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.