Abstract
Viruses infect members of domains Bacteria, Eukarya, and Archaea. While those infecting domain Eukarya are nearly universally described as “Viruses”, those of domain Bacteria, to a substantial extent, instead are called “Bacteriophages,” or “Phages.” Should the viruses of domain Archaea therefore be dubbed “Archaeal phages,” “Archaeal viruses,” or some other construct? Here we provide documentation of published, general descriptors of the viruses of domain Archaea. Though at first the term “Phage” or equivalent was used almost exclusively in the archaeal virus literature, there has been a nearly 30-year trend away from this usage, with some persistence of “Phage” to describe “Head-and-tail” archaeal viruses, “Halophage” to describe viruses of halophilic Archaea, use of “Prophage” rather than “Provirus,” and so forth. We speculate on the root of the early 1980's transition from “Phage” to “Virus” to describe these infectious agents, consider the timing of introduction of “Archaeal virus” (which can be viewed as analogous to “Bacterial virus”), identify numerous proposed alternatives to “Archaeal virus,” and also provide discussion of the general merits of the term, “Phage.” Altogether we identify in excess of one dozen variations on how the viruses of domain Archaea are described, and document the timing of both their introduction and use.
Highlights
Most viruses infecting archaea have nothing in common with those infecting bacteria, they are still considered as “bacteriophages” by many virologists, just because archaea and bacteria are both prokaryotes. [1]
Used is “Archaebacteria” (“These results indicate that these halophages, the host of which is included among the archaebacteria. . .”)
It is possible that this combined novelty provided some basis for a change in perspective, that is, from describing these infectious agents of domain Archaea as “Phages” to instead describing them primarily as “Viruses.” In particular, the observation of virions that were not phage-like was suggestive of a kinship between the viruses of what would come to be known as domain Archaea and viruses that otherwise are described as “Viruses,” that is, eukaryotic viruses. Consistent with this perspective, though placing the date of the transition approximately ten years later than as indicated here, is this 2012 sentiment from Felisberto-Rodrigues et al [58]: viruses infecting archaea are known since the early 1970s [11], they have only been studied in detail very recently. The notion that these viruses constitute a variety of bacteriophages with head and tail (Caudovirales), reinforced by the initial findings, was challenged by the analyses of samples isolated by Zillig and coworkers from extreme environments, rich in hyperthermophilic archaea, including the Icelandic solfatara [59]
Summary
Most viruses infecting archaea have nothing in common with those infecting bacteria, they are still considered as “bacteriophages” by many virologists, just because archaea and bacteria are both prokaryotes (without nucleus). [1]. Archaea as well as the qualification “Archae-” or “Archaeal”—as in, for instance, “Archaeal virus”—is both logical and reasonable, echoing, for example, the fairly common usage of “Bacterial virus” as an alternative to “Bacteriophage” or “Phage.” For approximately half of the 40 or so years that these viruses have been studied, the explicit phrase “Archaeal virus” did not exist in the published literature The absence of this phrase prior to the early 1990s reflects the replacement only in 1990 of “Archaebacteria” [9] with “Archaea” [10] as a descriptor of this cellular group. In terms of the viruses associated with each of these domains, an obvious question was whether those infecting members of domain Archaea should retain the “Phage” designation or instead assume the more general term of “Virus.” Here we consider the history of this issue especially in terms of published usage, focusing on the relatively long transition from “Bacteriophage” to “Archaeal virus.”. In terms of the viruses associated with each of these domains, an obvious question was whether those infecting members of domain Archaea should retain the “Phage” designation or instead assume the more general term of “Virus.” Here we consider the history of this issue especially in terms of published usage, focusing on the relatively long transition from “Bacteriophage” to “Archaeal virus.” We consider overall usage as determined by examination of individual publications
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