice.In general,the traditional way to prevent and treat rice blast is chemical control.But excessive use of chemical pesticides will have a great harm to human health and cause serious pollution to ecological environment.At present,the combination of resistant varieties screening and cultivation is the major method to prevent and control rice blast.In recent years,the use of natural products and biological pesticides and other biological control means have also shown a broad prospect.We found a new strain with a significant inhibitory effect on Magnaporthe grisea on Chinese herbal medicines named Rdx-5.The strain was further studied and its secondary metabolites produced during the fermentation were purified and identified.Rdx-5 is long rod-shaped,sparse flagella,athletic,gram-positive bacteria.After incubation on PDA medium plates for 24 h,the edges of the single colonies were irregular and the surface was slightly rough and pale yellow.The strain had a starch-decomposingeffect,and the strain was found to have great spores by microscopic examination.After 16S rDNA sequencing,it was identified as Bacillus megaterium.The antimicrobial composition produced by Rdx-5 still has a strong antibacterial effect after treatment at 100 ? for 30 min.In addition,in a strong acid,neutral,weak alkaline environment for 24 hours its antibacterial effectwill not change.But under strong alkaline conditions,the antibacterial effect decreased significantly.We isolated and purified the antibacterial substance of strain Rdx-5 by precipitation,column chromatography and high performance liquid chromatography.Finally,compound A was obtained and the molecular weight was determined to be 364.26.Through the molecular weight database search,we did not find any relevant reports of thecomposition,of which the molecular weight is below two scores after four decimal places.Presumably the substance is a new compound.The substance has independent intellectual property rights,which can apply for the relevant patents.Simulated field experiments showed that different concentrations of bacteria and sterilized fermentation broth had significant effect on the control of rice blast,and found that the prevention effect was better than the therapeutic effect.We speculate that the bacteria can be planted on the surface of rice plants and continue to produce antibiotics.Therefore,not only the bacteria can produce stable and reliable antibiotics,but also can be used as biocontrol for rice blast control.