Isolation of Marine Streptomyces, Characterization and Metabolites' Screening for Antibacterial Activity

Abstract

To combat drug resistant, searching of new broad-spectrum antibiotics is urgent and Marine Streptomyces can be potential new sources of antibacterial agents. With this aim, present study was carried out to search new, safe and effective antibacterial compounds. Twenty nine strains were isolated from marine sediments and soil samples of mangrove forest, Sundarban, Bangladesh using spread plate technique. Among them AIAH-5 and AIAH-10 were finally selected for further study owing to their promising activity against a series of pathogenic strains (done by streak plate method). The organisms were identified on the basis of cultural, morphological and biochemical properties. At least four compounds were isolated by chromatographic means, from the crude extracts of both organisms. But pure compounds, AI-5 and AI-10 were finally selected for their highest antibacterial efficacy. Antimicrobial activities of both AI-5 and AI-10 were performed against a series of pathogenic microorganisms. The minimum inhibitory concentrations (MIC) of the compound AI-5 and AI-10 varied between 8- 32 and 1- 4 µg/ml, respectively against a wide range test bacteria. The minimum bactericidal concentration (MBC) of the compound AI-5 and AI-10 were ranges from 16- 128 and 2- 16 µg/ml, respectively. The compound AI-5 and AI-10 also exhibited satisfactory activity against azithromycin and ciprofloxacin induced resistant Escherichia coli strain. This study demonstrates the diversity of the mangrove forest, Sundarbans, Bangladesh as a rich and interesting source of antibiotic molecules producing new and potential marine bacterial species.