Virus‐host interplay in high salt environments

Abstract

Interaction of viruses and cells has tremendous impact on cellular and viral evolution, nutrient cycling and decay of organic matter. Thus, viruses can indirectly affect complex processes such as climate change and microbial pathogenicity. During recent decades, studies on extreme environments have introduced us to archaeal viruses and viruses infecting extremophilic bacteria or eukaryotes. Hypersaline environments are known to contain strikingly high numbers of viruses (∼10(9) particles per ml). Halophilic archaea, bacteria and eukaryotes inhabiting hypersaline environments have only a few cellular predators, indicating that the role of viruses is highly important in these ecosystems. Viruses thriving in high salt are called haloviruses and to date more than 100 such viruses have been described. Virulent, temperate, and persistent halovirus life cycles have been observed among the known isolates including the recently described SNJ1-SNJ2 temperate virus pair which is the first example of an interplay between two haloviruses in one host cell. In addition to direct virus and cell isolations, metagenomics have provided a wealth of information about virus-host dynamics in hypersaline environments suggesting that halovirus populations and halophilic microorganisms are dynamic over time and spatially distributed around the highly saline environments on the Earth.

Halophilic viruses with varying biochemical and biophysical properties are amenable to purification with asymmetrical flow field-flow fractionation

“…Systematic searches for halophilic viruses and the available methods to cultivate halophilic microbes have rapidly increased the number of described haloarchaeal viruses (Atanasova et al 2015a;Atanasova et al 2016;Atanasova et al 2015b;Atanasova et al 2012;Luk et al 2014). Detailed genetic, biochemical and structural characterisations are nevertheless lacking for most isolates.…”

“…Halophilic archaea and their viruses dominate in extremely saline environments, whereas high temperature environments are rich sources for crenarchaeal viruses [see reviews by (Atanasova et al 2016;Luk et al 2014;Prangishvili 2013)]. However, the biology, virion composition and architecture of relatively few viruses isolated from extreme environments have been studied in molecular detail.…”

“…Conditions for maximal virus production are first optimised. For haloarchaeal viruses, this process is lengthy due to the relatively slow growth of the hosts as well as the low adsorption rates and long intracellular virus replication cycles (Atanasova et al 2016;Luk et al 2014). Purification steps are then adjusted to remove host and purification process -derived impurities.…”

“…They vary in size and morphology as well as in their biochemical and biophysical properties. Currently known halophilic archaeal viruses infect hosts belonging to the phylum Euryarchaeota, the class Halobacteria and represent four distinct virus morphotypes (Atanasova et al 2016). Icosahedral tailed viruses form the majority of haloarchaeal viruses described thus far (Atanasova et al 2015a), and their morphology resembles those of the double-stranded DNA bacteriophages of the order Caudovirales (Pietilä et al 2013c).…”

A Novel Type of Polyhedral Viruses Infecting Hyperthermophilic Archaea

“…There are reasons to believe that the known variety of archaeal viruses represents no more than the tip of an iceberg and that comprehensive information on them may shed light on the problems of origin and evolution of viruses and virus-host interactions (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28).…”