mimivirus

Mimivirus is a giant virus, one of the largest known viruses by genome size and capsid diameter. Discovered in 2003 in a cooling tower in Amiens, France, it was initially mistaken for a bacterium due to its large size. Mimivirus belongs to the Mimiviridae family.

This virus is characterized by its exceptionally large, icosahedral capsid, measuring approximately 750 nanometers in diameter. Inside this capsid, it houses a genome of double-stranded DNA, which is also unusually large for a virus, containing around 1.2 million base pairs. This extensive genome encodes for over 900 proteins, including many genes previously thought to be exclusive to cellular organisms, such as genes involved in amino acid synthesis and translation.

Mimivirus infects amoebae, particularly species of Acanthamoeba. Its replication cycle occurs within the cytoplasm of the host cell, a departure from the typical nuclear replication of many DNA viruses. The discovery of mimivirus and other giant viruses has challenged traditional definitions of viruses and blurred the lines between viruses and cellular life, prompting new research into viral evolution and the origins of life. Mimivirus is part of a group of viruses now referred to as nucleocytoplasmic large DNA viruses (NCLDVs).