Mimivirus

Mimivirus is a viral genus containing a single identified species named Acanthamoeba polyphaga mimivirus (APMV), or is a group of phylogenetically related large viruses (designated usually MimiN). In colloquial speech, APMV is more commonly referred to as just "mimivirus". Until October 2011, when a larger virus Megavirus chilensis was described, it had the largest capsid diameter of all known viruses. Mimivirus has a large and complex genome compared with most other viruses. Mimivirus, short for "mimicking microbe", is so called to reflect its large size and apparent Gram-staining properties.

Read more about Mimivirus:  Discovery, Classification, Structure, Genome, Replication, Implications For Defining "life"