Archaea Biology and Ecogenomics Division, University of Vienna, Vienna, Austria.
Center for Environmental Biotechnology, University of Tennessee, Knoxville, Tennessee, USA.
mBio. 2019 Sep 10;10(5):e02039-19. doi: 10.1128/mBio.02039-19.
The genomes of Asgard , a novel archaeal proposed superphylum, share an enriched repertoire of eukaryotic signature genes and thus promise to provide insights into early eukaryote evolution. However, the distribution, metabolisms, cellular structures, and ecology of the members within this superphylum are not well understood. Here we provide a meta-analysis of the environmental distribution of the Asgard archaea, based on available 16S rRNA gene sequences. Metagenome sequencing of samples from a salt-crusted lagoon on the Baja California Peninsula of Mexico allowed the assembly of a new and three genomes. Comparative analyses of all known and genomes revealed overlapping genome content, including central carbon metabolism. Members of both groups contained putative reductive dehalogenase genes, suggesting that these organisms might be able to metabolize halogenated organic compounds. Unlike the first report on , we identified genes encoding glycerol-1-phosphate dehydrogenase in all - and genomes, suggesting that these organisms are able to synthesize bona fide archaeal lipids with their characteristic glycerol stereochemistry. Microorganisms of the superphylum Asgard are considered to be the closest living prokaryotic relatives of eukaryotes (including plants and animals) and thus promise to give insights into the early evolution of more complex life forms. However, very little is known about their biology as none of the organisms has yet been cultivated in the laboratory. Here we report on the ecological distribution of Asgard and on four newly sequenced genomes of the and lineages that give insight into possible metabolic features that might eventually help to identify these enigmatic groups of archaea in the environment and to culture them.
古菌超门 Asgard 的基因组富含真核生物特征基因,有望为早期真核生物进化提供线索。然而,该超门成员的分布、代谢、细胞结构和生态尚未得到很好的理解。在这里,我们基于现有的 16S rRNA 基因序列,对古菌超门 Asgard 的环境分布进行了元分析。对来自墨西哥下加利福尼亚半岛盐壳泻湖的样本进行宏基因组测序,组装了一个新的 和三个 基因组。对所有已知的 和 基因组的比较分析显示,它们具有重叠的基因组内容,包括中心碳代谢。这两个组的成员都含有潜在的还原脱卤酶基因,表明这些生物体可能能够代谢卤代有机化合物。与关于 的第一份报告不同,我们在所有 - 和 基因组中鉴定出编码甘油-1-磷酸脱氢酶的基因,这表明这些生物体能够用其特征甘油立体化学合成真正的古菌脂质。Asgard 超门的微生物被认为是最接近真核生物(包括植物和动物)的原核生物,因此有望深入了解更复杂生命形式的早期进化。然而,由于这些生物体尚未在实验室中培养,因此对它们的生物学了解甚少。在这里,我们报告了 Asgard 的生态分布以及 和 谱系的四个新测序基因组,这些基因组为可能的代谢特征提供了深入的了解,最终可能有助于在环境中识别这些神秘的古菌群体并对其进行培养。
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