Pacmanvirus isolated from the Lost City hydrothermal field extends the concept of transpoviron beyond the family Mimiviridae.

Abstract

The microbial sampling of submarine hydrothermal vents remains challenging, with even fewer studies focused on viruses. Here we report the first isolation of a eukaryotic virus from the Lost City hydrothermal field, by co-culture with the laboratory host Acanthamoeba castellanii. This virus, named pacmanvirus lostcity, is closely related to previously isolated pacmanviruses (strains A23 and S19), clustering in a divergent clade within the long-established family Asfarviridae. Its icosahedral particles are 200 nm in diameter, with an electron-dense core surrounded by an inner membrane. Its genome of 395 708 bp (33% G + C) is predicted to encode 473 proteins. However, besides these standard properties, pacmanvirus lostcity was found associated with a new type of selfish genetic element, 7 kb in length, whose architecture and gene content are reminiscent of those of transpovirons, hitherto specific to the family Mimiviridae. Like previously described transpovirons, this element propagates as an episome within its host virus particles and exhibits partial recombination with its genome. In addition, an unrelated 2 kb long episome was also associated with pacmanvirus lostcity. Together, the transpoviron and the 2 kb episome might participate to exchanges between pacmanviruses and other large DNA virus families. It remains to be elucidated if the presence of these mobile genetic elements is restricted to pacmanviruses or was simply overlooked in other members of the Asfarviridae.