Asgard archaea capable of anaerobic hydrocarbon cycling

TLDR

Oceanic subsurface natural gas reservoirs host anaerobic microbial communities capable of hydrocarbon oxidation, including archaeal lineages. The study identifies the novel Asgard phylum Helarchaeota, which may oxidize hydrocarbons. Genomes of Helarchaeota were reconstructed from Guaymas Basin hydrothermal sediment metagenomes. Genomic analysis revealed methyl‑CoM reductase‑like enzymes and pathways for alkyl‑CoA oxidation and the Wood–Ljungdahl pathway, indicating Helarchaeota can anaerobically oxidize short‑chain hydrocarbons.

Abstract

Abstract Large reservoirs of natural gas in the oceanic subsurface sustain complex communities of anaerobic microbes, including archaeal lineages with potential to mediate oxidation of hydrocarbons such as methane and butane. Here we describe a previously unknown archaeal phylum, Helarchaeota, belonging to the Asgard superphylum and with the potential for hydrocarbon oxidation. We reconstruct Helarchaeota genomes from metagenomic data derived from hydrothermal deep-sea sediments in the hydrocarbon-rich Guaymas Basin. The genomes encode methyl-CoM reductase-like enzymes that are similar to those found in butane-oxidizing archaea, as well as several enzymes potentially involved in alkyl-CoA oxidation and the Wood-Ljungdahl pathway. We suggest that members of the Helarchaeota have the potential to activate and subsequently anaerobically oxidize hydrothermally generated short-chain hydrocarbons.