Euryarchaeal Viruses

The first archaeal virus, Hs1 infecting halophilic euryarchaeon Halobacterium species, was discovered in 1974 and now, over 45 years later, more than 110 euryarchaeal virus isolates are known, most of them discovered during the last 10 years. Euryarchaeal viruses form a diverse group of viruses differing in their virion morphologies, genome types, sequences, life cycles, and host ranges. Known virus isolates infect halophilic, methanogenic, or thermophilic members of the phylum Euryarchaeota . Their genomes are either linear or circular double-stranded or single-stranded DNA molecules. The majority of euryarchaeal viruses are halophilic and display icosahedral tailed morphology resembling bacteriophages of the order Caudovirales . Halophilic pleomorphic viruses discovered in 2009 form the second biggest group, assigned as the family Pleolipoviridae . In addition, icosahedral viruses with internal membrane ( Sphaerolipoviridae ), spindle-shaped ( Halspiviridae ) and spherical euryarchaeal viruses are known.