Partner 4 - Institut de Microbiologie de la Méditerranée - Achievements

Partner 4 - Dr. Jean-Michel Claverie & Hiroyuki Ogata, and team; CNRS UMR7256 - IGS, Marseille.

P4 focused on the analyses of genomes of major planktonic protists (Coccomyxa subellipsoidea, Emiliania huxleyi) and on the isolation and genomic investigation of giant DNA-viruses associated to marine protists (2 Pandoravirus, Phaeocystis globosa virus, 7 Emiliania huxleyi viruses, and Megavirus chilensis). This consisted in bioinformatics analysis of genome sequence data (assembly, finishing, annotation), fast phylogenetic methods for taxonomic assignment, and new statistical approaches to evidence virus/host co-occurrences from metagenomic data. Highlights for which the contribution of P4 was dominant includes:

  • The isolation and genomic characterization of the largest known species of Megaviridae: Megavirus chilensis, the analysis of which was instrumental to propose that these giant viruses evolved by genome reduction from an ancestral eukaryotic cell
  • The genomic characterization of a large DNA virus infecting the ubiquitous planktonic species Phaeocystis globosa, the analysis of which revealed that viruses of this family previously classified among the phycodnaviridae are in fact relative of the giant Megaviridae with which they establish a continuity in particle and genome size.
  • The discovery, genomic and proteomic characterization of a new family of giant DNA viruses that is so different from what is already known in term of virion structure, genome size and phylogenetic relationship, that it is questioning the standard theory about the unicity of the origin of cellular life on our planet.