Research On Diversity Of Antarctic Filamentous Fungi And Secondary Metabolites In Weddell Sea

Fungi have been an important source of drug lead compounds because of their ability to produce novel and diverse bioactive natural products. Due to the decline of discovering new strains, newly active metabolites in general habitat fungi, researchers turn search to the microbial resources in extreme environments. In consideration of unique and severe environment, the polar-derived fungi have shown novelty and diversity in biological species, functional genes and secondary metabolites, and have been became new research hotspots. In this paper, the diversity of filamentous fungi have been isolated from sediments of Weddell Sea in Antarctica, the diversity of species, functional genes, bioactivities and secondary metabolites had been assessed.A total of 102 fungal isolates were isolated from 9 marine sediments samples in Antarctica, which were identified 40 taxa by molecular sequencing of the rDNA-ITS and β-tubulin, after dereplicated by community morphologies characteristics, TLC and BOX-PCR. The diversity of marine filamentous fungi was investigated based on rDNA-ITS phylogenetic analysis and their potential in synthesizing bioactive natural products estimated by polyketide synthase (PKS) gene and non-ribosomal peptides synthase (NRPS) gene coupled with antimicrobial, antitumoral and antiviral activity analysis bioassay. Consequently, all 40 taxa represented the phyla Ascomycota embracing 17 various genera (Acremonium, Aspergillus, Chaetomium, Cladosporium, Epicoccum, Eurotium, Geomyces, Hansfordia, Lecanicillium, Nectria, Penicillium, Phialocephala, Phoma, Sarocladium, Scopulariopsis, Simplicillium, Valsonectria) and Basidiomycota embracing 1 genus of Wallemia. Among the 40 representatives, there were detected 30 PKS sequences sharing sequence homology with β-ketoacyl domain and 14 NRPS sequences related to A domain, this genome mining study indicating their genetic potential to produce diverse types of polyketides and nonribosomal peptides. Supported with in vitro antimicrobial (Escherichia coli, Proteusbacillus vulgaris, Staphlococcus aureus, Candida albicans), antitumoral (mouse lymph cancer cell line P388) and antiviral (influenza A virus H1N1) activity evaluation,14 isolates showed antimicrobial activity,17 isolates showed antitumor activity and only 4 isolates showed antiviral activity. Furthermore,50% isolates with PKS or NRPS gene displayed at least one strong bioactivity. Thus demonstrates the phylogenetically diverse marine derived fungi in Antarctic sediments, and highlights the potential of filamentous fungi in synthesizing bioactive natural products.Based on the approach of gene screening coupled with activity assessment, Simplicillium lamellicola strin HDN13-430 was selected to investigate its natural products with PKS gene, NRPS gene and antimicrobial activity.11 compounds were isolated from the ethyl acetate fermentation extracts by column chromatography of silica gel, Sephadex LH-20 and semi-preparative HPLC. And the structure have been elucidated including 2 new phenalenedione type products (1-2),2 new PKs-NRPs (3-4),1 new aliphatic hydrocarbon (5),1 new naphthoquinone natural product (6) and 5 known compounds (7-11)It can be concluded that Anarctic marine fungi revealed the diversity of species, functional genes and secondary metabolites. Hence, they are important resources for bioactive secondary metabolites and have great value for further study and development.