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Spindle shaped4/8/2023 Recently, we refined the evolutionary relationships among spindle-shaped viruses by assessing the morphological and genomic diversity of all available isolates infecting hosts belonging to phylogenetically distant archaeal lineages, including Thermococcales, Methanococcales, Desulfurococcales, and Sulfolobales ( 11). Among the morphotypes that are exclusively associated with archaea, spindle-shaped viruses are particularly widespread ( 11) and have been isolated from highly different environments, including deep-sea hydrothermal vents ( 12 – 14), hypersaline environments ( 15 – 18), anoxic freshwaters ( 19), cold Antarctic lakes ( 20), terrestrial hot springs ( 21 – 23), and acidic mines ( 24). Functional studies proved to be highly challenging due to the lack of similarity between the protein sequences and structures of archaeal viruses and those from other viruses and cellular organisms ( 6 – 10). Indeed, 11 novel viral families have been established by the International Committee for the Taxonomy of Viruses (ICTV) for the classification of archaeal viruses, emphasizing the uniqueness of rod-shaped, spindle-shaped, droplet-shaped, or even bottle-shaped particles that have never been observed among viruses infecting bacteria or eukaryotes ( 3). Remarkably, most of these viruses do not seem to be evolutionarily related to viruses of bacteria or eukaryotes and display a considerable diversity of unique virion morphotypes ( 3, 4). Viruses infecting extremophilic archaea have evolved to withstand very high temperatures, low or high pH, or near-saturating salt concentrations ( 1 – 5). A comparison of the contents of lipids isolated from the virus and its host cell suggests that GDGTs are acquired by the virus in a selective manner from the host cytoplasmic membrane, likely during progeny egress. Finally, we provide evidence indicating that SSV1 virions contain glycerol dibiphytanyl glycerol tetraether (GDGT) lipids, resolving a long-standing debate on the presence of lipids within SSV1 virions. In addition to the viral DNA-binding protein VP2, we show that viral particles contain the Sulfolobus solfataricus chromatin protein Sso7d. The virion proteins VP1, VP3, and VP4 undergo posttranslational modification by glycosylation, seemingly at multiple sites. Here, we have conducted an extensive biochemical characterization of highly purified SSV1 virions and identified four virus-encoded structural proteins, VP1 to VP4, as well as one DNA-binding protein of cellular origin. ![]() SSV1 is an attractive model for understanding virus-host interactions in Archaea however, the constituents and architecture of SSV1 particles remain only partially characterized. Sulfolobus spindle-shaped virus 1 (SSV1) is the best known member of the family and was one of the first hyperthermophilic archaeal viruses to be isolated. The larger of the two families, the Fuselloviridae, comprises tail-less, spindle-shaped viruses, which infect hosts from phylogenetically distant archaeal lineages. Currently, viruses with spindle- or lemon-shaped virions are exclusive to Archaea and belong to two distinct viral families. All rights reserved.Geothermal and hypersaline environments are rich in virus-like particles, among which spindle-shaped morphotypes dominate. ![]() Published by Houghton Mifflin Harcourt Publishing Company. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. The American Heritage® Student Science Dictionary, Second Edition.
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