Metagenomics and its application in identification of genetic diversity of microbial ecosystems

microorganisms are the base of life on the earth, and provide a high degree of biological diversity. This biodiversity can be used in improvement of our knowledge about new genes, metabolic pathways and their products. Identification of their genetic and biological diversity constitutes an important step of the research projects. Many microorganisms are nonculturable under in vitro conditions; therefore, it would limit our perception on physiology, genetic and ecology of microbial communities. Application of metagenomics tools (i.e. culture free methodologies for microbial diversity studies) provides good tools dominating this problem. Denaturing Gradient Gel Electrophoresis (PCR-DGGE) in metagenomics is one of the most efficient methods for differentiation of PCR fragments with the same size obtained as result of specific amplification of a determined gene through microbial community (e.g. 16S rDNA gene for prokaryotes and 18S rDNA gene for eukaryotes). In the other word, DGGE is a technique, which can separate fragments that are similar in size and different in sequence. Therefore, using DGGE methodology, diagnosis of microbial diseases and identification of microorganisms in environmental samples will be easier and faster. In this paper, we tried to report a short review on the mechanism, major applications, advantages and disadvantages of this technology.