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Related Concept Videos

Microbes and the Nitrogen Cycle01:26

Microbes and the Nitrogen Cycle

The nitrogen cycle is a complex biogeochemical process critical to maintaining the balance of nitrogenous compounds in ecosystems. This cycle involves multiple microbial-mediated transformations through which nitrogen changes oxidation states, supporting essential ecological functions and contributing to plant and microbial growth.Nitrogen Fixation and AmmonificationNitrogen fixation initiates the cycle by converting inert atmospheric nitrogen (N₂) into bioavailable ammonia (NH₃), a process...
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...
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: Jul 12, 2026

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

Nitrogen fixation in marine shipworms.

E J Carpenter, J L Culliney

    Science (New York, N.Y.)
    |February 14, 1975
    PubMed
    Summary

    Nitrogen fixation was discovered in four shipworm species, with high rates observed in Teredora malleolus. This process may significantly contribute to nitrogen availability for marine organisms consuming plant material.

    Area of Science:

    • Marine biology
    • Microbiology
    • Biogeochemistry

    Background:

    • Shipworms (wood-boring bivalves) are ecologically important in marine ecosystems.
    • Nitrogen is an essential nutrient for marine life, and its fixation is a key biogeochemical process.

    Purpose of the Study:

    • To investigate nitrogen fixation in shipworm species.
    • To identify bacteria responsible for nitrogen fixation within shipworms.
    • To quantify nitrogen fixation rates and understand factors influencing them.

    Main Methods:

    • Isolation and culturing of bacteria from shipworm guts.
    • Assaying nitrogen fixation rates using acetylene reduction assays.
    • Analyzing shipworm diet and nitrogen content.

    More Related Videos

    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

    Prospecting Microbial Strains for Bioremediation and Probiotics Development for Metaorganism Research and Preservation
    09:49

    Prospecting Microbial Strains for Bioremediation and Probiotics Development for Metaorganism Research and Preservation

    Published on: October 31, 2019

    Related Experiment Videos

    Last Updated: Jul 12, 2026

    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

    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

    Prospecting Microbial Strains for Bioremediation and Probiotics Development for Metaorganism Research and Preservation
    09:49

    Prospecting Microbial Strains for Bioremediation and Probiotics Development for Metaorganism Research and Preservation

    Published on: October 31, 2019

    Main Results:

    • Nitrogen fixation was associated with four shipworm species.
    • A novel anaerobic, cellulose-liquefying bacterium was isolated and capable of nitrogen fixation.
    • High nitrogen fixation rates (up to 1.5 µg N/mg dry weight/hour) were recorded in Teredora malleolus.
    • Juveniles of coastal species exhibited the highest fixation rates.
    • Nitrogen fixation activity was inversely correlated with dietary combined nitrogen.

    Conclusions:

    • Shipworms harbor nitrogen-fixing bacteria, contributing to their nitrogen budget.
    • Nitrogen fixation by shipworms could be a significant nitrogen source in marine environments.
    • This process may benefit other marine organisms that ingest shipworms or their byproducts.