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).