# Hydrogen-dependent dissimilatory nitrate reduction to ammonium enables growth of Campylobacterota isolates.
> 水素依存性の硝酸塩から亜硝酸塩・アンモニウムへの異化的還元によるCampylobacterota単離株の増殖


## Abstract

Two Campylobacterota strains, Aliarcobacter butzleri hDNRA1 and Sulfurospirillum sp. hDNRA2, were isolated and shown to sustain growth using molecular hydrogen (H2) as the exclusive electron donor for dissimilatory nitrate reduction to ammonium (DNRA). In both batch and chemostat cultures, DNRA activity was strictly contingent on H2 availability and proceeded with stoichiometric coupling to H2 oxidation, confirming that electrons for nitrite reduction originated solely from H2. Genomic and transcriptomic profiling identified group 1b [NiFe]-hydrogenase and cytochrome c552 nitrite reductase as the central catalytic enzymes. Chemostat experiments further demonstrated viability of hydrogenotrophic DNRA under nitrate-limiting, H2-excess conditions. Metagenomic surveys indicated that bacteria capable of this metabolism are taxonomically diverse and prevalent across multiple ecosystems, with notable abundance near deep-sea hydrothermal vents. These findings establish H2 as a standalone growth-supporting electron donor for DNRA and highlight the potential ecological relevance of this process in biogeochemical nitrogen and hydrogen cycling.

### Mechanism

Group 1b [NiFe]-hydrogenase oxidizes H2, and the resulting electrons are channeled through cytochrome c552 nitrite reductase to reduce nitrite to ammonium, enabling stoichiometrically coupled hydrogenotrophic DNRA.

## Bibliographic

- **Authors**: Heo H, Nguyen-Dinh T, Jung MY, Greening C, Yoon S
- **Journal**: ISME J
- **Year**: 2025 (2025-01-02)
- **PMID**: [40367351](https://pubmed.ncbi.nlm.nih.gov/40367351/)
- **DOI**: [10.1093/ismejo/wraf092](https://doi.org/10.1093/ismejo/wraf092)
- **PMC**: [PMC12286921](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12286921/)
- **Study type**: other
- **Delivery route**: in vitro
- **Effect reported**: not assessed

## Delivery context

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 40367351. https://h2-papers.org/en/papers/40367351
> **Source**: PubMed PMID [40367351](https://pubmed.ncbi.nlm.nih.gov/40367351/)