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Peer-reviewedCC BYNature

Eukaryotes’ closest relatives are internally simple syntrophic peptidotrophic archaea

  • Hiroyuki Imachi1
  • Masaru Konishi Nobu2
  • Shun’ichi Ishii3
  • Hiroki Hashiguchi4
  • Yuga Hirakata5
  • Naoki Hosogi6
  • Tetsuro Ikuta3
  • Yuta Isaji7
  • Makoto Miyata8
  • Masayuki Miyazaki3
  • Yuki Morono3,9
  • Kazuyoshi Murata10,11
14 more authors
  • Satoshi Okada10,12,3
  • Akihiro Narita13
  • Miyuki Ogawara3
  • Satoshi Okada3
  • Yumi Saito3
  • Sanae Sakai3
  • Shigeru Shimamura3
  • Yuhei O. Tahara8
  • Yoshihiro Takaki3
  • Yoshinori Takano7
  • Eiji Tasumi3
  • Katsuyuki Uematsu14
  • Toshihiro Yoshimura7
  • Ken Takai10,3
14 affiliations
  1. 1Institute for Extra-cutting-edge Science and Technology Avant-garde Research of Life (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan. [email protected]
  2. 2Institute for Extra-cutting-edge Science and Technology Avant-garde Research of Life (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan. [email protected]
  3. 3Institute for Extra-cutting-edge Science and Technology Avant-garde Research of Life (X-star), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
  4. 4EM Application Department, EM Business Unit, SI Business Operations, JEOL, Akishima, Japan
  5. 5Biomanufacturing and Process Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
  6. 6EM Research and Development Department 2, EM Business Unit, SI Business Operations, JEOL, Akishima, Japan
  7. 7Biogeochemistry Research Center (BGC), JAMSTEC, Yokosuka, Japan
  8. 8Graduate School of Science, Osaka Metropolitan University, Osaka, Japan
  9. 9Kochi Institute for Core Sample Research, JAMSTEC, Nankoku, Japan
  10. 10Exploratory Research Center on Life and Living Systems (ExCELLS), National Institute of Natural Sciences, Okazaki, Japan
  11. 11National Institute for Physiological Sciences, Okazaki, Japan
  12. 12Graduate School of Agriculture, Kyoto University, Kyoto, Japan
  13. 13Graduate School of Science, Nagoya University, Nagoya, Japan
  14. 14Department of Marine and Earth Sciences, Marine Work Japan, Yokosuka, Japan
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Abstract

Eukaryotes are theorized to have originated from an archaeal phylum Promethearchaeota (formerly ‘Asgard’ archaea) 1,2 . The first cultured representatives revealed valuable insight 3,4 but are distantly related to the first eukaryotic common ancestor (FECA), leaving many unknowns regarding this archaeon’s biology. Here, we report isolation of two strains belonging to the order proposed as FECA’s closest relative, ‘Hodarchaeales’, 5 as members of a pure co- and tri-culture with methanogenic partners. Both are obligately anaerobic, syntrophic, peptide-degrading, and mesophilic archaea that have simple internal cell structure and produce protrusions and vesicles, like Promethearchaeales 3,4 . All strains demonstrate behavior focused on cell construction rather than division, unlike typical prokaryotes 6 . Strain HC1 possesses genes associated with aerobic lifestyles but lacks complete pathways for aerobic respiration and co-cultures cannot grow under (micro)aerobic conditions, suggesting the genes support oxygen detoxification rather than respiration. Reflecting this, HC1 can survive and grow under microaerobic conditions only when aerobic organisms are present. Phylogenetic analyses indicate FECA may have possessed these genes and thus some aerotolerance. Physiological, genomic, and phylogenetic observations indicate FECA was a simple-celled anaerobic syntrophic peptide-degrading archaeon with a non-growth-centric lifestyle and potential adaptations towards an oxygenated planet—the archaea-eukaryote transition was steep in both cell structure and aerobiosis.

