EXTRACTION OF ANTIBIOTICS BY ACTINOMYCETES ISOLATED FROM EASTERN MOUNTAIN REGION OF NEPAL

Abstract

Bioactive compounds like antibiotic can be considered as a substance, produced by one microorganism, which inhibits the growth of another microorganism. Actinomycetes, slow growing gram-positive bacteria, are the major sources of bioactive compounds. The aim of this study was to screen antibiotic producing Actinomycetes for antibiosis from the soils of Eastern Mountain region of Nepal. Primary screening and secondary screening were performed by perpendicular streak method and agar well assay method respectively. Microbiological characterization was performed for identification of presumptive genera. Characterization of the antibacterial substances extracted from this isolate was done by Thin-layer chromatography (TLC) using Chloroform: Methanol (10:90) as the solvent system and iodine vapor as the visualizing agent. Altogether forty-one actinomycetes were isolated from soil samples but only one (2.4%) of the isolate showed antibacterial activity against both Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli, Salmonella Typhi Shigella spp., and Pseudomonas aeruginosa) test-bacteria in primary screening. Isolate M3 was selected for secondary screening because of its potent antibacterial activity. Minimum inhibitory concentration (MIC) of crude antibacterial substances was carried out by serial dilution method and found to be 2.5 mg/mL against test organisms. The chromatogram in TLC showed only one spot with Rf value 0.81 by the isolate suggesting that the isolate produced only one compound which was completely different from the spot with Rf value 0.89 produced by gentamycin. According to identification by Microscopy (1000X) and overall biochemical, and physiological characteristics, the isolate was considered as Streptomyces spp, a distinct taxonomic group.

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