Culture-Independent Approaches for Studying Viruses from Hypersaline Environments

Abstract

e Hypersaline close-to-saturation environments harbor an extremely high concentration of virus-like particles, but the number of haloviruses isolated so far is still very low. Haloviruses can be directly studied from natural samples by using different cultureindependent techniques that include transmission electron microscopy, pulsed-field gel electrophoresis, and different metagenomic approaches. Here, we review the findings of these studies, with a main focus on the metagenomic approaches. The analysis of bulk viral nucleic acids directly retrieved from the environment allows estimations of viral diversity, activity, and dynamics and tentative host assignment. Results point to a diverse and active viral community in constant interplay with its hosts and to a "hypersalineness" quality common to viral assemblages present in hypersaline environments that are thousands of kilometers away from each other.

Antarctic archaea–virus interactions: metaproteome-led analysis of invasion, evasion and adaptation

“…As such, haloarchaeoviruses in Deep Lake could potentially provide haloarchaeal hosts a mechanistic 'short cut' for acquiring novel genes, or portions of genes. In a hypersaline environment where viruses are the dominant predators (Oren et al, 1997;Kepner et al, 1998;Santos et al, 2007;Anesio and Bellas, 2011;Atanasova et al, 2012;Santos et al, 2012;Wilkins et al, 2013;Luk et al, 2014), and our data indicate in Deep Lake they can have broad host range, shuffling and mutating cell surface genes could bestow protection against more destructive haloarchaeoviruses (for example, virulent forms) by altering and/or replacing the receptors that the more harmful viruses require for attachment. The complexity of such interactions in Deep Lake would be consistent with the constant-diversity dynamics model which proposes that patterns of diversity in microbial populations arise through viral predation (Rodriguez-Valera et al, 2009).…”

“…Hypersaline lakes from warm-hot latitudes that harbor halophilic members of the Archaea (haloarchaea) tend to sustain a low abundance of higher trophic predators and support high viral densities (Oren et al, 1997;Santos et al, 2007;Atanasova et al, 2012;Santos et al, 2012;Luk et al, 2014). In polar lakes, metazoan grazers also tend to occur in low abundance, and viruses are hypothesized to have a key role in the microbial loop and to function as drivers of microbial evolution (Kepner et al, 1998;Anesio and Bellas, 2011;Wilkins et al, 2013).…”

Microbial diversity of hypersaline environments: a metagenomic approach

“…Cellular life in hypersaline habitats is dominated by prokaryotes (archaea and bacteria), with a few microbial eukaryotes, such as photosynthetic and heterotrophic protists and fungi, and the crustacean Artemia salina [1,[5][6][7][8]. Also, viruses are a significant part of the community [9,10]. The use of culture independent techniques typically demonstrated that the most abundant species in saturated brines are the square haloarchaeon Haloquadratum walsbyi and Salinibacter ruber though there are notable exceptions [11,12].…”

Determining virus-host interactions and glycerol metabolism profiles in geographically diverse solar salterns with metagenomics

“…The square archaeon Haloquadratum walsbyi and bacterioidete Salinibacter ruber are the two major components of saltern microbial communities at the highest salinities (Ventosa et al, 2015). In addition, hypersaline environments are estimated to have the highest densities of viruses (109/mL) among studied aquatic environments (Santos et al, 2012). Reduced viral decomposition in hypersaline conditions and a lack of protozoan predation may explain this extraordinarily high density (Santos et al, 2012).…”