Abstract:

To study the antimicrobial activity of forest litter fungi in the Greater Khingan Mountains, firstly, fungi were isolated by a method of spreading particles on plates, and the isolated fungi were preliminarily identified by the amplification and alignment of internal transcribed spacer sequences. The antibacterial activities were detected by a two-layer-plate diffusion method and monomeric compounds of targeted strains were separated by chromatography. Spectroscopic analyses were used to determine the chemical structures of the monomeric compounds. A 96-well plate liquid dilution method was used to detect their minimum inhibitory concentration. A total of 88 fungi were isolated, belonging to 57 genera and 74 taxa. Of them, the internal transcribed spacer sequence similarities of 18 fungi were not higher than 97%. Among them, the ethyl acetate extracts of 6 fungi had antibacterial activities, and the two fungal strains KNFL008 and KNFL040 had stronger antibacterial activities than the others. By a bioassay-guided separation, four monomeric compounds, A (1,3-2-hydroxy-5-pentaalkylbenzene), B (ergosterol), C (2-amino-3h-phenoxyzin-3-ketone) and D (2-acetylamino-3h-phenoxyzin-3-ketone), were separated. The minimum inhibitory concentration of compound A, B and C was tested as 3.13-200 μg/mL. Compound A and D were firstly isolated from fungal extracts. This study lays a foundation for the further resource development and utilization of litter fungi in the Greater Khingan Mountains.

Key words: the Greater Khingan Mountains, litter, fungus, antibacterial activity, secondary metabolites, compound separation