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Updated: May 23, 2026

Single Cell Micro-aspiration as an Alternative Strategy to Fluorescence-activated Cell Sorting for Giant Virus Mixture Separation
Published on: October 27, 2019
Genomics of Megavirus and the elusive fourth domain of Life
Matthieu Legendre1, Defne Arslan, Chantal Abergel
1Information Génomique et Structurale; Centre National de la Recherche Scientifique-Unité Propre de Recherche 2589; Aix-Marseille University; Institut de Microbiologie de la Méditerranée; Parc Scientifique de Luminy; Case 934; Marseille, France.
Abstract:
We recently described Megavirus chilensis, a giant virus isolated off the coast of Chile, also replicating in fresh water acanthamoeba. Its 1,259,197-bp genome encodes 1,120 proteins and is the largest known viral genome. Megavirus and its closest relative Mimivirus only share 594 orthologous genes, themselves sharing only 50% of identical residues in average. Despite this divergence, comparable to the maximal divergence exhibited by bacteria within the same division (e.g., gamma proteobacteria), Megavirus retained all of the genomic features unique to Mimivirus, in particular its genes encoding key-elements of the translation apparatus, a trademark of cellular organisms. Besides homologs to the four aminoacyl-tRNA synthetases (aaRS) encoded by Mimivirus, Megavirus added three additional ones, raising the total of known virus-encoded aaRS to seven: IleRS, TrpRS, AsnRS, ArgRS, CysRS, MetRS, TyrRS. This finding strongly suggests that large DNA viruses derived from an ancestral cellular genome by reductive evolution. The nature of this cellular ancestor remains hotly debated.
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