Archaeal diversity of Loki's Castle black smokers at the Arctic Mid-Ocean Ridge

Sampling

Hydrothermal vent systems harbor rich microbial communities ranging from aerobic mesophiles to anaerobic hyperthermophiles. Among these, members of the archaeal domain dominate the microbial communities in such extreme environments, partly because of their temperature- and mechanically-resistant membrane lipids. In this study, we use geochemical and molecular microbiological methods to investigate the abundance and diversity of archaea in black smoker chimneys from the newly discovered Loki's Castle hydrothermal vent field on the Arctic Mid-Ocean Ridge (AMOR) with vent fluid temperatures of 317°C and pH of 5.5. Archaeal glycerol dialkyl glycerol tetraether lipids (GDGTs) with 0 to 4 cyclopentane moieties were dominant in all sulfide samples and are most likely derived from both (hyper)thermophilic Euryarchaeota and Crenarchaeota, which are presumably involved in sulfur and iron reduction, as well as methanogenesis. GDGTs with an additional covalent bond between the isoprenoid hydrocarbon chains, so-called H-shaped GDGTs and also containing 0 to 4 cyclopentane rings, were present with similar abundances. These lipids are not often reported, but may be derived from sulfur-reducing members of the Thermococcaceae. Crenarchaeol has been detected in samples derived from the chimney exterior indicating the presence of Thaumarchaeota, involved in ammonia-oxidation (AOA) at lower ambient temperatures. Our observations based on 16S rDNA-based taxonomy and biomarker lipid analysis provide insight into microbial communities thriving within the porous sulfide structures of an active deep-sea hydrothermal vent, where microbial cycling of sulfur, hydrogen and methane predominantly by archaea may be the prevailing biogeochemical processes.

Method steps

1. Pipeline used: https://www.ebi.ac.uk/metagenomics/pipelines/4.1