Study On The Antibacterial Activity Of Neocucurbitaria Sp. And Its Secondary Metabolites From Litter In Daxinganlin

Fungi are important natural resources,have gained widespread concern by microbiologists and chemists.Fungi can produce numerous secondary metabolites that have made outstanding contributions to medicine,agriculture and other fields.In order to find biocontrol fungi against plant diseases and their active compounds,this study selected forest litters from the Greater Hinggan Mountains as materials,tried to isolate culturable fungi by particles on culture plates.Identified fungi by a molecular biology and morphological method,investigated antimicrobial activities by a well diffusion method,separate monomeric compounds by a bio-assay guided fractionation method.The results are as follows:A total of 52 fungal strains were isolated from litters in the Greater Khingan Mountains by using high-throughput-particle-plate method.The 52 fungal strains belonged to 4 phyla,7 classes and 21 families,among which 11 fungal strains showed ITS similarity of≤99.50%.Among them,SGSF801,SGSF812,SGSF824 and SGSF825showed antibacterial activity.The taxonomic status of four strains of litterfall fungi was established by molecular biological analysis and morphological analysis.The abundance and diversity of secondary metabolites of the fermentation extracts of 4 strains of fungi were analyzed by HPLC.Combined with the screening results of the anti-plant pathogen activities of the four fungi strains,the SGSF801 strain was selected for the isolation of secondary metabolites,and the effects of temperature,medium and p H on the growth of the strain as well as the biological activities and antioxidant activities of its extracts were measured.The strain SGSF801 was subjected to a large amount of fermentation to obtain the fermentation extract.Monomer compound 801A was isolated by silica gel column chromatography,thin layer chromatography,Sephadex LH-20 and analytical high performance liquid chromatography.It was identified as cercosporamide by ¹H-NMR,¹³C-NMR and HR-ESI-MS analysis.To sum up,this study found a new strain with antimicrobial activities that is Neocucurbitaria salicis-albae SGSF801 from 52 litter fungal strains,and identified its active monomeric compound as cercosporamide.This study laid the theoretical foundation of development and utilization of fungal resources from Greater Hinggan Mountains,and provided an alternative fungal strain and a lead compound for the research on biocontrol fungi.