How Ingested Soil Microbes Stimulate Greenhouse Gas Emissions and Iron Transformations of Earthworms

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Up to approximately 50% of soil-emitted nitrous oxide (N2O) might be derived from earthworms, a soil macrofauna that ingests soil microbial biomes. In the previous funding period, synergistic links were established between ingested denitrifiers and the emission of N2O and dinitrogen (N2) by earthworms. The new objectives (in abstracted form) are: to determine if earthworms emit nitric oxide (NO); to identify regulatory parameters responsible for changes in the structure and function of ingested microbial biomes associated with C- and N-transformations in the gut (molecular, microsensor, and reporter strain technologies; PCR-assisted isolation of target organisms); to correlate earthworm abundances with N2O and NO emissions in the field; to determine if earthworm ecotypes affect in situ gradients of nitrate, N2O, and O2 in casts and burrow-associated soils (wormsoil chambers, microsensors); to assess N2O emissions of worms from southern and northern hemispheres, and evaluate the microbes associated with these emissions (functional gene fingerprinting). This study will resolve primary links between C- and N-driven microbial processes that yield nitrogenous gases in the earthworm gut.