Author(s):

Dr. KS Santhosh, Dr. DS Akhila, Dr. MM Dechamma, Vittal Rajeshwari and Dr. A Devivaraprasad Reddy

Abstract: Mankind continue to transfigure the global nitrogen cycle at a record pace, reflecting an increased combustion of fossil fuels, growing demand for nitrogen in agriculture and industry, and pervasive inefficiencies in its use. This reactive nitrogen may be lost from ecosystems via leaching, as nitrate (NO₃^-), or as gaseous forms such as ammonia and nitrous oxide (N₂O). These nitrogen transformations are of significantly importance in both economic and environmental aspects. Regardless of more than 150 years of research on the nitrogen cycle there are still important questions to be answered with respect to nitrogen transformations and losses from terrestrial ecosystems. Nitrogen (N) is the seventh abundantly available element in the earth’s atmosphere and is the key component of biomolecules (amino acids, nucleotides). The enzyme nitrogenase (nif) catalyzes the nitrogen fixing activity, which is performed by a wide range of microorganisms across various phylogenetic groups. However, high levels of inorganic nitrogen which is not assimilated to operate biological systems pose adverse effects on the nitrogen tolerant organisms. Most organisms integrate nitrogen either from inorganic nitrogen sources like ammonia (NH₃), nitrite (NO₂^-) and nitrate (NO₃^-) or from organic nitrogen compounds. The link between biogeochemical nitrogen processes and microbial community dynamics can provide a more mechanistic understanding of the nitrogen cycle than the direct observation of nitrogen dynamics. Specific enzymes catalyze many of these reactions, and the molecular approach to study these enzymes are useful targets for understanding microbial processes such as assimilatory nitrate reduction, dissimilatory nitrate reduction, and N₂ fixation.

Pages: 909-915  |  1213 Views  313 Downloads

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