Abstract
The family Bicaudaviridae includes viruses that infect hyperthermophilic archaea in the genus Acidianus. The circular double-stranded DNA genome of Acidianus two-tailed virus consists of 62 730 bp, and replication can be either lytic or lysogenic. Virions undergo unique extracellular morphogenesis, being released from host cells as spindle-shaped particles that subsequently develop long tails, one at each of the two pointed ends. The spindle-shaped morphology represents a group of archaea-specific virion morphotypes. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Bicaudaviridae which is available at www.ictv.global/report/bicaudaviridae.