Mimivirus is one of the largest and most complex viruses known. The virus was first isolated in 1992 from amoebae growing in a water tower in Bradford. La Scola, B. et al. (2003) A giant virus in amoebae. Science 299: 2033.
Both the particle size and the genome size of mimivirus is larger than that of some small bacteria. The 1.2 Mbp genome, which contains 911 protein coding genes, provides sufficient information to allow the virus to perform most (but not quite all) of the functions of living cells. The complexity and magnitude of the Mimivirus genome, combined with the large size of the virus, calls into question some of the established divisions between viruses and single-celled organisms, as well as raising questions about their evolution. Suzan-Monti M. (2005) Genomic and evolutionary aspects of Mimivirus. Virus Res.
