Taxonomic analysis of fungal endophytes from Ampelopsis japonica by high-throughput sequencing and culture-dependent methods and the activity of the isolated strains against acne-associated pathogens

Abstract:

[Background] Medicinal plants harbor abundant fungal endophytes, producing host-related secondary metabolites with a variety of biological activities. [Objective] To analyze the diversity of endophytic fungi in the roots of medicinal species Ampelopsis japonica (Thunb.) Makino and isolate strains producing chemicals with anti-acne activity. [Methods] The taxonomic diversity of fungal endophytes was analyzed based on high-throughput sequencing and tissue isolation. The activity of metabolites of the endophytes against acne-associated pathogens was tested with agar diffusion method and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution.[Results] The endophytic fungi from the roots of A. japonica belonged to 93 genera, 73 families, 45 orders, 22 classes, and 8 phyla. The dominant genera were Tainosphaeria (20.86%) and Fusarium (15.38%). With the tissue isolation method, 83 fungal strains (12 genera) were isolated, among which Penicillium (24.10%), Trichoderma (14.46%),Cadophora (13.25%), and Fusarium (12.05%) dominated. The results of anti-acne bacteria activities of 17 representative strains showed that the strains with activities against Propionibacterium acnes and Staphylococcus aureus accounted for 11.76% and 23.53%, respectively. The fermentation broth of the endophytic Fusarium oxysporum BLR17 displayed obvious inhibitory effect on both pathogens. The MIC of its crude ethyl acetate extract against P. acnes and S. aureus was 7.81 μg/mL and 62.5 μg/mL, respectively, and the MBC was 7.81 μg/mL and 62.5 μg/mL, separately. [Conclusion] The endophytic fungi of A. japonica had high diversity and contained a certain proportion of anti-acne species resources. F. oxysporum BLR17 is expected to be a resource strain for screening the anti-acne bioactive compounds, which is worthy of further study.