Deep Marine Sediment-derived Actinomycetes Of The Arctic Ocean:Secondary Metabolism Genes Analysis, Antibacterial Activity Screening And Products Separation

Actinomycetes are a kind of important microorganisms who are responsible for the production of almost half of the discovered bioactive secondary metabolites. In addition, it becomes an inevitable trend to looking for new drugs from marine microorganisms today. As an important resources, the Arctic actinomycetes, however, have not been investigated and analysed systematically. It is cold and the water temperature is below0℃perennially in Arctic, about2/3of the ocean is covered by thick sea ice, as a result, this area turns out to be one of the coldest oceans.In order to adapt to the harsh environmental pressures, actinomycetes in the Arctic Ocean have evolved unique physiological and biochemical character and difference do occur in the secondary metabolite biosynthesis pathways with the strains separated from temperate and tropical areas. Thus, these actinomycetes may have the capacity to produce secondary metabolites which have novel in structure and possess biological activity.This paper does research in seventy actinomycetes isolated from deep sea sediments of5stations in the Chukchi Sea and the Canada Basin located in the Arctic Ocean. To assess the medicinal potential of these actinomycetes. a series of approaches were employed, including analysis of phylogenetic diversity, screening of secondary metabolism genes and detection of antibacterial activities.BOX-PCR fingerprinting analysis showed that isolates grouped into38different strains;16S rRNA gene sequence analysis revealed that these38strains belong to three genera:Streptomyces, Nocardiopsis and Pseudonocardia. Streptomyces are dominant which accounted for as much as83.8%.To assess the antibiotic biosynthetic potential of the Arctic strains, PCR screening approach was applied to detect the genes associated with seven secondary metabolites synthetase (type I polyketide, type Ⅱ polyketide, nonribosomal peptide, phenazine,6-deoxyhexose, halogenide, polyene polyketide) biosynthesis pathsways. PKS Ⅰ, CYP, NRPS and halogenase genes were observed in94.7%,86.8%,84.2% and65.8%of the strains. However, only23.7%,21.1%and7.9%of the strains possessed PKS II,6DOH and phzE genes, separately.The analysis of KS amino acid sequences (PKS I) provided that thirteen strains harbor the ability to produce rich and novel type I polyketides, like erythromycin, candicidin and some structural variants related to leinamycin, tirandamycin, lipomycin etc. Streptomyces. sp564F, with BLAST matches to three different PKSI pathways (candicidin. lipomysin. meridamycin). This provide evidence that this strain may be a rich source of diverse, polyketide-derived secondary metabolites.In antimicrobial assay, actinomycetes in our study show to antibacterial and antifungal activity. Besides.86.8%,97.4%and84.2%of the actinomycetes could respectively suppress the fecundity of Candida albicans, Staphylococcus aureus and Bacillus suhtilis in varying degrees respectively.Fermentation and chemical methods were performed to separate secondary metabolites of Slreplomyces564F, and eight purified compounds(564-01and564-02are alkaloids) and some minor samples from the collected HPLC peaks were obtained. The results by HPLC-Tof MS and NMR analysis suggest that Slreplomyces564F is a worthy producer of secondary metabolites, including alkaloids, macrolides, terpenes, peptide, fatty acids etc.The results revealed the novelty and diversity of actinomycetes and their secondary metabolites in deep-sea sediments of the Arctic Ocean. Through carrying out large-scale collection and researches on Arctic actinomycetes, will provide new opportunities to discover more novel active substances.