The Wonderful World of Archaeal Viruses

Abstract

This review presents a personal account of research on archaeal viruses and describes many new viral species and families, demonstrating that viruses of Archaea constitute a distinctive part of the virosphere and display morphotypes that are not associated with the other two domains of life, Bacteria and Eukarya. I focus primarily on viruses that infect hyperthermophilic members of the phylum Crenarchaeota. These viruses' distinctiveness extends from their morphotypes to their genome sequences and the structures of the proteins they encode. Moreover, the mechanisms underlying the interactions of these viruses with their hosts also have unique features. Studies of archaeal viruses provide new perspectives concerning the nature, diversity, and evolution of virus-host interactions. Considering these studies, I associate the distinctions between bacterial and archaeal viruses with the fundamental differences in the envelope compositions of their host cells.

Structure and assembly mechanism of virus-associated pyramids

“…Irradiation with UV-light is a routine strategy to induce lysogenic viruses, which in archaea are commonly integrated into the host genome or exist as episomal genetic elements in the host cytoplasm (Prangishvili 2013). No viral particles were found after UVirradiation of P. oguniense.…”

“…A hallmark of archaeal viruses is the high morphological diversity of the capsids that enclose their genetic material Pina et al 2011;Prangishvili 2013;Dellas et al 2014). Even though viruses have only been isolated from a limited set of archaeal species, the high structural diversity of those isolated has led to the description of several new viral families (Pina et al 2011;Krupovic et al 2016;Adriaenssens et al 2017).…”

Evolution of viruses and cells: do we need a fourth domain of life to explain the origin of eukaryotes?

“…Likewise, the contribution of viruses to the evolution of fundamental characteristics of cellular organisms remains at best highly speculative (e.g. the origin of cell walls to protect from viral infection [89]) or, when submitted to phylogenetic analysis, simply unsupported (e.g. the viral origin of the DNA replication machinery of bacteria [47]).…”

Viral assemblage composition in Yellowstone acidic hot springs assessed by network analysis

“…These archaeal viruses comprise members originally isolated from high temperature environments (37 of the 67 viruses) and viruses not expected to be present in hot spring environments (30 mostly halophile viruses from mesophilic environments), such as those infecting members of the Euryarchaeota (for a review of archaeal viruses, see Prangishvili, 2013;Dellas et al, 2014). The vast majority of known viral genomes did not map to any of the network clusters (1786/1812).…”

“…These extreme environmental conditions favor not only the Archaea but also result in a relatively simplified microbial community structure. A number of viruses, exclusively archaeal, have been isolated out of these environments (Rice et al, 2001;Mochizuki et al, 2011;Pina et al, 2011;Prangishvili, 2013). These conditions offer a tractable system to study virus-host relationships, as well as viral and host community structure and stability.…”