Iridoviridae

Iridoviridae is a family of viruses with double-stranded DNA genomes. Amphibia, fish, invertebrates, lepidoptera, and orthoptera insects serve as natural hosts. There are currently 12 species in this family, divided among two subfamilies and 5 genera. Iridoviridae is a family of viruses with double-stranded DNA genomes. Amphibia, fish, invertebrates, lepidoptera, and orthoptera insects serve as natural hosts. There are currently 12 species in this family, divided among two subfamilies and 5 genera. The name is derived from Iris the Greek goddess of the rainbow. This name was chosen because of the 'rainbow-like' iridescence observed in heavily infected insects and pelleted samples of invertebrate iridoviruses.It may refer to any member of the Iridoviridae family or a particular genus within Iridoviridae. Group: dsDNA Other species include the shrimp haemocyte iridescent virus. The virions are icosahedral with triangulation number (T) = 189–217, 120–350 nm in diameter and made up of three domains: an outer proteinaceous capsid, an intermediate lipid membrane, and a central core containing DNA-protein complexes. Some of the viruses also have an outer envelope. The presence or absence of an envelope depends on whether they budded from the cell membrane (enveloped viruses) or were arranged in paracrystalline arrays within the host cell cytoplasm and then were released by cell lysis (unenveloped viruses). The linear genome varies between 150 and 303 kilobases in length. It contains terminal and redundant sequences and is circularly permuted. Members of this family differ in their degree of genome methylation. The genera Chloriridovirus and Iridovirus lack a highly methylated genome. Members of the Lymphocystivirus, Megalocytivirus, and Ranavirus genera have genomes with about 25% of their cytosine residues methylated by a virally encoded DNA methyltransferase. Similar to the herpes viruses, transcription occurs in three stages: immediate-early, delayed-early, and late. Positive induction and negative feedback mechanisms exist in each stage, mediated by products of the other stages.