The energy-consuming biological nitrogen fixation process is essential for a positive input of usable nitrogen on earth. The ATP-dependent evolution of hydrogen by nitrogenase results in a considerable loss of energy from the nitrogen fixation process. However, the evolved hydrogen can be recycled via an hydrogen oxidizing electron transport system. The cytochrome components involved in hydrogen oxidation and the role they play in protecting nitrogenase from oxygen damage, and supplying ATP to nitrogenase are poorly understood. This research uses mutant analyses approaches toward understanding and assessing the roles of terminal oxidases in nitrogen fixation and various substrate oxidations using Azotobacter vinelandii. The approaches include the isolation and characterization of mutants with deletions in cytochrome o and d genes.%%% Increasing world population combined with dwindling fuel reserves makes increased dependence on nitrogen fixation likely. Since most experts believe that the nitrogen fixation process is energy (ATP) limited, factors that result in efficient use of otherwise wasted energy (such as hydrogen) deserve research attention. Hydrogen oxidation by the bacterium Azotobacter has been shown to allow the nitrogen fixing enzyme to function optimally. The study of hydrogen-oxidizing electron transport and its regulation shows promise for increasing nitrogen fixation.***//
