Journal: Nature / Year: 2020 Title: Isolation of an archaeon at the prokaryote-eukaryote interface. Authors: Hiroyuki Imachi / Masaru K Nobu / Nozomi Nakahara / Yuki Morono / Miyuki Ogawara / Yoshihiro Takaki / Yoshinori Takano / Katsuyuki Uematsu / Tetsuro Ikuta / Motoo Ito / Yohei Matsui / ...Authors: 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 / Abstract: The origin of eukaryotes remains unclear. Current data suggest that eukaryotes may have emerged from an archaeal lineage known as 'Asgard' archaea. Despite the eukaryote-like genomic features that ...The origin of eukaryotes remains unclear. Current data suggest that eukaryotes may have emerged from an archaeal lineage known as 'Asgard' archaea. Despite the eukaryote-like genomic features that are found in these archaea, the evolutionary transition from archaea to eukaryotes remains unclear, owing to the lack of cultured representatives and corresponding physiological insights. Here we report the decade-long isolation of an Asgard archaeon related to Lokiarchaeota from deep marine sediment. The archaeon-'Candidatus Prometheoarchaeum syntrophicum' strain MK-D1-is an anaerobic, extremely slow-growing, small coccus (around 550 nm in diameter) that degrades amino acids through syntrophy. Although eukaryote-like intracellular complexes have been proposed for Asgard archaea, the isolate has no visible organelle-like structure. Instead, Ca. P. syntrophicum is morphologically complex and has unique protrusions that are long and often branching. On the basis of the available data obtained from cultivation and genomics, and reasoned interpretations of the existing literature, we propose a hypothetical model for eukaryogenesis, termed the entangle-engulf-endogenize (also known as E) model.
Cryogen name: ETHANE / Chamber humidity: 95 % / Chamber temperature: 277 K / Instrument: FEI VITROBOT MARK IV
Sectioning
Other: NO SECTIONING
Fiducial marker
Manufacturer: Sigma-Aldrich / Diameter: 15 nm
-
Electron microscopy
Microscope
JEOL 2200FS
Temperature
Min: 76.0 K / Max: 77.0 K
Specialist optics
Energy filter - Name: In-column Omega Filter / Energy filter - Slit width: 20 eV
Image recording
Film or detector model: DIRECT ELECTRON DE-20 (5k x 3k) / Digitization - Dimensions - Width: 5120 pixel / Digitization - Dimensions - Height: 3840 pixel / Digitization - Frames/image: 3-25 / Number grids imaged: 1 / Number real images: 63 / Average exposure time: 1.0 sec. / Average electron dose: 1.5 e/Å2
Electron beam
Acceleration voltage: 200 kV / Electron source: FIELD EMISSION GUN
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