The Effect of Selective Pressure on Mimivirus Ability to Infect Human Cells

One of the largest viruses on Earth has been found in human cells and this is how it might have happened.

Until recently, the potential size of a virus was assumed much smaller than even the smallest bacterium. Nothing larger had been found, and nothing with a genome size that even came close to comparing had been discovered. Viral diversity, however, was and still is grossly underestimated. In 1992, isolates of the amoeba Acanthamoeba polyphaga revealed an unusual particle that stained gram-positively, and was initially though to be a bacterium. It was called Bradfordcoccus until 2003, when a team of scientists at the Université de la Méditerranée identified the organism as mimivirus. Until the later discovery of even larger viruses, such as Cafeteria roenbergensis, it was thought to be the largest virus in existence and even today blurs the lines between viruses and intracellular parasites (3).

Mimivirus, also known as Acanthamoeba polyphaga mimivirus (APMV), was initially discovered primarily as a pathogen of amoebas. It was discovered in Acanthamoeba polyphaga while searching for Legionella bacteria, the causative agent of legionellosis, in cooling systems of air-conditioning (6). Mimivirus was initially thought to be a small bacterium due to its size, but was later found to be a massive…