Non-syntrophic methanogenic hydrocarbon degradation by an archaeal species

The methanogenic degradation of oil hydrocarbons can proceed through syntrophic partnerships of hydrocarbon-degrading bacteria and methanogenic archaea(1-3). However, recent culture-independent studies have suggested that the archaeon 'Candidatus Methanoliparum' alone can combine the degradation of long-chain alkanes with methanogenesis(4,5). Here we cultured Ca. Methanoliparum from a subsurface oil reservoir. Molecular analyses revealed that Ca. Methanoliparum contains and overexpresses genes encoding alkyl-coenzyme M reductases and methyl-coenzyme M reductases, the marker genes for archaeal multicarbon alkane and methane metabolism. Incubation experiments with different substrates and mass spectrometric detection of coenzyme-M-bound intermediates confirm that Ca. Methanoliparum thrives not only on a variety of long-chain alkanes, but also on n-alkylcyclohexanes and n-alkylbenzenes with long n-alkyl (C->= 13) moieties. By contrast, short-chain alkanes (such as ethane to octane) or aromatics with short alkyl chains (C-<= 12) were not consumed. The wide distribution of Ca. Methanoliparum(4-6) in oil-rich environments indicates that this alkylotrophic methanogen may have a crucial role in the transformation of hydrocarbons into methane.

Automated summary

Recent studies have shown that the archaeon 'Candidatus Methanoliparum' can independently degrade long-chain hydrocarbons and produce methane. This alkylotrophic methanogen is widely distributed in oil-rich environments and may play a crucial role in transforming hydrocarbons into methane.