Microorganisms in the soil shape the global carbon cycle


Composition of the soil microbiome and its role in organic matter cycling in different soil habitats. Credit: Nature Reviews Microbiology (2022). DOI: 10.1038/s41579-022-00695-z

Whether dead or alive, soil microorganisms play an important role in the biogeochemical carbon cycle in the terrestrial biosphere. But what specific role does death play for the bacteria, fungi, and microfauna that make up the soil microbiome?

That’s the subject of a new review by scientists and collaborators at Lawrence Livermore National Laboratory (LLNL). The article published in Nature Reviews Microbiologydescribes how living and dead microorganisms profoundly influence terrestrial biogeochemistry by forming and degrading soil organic matter – the largest terrestrial store of organic carbon and nitrogen on the planet and a major source of other important macronutrients and micronutrients.

By shaping the turnover of organic soil matter, soil microorganisms influence the atmospheric CO concentration2 and global climate and help provide important ecosystem services such as soil fertility, carbon sequestration, crop productivity and soil health.

“Our new understanding of how organic matter circulates through soil underscores the importance of both living and dead microorganisms in the formation of soil organic carbon. It is increasingly possible to use this understanding in biogeochemical models and better predict how ecosystems will function under new climate regimes,” said LLNL scientist Noah Sokol, lead author of the paper.

The soil microbiome is the most diverse community in the biosphere, housing at least a quarter of all biodiversity on Earth. Tens of millions of species of bacteria, archaea, fungi, viruses, and microeukaryotes coexist underground, although only a few hundred thousand have been characterized in detail. A single gram of surface soil can contain more than 109 bacterial and archaeal cells, trillions of viruses, and tens of thousands of protists. However, the influence of the soil microbiome on biogeochemistry goes far beyond the metabolic activities of living organisms.

“Dead microorganisms accumulate in the soil because their cell remains stick to the mineral matrix. Their dead biomass can account for up to 50% of soil organic matter. That means dead microbial biomass in soil is one of the largest stores of organic carbon on the planet,” said Jennifer Pett-Ridge, LLNL project leader and director of the Department of Energy’s (SFA) Microbes Persist Soil Microbiome Scientific Focus Area.

Recent advances in DNA sequencing and isotope tracing allow the LLNL team to understand the unique properties of soil microbes – even those that cannot be cultured in the laboratory. By analyzing genetic and biochemical signatures, the team can infer the ecological relationships that control who lives and who dies in complex soil food webs.

Because soil microbial necromass (organic material composed of or derived from dead organisms) represents one of the world’s most important pools of carbon and other nutrients, the authors report that the mechanism and rate of microbial death likely involves the terrestrial biogeochemical cycle influence – an idea They are currently testing in a series of experiments that are part of the LLNL’s soil microbiome SFA. The SFA team is also setting up experiments to study how different traits of microorganisms affect the cycling of organic matter in soils. Team members are working to integrate this feature-based approach into models that predict soil biogeochemical dynamics and improve the ability to predict changes in the global carbon cycle.

The team is developing a microscope to image microbes in soil and plants at the micrometer scale

More information:

Noah W. Sokol et al, Life and Death in the Soil Microbiome: How Ecological Processes Affect Biogeochemistry, Nature Reviews Microbiology (2022). DOI: 10.1038/s41579-022-00695-z

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Lawrence Livermore National Laboratory

Dead or Alive: Soil Microorganisms Shape the Global Carbon Cycle (2022, March 3)
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