Micro-scale organization of non-cyanobacterial diazotrophs drives nitrogen fixation in marine particles
Abstract
Dinitrogen (N₂) fixation supplies reactive nitrogen to the ocean, and non-cyanobacterial diazotrophs (NCDs) are increasingly recognized as contributors. Marine particles have been theorized as hotspots where low oxygen and labile carbon favor N₂ fixation by NCDs, but empirical proof is lacking. Here, we show that particle-NCD associations in a controlled model where Vibrio diazotrophicus colonizes laboratory-generated diatom aggregates. Using nitrogenase (NifH) immunolabeling and a respiration probe, we map cell activity across particles, while bulk 15 N₂ tracing quantifies N₂ fixation and membrane-inlet mass spectrometry O₂/Ar tracks respiration. We find a clear metabolic succession: respiring cells represented 50% of total cells at 12 h, followed by an increase at 24 h in NifH-positive cells (30%), with higher relative abundances observed toward particle interiors. NCDs are up to 1500 times more concentrated in particles than in the surrounding seawater, with nitrogenase-expressing cells showing a 1.5-fold higher relative abundance in particle cores compared with the peripheries after 24 h without bioavailable nitrogen. The spatial arrangement of V.diazotrophicus within aggregates is associated with conditions favourable for N₂ fixation in particle interiors, supporting the view that particles act as micro-niches for heterotrophic diazotrophy. Our results provide empirical evidence that the spatial distribution of NCDs within particles influences their nitrogen fixation potential.
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BibTeX
@article{coet2026microscale,
title = {{Micro-scale organization of non-cyanobacterial diazotrophs drives nitrogen fixation in marine particles}},
author = {Arthur Coët and Olivier Grosso and Nicolas Brouilly and Pierre Ronceray and Mar Benavides},
journal = {Communications Biology},
year = {2026},
month = sep,
doi = {10.1038/s42003-026-10971-w},
url = {https://hal.science/hal-05762672v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Micro-scale organization of non-cyanobacterial diazotrophs drives nitrogen fixation in marine particles
AU - Arthur Coët
AU - Olivier Grosso
AU - Nicolas Brouilly
AU - Pierre Ronceray
AU - Mar Benavides
PY - 2026
DA - 2026/09/16
JO - Communications Biology
DO - 10.1038/s42003-026-10971-w
UR - https://hal.science/hal-05762672v1
AB - Dinitrogen (N₂) fixation supplies reactive nitrogen to the ocean, and non-cyanobacterial diazotrophs (NCDs) are increasingly recognized as contributors. Marine particles have been theorized as hotspots where low oxygen and labile carbon favor N₂ fixation by NCDs, but empirical proof is lacking. Here, we show that particle-NCD associations in a controlled model where Vibrio diazotrophicus colonizes laboratory-generated diatom aggregates. Using nitrogenase (NifH) immunolabeling and a respiration probe, we map cell activity across particles, while bulk 15 N₂ tracing quantifies N₂ fixation and membrane-inlet mass spectrometry O₂/Ar tracks respiration. We find a clear metabolic succession: respiring cells represented 50% of total cells at 12 h, followed by an increase at 24 h in NifH-positive cells (30%), with higher relative abundances observed toward particle interiors. NCDs are up to 1500 times more concentrated in particles than in the surrounding seawater, with nitrogenase-expressing cells showing a 1.5-fold higher relative abundance in particle cores compared with the peripheries after 24 h without bioavailable nitrogen. The spatial arrangement of V.diazotrophicus within aggregates is associated with conditions favourable for N₂ fixation in particle interiors, supporting the view that particles act as micro-niches for heterotrophic diazotrophy. Our results provide empirical evidence that the spatial distribution of NCDs within particles influences their nitrogen fixation potential.
SN - 2399-3642
ER -