Any of a diverse group of DNA viruses that have unusually large capsids, comparable in size with small bacteria, and contain large genomes. For example, Mimivirus, which infects a type of amoeba, is the largest known virus, measuring 600 nm in diameter, and has a genome size of roughly 1.2 Mb. Other NCLDVs include the phycodnaviruses (which infect algae), poxviruses, African swine fever virus, and iridoviruses, all of which infect metazoan animals. All are equipped with most of the genes needed for replication of their DNA and virion assembly: they either replicate in the cytoplasm of their host cells or pass to the cytoplasm after beginning their replication in the nucleus. The relationship of NCLDVs to the other kingdoms of life is contentious. Some regard their large genomes as evidence that NCLDVs have undergone reductive evolution from more complex cellular predecessors, and may represent ancestors of cellular life forms, whereas an alternative explanation is that they have acquired many of their genes by accretion from their hosts.
Subjects: Biological Sciences.