EMD-15990

Tomography
EMD-15990 Deposition: 20/10/2022
Map released: 21/12/2022
Last modified: 25/01/2023
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EMD-15990

cryo-tomogram of Ca. L. ossiferum protrusions

EMD-15990

Tomography
EMD-15990 Deposition: 20/10/2022
Map released: 21/12/2022
Last modified: 25/01/2023
Overview Sample Experiment Validation Volume Browser Additional data Links
Sample Organism: unidentified
Sample: Ca. L. ossiferum
Raw data: EMPIAR-11269

Deposition Authors: Rodrigues-Oliveira T, Wollweber F , Ponce-Toledo R, Xu J , Rittmann S, Klingl A, Pilhofer M , Schleper C
Actin cytoskeleton and complex cell architecture in an Asgard archaeon.
PUBMED: 36544020
DOI: doi:10.1038/s41586-022-05550-y
ISSN: 1476-4687
ASTM: NATUAS
Abstract:
Asgard archaea are considered to be the closest known relatives of eukaryotes. Their genomes contain hundreds of eukaryotic signature proteins (ESPs), which inspired hypotheses on the evolution of the eukaryotic cell1-3. A role of ESPs in the formation of an elaborate cytoskeleton and complex cellular structures has been postulated4-6, but never visualized. Here we describe a highly enriched culture of 'Candidatus Lokiarchaeum ossiferum', a member of the Asgard phylum, which thrives anaerobically at 20 °C on organic carbon sources. It divides every 7-14 days, reaches cell densities of up to 5 × 107 cells per ml and has a significantly larger genome compared with the single previously cultivated Asgard strain7. ESPs represent 5% of its protein-coding genes, including four actin homologues. We imaged the enrichment culture using cryo-electron tomography, identifying 'Ca. L. ossiferum' cells on the basis of characteristic expansion segments of their ribosomes. Cells exhibited coccoid cell bodies and a network of branched protrusions with frequent constrictions. The cell envelope consists of a single membrane and complex surface structures. A long-range cytoskeleton extends throughout the cell bodies, protrusions and constrictions. The twisted double-stranded architecture of the filaments is consistent with F-actin. Immunostaining indicates that the filaments comprise Lokiactin-one of the most highly conserved ESPs in Asgard archaea. We propose that a complex actin-based cytoskeleton predated the emergence of the first eukaryotes and was a crucial feature in the evolution of the Asgard phylum by scaffolding elaborate cellular structures.