ABSTRACT
It is widely recognized that 93%–98% of the microbes present in the environment are not easily culturable. Oceans, glaciers, deserts, and almost every other environment on earth are being sampled for the identication of microorganisms. In all natural environments, soil and sludge are probably the most challenging environments for microbiologists, with respect to the microbial community size and the diversity of species present. About 4 × 107 prokaryotic cells are present in one gram of forest soil whereas the same amount of cultivated soil and grasslands contains nearly 2 × 109 prokaryotic cells. Estimating the total microbial diversity/dynamics in any environment is a persisting challenge especially during bioremediation to clean up contaminants. In actual fact, most of the species in different environments have never been described, and this condition will not change until fresh culture techniques are developed. At present the numerous approaches that are used to walk around the diversity of microbial communities are not satisfactory because of the limitations of culturing methods. “Metagenomics” tries to conquer this blockage by developing and using culture-independent approaches. Metagenomics is a cultural independent genomics analysis of a majority of microorganisms growing in the natural environment which has the potential to respond to fundamental queries in the eld of microbiology. Metagenomics, also called ecological genomics, environmental genomics, or community genomics, is the whole genome shotgun approach to sequence genome from entire communities of microorganisms in different environmental samples.
