[B-CG07] 岩石生命相互作用とその応用

[BCG07-08] Genome-resolved metaproteogenomic and nanosolid characterizations of an inactive vent chimney dominated by enigmatic DPANN archaea

*鈴木 庸平¹、幸塚 麻里子¹ (1.東京大学大学院理学系研究科)

Recent successes in the cultivation of DPANN archaea with their hosts have demonstrated an episymbiotic lifestyle, whereas the lifestyle of DPANN archaea in natural habitats is largely unknown. A free-living lifestyle is speculated in oxygen-deprived fluids circulated through rock media, where apparent hosts of DPANN archaea are lacking. Alternatively, DPANN archaea may be detached from their hosts and/or rock surfaces. To understand the ecology of rock-hosted DPANN archaea, rocks rather than fluids should be directly characterized. Here, we show the dominance of Pacearchaeota, one of the widespread and enigmatic lineages of DPANN archaea, in a deep-sea hydrothermal vent chimney without fluid venting. Metagenomic analysis of the inner chimney wall comprised of chalcopyrite (CuFeS₂) revealed a symbiotic lifestyle of the chimney Pacearchaeota, based on the lack of biosynthetic genes for nucleotides, amino acids, cofactors, and lipids. Genome-resolved metaproteomic analysis clarified the co-occurrence of bacteria actively fixing carbon and nitrogen and thermophilic archaea in the inner chimney wall. By spectroscopic methods using submicron soft X-ray and infrared beams, the habitat of these microbial pupulations was specified to silica-filled pores in the inner wall. Pacearchaeota has ecological advantages in the chimney interior where the colonization of small cells is preferable after the infilling of mineral pores by hydrothermal silica deposition.