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Related Concept Videos

The Nitrogen Cycle01:49

The Nitrogen Cycle

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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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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.
The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen (N2) from the air, but this...
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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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Urea Cycle01:23

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The urea cycle describes how liver cells convert ammonia to urea. Ammonia is a toxic waste product of protein catabolism. Land animals must convert ammonia into the less toxic urea which can be safely eliminated by the kidneys through urine. Marine animals excrete ammonia directly, and the surrounding water dilutes the ammonia to safe levels.
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Carbon-dioxide Fixation01:28

Carbon-dioxide Fixation

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Carbon dioxide fixation in prokaryotes enables the assimilation of inorganic carbon into organic molecules, supporting biosynthetic pathways, sustaining ecosystems, and contributing to the global carbon cycle. It also has industrial applications in carbon capture and bioproduct synthesis. Autotrophic organisms rely on this process to utilize CO₂ as a carbon source in diverse environments.The Calvin CycleThe Calvin cycle is the most widespread carbon fixation mechanism, primarily used by...
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Metabolism of Chemolithotrophs01:15

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Chemolithotrophs are microorganisms that obtain energy by oxidizing inorganic molecules such as hydrogen gas (H₂), ammonia (NH₃), reduced sulfur compounds (H₂S, S²⁻), and ferrous iron (Fe²⁺). Unlike heterotrophic organisms that rely on organic carbon, chemolithotrophs transfer electrons from these inorganic donors to the electron transport chain (ETC), generating a proton motive force (PMF) that drives ATP synthesis through oxidative phosphorylation.
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On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes
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Cyclic Conversions in the Nitrogen Cycle.

Robbert Kleerebezem1, Sebastian Lücker2

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Frontiers in Microbiology
|April 16, 2021
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Summary
This summary is machine-generated.

Complete ammonia-oxidizing Nitrospira bacteria may use an anammox-like metabolism or scavenge oxygen. This explains their ecological niche in low-oxygen environments by enabling ammonia oxidation to nitrate.

Keywords:
anammoxdenitrificationnitrificationstoichiometrythermodynamics

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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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Area of Science:

  • Microbiology
  • Environmental Science
  • Biogeochemistry

Background:

  • The nitrogen cycle involves complex conversions with strict biochemical limitations.
  • Anaerobic ammonium oxidation (anammox) bacteria utilize nitrite, not nitrate, as an electron acceptor.
  • Nitrite is essential for inorganic carbon fixation in anammox bacteria's anabolism.

Purpose of the Study:

  • To explain the ecological role of complete ammonia-oxidizing (comammox) Nitrospira bacteria.
  • To propose scenarios for comammox Nitrospira spp. in oxygen-limited environments.
  • To investigate the biochemical basis for comammox bacteria's niche.

Main Methods:

  • Analysis of nitrogen cycle conversions and biochemical constraints.
  • Hypothesizing metabolic pathways for comammox Nitrospira based on known processes.
  • Considering the implications of ammonia oxidation to nitrate.

Main Results:

  • Comammox Nitrospira may perform an anammox-like metabolism using nitrite.
  • Alternatively, comammox Nitrospira might scavenge oxygen for ammonia activation and use nitrate as a terminal electron acceptor.
  • Both proposed pathways necessitate ammonia oxidation to nitrate.

Conclusions:

  • The cyclic nature of nitrogen conversions influences microbial metabolism.
  • Comammox Nitrospira's ecological role is likely tied to their ability to oxidize ammonia to nitrate.
  • This capability potentially defines a unique niche for comammox bacteria in oxygen-limited ecosystems.