Soil Microbes Eat Nitrous Oxide, a Potent Greenhouse Gas
The use of large amounts of nitrogen fertilizer in modern agriculture has resulted in massive releases of nitrous oxide (N2O) into the atmosphere. Although shorter lived than CO2, N2O is over 300 times more potent as a greenhouse gas, so understanding its role and behavior in global climate change is important. Soil microbes naturally consume ammonia in fertilizers, converting it into N2O or dinitrogen gas (N2), a harmless component of the atmosphere. Previous attempts to estimate the abundance of microbes that perform these processes have significantly overestimated N2O production, suggesting that a large, but undetected group of microbes is converting ammonia to N2. In a new study, researchers have used a comparative genomics approach to identify new gene sequences involved in conversion of ammonia to N2 and demonstrated that this genetic pathway is present in several abundant groups of soil microbes not previously thought to be involved in nitrogen conversion. Preliminary experiments suggest that these organisms are capable of this form of metabolism in the laboratory and that the relevant genes are present in soil samples. These results have revealed an important missing piece in our understanding of the terrestrial nitrogen cycle. Further research on the physiology of these organisms and determination of their environmental abundance should improve model predictions for release of greenhouse gasses from soils of bioenergy landscapes or other agricultural systems.
Sanford, R. A., D. D. Wagner, Q. Wu, J. C. Chee-Sanford, S. H. Thomas, C. Cruz-García, G. Rodríguez, A. Massol-Deyá, K. K. Krishnani, K. M. Ritalahti, S. Nissen, K. T. Konstantinidis, and F. E. Löffler. 2012. “Unexpected Nondenitrifier Nitrous Oxide Reductase Gene Diversity and Abundance in Soils,” Proceedings of the National Academy of Sciences USA 109(48), 19709–714. DOI: 10.1073/pnas.1211238109.