A Study on the Antibacterial Secondary Metabolites from Marine-derived Streptomyces bacillaris

Abstract

The actinomycetes from diverse marine environments are very prolific sources of structurally unique and biologically active metabolites. The decline in the efficiency of discovering antibiotics from terrestrial microbes has increased natural products chemists interest in investigating the chemistry of marine microorganisms, particularly as antibiotic resistance emerges as a significant threat to human health. In this study, 406 marine-derived actinomycetes provided by Korea Institute of Ocean Science & Technology were screened to search for antimicrobial compounds. Among them, the actinomycete strain 38C, which showed potent antibacterial activity, was further examined. This strain was identified as Strptomyces bacillaris by 16s rRNA analysis. The bacterium was cultured in GTYB50 at 28℃ for 5 days and the culture broth was extracted with organic solvents. Bioassay-guided separation of the crude extract using various chromatographic techniques yielded an active compound. On the basis of the results of combined spectroscopic data, this compound was determined to be medermycin, a pyranonaphthoquinone. The antimicrobial activity of medermycin was evaluated against various pathogenic bacteria and fungi. This compound exhibited potent inhibitory activities against Gram-positive and Gram-negative bacteria including MRSA.