Of the eight familys of viruses known to infect the archaeon order Sulfolobales the best characterized virus family is the family Fuselloviridae, of which the Sulfolobus spindle-shaped virus 1 (SSV1) is the type virus. SSV1 was isolated from S. shibatae, a hyperthermophilic acidophilic aerobe similar to S. solfataricus (1). The virus particle is approximately 60x90 nm with a small tail protruding from one end approximately 10 nm long and is composed of three structural proteins and 15,465 bases of covalently closed circular, double stranded DNA (2). Despite extensive study including crystallization of three proteins encoded by the viruses 34 open reading frames, definite function has been shown for only four of these ORFs products, the three structural protiens and the integrase (3).Consequently, little is known about the reproductive cycle of the SSV1 virus.
Similar to Lambda, SSV1 virus production can be induced by UV irradiation . Induction increases viral production from a very low basal level to approximately 1x107 virus particles / L after a 4 hour eclipse, reaching maximum production in 12 to 16 hours post-induction in the natural host (1). Based on the presence of turbid plaques seen when the virus infects lawns of S. solfataricus and the lack of visible cell lysis in liquid culture or TEM, the virus appears to bud from it’s host rather than to lyse cells (4). Our observations show that virus production in the host lab host S. solfataricus has a higher basal production rate than in it’s natural host S. Shibatae, however this titer may be affected by other cell stresses such as oxidative damage and temperature change during growth in the lab.
Another similarity to Lambda is the ability to integrate it's genome into it's host. This is accomplished by an integrase gene. This gene belongs to a large family of integrases and recombinases known as tyrosine recombinases
At the present time there are three other Fueslloviruse genome sequences in the public database, SSV2 isolated from terrestrial hot springs in Iceland, SSV-RH isolated from the Ragged Hills area of Yellowstone National Park, and SSV-K1, isolated from Kamchatka, Russia. Comparatively these viruses show similar genome arrangements, however the genes themselves show a relatively small degree of similarity (see (3)).
1. Martin, A., S. Yeats, D. Janekovic, W.-D. Reiter, W. Aicher, and W. Zillig. 1984. SAV1, a temperate u.v.-inducible DNA virus-like particle from the archaebacterium Sulfolobus acidocaldaricus isolate B12. EMBO J 3:2165-2168.
2. Palm, P., C. Schleper, B. Grampp, S. Yeats, P. McWilliam, W. D. Reiter, and W. Zillig. 1991. Complete nucleotide sequence of the virus SSV1 of the archaebacterium Sulfolobus shibatae. Virology 185:242-50.
3. Wiedenheft, B., K. Stedman, F. Roberto, D. Willits, A. K. Gleske, L. Zoeller, J. Snyder, T. Douglas, and M. Young. 2004. Comparative genomic analysis of hyperthermophilic archaeal Fuselloviridae viruses. J Virol 78:1954-61