From Atmospheric Nitrogen to Bioactive Nitrogen Oxides
The enrichment of the biosphere with reactive nitrogen from anthropogenic origin, in combination with increased consumption of vegetables and (preserved) animal products, has led to increased intake by humans of nitrite and nitrate. Nitrate and nitrate-forming salts are among the key components of fertilizers and the increased dependency of farming practices on such fertilizers over several decades has led to increasing levels of human exposure. Elemental nitrogen is fixed by several mechanisms including lightning fixation and by symbiotic organisms in the soil. Plants and vegetables use these nitrogen intermediates as an energy source necessary for growth. Understanding nitrogen fixation in the environment by micro-organisms will help in our understanding of the role of nitrite, nitrite, and nitric oxide in humans. The scope of this chapter is to review the mechanisms of nitrogen fixation and how this relates to human nitrogen cycle and human health and disease.
KeywordsNitrogen fixation Bacteria Symbiosis Nitrate reductase Fertilizers Denitrification
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