# The unusual cell biology of the hyperthermophilic Crenarchaeon Ignicoccus hospitalis.
> 超好熱性クレン古細菌Ignicoccus hospitalisの特異な細胞生物学的特性


## Abstract

Ignicoccus hospitalis is an anaerobic, obligate chemolithoautotrophic hyperthermophile that uses molecular hydrogen as an electron donor for elemental sulfur reduction. This review describes the organism's remarkable cellular architecture, including a double-membrane cell envelope lacking an S-layer, extracellular fiber appendages, and a novel CO2 fixation route known as the dicarboxylate/4-hydroxybutyrate pathway. An intermembrane compartment (IMC) of variable width (20–1,000 nm) contains numerous vesicles potentially involved in lipid or protein transport. Immunoelectron microscopy revealed that the A1AO ATP synthase, the H2:sulfur oxidoreductase complex, and acetyl-CoA synthetase localize to the outermost membrane, making I. hospitalis the first known prokaryote with an energized outer membrane and extracytoplasmic ATP synthesis. This spatial separation of energy conservation from DNA replication and protein biosynthesis raises fundamental questions about membrane function and metabolic exchange with its archaeal partner Nanoarchaeum equitans.

### Mechanism

The H2:sulfur oxidoreductase complex and A1AO ATP synthase are localized to the outermost cellular membrane, enabling energy conservation and ATP synthesis outside the cytoplasm, with molecular hydrogen serving as the primary electron donor.

## Bibliographic

- **Authors**: Huber H, Küper U, Daxer S, Rachel R
- **Journal**: Antonie Van Leeuwenhoek
- **Year**: 2012
- **PMID**: [22653377](https://pubmed.ncbi.nlm.nih.gov/22653377/)
- **DOI**: [10.1007/s10482-012-9748-5](https://doi.org/10.1007/s10482-012-9748-5)
- **Study type**: review
- **Delivery route**: not specified
- **Effect reported**: not assessed

## 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 22653377. https://h2-papers.org/en/papers/22653377
> **Source**: PubMed PMID [22653377](https://pubmed.ncbi.nlm.nih.gov/22653377/)