# Carbon amendments in soil microcosms induce uneven response on H2 oxidation activity and microbial community composition.
> 土壌マイクロコズムへの炭素添加がH2酸化活性と微生物群集組成に不均一な影響を与える


## Abstract

High-affinity H2-oxidizing bacteria (HA-HOB) in soil constitute the primary biological sink for atmospheric H2. This study examined how carbon source recalcitrance and concentration influence HA-HOB activity and community diversity using soil microcosms amended with sucrose, starch, or cellulose at doses ranging from 0 to 5% Ceq soildw⁻¹. Among all treatments, only 0.1% cellulose stimulated HA-HOB activity. In contrast, sucrose addition caused the most pronounced suppression, with approximately 50% reduction in activity at 1% Ceq soildw⁻¹, accompanied by decreased bacterial and fungal alpha diversity and reduced abundance of the high-affinity group 1h/5 [NiFe]-hydrogenase gene (hhyL). A quantitative classification framework was developed to assign carbon preference traits to 16S rRNA, ITS, and hhyL genotypes, though taxonomic-level responses were heterogeneous. The findings indicate that HA-HOB activity is more readily stimulated by low concentrations of recalcitrant carbon, whereas labile carbon-rich conditions represent an unfavorable niche, likely through catabolic repression of hydrogenase expression.

### Mechanism

Labile carbon sources such as sucrose induce catabolic repression of hydrogenase in HA-HOB, suppressing H2 oxidation activity, whereas low-dose recalcitrant carbon like cellulose promotes HA-HOB activity, likely by supporting niche conditions favorable to these organisms.

## Bibliographic

- **Authors**: Baril X, Constant P
- **Journal**: FEMS Microbiol Ecol
- **Year**: 2023 (2023-11-13)
- **PMID**: [38040657](https://pubmed.ncbi.nlm.nih.gov/38040657/)
- **DOI**: [10.1093/femsec/fiad159](https://doi.org/10.1093/femsec/fiad159)
- **PMC**: [PMC10716739](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10716739/)
- **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 38040657. https://h2-papers.org/en/papers/38040657
> **Source**: PubMed PMID [38040657](https://pubmed.ncbi.nlm.nih.gov/38040657/)