Résumé : Invité par Bénédicte Michel, équipe Stabilité de l’ADN bactérien
Lieu : Auditorium - Bâtiment 21, campus de gif
Résumé : The last decade witnessed the discovery of four families of giant viruses infecting Acanthamoeba. They have genome encoding from 500 to 2000 genes, a large fraction of which encoding proteins of unknown origin. These unique proteins meant to recognize and manipulate the same building blocks as cells raise the question on their origin as well as the role viruses played in the cellular word evolution. The Mimiviridae and the Pandoraviridae are increasingly populated by members from very diverse habitats and are ubiquitous on the planet. The two other families were first isolated from a 30,000 years old permafrost sample and were named Pithovirus and Mollivirus sibericum. While we know that at least one modern relative of Pithovirus was spotted decade ago in Acanthamoeba cells, to date there is only one representative of the Molliviridae family. The study of their replicative cycle in their common host revealed a common strategy to infect Acanthamoeba, beginning with the spectacular opening of the virions followed by a fusion with the membrane of the host vacuole. Then the various giant virus families exhibit either cytoplasmic or nucleocytoplasmic replication cycles with a gradation in their dependency to the host nucleus. I will describe their respective cycles as observed by electron microscopy in the light of the viral and host protein expression dynamic. Giant viruses thus present very diverse physiologies, not correlated with virion’s morphologies and genome complexities.
Lieu : Auditorium - Bâtiment 21, campus de Gif