第1282回 Giant viruses: the new frontier of virology | 京都大学 ウイルス・再生医科学研究所

京都大学 ウイルス・再生医科学研究所

第1282回 Giant viruses: the new frontier of virology

日時: 2018年3月9日 (金) 16:00 〜 17:30
場所: ウイルス再生研2号館(旧ウイルス研本館)1階 セミナー室
演者: Prof. Jean-Michel Claverie (Genomics and Bioinformatics, Aix-Marseille University School of Medicine, Director of the Mediterranean Institute of Microbiology of CNRS, France)
演題: Giant viruses: the new frontier of virology

講演要旨

More than a century ago, the notion of “virus” was introduced to designate infectious agents invisible to the light microscope and capable of passing through “sterilizing” filters. In addition to their extremely small size, most viruses studied over the years also exhibited minimal genomes and gene contents, almost entirely relying on cell-encoded functions to multiply, as expected from absolute intracellular parasites. Unexpectedly, the last ten years have seen the discovery of 4 different families of eukaryotic “giant viruses” exhibiting particles of cellular dimensions as well as gene contents overlapping in size with that of bacteria and some parasitic eukaryotes1-5. Although most presently known giant viruses have been isolated using Acanthamoeba as laboratory host, related members are now starting to be found in other protozoa, such as marine picoplankton species the populations of which they regulate. Representatives of two families of giant viruses have been revived from a layer of Siberian permafrost radiocarbon dated from 30.000 years ago, raising concern that pathogenic viruses from long past epidemics might also remain infectious and resurface in circumpolar regions as a consequence of global warming and industrial exploitations.

The unexpected abundance, ubiquity and diversity of giant viruses, as well as the alien nature of their gene contents deeply challenge conventional conceptions about the origin and evolution of all DNA viruses and raise the question of their evolutionary relationship with the cellular domains forming today’s Tree of Life, and possibly other long extinct cellular lineages.

I will conclude by discussing the nature of the epistemological barrier that delayed the discovery of the most easily visible viruses, most of which were spotted 10 year before their viral nature was eventually recognized6.

1) La Scola B, et al. (2003) Science. 2) Raoult D, et al. (2004) Science. 3) Philippe N, et al. (2013) Science. 4) Legendre M, et al. (2014) Proc Natl Acad Sci USA. 5) Legendre M, et al. (2015) Proc Natl Acad Sci USA. 6) Claverie JM, Abergel C. (2016) Stud Hist Philos Biol Biomed Sci.

Claverie博士は2003年に最初の“巨大”ウイルスであるミミウイルスを発見して以降、シベリアの永久凍土などの環境から多くの巨大ウイルスを発見し、その性状や進化を解析されています。巨大ウイルスの謎に迫る最新の研究成果についてお話をして頂きます。

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