Screening of Antibiotic Producing Actinomycetes for Antibiosis from Soil of Siraha, Nepal (original) (raw)

2017, Himalayan journal of science and technology

Actinomycetes are gram positive bacteria widely distributed in natural and man-made environments. They are found in large numbers in soils, fresh waters, lake, river bottoms, manures, composts, dust as well as on plant residues and food products. However, the diversity of actinomycetes that produce secondary metabolites can be determined by different physical, chemical and geographical factors (Ogunmwonyi et al., 2010). As there is increasing trends of antibiotic resistant microorganisms, the search for novel antibiotics is necessary. In this case, actinomycetes are the best common sources of novel antibiotics (Okami & Hotta, 1988). The diversity of terrestrial actinomycetes is of great signi cance in several areas of medical sciences, particularly in antibiotic production (Magarvey et al., 2004). Out of 22,500 biologically active compounds obtained from microbes, 45% are from actinomycetes (Berdy, 2005). Need of new antimicrobial agents is greater than before because of the emergence of new multidrug resistance in common pathogens, rapid emergence of new infections, and the use of multidrug resistant pathogens in bioterrorism (Spellberg et al., 2004). Antibiotic resistant bacteria have been great problems in the treatment ofi nfectious diseases which are still the second leading cause of death worldwide (WHO 2002 and Luzhetskyy et al., 2007). In the search for novel antibiotics, a study in Nepal revealed that twenty seven actinomycetes isolated from soil samples of Mount Everest region were reported to have antibacterial activity (Gurung et al., 2009). Likewise, One hundred and seventeen antibiotic producing actinomycetes were isolated from non-agricultural wasteland, alkaline soils and compost rich garden soil (Kumar et al., 2010). Twenty species of actinomycete were isolated from marine soil samples in which s three showed signi cant antimicrobial activity against Staphylococcus aureus Escherichia coli and (Kalyani et al., 2012). These all evidences show the abundant presence of actinomycetes having antimicrobial activity. In this regard, Terai (75-600 m), a warm region of Nepal, is of a signi cant interest. Sun radiations and seasonal variations create extreme environment which likely to harbor unusual microorganisms. This poorly studied habitation increases the chances of nding novel microorganisms. Therefore, the present study was undertaken to isolate and characterize antibacterial actinomycetes from soil samples of Siraha, a warm district of Terai, Nepal.