Plant available nitrogen in the soil is transformed into nitrogen gas in a process that can be viewed as either a service or a problem. Chris Jones from the Swedish University of Agricultural Studies has studied the ecology of the very diverse microorganism communities that are involved in this process.
The process by which nitrogen is exchanged between the atmosphere and the biosphere is referred to as the nitrogen cycle, which is predominantly mediated by microorganisms. One of the key processes in the nitrogen cycle is denitrification, which converts biosphere nitrogen back into nitrogen gas, thus closing the cycle.
Denitrification is performed by a diverse range of microorganisms, and can be viewed as an ‘ecosystem service’ in that it removes excess nitrate, which is a significant health hazard and environmental pollutant. However, it can also be problematic in that denitrification results in the loss of nitrogen applied as fertilizers in agricultural systems, as well as the release of nitrous oxide, a potent greenhouse gas.
With the predicted increase in nitrogen fertilization due to increased agricultural production, understanding the ecology of denitrification is critical for developing sustainable resource management practices. In a thesis from the Swedish University of Agricultural Studies (SLU), Chris Jones specifically examines the ecology of microorganisms that perform denitrification at four different scales.
At the genetic level, he found that the evolution of the denitrification pathway has resulted from a combination of different genetic mechanisms. Studies on individual denitrifying bacteria demonstrated that denitrifying activity, particularly the production of nitrous oxide, is best defined as an interaction between genetic and environmental factors. Additionally, he found that communities of denitrifying bacterial species in soil may produce or adsorb nitrous oxide, depending on the genetic makeup of the denitrifying community.
The final study revealed that the denitification gene diversity is shaped by environmental factors, such as salinity or nitrate concentrations, over a wide range of ecosystems. Further research into the dynamics of genetic and environmental interactions will improve our utilization of denitrification as an ecosystem service.
Christopher Jones, Department of Microbiology, Swedish University of Agricultural Sciences (SLU), defended his thesis Denitrification: From Genes to Ecosystems on December 3:rd 2010. The opponent was Professor Professor Bess Ward, Princeton University, USA.
More information:
Christopher Jones, +46 (0)18-67 32 22, chris.jones@mikrob.slu.se
www-mikrob.slu.se/MECO/
Link to the complete thesis:
http://diss-epsilon.slu.se:8080/archive/00002376/
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