Extraction and Identification of Antibacterial Secondary Metabolites from Marine Streptomyces sp. VITBRK2.

Actinomycetes were isolated from marine sediment samples collected from the east coast of Chennai, Tamil Nadu, India. Well diffusion and agar plug methods were used for the evaluation of antibiotic production by these isolates against drug resistant Methicillin- resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococci (VRE). The potential isolate VITBRK2 was mass cultured for morphological and physiological characterization. The culturing conditions of the isolate were optimized and the recommendations of International Streptomyces Project were followed for the assimilation of carbon and nitrogen sources. The isolate was identified by comparing the properties with representative species in the key of Nonomura and Bergey's Manual of Determinative Bacteriology. Ethyl acetate extract prepared from the cell free culture broth of the isolate was analyzed using HPLC- diode array technique to characterize the metabolites and identify the antibiotics. VITBRK2 was found to be Gram-positive rod grey color aerial mycelium production. It was also non motile in nature with spiral spore chain morphology. VITBRK2 was identified as Streptomyces and designated as Streptomyces sp. VITBRK2. HPLC-DAD analysis showed the presence of indolo compounds (3- methyl-indole and 2-methyl- indole) along with amicoumacin antibiotic. The observed activity of Streptomyces sp. VITBRK2 against MRSA and VRE strains may be due to the presence of indolo compounds in the isolate. The results of this study suggested that secondary metabolites produced by Streptomyces sp. VITBRK2 could be used as a lead to control drug resistant bacterial pathogens.