Metagenomics in Polluted Aquatic Environments

Abstract

Metagenomics is defined as the culture-independent genomic analysis of biological assemblages providing access to the whole set of genes and genomes from a sample. It encompasses a variety of techniques that are based on (i) total DNA extraction from samples followed by PCR amplification of specific genes, (ii) library construction or amplification and sequencing of the whole genetic material. These methodologies have successfully been applied in studies of composition, dynamics, and functions of microbial communities in a variety of ecosystems including those subjected to anthropogenic modifications (Gilbert & Dupont, 2011). Culture independent methods allow the analysis of a set of metabolic genes from microbial communities, which can be used to determine how environmental conditions such as pollution can shape community composition and the diversity of genes associated with biogeochemical cycles such as those of carbon, nitrogen, and phosphorus (Singh et al., 2009). This approach is also useful for the discovery of novel environmental microorganisms and genes, with important applications for biotechnology, medicine, and bioremediation (Cardoso et al., 2011). This applicability has resulted in a recent sharp increase in studies focusing in the metagenomic analysis of polluted sites. Their aim is to characterize microbial communities from a diverse set of environments such as freshwater, marine sediments, open ocean, pelagic ecosystems, soil, and host-associated communities. An example of these initiatives is the Global Ocean Sampling Expedition (GOS), which assessed the genetic diversity of marine microbial communities around the Earth. Since 2003, an enormous amount of data has been generated by GOS helping scientists to reveal the microbial diversity and also allowing them to better understand microbial phylogeny and ecology (Gilbert & Dupont, 2011).