# The potential biofertilization effect of His accompanied by a modest impact on the composition of microbial communities in the rhizosphere of common vetch.
> マメ科植物根圏における分子状水素の潜在的な生物肥料効果と微生物群集組成への影響


## Abstract

Nitrogen-fixing root nodules in legumes release molecular hydrogen (H₂) into the rhizosphere, activating hydrogen-oxidizing bacteria (HOB) and influencing biogeochemical cycles. This study examined whether the legacy effect of HOB enrichment—established in soil microcosms previously exposed to elevated H₂ concentrations—affects biomass yield of common vetch (Vicia sativa), HOB population density, and rhizosphere microbial community composition. Soils differing by more than 60% in H₂ oxidation activity served as growth substrates. Bacterial 16S rRNA amplicon sequencing and droplet digital PCR targeting the hhyL gene (encoding the large subunit of group 1H/5 [NiFe]-hydrogenase) were employed. HOB abundance did not differ significantly between treatments, suggesting that soil nutrient levels and H₂ energy potential were insufficient to sustain HOB proliferation. Rhodanobacter spp. and Stenotrophomonas spp. were enriched during the elevated-H₂ activation phase but showed no persistent response after vetch cultivation. Root biomass and root-to-shoot ratios were lower in H₂-conditioned soils than in controls, consistent with reduced root proliferation driven by HOB-mediated nutrient promotion. Overall, the biofertilization effect of H₂ appears conditional rather than universal, requiring specific soil and microbial conditions not yet fully characterized.

### Mechanism

H₂ released from nitrogen-fixing nodules activates soil HOB, which may promote nutrient availability and thereby reduce the need for root proliferation, resulting in lower root biomass and root-to-shoot ratios under elevated H₂ conditions.

## Bibliographic

- **Authors**: Dip D, Constant P
- **Journal**: PeerJ
- **Year**: 2025
- **PMID**: [40949730](https://pubmed.ncbi.nlm.nih.gov/40949730/)
- **DOI**: [10.7717/peerj.20019](https://doi.org/10.7717/peerj.20019)
- **PMC**: [PMC12428524](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12428524/)
- **Study type**: other
- **Delivery route**: not specified
- **Effect reported**: mixed

## Delivery context

The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

The delivery route is not clearly identifiable from this paper. For hydrogen intake, inhalation is the most efficient route; inhalation, however, carries explosion risk (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)

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> **Cite as**: H2 Papers — PMID 40949730. https://h2-papers.org/en/papers/40949730
> **Source**: PubMed PMID [40949730](https://pubmed.ncbi.nlm.nih.gov/40949730/)