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Organic N Turnover in Soil: An Overlooked Component of C Cycling

EMSL Project ID


It is now generally accepted that most of the organic matter in soils consists of materials that have been processed by the microbial community. Indeed, "necromass"--the remains of dead microbial cells--likely makes up most of the soil organic matter. Thus, microorganisms are not only vital as catalysts of organic matter turnover but the components of their necromass are the compounds that are recycled. Our goal is to quantify the enzymatic mechanisms involved in the recycling of microbial necromass in soil (i.e., residual proteins, nucleic acids, and cell wall components of dead microbial cells) and measure the products of this turnover. This requires the identification of the corresponding extracellular enzymes and the characterization of their degradation products. In the past, potential extracellular enzyme activity has commonly been measured, but this does not provide insight into the diversity of these enzymes nor the organisms responsible for their production. We will use activity based probes developed by EMSL scientists to selectively isolate classes of extracellular enzymes (e.g., serine proteases, metalloproteases, chitinases) and use the EMSL metaproteomic pipeline to sequence these enzymes and identify their origin, something that has not been done before in soils. In order to identify the products of enzymatic degradation, we will add necromass (killed bacteria and fungi, and their major cellular constituents) to soil in an incubation study. Periodically we will collect the dissolved organic matter and use metabolomics analysis techniques pioneered by EMSL scientists to identify the constituents of the dissolved organic matter produced during necromass decomposition. This represents a cutting-edge application of metabolomics to soil biogeochemical cycling. Achieving these objectives will provide better understanding of how C and N are cycled in soils and how this cycling is linked to the microorganisms involved in these processes. Such information will provide insights into the integration of multiple 'omics methods and ultimately inform and improve biogeochemical models.

Project Details

Project type
Large-Scale EMSL Research
Start Date
End Date


Principal Investigator

David Myrold
Oregon State University


Ryan Mueller
Oregon State University

Team Members

Markus Kleber
Oregon State University

Mary Lipton
Environmental Molecular Sciences Laboratory