Study on Antimicrobial Activities of Actinomycetes Isolated From Soils of Different Parts of Khumbu Region

Abstract

The present study has been carried out at the laboratory of National Academy scienceand Technogy between 2006 October to 2007 September. The soil samples (N=4) collected from different places of ‘Khumbu’ region, Nepal(2500-5050m altitude) were processed to isolate antif ungal and antibacterial Actinomycetes. Altogether 22 isolates of Actinomycetes were isolated. In all isolates, 18 isolates were identified to genus level of which 11 isolates belonged to genus Streptomyces, three isolates belonged to Micromonospora, and two isolates belonged to Nocardia and one each belonging to Actinomadura and Strep to verticillium. All the eighteen isolates were screened for their antimicrobial activities against targetcultures viz; plant pathogenic fungi:Alternariaspp., Fusarium oxysporum, Fusariummoniliforme,Geotricum spp., Gloeosporium sporioides, Helminthosporium spp. andSclerotinia spp. and bacterial pathogens: Bacillus subtilis, Staphylococcus aureus,Enterobacter spp., Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris,Pseudomonas aeruginosa, Citrobacterspp.,SalmonellaparatyphiAand Shigellaspp. In all Actinomycetes isolates, 14 isolates which showed antimicrobial activity, 5isolates showed activity only against gram positive bacteria while 5 showed broad hostrange showing activity against both gram positive and gram negative bacteria. However, only two isolates X1 and C4 belonging to Streptomyces spp. were activeagainst all the target fungal cultures. Out of all potential antifungal and antibacterial isolates, X1 and C4 and one isolate Ch9belonging to Actinomadura spp. were chosen for the antimicrobial compoundproduction and extraction of bioactive compound. The fermentation was carried out for 21 days using starch casein broth and the cell freesupernatant was subjected for solvent extraction. The extracted residue also showedbroad spectrum antibacterial and antifungal activity against target organisms. The bioactive residues (crude extracts) were dissolved in chloroform and run in silicagel precoates separately using chloroform: methanol (40:1) as the solvent system. Thecrude extract of isolate X1 gave two spots having R 0.58 and 0.66 and that of Ch9 andC4 each gave single spot having R f vi f 0.79 and 0.66 respectively. Key words: Actinomycetes, Antimicrobial activities, bioactive secondary metabolite,Khumbu,Streptomycesspp.