Mimiviruses are double-stranded DNA with a genome size of approximately 1.2 million base pairs and 1018 protein coding genes including the new genes discovered recently. The Mimivirus genome is circular and belongs in the family Mimiviridae. Some scientists argue that the genome of Mimivirus is linear and NOT circular, however there were no sources confirming the conformation of the genome. Based on an electron microscope study, the virions are nonenveloped icosahedrons with a diameter of 400-750 nm (Kuznetsov, 2010). Atomic force microscopy (AFM) is an imaging method with capabilities of observing small microorganisms at a very high-resolution. This method was able to demonstrate the 20-icosahedral faces of the Mimivirus capsids (Xiao, 2009). The Mimivirus contains an 80 nm fibrils attached to the capsid and is classified as Baltimore classification I.
Mimivirus contains a coated layer of proteins on the icosahedral capsid that in some ways mimic the cell wall of Gram-positive bacteria. This protein coat was believed to be a concealment to fool the ameboid host into thinking that the virion is a bacterium, which causes the host to submit to eating its lunch (Claverie, 2009). Scientists believed that the outer protein coat may serve for another purpose.
This is a video depicting the Mimivirus viral genome capsid from youtube. Mimivirus has 20-icosahedral faces, 80 nm fibrils, 1018 protein genes (including the new genes discovered) and ~1.2 million base pairs.