Isolation Of An archaeon At The Prokaryote-Eukaryote Interface

The origin of eukaryotes remains enigmatic. Current data suggests that eukaryotes may have risen from an archaeal lineage known as “Asgard archaea”.

Despite the eukaryote-like genomic features found in these archaea, the evolutionary transition from archaea to eukaryotes remains unclear due to the lack of cultured representatives and corresponding physiological insight. Here we report the decade-long isolation of a Lokiarchaeota-related Asgard archaeon from deep marine sediment. The archaeon, “Candidatus Prometheoarchaeum syntrophicum strain MK-D1”, is an anaerobic, extremely slow-growing, small cocci (∼550 nm), that degrades amino acids through syntrophy.

Although eukaryote-like intracellular complexities have been proposed for Asgard archaea, the isolate has no visible organella-like structure. Ca. P. syntrophicum instead displays morphological complexity – unique long, and often, branching protrusions. Based on cultivation and genomics, we propose an “Entangle-Engulf-Enslave (E3) model” for eukaryogenesis through archaea-alphaproteobacteria symbiosis mediated by the physical complexities and metabolic dependency of the hosting archaeon.

Hiroyuki Imachi, Masaru K. Nobu, Nozomi Nakahara, Yuki Morono, Miyuki Ogawara, Yoshihiro Takaki, Yoshinori Takano, Katsuyuki Uematsu, Tetsuro Ikuta, Motoo Ito, Yohei Matsui, Masayuki Miyazaki, Kazuyoshi Murata, Yumi Saito, Sanae Sakai, Chihong Song, Eiji Tasumi, Yuko Yamanaka, Takashi Yamaguchi, Yoichi Kamagata, Hideyuki Tamaki, Ken Takai
doi: https://doi.org/10.1101/726976
This article is a preprint and has not been certified by peer review
https://www.biorxiv.org/content/10.1101/726976v2
Astrobiology