AA-75 grew on saturated fatty acids ranging from C7:0 to C18:0 and on unsaturated fatty acids including C16:1, C18:1 and C18:2, using these compounds to generate methane. The result directly addresses the classical syntrophic model of anaerobic degradation. In that model, bacteria break down large organic molecules and pass simple C1 and C2 products, such as methanol or acetate, to methanogenic archaea, which occupy the terminal role in methane production.

The isolation of AA-75 shows that this division of labor is not obligatory: at least one archaeon can perform both the oxidation of fatty-acid chains and the conversion of the resulting carbon into methane. The researchers call this process lipotrophic methanogenesis. Its metabolic machinery links β-oxidation of fatty acids to the Wood–Ljungdahl pathway and to the canonical methyl-tetrahydromethanopterin:coenzyme M methyltransferase and methyl-coenzyme M reductase complexes, together with an intracellular electron-transfer system.

A formaldehyde–methanol branch probably provides an auxiliary route for C1 metabolism during methanogenesis. Carbon-isotope analysis distinguished methane produced from stearate, a saturated C18:0 fatty acid, from methane generated through canonical methanogenic pathways. Stearate-derived methane was moderately enriched in carbon-13, with δ13C–CH4 values of −40.0‰ to −36.3‰, whereas canonical methanogenic pathways are associated with strong carbon-13 depletion.

This measured difference is part of the evidence that lipotrophic methanogenesis constitutes a distinct metabolic process. The study establishes the behavior of one thermophilic Archaeoglobi isolate from a petroleum reservoir; the reported results do not determine the prevalence of fatty-acid-consuming methanogens or their quantitative contribution to methane formation elsewhere. By documenting fatty-acid oxidation and methane production in a single archaeon, the research challenges the assumption that methanogens are restricted to consuming simple products supplied by partner organisms.

AA-75 indicates that methanogens can also act as primary degraders of complex organic matter. That finding calls for refinement of models describing how carbon moves through the deep subsurface and is converted into methane, while leaving open the relative roles of direct lipotrophic methanogenesis and syntrophic cooperation in natural microbial communities.

Subject of Research: Pure-culture study of lipotrophic methanogenesis in a thermophilic Archaeoglobi archaeon

Article Title: A single archaeon couples long-chain fatty acid oxidation to methanogenesis

Article References: Yi, Y., Cao, Z., Wu, K., Ding, H., Fu, L., Gao, W., Li, L., Zhou, L., Zhou, Z., Dai, L., Lu, Y., & Cheng, L. (2026). A single archaeon couples long-chain fatty acid oxidation to methanogenesis. Nature. https://doi.org/10.1038/s41586-026-11207-x

Image Credits: AI Generated

DOI: 10.1038/s41586-026-11207-x

Keywords: Archaeoglobi, lipotrophic methanogenesis, Methanoglobus dolicholipophagus, fatty-acid oxidation, methanogenesis, pure culture, petroleum reservoir, carbon isotope, deep subsurface, carbon cycling, single, archaeon