Nitrogen constitutes 78% of the Earth's atmosphere and inevitably occupies a predominant role in marine and terrestrial nutrient biogeochemistry and the global climate. Callous human activities, like the excessive industrial nitrogen fixation and the incessant burning of fossil fuels, have caused a massive acceleration of the nitrogen cycle, which has, in turn, led to an increasing trend in eutrophication, smog formation, acid rain, and emission of nitrous oxide, which is a potent greenhouse gas, 300 times more powerful in warming the Earth's atmosphere than carbon dioxide.