Denitrification is a key process in the biochemical N cycle in the biosphere, by which inorganic nitrogen is converted into molecular nitrogen.
Bacteria of the genus Bradyrhizobium are well-known for their ability t fix dinitrogen both in free-living and symbiotic associations with legumes. They are also able to denitrify, so that they may grow under anaerobic conditions with nitrate as the only nitrogen source. Two respiratory nitrate reductases from B. japonicum have been purified and characterized and mutants unable to grow at low 02 tension in the presence of nitrate have been identified.
It is proposed to undertake a molecular characterization of the B. japonicum nitrate respiration pathway. This will involve characterizing the nitrate reductase structural genes and other genes involved in their regulation. Finally, the posible relationships between denitrification and biological nitrogen fixation will be established.