Recently, the Submarine Life & Environment (SLOE) Team from the School of Oceanography and State Key Laboratory of Submarine Geoscience and Delimitation at Shanghai Jiao Tong University published a research paper titled “Evidence of direct methane production from long‑chain fatty acids by thermophilic Archaeoglobi” in Nature Microbiology. Tiantian Yu, Assistant Research Professor at the School of Oceanography, serves as the first author. Professor Fengping Wang and Tiantian Yu are the co‑corresponding authors, and Shanghai Jiao Tong University, School of Oceanography is the primary affiliation of this work.

I. Challenging Established Scientific Understanding: Discovery of Archaea Capable of Degrading Long‑chain Fatty Acids Independently

Long‑chain fatty acids are ubiquitous organic molecules across Earth’s environments. Traditionally, the scientific community held the view that methanogenic degradation of long‑chain fatty acids must rely on syntrophic metabolic partnerships between bacteria and archaea: bacteria first break down long‑chain fatty acids into small‑molecule compounds, which archaea then convert into methane. This “syntrophic” model has long been regarded as a classic paradigm for anaerobic organic‑matter degradation in nature.

However, this study overturns that consensus. The team enriched and cultivated a novel methanogenic archaeon, Ca. M. sphaerolipidus, and demonstrated that this archaeon can independently complete the full transformation of long‑chain fatty acids into methane (Figure 1).

Figure 1 Schematic diagram illustrating archaea capable of independently completing the full conversion of long‑chain fatty acids to methane

     Continuous methane production was detected in oleic‑acid‑amended cultures. Metagenomic and metatranscriptomic sequencing revealed that the relative abundance of Ca. M. sphaerolipidus reached 70%–94% at the DNA level and 70%–86% at the RNA level. Stable‑isotope tracing experiments further confirmed that exogenously supplied ¹³C‑labelled oleic acid was directly converted into ¹³C‑labelled methane and carbon dioxide (Figure 2). In addition to oleic acid, this archaeon can also utilise methanol for methanogenesis (Figure 2).

Figure 2 Methane production and community composition of Ca. M. sphaerolipidus enrichment cultures using oleic acid / methanol as substrates.

    The genome of Ca. M. sphaerolipidus fully encodes the β‑oxidation pathway, the Wood‑Ljungdahl pathway (WLP), as well as key methanogenic complexes: methyl‑coenzyme‑M reductase (MCR) and methyltransferase (MTR). Equipped with this genetic repertoire, the archaeon can convert long‑chain fatty acids to methane without bacterial syntrophic partners. Transcriptomic data show that relevant genes are highly expressed under oleic‑acid‑supplemented culture conditions (Figure 3).

Figure 3 Metabolic pathways and corresponding gene transcription profiles of Ca. M. sphaerolipidus for methanogenesis from oleic acid and methanol.

II. Rewriting the “Menu” of Methanogenic Archaea

Methanogenic archaea are obligate anaerobic microorganisms that gain energy through methanogenesis and contribute roughly two‑thirds of global methane emissions. Previously known substrate utilisation modes for methanogenic archaea include carbon‑dioxide‑reductive methanogenesis, acetoclastic methanogenesis, methylotrophy, methyl reduction, methoxydotrophy, and the recently reported alkylotrophy. The discovery of Ca. M. sphaerolipidus adds long‑chain fatty acids to the substrate “menu” of methanogenic archaea, bringing the total number of recognised methanogenic pathways to seven (Figure 4). The research team named this brand‑new methanogenic mode “liparotrophy”.

The team also surveyed 94 genomes assigned to the genus Ca. Methanoglobus from public databases. Thirty‑three of these genomes carry the key methanogenic gene mcr, and can be grouped into five metabolic types based on substrate‑utilisation genes. This finding indicates that the genus Ca. Methanoglobus harbours diverse capacities for methanogenesis and methane oxidation, and may play far more versatile ecological roles in natural environments than previously appreciated.

Figure 4 Schematic diagram depicting the discovery of the “seventh” methanogenic mode.

This study not only pushes back the conceptual boundaries of methanogenic archaeal metabolism but also provides a new microbial mechanism for understanding the fate of long‑chain fatty acids in Earth’s carbon cycle. Long‑chain fatty acids are major components of terrestrial plants and marine phytoplankton and represent a substantial fraction of the global organic‑carbon pool. Archaea affiliated with Ca. Methanoglobus are likely widespread in high‑temperature anaerobic habitats including marine hydrothermal vents, terrestrial hot springs and oil reservoirs. Their capacity for independent long‑chain‑fatty‑acid‑dependent methanogenesis may have profound implications for reassessing global methane‑emission budgets.

Acknowledgements

This research was supported by the National Natural Science Foundation of China (Grants 42230401, 42276139), the Science and Technology Innovation Action Plan of the Shanghai Science and Technology Commission (Grant 24HC2810200), the SJTU 2030 Initiative (Grant WH510244001), and the Ocean Negative Carbon Emission (ONCE) project.

Paper link:

[https://trebuchet.public.springernature.app/get_content/34c4967c](https://trebuchet.public.springernature.app/get_content/34c4967c)‑7cd4‑4e95‑ad20‑eefa908a75bd?utm_source=rct_congratemailt&utm_medium=email&utm_campaign=nonoa_20260915&utm_content=10.1038/s41564‑026‑02490‑5

Contributed by the SLOE Team