The Value and Significance of Metagenomics of Marine Environments

Microbes have played a fundamental role in the natural history of our planet, and have done so for billions of years. They have adapted to Earth’s many environments from the mild to the very extreme. Studying their diversity and their way of life is critical for understanding their full impact on the global ecology. Although the field of metagenomics is still young, it has unravelled a wider microbial diversity that had otherwise been completely overlooked by the traditional methods of microbiology. There are three major metagenomic themes: (a) marker metagenomics that surveys microbial community structure by targeting the highly-conserved 16S rRNA gene, (b) functional metagenomics that takes the total environmental DNA, from which it infers the metabolic potential of the microbial community, and (c) identification of novel enzymes. Functional metagenomics has added to our understanding of microbial ecology and their role in the global geochemical cycles. Some of the most important contributions from this field include the discovery that proteorhodopsin is widespread in marine environments [1], which explains how bacteria are able to thrive in oligotrophic environments. Another exciting discovery is the recovery of ammonium monooxygenase from an archaeal genomic fragment where until then it was believed to be exclusive to bacteria [1,2]. Metagenomics has also led to several novel insights into the various geochemical cycles including phosphorus, sulfur, carbon, and nitrogen. Comparing genomic information of microbes from different environments provides evidence for their niche adaptations. The landmark metagenomic sampling that was carried out in the Sargasso Sea revealed high microbial diversity [1], while the microbial community that was reported in another landmark metagenomic study based on samples from an acid mine drainage revealed a far less complex community [3]. Other metagenomic studies that compared the metabolic potential of microbial communities from differing environments, e.g., agricultural soil, sea surface, and deep-sea whale carcasses, have shown noticeable differences in the enrichment of various genes that supports microbial lifestyle in their niche [4,5]. The field of metagenomics has allowed us to tap into a vast microbial diversity that has, for long, eluded the traditional microbiology methods. Beyond simply counting new species, metagenomics has also helped establish the link between the gene pool available to a microbial community and the environmental parameters that surround them. The explosion in metagenomics data, especially those from extreme environments, has provided a fresh source for novel biocatalysts that may be of value to the biotechnological sector [6]. The journal Genomics, Proteomics & Bioinformatics (GPB) has compiled a Special Issue on Metagenomics of Marine Environments. We have selected seven papers for inclusion in this special issue. The accepted contributions cover various