Structure and function of the global ocean microbiome.

© C.Guiguand/Tara Oceans

Tara Oceans

Sunagawa, Coelho, Chaffron, et al.

DOI: 10.1126/science.1261359

Structure and function of the global ocean microbiome

Microorganisms and viruses (<3 micron) dominate the marine environment with 104 to 106 cells in each milliliter of seawater. They are well recognized for their role in driving major global biogeochemical processes and given their importance, it is of fundamental interest to answer basic questions, such as: who are they? What do they do? and how are they affected by their environment? The researchers tackled such questions for the first time at planetary scale by metagenomics, which is the large-scale sequencing of the genetic material of marine microorganisms of various sizes at several depth layers in all major oceans in the context of many physicochemical parameters.

Tara Ocean’s broad sampling coverage of the marine environment facilitated the analysis of vast amounts of DNA sequencing data in the order of 2,000 human or 2 million bacterial genomes. The derived ocean microbial reference gene catalog comprising 40 million, mostly novel genes from viruses, prokaryotes and picoeukaryotes, is a blueprint for the diverse functionality of these organisms and represents a rich resource for various follow-up studies.

In an initial analysis, the scientists could, for example, disentangle partly co-correlated, and thus confounding environmental parameters that influence the formation of microbial communities and identified temperature as the main driving force in the sunlit ocean. This implies that global warming will also have a large impact on microbial communities that are invisible to the naked eye, but forming the basis for photosynthesis and marine food webs.

Furthermore, a comparison between gene families that are core to the functioning of ocean microbial communities and those in the human gut revealed that more than half of them are shared, indicating common principles of microbial life in these very distinct ecosystems.

Taken together the establishment of the ocean microbial reference gene catalog and the demonstration of its utility represent important steps towards capturing microbial biodiversity and their function on the planet in the context of climate change.

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