Our understanding of archaeal virus diversity and structure is just beginning to emerge. Here we describe a new archaeal virus, tentatively named Metallosphaera turreted icosahedral virus (MTIV), that was isolated from an acidic hot spring in Yellowstone National Park, USA. Two strains of the virus were identified and were found to replicate in an archaeal host species closely related to Metallosphaera yellowstonensis. Each strain encodes a 9.8- to 9.9-kb linear double-stranded DNA (dsDNA) genome with large inverted terminal repeats. Each genome encodes 21 open reading frames (ORFs). The ORFs display high homology between the strains, but they are quite distinct from other known viral genes. The 70-nmdiameter virion is built on a T=28 icosahedral lattice. Both single particle cryoelectron microscopy and cryotomography reconstructions reveal an unusual structure that has 42 turret-like projections: 12 pentameric turrets positioned on the icosahedral 5-fold axes and 30 turrets with apparent hexameric symmetry positioned on the icosahedral 2-fold axes. Both the virion structural properties and the genome content support MTIV as the founding member of a new family of archaeal viruses.
Bibliographical noteFunding Information:
This work was supported by NSF grant DEB-4W4596 to M.J. Y., and it was performed under Yellowstone National Park research permit YELL-2016-SCI-5090. Funding was also provided by National Science Foundation, grant MCB-1413534, to C.M.L. The M. J. Murdock Charitable Trust also funded instrumentation on which cryo-electron microscopy was performed. Special thanks to Susan Brumfield for assistance with electron microscopy.
© 2017 American Society for Microbiology.
- Archaeal virus
- Cryo-electron microscopy
- Environmental virology
- Viruses in extreme environments