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Related Concept Videos

Inorganic Nitrogen Assimilation01:22

Inorganic Nitrogen Assimilation

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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

Overview of Nitrogen Metabolism

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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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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 Metabolism01:40

Overview of Metabolism

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Living cells constantly carry out various chemical reactions which are necessary for their proper functioning. These reactions are interlinked to one another via multiple pathways. The collection of these chemical reactions is known as metabolism.
Plant Metabolism
Sunlight, the primary source of energy in plants, is first absorbed by the chlorophyll pigments present in their leaves. Plants then use this energy to carry out photosynthesis, where water is oxidized into oxygen and carbon dioxide...
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Metabolism of Chemolithotrophs01:15

Metabolism of Chemolithotrophs

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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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Preparation of Amines: Reduction of Oximes and Nitro Compounds01:29

Preparation of Amines: Reduction of Oximes and Nitro Compounds

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Oximes can be reduced to primary amines using catalytic hydrogenation, hydride reduction, or sodium metal reduction. The reduction of aliphatic and aromatic nitro compounds to primary amines takes place by either catalytic hydrogenation or by using active metals like Fe, Zn, and Sn in the presence of an acid.
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...
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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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Lowering the Mo limit for nitrogen fixation by Mo-nitrogenase.

Zackry Stevenson1, Dylan L Schultz2, Michelle Chamberlain1

  • 1Iowa State University, Department of the Earth, Atmosphere, and Climate, Ames, IA USA.

Communications Earth & Environment
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Summary

Early life

Keywords:
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Area of Science:

  • Biogeochemistry
  • Microbiology
  • Paleoceanography

Background:

  • Archean ocean primary productivity may have been limited by nitrogen availability.
  • Low molybdenum levels suggest early nitrogen fixation used alternative nitrogenases (vanadium or iron).

Purpose of the Study:

  • Investigate nitrogen fixation in conditions mimicking the early Earth's marine environment.
  • Determine if alternative nitrogenases are essential for nitrogen fixation at low molybdenum concentrations.

Main Methods:

  • Studied a Cyanobacteria-dominated lake with low sulfate and molybdenum.
  • Analyzed nitrogen fixation rates and nitrogenase presence using metagenomics and metatranscriptomics.
  • Conducted molybdenum addition experiments.

Main Results:

  • Nitrogen fixation occurred at molybdenum levels 100x lower than modern oceans.
  • Molybdenum addition did not enhance nitrogen fixation, indicating diazotrophs were not limited.
  • Only molybdenum-iron nitrogenase was detected; alternative nitrogenases were not required.

Conclusions:

  • Low sulfate and efficient uptake may mitigate molybdenum limitation for nitrogen fixation.
  • Molybdenum bioavailability is strongly influenced by sulfate concentrations.
  • Alternative nitrogenases are not essential for nitrogen fixation in low-molybdenum environments.