nitrogen fixation Archives

Dark colored bars indicate time periods when all three clock models agree that the metabolism existed, light colored bars represent the oldest age predicted by any of the three clock models, and dashed lines represent the oldest confidence intervals. Isotopic evidence of biological N2 fixation (BNF) is presented in black (see main text for references), with the gray area representing more putative isotopic evidence of biological N2 fixation. Paleoarc. represents the Paleoarchean, Mesoarc. represents the Mesoarchean, Neoarc. represents the Neoarchean, Neoptz. represents the Neoproterozoic. -- Science Advances via PubMed

Abiotic Sources Of Fixed Nitrogen Sustained Early Ecosystems For Several Hundred Million Years After The Origin Of Life

by Keith CowingJune 23, 2026June 23, 2026

Nitrogen (N) plays a crucial role in controlling biological productivity. However, it remains unknown how Earth’s earliest ecosystems accessed bioavailable forms of nitrogen.

Schematic of methods used to insert ancestral genes into the host A. vinelandii genome -- Nature Communications

Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Fossils & Paleontology, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Press Release

Resurrecting Ancient Enzymes in NASA’s Search For Life Beyond Earth

by Keith CowingMarch 27, 2026March 27, 2026

NASA-supported scientists have resurrected an enzyme first used by organisms on Earth 3.2-billion years ago and, in the process, have validated a chemical biosignature in rocks that is used to […]

Nicholas Ray, assistant professor in the School of Marine Science and Policy at the University of Delawarew, was part of a National Science Foundation research coordination network that released a paper focused on nitrogen fixation in freshwater and coastal ecosystems. Here, he conducts the lab work for one method of measuring sediment-water N2 fluxes (including N-fixation). Credit Photos courtesy of Nicholas Ray/ University of Delaware

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Gaia - Planetary Perspectives, Microbiology & Virology, Press Release, Sample Return, Water/Hycean Worlds & Oceanography

Small Aquatic Systems Found To Fix 15% Of Earth’s Nitrogen

by Keith CowingNovember 9, 2025November 9, 2025

Nitrogen is vital for all known life. Yet most nitrogen on Earth is in the atmosphere as di-nitrogen gas, which many organisms can’t use. Fortunately, there are microbes that can […]

Hadean Earth - credit: Alec Brenner via Harvard University

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Fossils & Paleontology, Habitable Zones, Microbiology & Virology, Status Report, Water/Hycean Worlds & Oceanography

New Estimates of Nitrogen Fixation on Early Earth

by Keith CowingSeptember 17, 2024September 17, 2024

Fixed nitrogen species generated by the early Earth’s atmosphere are thought to be critical to the emergence of life and the sustenance of early metabolisms.

Evolution and function of the nitroplast - Multiple organelles in eukaryotic cells, including mitochondria, chloroplasts, and nitroplasts, evolved from the integration of endosymbiotic bacteria. In Braarudosphaera bigelowii, the chloroplast fi xes inorganic carbon to produce glucose, which feeds the respiratory chain in mitochondria that produces adenosine triphosphate (ATP), which in turn fuels nitrogen fi xation in the nitroplast. Glucose, ammonia, and ATP generated by the organelles, together with externally incorporated compounds (phosphorous, mineral nutrients, and vitamins), are the building blocks for cell metabolism, resulting in cell growth and division. -- Science

Biochemistry & Organic Chemistry, Biophysics, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Press Release

The Nitroplast Revealed: A Nitrogen-fixing Organelle In A Marine Alga

by Keith CowingApril 20, 2024April 20, 2024

A nitrogen-fixing bacterial endosymbiont of marine algae is evolving into a nitrogen-fixing organelle, or nitroplast, according to a new study, thereby expanding a function that was thought to be exclusively […]

A light microscopy image shows the marine haptophyte algae Braarudosphaera bigelowii with a black arrow pointing to the nitroplast organelle. (Photo credit: Tyler Coale)

Biophysics, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Plant Biology, Press Release

