Antibacterial secondary metabolites produced by marine Streptomyces sp. MMHS020

Abstract:

[Background] Marine microorganisms flourishing in diverse marine environments are widely recognized as rich sources of natural products. [Objective] Based on a Streptomyces sp. MMHS020 strain isolated from marine sediment, this study aimed to optimize fermentation conditions for abundant metabolites, and exploit the potential of the strain in antibacterial and antitumor activities. [Methods] Using a one strain-many compounds (OSMAC) approach, active metabolites were produced by strain MMHS020. Antibacterial activity for six indicator bacteria strains were traced using two-layer plate method. The metabolites were separated and purified by silica gel column chromatography, Sephadex column chromatography, and preparative chromatography. The compounds were elucidated by means of spectral analysis including ESI-MS, 1H-NMR, and 13C-NMR. [Results] Strain MMHS020 could produce diverse metabolites of antibacterial activity to inhibit the growth of all indicator bacteria such as Bacillus subtilis, Mycobacterium tuberculosis, and Micrococcus luteus when cultivated under high salt condition. Three compounds: nocardamine (1), ergosterol (2), and staurosporine (3) were isolated from the fermentation broth of strain MMHS020. Staurosporine was of inhibitory activity to Candida albicans, and nocardamine for the others. [Conclusion] Marine-derived Streptomyces sp. MMHS020, which produces a variety of bioactive metabolites, could be potentially developed as a novel antimicrobial agent.