Isolation and Identification of Actinomycetes from Mangrove Soil and Extraction of Secondary Metabolites for Antibacterial Activity

The mangrove ecosystem of India is an extensively unexplored source for actinomycetes with the potential to produce secondary metabolites of biological importance. In this study, twenty two actinomycetes were isolated from different soil samples collected from the Bhitarkanika mangrove forest along Odisha coast, India. These isolates were identified as Streptomyces sp. based on their morphological, physiological and biochemical characteristics as described in the International Streptomyces Project. Out of twenty two actinomycetes (designated as BSA-1 to BSA-22) isolates, only four isolates (BSA-5, BSA-10, BSA-11 and BSA-15) displayed significant antimicrobial properties in term of antagonistic activity against six human pathogenic bacterial strains (Staphylococcus aureus, Shigella flexneri, Bacillus licheniformis, Bacillus brevis, Pseudomonas aeruginosa and Escherichia coli). All these isolates exhibited excellent antimicrobial activity in a range of 14.0-22.0 mm as inhibition zone against the above studied human pathogens with highest activity displayed by the isolate BSA-11. The isolate, Streptomyces sp. BSA-11 was further identified up to the species level by 16S rRNA gene sequence analysis. The BLAST analysis confirmed that Streptomyces sp. BSA-11 was homologous to Streptomyces himastatinicus of order Actinomycetles and class Actinobacteria. The novel actinomycete, Streptomyces himastatinicus BSA-11 from Bhitarkanika has the ability to produce extracellular potent bioactive compounds which can be a potential source of many antimicrobials.