#74: Meet the Megavirus


One day last year while boating off the coast of Chile, Jean-Michel Claverie hauled in his dream catch: the world’s largest virus. The scientist and his team at the Structural and Genomic Information Laboratory in France described the find in a paper last October as a “Megavirus.” With a body capsule measuring 440 nanometers across, Megavirus is 12 percent larger than the next-largest virus, the amoeba-infecting Mimivirus. Its record-setting girth also holds the longest known viral genome, with DNA that stretches for 1.26 million base pairs, and contains an estimated 1,120 protein-coding genes, 14 percent more than Mimivirus’s genome. Claverie thinks even more extreme microbes could be out there. “Viruses with twice that much DNA might turn up,” he says. “We have no idea of the limit.”