The majority of modern clinically important drugs have been isolated directly from natural sources, or, were inspired by natural products of microbial origin. However, in spite of this, the estomated vast majority of 1011-1012 microbial species have remained largely untapped because of the constraints of traditional isolation and cultivation approaches. Over the years the antibiotics isolated from microbial sources have been rendered useless, as their overuse has resulted in the emergence of pathogens showing antibiotic resistance to antibiotics. In the wake of growing antibiotic resistance, coupled with slow pace of discovery of new antibiotic producers, there is a growing demand for novel approaches. Metagenomics is a very promissing approach for the discovery of new secondary metabolites because it relies on the sequencing of several genomes of microorganisms from the environment, which are a potential source. It enables the detection of genes and biosynthetic pathways of both culturable and nonculturable microorganisms. The development of functional and sequence-based metagenomics paves the way for discovery of new gene clusters for the production of biologically active substances with biotechnologically interesting applications. Progess of next-generation sequencing and development of computer tools have also overcome some of the barriers in secondary metabolites discovery. Therefore, in the scope of this work, we will summarize the history of metagenomics and then focus on metagenomic analysis and its approaches. In the second part, we present use metagenomics approaches in identification of secondary metabolites of microbial origin.
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