The First Known Nitrogen-fixing Organelle

by Keith CowingApril 12, 2024April 12, 2024

Modern biology textbooks assert that only bacteria can take nitrogen from the atmosphere and convert it into a form that is usable for life. Plants that fix nitrogen, such as […]

Linear volumetric scaling in the B. bigelowii/UCYN-A symbiosis -- (A) Light microscopy image of the haptophyte B. bigelowii in symbiosis with UCYN-A (scale bar, 2 μm; image courtesy of Wing Kwan Esther Mak and Kyoko Hagino). (B) Upper panel: UCYN-A volume (sublineages UCYN-A1, -A2, and -A3; see inset) as a function of associated haptophyte cell volume; lower panel: chloroplast volume as a function of associated haptophyte cell volume; inset in lower panel: UCYN-A volume vs. chloroplast volume of associated host cells. (C) Composite of catalized reporter deposition fluorescence in situ hybridization (CARD-FISH) images showing the range of sizes of the different UCYN-A sublineages (left images: UCYN-A1 sublineage; middle images: UCYN-3 sublineage; right images: UCYN-A2 sublineage) and their symbiotic haptophyte partners. Images were taken under blue (green-labeled haptophytes with Alexa 488 stain) and green (red-labeled UCYN-A with Alexa 594 stain) excitation wavelengths (STAR Methods) (scale bar, 5 μm). -- Cell

Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Press Release

Evolution In Action? New Study Finds Possibility Of Nitrogen-fixing Organelles

by Keith CowingApril 4, 2024April 4, 2024

Nitrogen is a nutrient essential for all life on Earth. Although nitrogen gas (N2) is plentiful, it is largely unavailable to most organisms without a process known as nitrogen fixation, […]

NifH2 cycle of Mo-nitrogenase. The NifH2 homodimer is shown in blue; it houses two nucleotide binding sites and a [4Fe-4S] redox active cluster. One catalytic half (NifDK) of the NifD2K2 heterotetramer is shown in yellow (K) and green (D); each catalytic half houses one [8Fe-7S] (Pcluster) and a [7Fe-9S-Mo-C-homocitrate] (FeMo-co) active site metallocluster. When NifH2 binds to NifDK an electron is transferred from the [4Fe-4S] cluster to FeMo-co mediated by P-cluster. NifH2 then hydrolyzes 2 ATP, dissociates with MgADP bound and an oxidized [4Fe4S] cluster. MgADP is then exchanged for MgATP and the [4Fe-4S] cluster is reduced, preparing NifH2 for binding and electron transfer. -- biorxiv.org

Biochemistry & Organic Chemistry, Biophysics, Genomics, Proteomics, Bioinformatics, Status Report

The Origins Of ATP Dependence In Biological Nitrogen Fixation

by Keith CowingFebruary 27, 2024February 27, 2024

Life depends on a conserved set of chemical energy currencies that are relics of early biochemistry. One of these is ATP, a molecule that, when paired with a divalent metal […]

Structure and genetics of the nitrogenase G-subunit. A) Left, crystallographic structure of the extant A. vinelandii Vnf nitrogenase complex (VnfH, PDB 6Q9336; VnfDGK, PDB 5N6Y22 ) containing the G-subunit (dark blue). The Anf nitrogenase is inferred to be comparable in its multimeric structure, binding FeFe-co instead of FeV-co. Right, crystallographic structure of the extant Nif nitrogenase complex (NifH, PDB 1M3437; NifDK, PDB 3U7Q38) lacking the G subunit. B) Secondary structure of the Vnf G-subunit. C) Arrangement of the Nif, Vnf, and Anf structural genes in A. vinelandii. Vnf/AnfG (dark blue) is located between Vnf/AnfD and Vnf/AnfK genes. -- biorxiv.org

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Microbiology & Virology, Plant Biology, Status Report

An Orphan Protein Drove The Ecological Expansion Of Nitrogen Fixation

by Keith CowingApril 10, 2023April 10, 2023

Nitrogenases have catalyzed biological nitrogen fixation for billions of years and revolutionized planet Earth by supplying essential nitrogen to the biosphere.