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Inorganic Nitrogen Assimilation01:22

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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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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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Microorganisms play a pivotal role in maintaining ecosystem balance by recycling essential elements such as carbon, nitrogen, and phosphorus, as well as supporting processes like bioremediation, wastewater treatment, and biofuel production.Microbes in Elemental CyclesIn the carbon cycle, microorganisms decompose organic matter, releasing carbon dioxide via aerobic respiration. This carbon dioxide is subsequently used by photosynthetic organisms to synthesize organic compounds, closing the...
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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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Organisms exhibit remarkable metabolic diversity, categorized based on how they acquire energy and carbon. These strategies enable survival in various ecological niches and are essential for maintaining energy flow and nutrient cycling within ecosystems.Energy and Carbon SourcesOrganisms are classified as phototrophs or chemotrophs based on energy acquisition. Phototrophs use light as their energy source, while chemotrophs rely on oxidizing chemical compounds. Further differentiation arises...
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Complete nitrification by a single microorganism.

Maartje A H J van Kessel1, Daan R Speth1, Mads Albertsen2

  • 1Department of Microbiology, IWWR, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands.

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

Researchers discovered complete ammonia oxidation (comammox) in Nitrospira bacteria, a process previously thought impossible. This finding redefines our understanding of the nitrogen cycle and microbial metabolism.

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Area of Science:

  • Microbiology
  • Biogeochemistry
  • Environmental Science

Background:

  • Nitrification is a key two-step process in the nitrogen cycle, involving ammonia-oxidizing and nitrite-oxidizing microorganisms.
  • Complete ammonia oxidation (comammox) was theoretically possible but organisms performing it remained undiscovered.

Purpose of the Study:

  • To discover and characterize microorganisms capable of complete ammonia oxidation.
  • To investigate the enzymes and genetic basis for comammox.

Main Methods:

  • Enrichment and isolation of novel microorganisms.
  • Genomic analysis to identify key enzymes.
  • Phylogenetic analysis of ammonia monooxygenase (AMO) enzymes.

Main Results:

  • Two Nitrospira species capable of complete ammonia oxidation were identified.
  • These organisms possess unique AMO enzymes, distinct from known ammonia oxidizers.
  • Misclassified amoA sequences in public databases were recognized as belonging to comammox bacteria.

Conclusions:

  • The discovery of comammox in Nitrospira fundamentally changes the understanding of the nitrogen cycle.
  • This finding has implications for microbial ecology, biogeochemical cycling, and the evolution of metabolic pathways.