oa A SINGLE ARCHAEON COUPLES HYDROCARBON DEGRADATION TO METHANOGENESIS

Methanogenic hydrocarbon degradation is the dominant biodegradation process in crude oil, and so far was described for syntrophic associations of hydrocarbon-degrading bacteria and methanogenic archaea. Recent culture-independent studies suggest that the archaeon ‘Candidatus Methanoliparum’ performs both reactions, involving alkyl-coenzyme M reductases for the activation of alkanes and canonical methyl coenzyme M reductases for methane formation. Here, we cultured ‘Ca. Methanoliparum’. Metatranscriptomics and isotope labelling experiments confirm the suggested pathway for the degradation of hexadecane to methane in this archaeon. Mass spectrometry identified CoM- bound intermediates for the activation of long-chain n-alkanes, n-alkylcyclohexanes and n-alkylbenzenes, showing the wide substrate range of this archaeon. The wide distribution of the ’Ca. Methanoliparum in reservoirs indicates that this alkylotrophic methanogen may play a vital role in the frequently observed transformation of reservoir oil constituents into methane,