Aix Marseille Université, CNRS, IGS, Information Génomique & Structurale (UMR7256), Institut de Microbiologie de la Méditerranée (FR 3489), Marseille, France
Aix Marseille Université, CNRS, IGS, Information Génomique & Structurale (UMR7256), Institut de Microbiologie de la Méditerranée (FR 3489), Marseille, France.
J Virol. 2020 Mar 31;94(8). doi: 10.1128/JVI.01997-19.
Microbes trapped in permanently frozen paleosoils (permafrost) are the focus of increasing research in the context of global warming. Our previous investigations led to the discovery and reactivation of two -infecting giant viruses, and , from a 30,000-year old permafrost layer. While several modern pithovirus strains have since been isolated, no contemporary mollivirus relative was found. We now describe , a close relative to , isolated from surface soil sampled on the bank of the Kronotsky River in Kamchatka, Russian Federation. This discovery confirms that molliviruses have not gone extinct and are at least present in a distant subarctic continental location. This modern isolate exhibits a nucleocytoplasmic replication cycle identical to that of Its spherical particle (0.6 μm in diameter) encloses a 648-kb GC-rich double-stranded DNA genome coding for 480 proteins, of which 61% are unique to these two molliviruses. The 461 homologous proteins are highly conserved (92% identical residues, on average), despite the presumed stasis of for the last 30,000 years. Selection pressure analyses show that most of these proteins contribute to virus fitness. The comparison of these first two molliviruses clarify their evolutionary relationship with the pandoraviruses, supporting their provisional classification in a distinct family, the , pending the eventual discovery of intermediary missing links better demonstrating their common ancestry. Virology has long been viewed through the prism of human, cattle, or plant diseases, leading to a largely incomplete picture of the viral world. The serendipitous discovery of the first giant virus visible under a light microscope (i.e., >0.3 μm in diameter), mimivirus, opened a new era of environmental virology, now incorporating protozoan-infecting viruses. Planet-wide isolation studies and metagenome analyses have shown the presence of giant viruses in most terrestrial and aquatic environments, including upper Pleistocene frozen soils. Those systematic surveys have led authors to propose several new distinct families, including the , , , , and We now propose to introduce one additional family, the , following the description of , the first modern relative of , previously isolated from 30,000-year-old arctic permafrost.
微生物被困在永久性冻结的古土壤（永久冻土）中，这是在全球变暖背景下日益受到关注的研究焦点。我们之前的研究导致了两个感染性巨型病毒的发现和复活， 和 ，来自 30000 年前的永久冻土层。虽然此后已经分离出几种现代 pithovirus 株，但没有发现当代 mollivirus 相关病毒。我们现在描述了 ，一种与 密切相关的病毒，从俄罗斯联邦堪察加半岛克罗诺茨基河岸边的表层土壤中分离出来。这一发现证实了 molliviruses 并未灭绝，至少在遥远的亚北极大陆地区仍然存在。这个现代分离株表现出与 相同的核质复制周期。它的球形颗粒（直径 0.6μm）包含一个 648kb 的富含 GC 的双链 DNA 基因组，编码 480 种蛋白质，其中 61%是这两种 molliviruses 所特有的。461 个同源蛋白高度保守（平均 92%相同的残基），尽管在过去的 30000 年中， 被认为是静止的。选择压力分析表明，这些蛋白质中的大多数都有助于病毒的适应性。对这两种 molliviruses 的比较阐明了它们与 pandoraviruses 的进化关系，支持它们在一个单独的家族中临时分类，等待最终发现更好地证明它们共同祖先的中间缺失环节。病毒学长期以来一直通过人类、牛或植物疾病的视角来看待，导致对病毒世界的了解非常不完整。第一个在光学显微镜下可见的巨型病毒（即直径>0.3μm）的偶然发现，即 mimivirus，开辟了环境病毒学的新时代，现在包括感染原生动物的病毒。全球范围的隔离研究和宏基因组分析表明，巨型病毒存在于大多数陆地和水生环境中，包括上更新世的冻结土壤。这些系统调查促使作者提出了几个新的不同家族，包括 、 、 、 和 。我们现在提议引入一个额外的家族， ，在描述了第一个从 30000 年前的北极永久冻土中分离出来的 之前现代相关病毒 之后。
