Enrichment method for the isolation of bioactive actinomycetes from mangrove sediments of Andaman Islands, India

Various pre-treatment methods and three different media were employed for the isolation of bioactive actinomycetes from mangrove sediments of Andaman and Nicobar Islands, India. Sediments from four different sites of mangrove forest were collected and pre-treated by dry heat method, and the media were supplemented with cycloheximide 80 ?g/mL and nalidixic acid 75 ?g/mL. The mean actinomycetes population density in sediment samples were recorded as 22 CFU-10-6/gm in KUA medium followed by 12 CFU-10-6/gm in AIA medium and 8 CFU-10-6/gm in SCA medium. A total of 42 actinomycetes were isolated, and all the isolates were evaluated for their antibacterial activity against pathogenic bacteria on two different media. Among 42 isolates tested, 22 species were found to be antibacterial metabolite producer against test bacteria namely, Staphylococcus aureus, Bacillus subtilis, Salmonella typhi and Klebsiella pneumoniae. Particularly, the actinomycete strains such as A101, A102, A107, A116, A121, A125, A130, F101, F102, F104, F106, De101 and De102 significantly inhibited the growth of all bacteria which were tested. Of these strains, A107 was identified as Streptomyces spp. This strain had the maximum activity against all used pathogens on both medium. Hence, the isolation, characterization and studies of secondary metabolites of actinomycetes from mangrove sediments in Andaman and Nicobar Island could be a pathway for discovery of antibiotics from marine actinomycetes.