Giant Irises

The term 'giant virus' was coined in the late 1990s to describe chloroviruses of the family Phycodnaviridae, which were found to have unusually large genomes. The term was further cemented in scientific literature after the characterization of Acanthamoeba polyphaga Mimivirus (APMV) in 2003 and its genetic sequencing in 2004 that revealed its genome was 1.2 million base pairs long, larger than the sequenced genomes of many bacteria. It was initially discovered in 1992 infecting Acanthamoeba polyphaga and mistakenly identified as a gram-positive bacteria. The emerging concept of the 'giant' virus led to the term 'girus' being coined to refer to the group in 2006. In 2008, the first…

While the exact criteria used in the scientific literature varies, giant viruses are usually defined as those with virions larger than 200-300 nanometers in their smallest dimension (making them visible by light microscopy) and a genome size greater than 200-300 kb pairs. All known giant viruses belong to the Nucleocytoviricota, the nucleocytoplasmic large DNA viruses, meaning they are known to replicate in both the host cell nucleus and cytoplasm, and have large, double-stranded DNA genomes. Although all giant viruses belong to this phylum, they are not a monophyletic group, as some members of the Nucleocytoviricota, such as the genus Prasinovirus, are not giant viruses. The large genomes…