Thaspiviridae is a family of incertae sedis spindle-shaped viruses. The family contains a single genus, Nitmarvirus, which contains a single species, Nitrosopumilus spindle-shaped virus 1 (NSV1, Nitmarvirus maris).
Thaspiviridae are known to infect mesophilic ammonia-oxidizing archaea of the genus Nitrosopumilus.
The virion is spindle-shaped, measuring 64ñ3âÂÂnm in diameter and 112ñ6âÂÂnm in length, with short fibres at one pole. Its morphology is very similar to that of the members of the families Fuselloviridae and Halspiviridae, which infect hyperthermophilic and hyperhalophilic archaea, respectively.
Its genome is linear dsDNA of length 27âÂÂ29 kbp, with 176âÂÂbp terminal inverted repeats. The virus genome is predicted to carry 48 genes. With the exception of protein-primed B DNA polymerase, which is also found in several groups of archaeal viruses and non-viral mobile genetic elements that also have linear genomes with terminal inverted repeats, the proteins encoded by Nitrosopumilus spindle-shaped virus 1 are unrelated to those of other archaeal and bacterial viruses.
The virus is non-lytic (capable of exiting host cells without killing them), and chronic (can be demonstrated in the body at all times and the disease may be present or absent for an extended period of time). The virus genome is likely to be replicated by the virus-encoded protein-primed family B DNA polymerase, as has been inferred for other viruses. The virus also encodes a proliferating cell nuclear antigen which is also likely to be involved in viral genome replication.