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Cite

BibTeXRIS
BibTeX
@article{imachi2026eukaryotes,
  title = {{Eukaryotes’ closest relatives are internally simple syntrophic peptidotrophic archaea}},
  author = {Hiroyuki Imachi and Masaru Konishi Nobu and Shun’ichi Ishii and Hiroki Hashiguchi and Yuga Hirakata and Naoki Hosogi and Tetsuro Ikuta and Yuta Isaji and Makoto Miyata and Masayuki Miyazaki and Yuki Morono and Kazuyoshi Murata and Satoshi Okada and Akihiro Narita and Miyuki Ogawara and Satoshi Okada and Yumi Saito and Sanae Sakai and Shigeru Shimamura and Yuhei O. Tahara and Yoshihiro Takaki and Yoshinori Takano and Eiji Tasumi and Katsuyuki Uematsu and Toshihiro Yoshimura and Ken Takai},
  journal = {Nature},
  year = {2026},
  month = oct,
  doi = {10.1038/s41586-026-11170-7},
  url = {https://doi.org/10.1038/s41586-026-11170-7},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Eukaryotes’ closest relatives are internally simple syntrophic peptidotrophic archaea
AU  - Hiroyuki Imachi
AU  - Masaru Konishi Nobu
AU  - Shun’ichi Ishii
AU  - Hiroki Hashiguchi
AU  - Yuga Hirakata
AU  - Naoki Hosogi
AU  - Tetsuro Ikuta
AU  - Yuta Isaji
AU  - Makoto Miyata
AU  - Masayuki Miyazaki
AU  - Yuki Morono
AU  - Kazuyoshi Murata
AU  - Satoshi Okada
AU  - Akihiro Narita
AU  - Miyuki Ogawara
AU  - Satoshi Okada
AU  - Yumi Saito
AU  - Sanae Sakai
AU  - Shigeru Shimamura
AU  - Yuhei O. Tahara
AU  - Yoshihiro Takaki
AU  - Yoshinori Takano
AU  - Eiji Tasumi
AU  - Katsuyuki Uematsu
AU  - Toshihiro Yoshimura
AU  - Ken Takai
PY  - 2026
DA  - 2026/10/28
JO  - Nature
DO  - 10.1038/s41586-026-11170-7
UR  - https://doi.org/10.1038/s41586-026-11170-7
AB  - Eukaryotes are theorized to have originated from an archaeal phylum Promethearchaeota (formerly ‘Asgard’ archaea) 1,2 . The first cultured representatives revealed valuable insight 3,4 but are distantly related to the first eukaryotic common ancestor (FECA), leaving many unknowns regarding this archaeon’s biology. Here, we report isolation of two strains belonging to the order proposed as FECA’s closest relative, ‘Hodarchaeales’, 5 as members of a pure co- and tri-culture with methanogenic partners. Both are obligately anaerobic, syntrophic, peptide-degrading, and mesophilic archaea that have simple internal cell structure and produce protrusions and vesicles, like Promethearchaeales 3,4 . All strains demonstrate behavior focused on cell construction rather than division, unlike typical prokaryotes 6 . Strain HC1 possesses genes associated with aerobic lifestyles but lacks complete pathways for aerobic respiration and co-cultures cannot grow under (micro)aerobic conditions, suggesting the genes support oxygen detoxification rather than respiration. Reflecting this, HC1 can survive and grow under microaerobic conditions only when aerobic organisms are present. Phylogenetic analyses indicate FECA may have possessed these genes and thus some aerotolerance. Physiological, genomic, and phylogenetic observations indicate FECA was a simple-celled anaerobic syntrophic peptide-degrading archaeon with a non-growth-centric lifestyle and potential adaptations towards an oxygenated planet—the archaea-eukaryote transition was steep in both cell structure and aerobiosis.
SN  - 0028-0836
SN  - 1476-4687
ER  -