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Overview of Nitrogen Metabolism01:20

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Nitrogen is a very important element for life because it is a major constituent of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds and stored in the form of  ammonia, ammonium ions, nitrate, nitrite, or  nitrogen gas by many metabolic processes. Many of these metabolic processes are carried out only by prokaryotes.
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Nitrogen is an essential element in biological systems, forming a crucial component of proteins, nucleic acids, and other cellular constituents. Many bacteria and archaea acquire nitrogen in the form of nitrate (NO₃⁻) or ammonia (NH₃), which are then assimilated into biomolecules through specific enzymatic pathways.Assimilatory Nitrate ReductionWhen nitrate enters the cell, it undergoes a two-step reduction process known as assimilatory nitrate reduction. Initially, the enzyme...
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Nitrogen atoms, present in all proteins and DNA, are recycled between abiotic and biotic components of the ecosystem. However, the primary form of nitrogen on Earth is nitrogen gas, which cannot be used by most animals and plants. Thus, nitrogen gas must first be converted into a usable form by nitrogen-fixing bacteria before it can be cycled through other living organisms. The use of nitrogen-containing fertilizers and animal waste products in human agriculture has greatly influenced the...
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Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.
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Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
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Complete nitrification by Nitrospira bacteria.

Holger Daims1, Elena V Lebedeva2, Petra Pjevac1

  • 1Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.

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|November 27, 2015
PubMed
Summary
This summary is machine-generated.

Researchers discovered a novel bacterium capable of complete nitrification, oxidizing ammonia to nitrate in one step. This finding challenges the long-held view of nitrification as a two-step process and highlights the role of Nitrospira in nitrogen cycling.

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Area of Science:

  • Microbiology
  • Environmental Science
  • Biochemistry

Background:

  • Nitrification is crucial for nitrogen cycling, traditionally viewed as a two-step process.
  • Microorganisms responsible for ammonia oxidation and nitrite oxidation were considered distinct.
  • The energetic advantage of complete nitrification suggested a single organism could perform both steps.

Purpose of the Study:

  • To investigate the century-old puzzle of functional separation in nitrification.
  • To discover and cultivate microorganisms capable of complete nitrification.
  • To understand the genetic basis and ecological significance of complete nitrification.

Main Methods:

  • Isolation and cultivation of a novel bacterium from the Nitrospira genus.
  • Genomic analysis to identify metabolic pathways.
  • Metagenomic analysis of environmental samples.

Main Results:

  • Discovery and cultivation of a completely nitrifying bacterium within the Nitrospira genus.
  • Genomic analysis revealed pathways for both ammonia and nitrite oxidation in this organism.
  • Genes for ammonia monooxygenase and hydroxylamine dehydrogenase were found in Nitrospira and environmental metagenomes.

Conclusions:

  • Completely nitrifying Nitrospira challenge the established two-step model of nitrification.
  • These organisms are concurrently active in ammonia oxidation to nitrate during growth.
  • Completely nitrifying Nitrospira are significant players in global nitrogen-cycling microbial communities.