Antimicrobial Activity of Marine Actinomycete, Nocardiopsis sp. VITSVK 5 (FJ973467)

Abstract

The aim of the present study was to isolate and to indentify the actinomycetes having antagonistic activity. An actinomycetes strain isolated from marine sediment samples collected at the Puducherry coast of India, showed antibacterial activity against selected microbial pathogens. The nutritional requirements and cultural conditions for maximal growth and yield of secondary metabolites have been optimized under shakeflask conditions. The growth and yield of secondary metabolites was maximal with the use of ISP 1 medium supplemented with sea water, pH 7.4, and incubation temperature of 28℃, salt tolerance of 2% and incubation time of 4-7 days. Based on morphological, biochemical, physiological and phylogenetic characterization, the strain was identified as Nocardiopsis sp. VITSVK5 (FJ973467). The petroleum ether extract (1000μg/ml) obtained from the isolate showed significant antibacterial activity against Gram negative bacteria- Escherichia coli (20 mm), Pseudomonas aeruginosa (18 mm) and Klebsiella pneumonia (15 mm) and Gram positive bacteria- Enterococcus faecalis (20 mm), Bacillus cereus (13 mm) and Staphylococcus aureus (6 mm) when compared with streptomycin (25μg/disc). The ethyl acetate extract (1000μg/ml) showed antifungal activity against Aspergillus fumigatus (23 mm), Aspergillus flavus (15 mm) and Aspergillus niger (12 mm) when compared with amphotericin-B (25μg/disc). The chloroform extract (1000μg/ml) was very effective against yeasts, Candida cruzi (18 mm), Candida tropicans (15 mm) and Candida albicans (14 mm) when compared to streptomycin (25μg/disc). In conclusion the isolated strain has broad spectrum of antagonistic activity against Gram positive and Gram negative bacteria and Aspergillus sp.