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Related Concept Videos

Overview of Nitrogen Metabolism01:20

Overview of Nitrogen Metabolism

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 nitrogen...
Inorganic Nitrogen Assimilation01:22

Inorganic Nitrogen Assimilation

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 nitrate reductase...
Carbon-dioxide Fixation01:28

Carbon-dioxide Fixation

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...
The Nitrogen Cycle01:49

The Nitrogen Cycle

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...
Microbes and Climate Change01:27

Microbes and Climate Change

Microorganisms are pivotal agents in Earth's biogeochemical cycles, significantly influencing climate dynamics through their metabolic activities. These microbes modulate the levels of key greenhouse gases by both contributing to and helping mitigate climate change.Microbial Contributions to Greenhouse Gas EmissionsRising global temperatures accelerate microbial metabolism, which, in turn, speeds up the decomposition of organic matter. This process releases carbon dioxide (CO₂) through...
Metabolism of Chemolithotrophs01:15

Metabolism of Chemolithotrophs

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. However, because inorganic electron donors...

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Related Experiment Video

Updated: May 8, 2026

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
08:05

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

Published on: October 7, 2020

Changes in North Atlantic nitrogen fixation controlled by ocean circulation.

Marietta Straub1, Daniel M Sigman, Haojia Ren

  • 1Geological Institute, Department of Earth Sciences, ETH Zurich, 8092 Zurich, Switzerland. marietta.straub@alumni.ethz.ch

Nature
|August 23, 2013
PubMed
Summary
This summary is machine-generated.

Oceanic fixed nitrogen fuels phytoplankton productivity. Past North Atlantic nitrogen fixation cycles were driven by phosphorus supply, linked to ocean circulation and orbital cycles, not temperature or iron.

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The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
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The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations

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Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems
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Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

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Related Experiment Videos

Last Updated: May 8, 2026

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
08:05

Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

Published on: October 7, 2020

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations
10:11

The Benthic Exchange of O2, N2 and Dissolved Nutrients Using Small Core Incubations

Published on: August 3, 2016

Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems
09:38

Understanding Dissolved Organic Matter Biogeochemistry Through In Situ Nutrient Manipulations in Stream Ecosystems

Published on: October 29, 2016

Area of Science:

  • Paleoceanography
  • Biogeochemistry
  • Marine Nitrogen Cycle

Background:

  • Oceanic fixed nitrogen is crucial for phytoplankton productivity and carbon export.
  • Variations in fixed nitrogen reservoirs may influence glacial-interglacial atmospheric CO2 levels.
  • Marine nitrogen fixation, the primary source of fixed nitrogen, is influenced by temperature, iron, and phosphorus.

Observation:

  • Reconstructed North Atlantic nitrogen fixation over 160,000 years using planktonic foraminifera isotopes.
  • Observed changes were not explained by temperature, dust (iron), or denitrification.
  • A ~23,000-year cycle in nitrogen fixation was identified.

Findings:

  • Nitrogen fixation cycles correlate with orbitally driven upwelling, importing excess phosphorus into the North Atlantic.
  • Nitrogen fixation decreased during glacial stages 6 and 4 due to shoaled North Atlantic Deep Water.
  • Excess phosphorus availability, controlled by ocean circulation and orbital cycles, is the primary driver of North Atlantic nitrogen fixation.

Implications:

  • Excess phosphorus is identified as the master variable controlling North Atlantic nitrogen fixation.
  • Past variations in phosphorus supply were dominated by ocean circulation responses to orbital cycles.
  • Understanding these past dynamics is key to predicting future ocean biogeochemical responses.