Hot crenarchaeal viruses reveal deep evolutionary connections.

The discovery of archaeal viruses provides insights into the fundamental biochemistry and evolution of the Archaea. Recent studies have identified a wide diversity of archaeal viruses within the hot springs of Yellowstone National Park and other high-temperature environments worldwide. These viruses are often morphologically unique and code for genes with little similarity to other known genes in the biosphere, a characteristic that has complicated efforts to trace their evolutionary history. Comparative genomics combined with structural analysis indicate that spindle-shaped virus lineages might be unique to the Archaea, whereas other icosahedral viruses might share a common lineage with viruses of Bacteria and Eukarya. These studies provide insights into the evolutionary history of viruses in all three domains of life. [ABSTRACT FROM AUTHOR]