His1, an archaeal virus of the Fuselloviridae family that infects Haloarcula hispanica

Abstract

A novel archaeal virus, His1, was isolated from hypersaline waters in southeastern Australia. It was lytic, grew only on Haloarcula hispanica (titers of up to 10(11) PFU/ml), and displayed a lemon-shaped morphology (74 by 44 nm) previously reported only for a virus of the extreme thermophiles (SSV1). The density of His1 was approximately 1.28 g/ml, similar to that of SSV1 (1.24 g/ml). Purified particles were resistant to low salt concentrations. The genome was linear, double-stranded DNA of 14.9 kb, similar to the genome of SSV1 (15.5 kb). Morphologically, this isolate clearly belongs to the recently proposed Fuselloviridae family of archaeal viruses. It is the first member of this family from the extremely halophilic archaea, and its host, H. hispanica, can be readily manipulated genetically.

FIG. 1

Electron micrograph of the halophilic virus His1, taken at a magnification of ×60,000 and negatively stained with uranyl acetate (2% [wt/vol]). Flagella of the host are also visible in this purified preparation. Bar, 100 nm.

FIG. 2

Agarose gel electrophoresis of His1 DNA, uncut (U) and cleaved with a number of endonuclease restriction enzymes: AseI (A), AvaI (Av), DraI (D), NaeI (Na), NdeI (N), and SspI (S). DNA size markers (in kilobases) are shown on the left.

FIG. 3

Physical map of the genome of the virus His1. The map was constructed with five endonuclease restriction enzymes: AseI, AvaI, DraI, NaeI, and SphI. The numbers within the map correspond to fragment numbers in Table 1, and a scale is shown beneath the map.