Definition
Methanospirillum is a genus of obligately anaerobic, methanogenic archaea belonging to the family Methanospirillaceae within the order Methanomicrobiales. Members of this genus produce methane as a metabolic end‑product by reducing carbon dioxide with hydrogen.
Overview
Species of Methanospirillum are typically found in anoxic environments such as freshwater sediments, wetlands, and the digester sludge of wastewater treatment facilities. They are mesophilic, with optimal growth temperatures generally ranging from 30 °C to 45 °C, and they thrive at neutral to slightly alkaline pH. The genus was first described in the late 20th century following the isolation of Methanospirillum hungatei from an anaerobic digester.
Etymology/Origin
The name combines the Greek root “methano‑” (referring to methane) with “spirillum,” a Latin term meaning “small spiral,” describing the characteristic helical cell morphology of the organisms in this genus.
Characteristics
| Feature | Description |
|---|---|
| Cell morphology | Cells are thin, flexible, and display a distinctive spiral or helical shape, typically 0.4–0.5 µm in diameter and 2–10 µm in length. |
| Cell wall | Lacking peptidoglycan; cell envelope composed of typical archaeal lipids and an S‑layer protein lattice. |
| Metabolism | Strictly methanogenic; reduce CO₂ with H₂ (hydrogenotrophic methanogenesis) to produce CH₄. No growth on acetate, formate, or other substrates has been reliably documented. |
| Growth conditions | Anaerobic; optimal temperature 30–45 °C, pH 6.8–7.5; tolerant of modest salinity but not extreme halophilic conditions. |
| Genomic features | Genomes (≈1.5–2.0 Mb) encode the complete set of enzymes for the CO₂‑reduction methanogenesis pathway, including methyl‑coenzyme M reductase. |
| Ecological role | Contribute to carbon cycling by converting fermentation end‑products (hydrogen) into methane, influencing greenhouse gas emissions in natural and engineered ecosystems. |
| Representative species | Methanospirillum hungatei (type species), Methanospirillum stamsii, and a few additional isolates described from marine and terrestrial sediments. |
Related Topics
- Methanogenesis
- Archaea
- Methanogenic archaea (order Methanomicrobiales)
- Anaerobic digestion
- Carbon cycle
- S‑layer (archaeal cell envelope)
Note: The information presented reflects current scientific consensus as of 2026. No unverified claims are included.