Production of potent antimicrobial agent by actinomycete, Streptomyces sannanensis strain SU118 isolated from phoomdi in Loktak Lake of Manipur, India

Background: Actinomycetes have provided a wealth of bioactive secondary metabolites with interesting activities such as antimicrobial, antiviral and anticancer. The study aims at isolation, characterization and the antimicrobial potentiality of Streptomyces sannanensis SU118 obtained from Phoomdi, a unique habitat of Loktak Lake of Manipur, India. Results: An actinomycete strain isolated from Phoomdi soil of Loktak Lake of Manipur, India was identified as Streptomyces sannanensis SU118. It is a Gram-positive filamentous bacterium which exhibits antimicrobial activity only against Gram-positive bacteria, while Gram-negative organisms were not affected. Glucose Soyabean meal broth was found to be the suitable medium for antibiotic production at 28 degrees C for seven days of incubation. The antimicrobial agent produced by the strain was extracted with ethyl acetate as solvent and purified by thin layer chromatography. Screening and bioassay - guided fractionation of the ethyl acetate extract from the culture filtrate led to the isolation of an active potential compound (R-f value 0.56) with lambda(max) 275.0 nm which has got the lowest minimum inhibitory concentration (0.5 mu g/ml) against Staphylococcus aureus MTCC 96 and Staphylococcus aureus (clinical isolate), whereas highest (3.0 mu g/ml) was recorded against Mycobacterium smegmatis MTCC 6 and Bacillus circulans MTCC 8074. Conclusion: This study has therefore uncovered the potential of exploring virgin untapped habitats in the Indo-Burma biodiversity hot spot region as reservoir of promising antimicrobial metabolite producer. These results highlighted the scope for further characterization of the metabolite and could be a candidate in the generation of new antimicrobial agents.