Isolation And Identification Of Endophytic Bacteria And Discovery Of Active Substances In Dendrobium Nobile

The stalk rot of Dendrobium nobile,which is a most serious disease on the growth of Dendrobium nobile,resulting in a serious decline in the yield of Dendrobium nobile and serious economic losses.Pathogen is a fungus of the asexual type of endophytic fungi is Pestalotiopsis.In order to avoid the use of excessive chemical pesticides in the prevention and treatment of related diseases,it is a good idea to find a natural source of pesticides.In order to find a green biological prevention and control methods to prevent Dendrobium nobile stem rot.In this study,we studied the isolation and identification of endophytic bacteria from different tissues(roots,stems and leaves)of Dendrobium nobile.Four endophytic bacteria,which can infecte the growth of pathogenic fungi of Dendrobium nobile,were obtained and identificted by morphological observation and 16 S rDAN molecular biology.Three of them were identified as Bacillus and one was Paenibacillus polymyxa.In this paper,the active metabolites of Paenibacillus polymyxa were further studied.To antibacterial activity as the guide and the best medium for Paenibacillus polymyxa was screened as PDB medium with the best fermentation time of 7 days.By optimizing the extraction method of the fermentation broth,the results showed that methanol was used to extract from the fermentation broth with concentrate,and the active substance could be extracted with high efficiency.After the separation,purification and identification of the metabolites,the antifungal substances were identified as fusaricidin family compounds and its structurewere were identified by high resolution mass spectrometry.In vitro,the inhibitory mycelial growth rate method was used to test the effect of fusaricidin on Pestalotiopsis.The results show that the EC50 values are between 3-10 ?g/m L.fusaricidin A / B substance(final concentration 3.29 ?g / mL)was added the pathogenic fungus culture after 24 hours of incubation and the total bacterial protein was extracted at 3 and 12 hours after dosing.Labele-free quantitative proteomics method was used to analyze differentially expressed proteins.The bioinformatics analysis of the differential proteins showed that the mechanism of the active substances on the growth of pathogenic fungi was mainly in the oxidation of phosphorylation and amino acid biosynthesis.This foundation is laid for further clarifying the exact mechanism of these active substances in controlling fungal diseases.