The ICM reveals the genome of more than 500 microorganisms of the Arctic Ocean, 80% of which were unknown

A team of researchers led by the Institut de Ciències del Mar (ICM) of Barcelona has revealed the genome of more than 500 marine microorganisms, more than 80% of which belong to previously unknown species. This shows how limited our knowledge of these organisms is in one of the most remote areas of the planet, the Arctic Ocean. All the details of this research are reported in an article published this week in the journal Nature Microbiology.

Knowledge about these microorganisms is key to understanding and predicting their responses to environmental changes, which could have a significant impact on climate dynamics, not only in polar areas, but also in other latitudes, as marine microorganisms are the main drivers of global biogeochemical cycles.

This is especially relevant in the current context of global change, since polar regions are particularly sensitive to climate variations. For instance, in the Arctic, the accelerated melting of glaciers, permafrost and changes in the extent of sea ice thickness lead to environmental changes with a strong impact on local ecosystems and societies.

"Modelling the impacts of climate change on the Arctic ecosystem requires knowledge of the main microbial actors, their dynamics, their activity patterns and their metabolic potential", explains the ICM researcher and lead author of the study Silvia G. Acinas, who stresses that until now no one had assessed the microbial diversity of the Arctic oceanic regions in such detail.

To carry out this work, researchers analysed sea water samples collected during the Tara Oceans Polar Circle expedition, the last sampling of the Tara Oceans expedition (2009-2013), that covered several arctic oceanic regions across different marine protected areas during 7 months.

In this regard, Marta Royo Llonch, another ICM researcher and first author of the study, points out that “the use of modern bioinformatic approaches to obtain microbial genomes, higher sequencing effort - and standardized plankton sampling protocols, has allowed us to obtain the most comprehensive dataset of uncultured prokaryotic genomes to date, which we have named the Arctic MAGs Catalogue (Metagenome Assembled Genomes, MAGs)”.

Unique and versatile microorganisms

Another highlight of the work is that there are many species that are thought to be exclusive to polar areas, and many of them displayed a restricted habitat distribution in the Arctic Ocean, especially in deeper waters.

“We have identified key bacteria and archaea genomes exclusive to the polar oceans and specifically from the Arctic that are most active in terms of gene expression and therefore with an important role in the biogeochemical cycles of this ecosystem. These polar microbial genomes should serve as the baseline dataset for future monitoring of the state of the Arctic Ocean”, states the ICM researcher Pablo Sánchez, another co-author of the study.

Some of the microorganisms described in this catalogue show great metabolic versatility and are mixotrophs, that is, they use different sources of energy and carbon to function, either as autotrophs or heterotrophs. According to the authors, these characteristics may provide Arctic microorganisms with greater resilience, allowing them to better respond to environmental changes.

In the authors' opinion, future studies should focus on monitoring these species, since some of them might be more susceptible to the effects of climate change due to their restricted distribution, and it will help to better understand the conservation status of the Arctic Ocean. 

Apart from the ICM, the Centro Nacional de Biotecnología (CNB-CSIC, Carlos Pedrós-Alió) and other centres in France (Genoscope, ENS, CEA, CNRS, Université Paris Saclay, Sorbonne Université, Université de Nantes, University of Western Brittany), Germany (EMBL, MDC Berlin, University of Würzburg, Bremen University), Italy (SZN), Belgium (KU Leuven, VUB), Switzerland (ETH Zürich), US (University of Maine, Bigelow Laboratory for Ocean Sciences, The Ohio State University), Canada (Université Laval, Quebec) and Japan (Kyoto University) all belonging to the Tara Oceans consortium, have also participated in the study with the support of Tara Ocean Foundation.