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Comment
. 2022 Jan 27:11:3.
doi: 10.12703/r-01-000005. eCollection 2022.

Origin of eukaryotes: What can be learned from the first successfully isolated Asgard archaeon

Sonja Albers  1 , Jonathan Ashmore  2 , Thomas Pollard  3 , Anja Spang  4 , Jizhong Zhou  5
Affiliations
Comment

Origin of eukaryotes: What can be learned from the first successfully isolated Asgard archaeon

Sonja Albers et al. Fac Rev. .

Abstract

The origin of cellular complexity characterizing eukaryotic cells remains a central unresolved issue in the study of diversification of cellular life on Earth. The isolation by Imachi et al.1 of a member of the Asgard archaea2 - a contemporary relative of organisms thought to have given rise to eukaryotic cells about 2 billion years ago - now promises new insight. The complete genome sequence of the isolated Lokiarchaeum strain confirms that the eukaryotic signature proteins (ESPs) previously identified in the Lokiarchaeota3 and other Asgard archaea2 are indeed encoded by these archaeal genomes and do not represent contamination from eukaryotes. These ESPs encode homologs of eukaryotic actins, small GTPases and the ESCRT complex proteins and are required for the functioning of complex eukaryotic cells. The new, slowly growing, anaerobic laboratory strain allows a first direct look at these organisms and provides key insights into the morphology and metabolism of an Asgard archaeal organism. The work has provided valuable information for other laboratories that aim to isolate and characterize related organisms from other environments.

Keywords: Archeon; Asgard archaea; Eukaryotes; MK-D1.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1. Tree of life
Schematic illustration of a simplified and hypothetical tree of life in which the first eukaryotic common ancestor is indicated to have emerged from a symbiosis of an Asgard archaeal host (purple arrow) and an alpha-proteobacterial symbiont (orange arrow). The last eukaryotic common ancestor stood at the root of all extant eukaryotic representatives. Candidatus Prometheoarchaeum syntrophicum MK-D1, which was isolated by Imachi et al., is depicted in red and represents the first cultivated representative of the Asgard archaea, though on a distinct branch of the tree from that of the proposed Lokiarchaeal eukaryotic ancestor, which belongs to the Heimdallarchaeota.
Figure 2
Figure 2. SEM image of strain MK-D1 of Candidatus Prometheoarchaeum syntrophicum
Credit: H. Imachi, M. K. Nobu, and JAMSTEC.
See this image and copyright information in PMC

Comment on

  • Isolation of an archaeon at the prokaryote-eukaryote interface.
    Imachi H, Nobu MK, Nakahara N, Morono Y, Ogawara M, Takaki Y, Takano Y, Uematsu K, Ikuta T, Ito M, Matsui Y, Miyazaki M, Murata K, Saito Y, Sakai S, Song C, Tasumi E, Yamanaka Y, Yamaguchi T, Kamagata Y, Tamaki H, Takai K. Imachi H, et al. Nature. 2020 Jan;577(7791):519-525. doi: 10.1038/s41586-019-1916-6. Epub 2020 Jan 15. Nature. 2020. PMID: 31942073 Free PMC article.

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    2. Faculty Opinions Recommendation

    1. Zaremba-Niedzwiedzka K, Caceres EF, Saw JH, Bäckström D, Juzokaite L, Vancaester E, Seitz KW, Anantharaman K, Starnawski P, Kjeldsen KU, Stott MB, Nunoura T, Banfield JF, Schramm A, Baker BJ, Spang A, Ettema TJG. 2017. Asgard archaea illuminate the origin of eukaryotic cellular complexity Nature 541:353–358. 10.1038/nature21031 - DOI - PubMed

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    2. Faculty Opinions Recommendation

    1. Spang A, Stairs C, Dombrowski N, Eme L, Lombard J, Cáceres EF, Greening C, Baker BJ, Ettema TJG. 2019. Proposal of the reverse flow model for the origin of the eukaryotic cell based on comparative analyses of Asgard archaeal metabolism Nat Microbiol 4:1138–1148. 10.1038/s41564-019-0406-9 - DOI - PubMed

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    2. Faculty Opinions Recommendation