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1.  Reversible Inactivation and Desiccation Tolerance of Silicified Viruses 
Journal of Virology  2013;87(24):13927-13929.
Long-distance host-independent virus dispersal is poorly understood, especially for viruses found in isolated ecosystems. To demonstrate a possible dispersal mechanism, we show that bacteriophage T4, archaeal virus Sulfolobus spindle-shaped virus Kamchatka, and vaccinia virus are reversibly inactivated by mineralization in silica under conditions similar to volcanic hot springs. In contrast, bacteriophage PRD1 is not silicified. Moreover, silicification provides viruses with remarkable desiccation resistance, which could allow extensive aerial dispersal.
PMCID: PMC3838281  PMID: 24109222
3.  Differential virus host-ranges of the Fuselloviridae of hyperthermophilic Archaea: implications for evolution in extreme environments 
An emerging model for investigating virus-host interactions in hyperthermophilic Archaea is the Fusellovirus-Sulfolobus system. The host, Sulfolobus, is a hyperthermophilic acidophile endemic to sulfuric hot springs worldwide. The Fuselloviruses, also known as Sulfolobus Spindle-shaped Viruses (SSVs), are “lemon” or “spindle”-shaped double-stranded DNA viruses, which are also found worldwide. Although a few studies have addressed the host-range for the type virus, Sulfolobus Spindle-shaped Virus 1 (SSV1), using common Sulfolobus strains, a comprehensive host-range study for SSV-Sulfolobus systems has not been performed. Herein, we examine six bona fide SSV strains (SSV1, SSV2, SSV3, SSVL1, SSVK1, SSVRH) and their respective infection characteristics on multiple hosts from the family Sulfolobaceae. A spot-on-lawn or “halo” assay was employed to determine SSV infectivity (and host susceptibility) in parallel challenges of multiple SSVs on a lawn of a single Sulfolobus strain. Different SSVs have different host-ranges with SSV1 exhibiting the narrowest host-range and SSVRH exhibiting the broadest host range. In contrast to previous reports, SSVs can infect hosts beyond the genus Sulfolobus. Furthermore, geography does not appear to be a reliable predictor of Sulfolobus susceptibility to infection by any given SSV. The ability for SSVs to infect susceptible Sulfolobus host does not appear to change between 65°C and 88°C (physiological range); however, very low pH appears to influence infection. Lastly, for the virus-host pairs tested the Fusellovirus-Sulfolobus system appears to exhibit host-advantage. This work provides a foundation for understanding Fusellovirus biology and virus-host coevolution in extreme ecosystems.
PMCID: PMC3426928  PMID: 22936928
Archaea; Crenarchaea; Fusellovirus; halo assay; host-range; hyperthermophilic; Sulfolobus; Sulfolobus spindle-shaped virus
4.  A novel virus genome discovered in an extreme environment suggests recombination between unrelated groups of RNA and DNA viruses 
Biology Direct  2012;7:13.
Viruses are known to be the most abundant organisms on earth, yet little is known about their collective origin and evolutionary history. With exceptionally high rates of genetic mutation and mosaicism, it is not currently possible to resolve deep evolutionary histories of the known major virus groups. Metagenomics offers a potential means of establishing a more comprehensive view of viral evolution as vast amounts of new sequence data becomes available for comparative analysis.
Bioinformatic analysis of viral metagenomic sequences derived from a hot, acidic lake revealed a circular, putatively single-stranded DNA virus encoding a major capsid protein similar to those found only in single-stranded RNA viruses. The presence and circular configuration of the complete virus genome was confirmed by inverse PCR amplification from native DNA extracted from lake sediment. The virus genome appears to be the result of a RNA-DNA recombination event between two ostensibly unrelated virus groups. Environmental sequence databases were examined for homologous genes arranged in similar configurations and three similar putative virus genomes from marine environments were identified. This result indicates the existence of a widespread but previously undetected group of viruses.
This unique viral genome carries implications for theories of virus emergence and evolution, as no mechanism for interviral RNA-DNA recombination has yet been identified, and only scant evidence exists that genetic exchange occurs between such distinct virus lineages.
This article was reviewed by EK, MK (nominated by PF) and AM. For the full reviews, please go to the Reviewers' comments section.
PMCID: PMC3372434  PMID: 22515485
Non-retroviral RNA virus integration; RNA-DNA recombination; Viral metagenomics; Metaviromics; Virus ecology; Viral diversity; Modular theory of virus evolution; Interviral lateral gene transfer; RNA World; DNA World; Virus World
5.  pING Family of Conjugative Plasmids from the Extremely Thermophilic Archaeon Sulfolobus islandicus: Insights into Recombination and Conjugation in Crenarchaeota 
Journal of Bacteriology  2000;182(24):7014-7020.
A novel family of conjugative plasmids from Sulfolobus comprising the active variants pING1, -4, and -6 and the functionally defective variants pING2 and -3, which require the help of an active variant for spreading, has been extensively characterized both functionally and molecularly. In view of the sparse similarity between bacterial and archaeal conjugation and the lack of a practical genetic system for Sulfolobus, we compared the functions and sequences of these variants and the previously described archaeal conjugative plasmid pNOB8 in order to identify open reading frames (ORFs) and DNA sequences that are involved in conjugative transfer and maintenance of these plasmids in Sulfolobus. The variants pING4 and -6 are reproducibly derived from pING1 in vivo by successive transpositions of an element from the Sulfolobus genome. The small defective but mobile variants pING2 and -3, which both lack a cluster of highly conserved ORFs probably involved in plasmid transfer, were shown to be formed in vivo by recombinative deletion of the larger part of the genomes of pING4 and pING6, respectively. The efficient occurrence of these recombination processes is further evidence for the striking plasticity of the Sulfolobus genome.
PMCID: PMC94828  PMID: 11092863

Results 1-5 (5)