Genomic Insights into Redox-Driven Microbial Processes for Carbon Decomposition in Thawing Arctic Soils and Permafrost

The Science

As the Arctic warms, thawing permafrost unlocks carbon, potentially accelerating climate change by releasing greenhouse gases. This research delves into the underlying biogeochemical processes mediated by the soil microbial community in response to wet and anaerobic conditions akin to an Arctic summer thaw.

The Impact

Climate change is rapidly transforming Arctic landscapes where increasing soil temperatures speed up permafrost thaw. Understanding how soil microbes break down vast Arctic soil carbon, especially under the anaerobic conditions of thawing permafrost, is important to determine future changes.

Summary

A team of researchers studied microbial community dynamics and soil carbon decomposition potential in permafrost and active layer soils under anaerobic laboratory conditions that simulated an Arctic summer thaw. The microbial and viral compositions in the samples were analyzed based on metagenomes, metagenome-assembled genomes, and metagenomic viral contigs (mVCs). Following permafrost thawing, fermentative bacteria dominated the microbial composition. The increase in iron and sulfate-reducing microbes significantly limits methane (CH₄) production from thawed permafrost, underscoring the competition within microbial communities. Potential carbon decomposition leading to carbon dioxide (CO₂) via fermentation can limit the substrate pool and cause high CO₂ to CH₄ ratios in Arctic soils under post-thaw anaerobic conditions.

The team explored the growth strategies of microbial communities and found slow growth was the major strategy in both the active layer and permafrost. This study challenges the assumption that fast-growing microbes mainly respond to environmental changes like permafrost thaw. Instead, observations indicate a common strategy of slow growth among microbial communities, likely due to the thermodynamic constraints of soil substrates and electron acceptors and the need for microbes to adjust to post-thaw conditions. The mVCs harbored a wide range of auxiliary metabolic genes that may support cell protection from ice formation in virus-infected cells.

Principal Investigator

Neslihan Taş
Lawrence Berkeley National Laboratory
[email protected]

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

The Next-Generation Ecosystem Experiments Arctic project is supported by the Biological and Environmental Research (BER) program in the U.S. Department of Energy’s (DOE) Office of Science. Funding in part was provided by the BER’s Early Career Research program. Sequencing was conducted by the Joint Genome Institute (https://ror.org/04xm1d337), a DOE Office of Science User Facility operated under contract number DE-AC0205CH11231 to Lawrence Berkeley National Laboratory. Additional support was provided by the Microbiomes in Transition Initiative Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory, which is operated by Battelle for DOE under Contract DE-AC06-76RL01830.

References