25126:2ba61e4a-a911-483b-ba5e-e0ad8afd3b38
Anaerobic ethane oxidation by archaea in the Guaymas Basin
Cold seeps and hydrothermal vents deliver large amounts of gaseous alkanes into marine surface sediments. Consortia of archaea and partner bacteria thrive on the oxidation of these alkanes and its coupling to sulfate reduction. The inherently slow growth of the involved organism and the lack of pure cultures have impeded the understanding of the molecular mechanisms of alkane degradation. Here, we established two enrichments at two different temperatures (37 and 50 °C) using hydrothermal sediments of the Guaymas Basin (Gulf of California) and ethane as substrate. Both of them contain microbial consortia dominated by the novel ethane oxidizer Candidatus Ethanoperedens thermophilum (GoM-Arc1 clade) and the partner bacterium Candidatus Desulfofervidus auxilii. To study the 50°C enrichment in relation to the original environment, we performed 16S amplicon sequencing for bacteria and archaea in the 50 °C enrichment, the original sediment and sediment samples incubated with methane or no substrate. Additionally, DNA from the 37 and 50°C cultures was sequenced with Pacbio technology. The low strain diversity in this culture allowed retrieving a closed genome of Ca. E. thermophilum. Its genome contains a highly divergent methyl-coenzyme M reductase (MCR), which is highly expressed according to transcriptomic data obtained from triplicates of the 50°C enrichment.