小柯机器人

奥地利维也纳大学Christa Schleper等研究人员合作揭示阿斯加德古菌的肌动蛋白细胞骨架和复杂的细胞结构。相关论文于2022年12月21日在线发表于国际学术期刊《自然》。

研究人员报道了一种高度富集的“Lokiarchaeum ossiferum”的培养物，它是阿斯加德门的一个成员，在20℃的有机碳源上厌氧生长。它每7-14天分裂一次，细胞密度达到每毫升5×10⁷个。与以前培养的单一阿斯加德菌株相比，它的基因组明显更大。真核细胞特征蛋白（ESP）占其蛋白质编码基因的5%，包括四个肌动蛋白同源物。研究人员用低温电子断层扫描对富集培养物进行了成像，确定了“Ca. L. ossiferum”的细胞，以其核糖体的特征扩展段为基础。细胞表现出球状的细胞体和带有频繁收缩的分支突起的网络。细胞包膜由一个单一的膜和复杂的表面结构组成。一个长距离的细胞骨架延伸到整个细胞体、突起和收缩处。细丝的扭曲的双链结构与F-肌动蛋白一致。免疫染色表明，这些细丝包括Lokiactin，即阿斯加德古菌中最高度保守的ESP之一。

研究人员提出，复杂的基于肌动蛋白的细胞骨架早于第一个真核生物的出现，并且是阿斯加德门演化过程中的一个重要特征，它为复杂的细胞结构提供了支架。

据了解，阿斯加德古菌被认为是已知的最接近真核生物的亲属。它们的基因组含有数百种ESP，这激发了人们对真核细胞演化的假说。ESP在精心设计的细胞骨架和复杂的细胞结构的形成中的作用已被推测出来，但从未被可视化。

附：英文原文

Title: Actin cytoskeleton and complex cell architecture in an Asgard archaeon

Author: Rodrigues-Oliveira, Thiago, Wollweber, Florian, Ponce-Toledo, Rafael I., Xu, Jingwei, Rittmann, Simon K.-M. R., Klingl, Andreas, Pilhofer, Martin, Schleper, Christa

Issue&Volume: 2022-12-21

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 cell1,2,3. A role of ESPs in the formation of an elaborate cytoskeleton and complex cellular structures has been postulated4,5,6, 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 7–14days, 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.

DOI: 10.1038/s41586-022-05550-y

Source: https://www.nature.com/articles/s41586-022-05550-y

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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