A single archaeon couples long-chain fatty acid oxidation to methanogenesis.

A thermophilic archaeon can directly degrade saturated and unsaturated fatty acids into methane, challenging the idea that methanogenesis requires syntrophic cooperation.

• Why it matters: Understanding how complex organic compounds are converted to methane in deep subsurface environments is crucial for models of global carbon cycling and energy flow, but experimental validation of direct fatty acid methanogenesis was lacking.
• What they did: The study isolated Methanoglobus dolicholipophagus AA-75 from a petroleum reservoir and demonstrated its ability to produce methane from fatty acids ranging from C7:0 to C18:0 and certain unsaturated fatty acids, using lipotrophic methanogenesis involving β-oxidation and the Wood-Ljungdahl pathway.
• The result: Methane from stearate was moderately 13 C-enriched, indicating a distinct pathway from canonical methanogenesis, which suggests methanogens can serve as primary degraders of complex organic matter, revising current models of deep biosphere carbon cycling.