Cloning the Metagenome to Access the Biodiversity of Unculturable Bacteria

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Introduction
Being the essential part of earth’s microbiota and their involvement in chemical, physical and biological transformations, bacteria are considered as a very important group of microorganisms. Those bacteria which cannot be grown easily on artificial nutrient media are referred as unculturables. The evidence for the presence of yet to be cultivated bacteria came from the molecular data. The capability to obtain DNA sequence information from an environmental sample by PCR manipulations and direct sequencing allowed identification of these phylogenetically important groups. When a sample is collected from environment, the total number of bacterial cells within sample is extremely high, which is not appropriate for isolation of
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Introduction
Being the essential part of earth’s microbiota and their involvement in chemical, physical and biological transformations, bacteria are considered as a very important group of microorganisms. Those bacteria which cannot be grown easily on artificial nutrient media are referred as unculturables. The evidence for the presence of yet to be cultivated bacteria came from the molecular data. The capability to obtain DNA sequence information from an environmental sample by PCR manipulations and direct sequencing allowed identification of these phylogenetically important groups. When a sample is collected from environment, the total number of bacterial cells within sample is extremely high, which is not appropriate for isolation of uncharacterized bacteria. Few methods can be applied to reduce the number of microorganisms in mixed samples before cultivation. The majority of culture media are nutrient-rich. It is now thought that these conditions may favors the growth of faster growing bacteria at the expense of slow growing species, some of which grow in nutrient poor environments and may be inhibited by substrate-rich conventional media (Deming and Baross, 2000).
There are certain reasons behind the unculturability of microorganisms. It could be that the organism has a low prevalence or is particularly slow growing has been over looked in cultural analyses. Many genetically distinct phenotypes are phenotypically indistinguishable for example few bacteria are

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