High-Level Diversity of Tailed Phages, Eukaryote-Associated Viruses, and Virophage-Like Elements in the Metaviromes of Antarctic Soils

Abstract

dThe metaviromes of two distinct Antarctic hyperarid desert soil communities have been characterized. Hypolithic communities, cyanobacterium-dominated assemblages situated on the ventral surfaces of quartz pebbles embedded in the desert pavement, showed higher virus diversity than surface soils, which correlated with previous bacterial community studies. Prokaryotic viruses (i.e., phages) represented the largest viral component (particularly Mycobacterium phages) in both habitats, with an identical hierarchical sequence abundance of families of tailed phages (Siphoviridae > Myoviridae > Podoviridae). No archaeal viruses were found. Unexpectedly, cyanophages were poorly represented in both metaviromes and were phylogenetically distant from currently characterized cyanophages. Putative phage genomes were assembled and showed a high level of unaffiliated genes, mostly from hypolithic viruses. Moreover, unusual gene arrangements in which eukaryotic and prokaryotic virus-derived genes were found within identical genome segments were observed. Phycodnaviridae and Mimiviridae viruses were the second-mostabundant taxa and more numerous within open soil. Novel virophage-like sequences (within the Sputnik clade) were identified. These findings highlight high-level virus diversity and novel species discovery potential within Antarctic hyperarid soils and may serve as a starting point for future studies targeting specific viral groups.

Genetic signatures indicate widespread antibiotic resistance and phage infection in microbial communities of the McMurdo Dry Valleys, East Antarctica

“…3). This is consistent with a recent study that identified greatest abundance of Myoviridae (21 %) and Siphoviridae (53 %) in Antarctic hypoliths (Zablocki et al 2014). The Levriviridae are found worldwide, and isolated strains infect gram-negative bacteria (Hulo et al 2011).…”

“…The nearubiquity of vial signature recovery in this study is consistent with theory regarding phage distribution in natural environments (Breitbart and Rohwer 2005). A recent study of the Antarctic hypolithic metavirome indicated that a range of microbial physiological pathways may also be encoded Error bars represent standard deviation of the mean for three independent GeoChip replicates, where these are not visible standard deviation is less than the minimum scale increment within phage genomes, in addition to virulence, disease and defence functions (Zablocki et al 2014). Thus, high viral loads in microbial communities in extreme environments may also reflect, in part, acquisition of favourable auxiliary metabolism genes (Roossinck 2011) and may even increase bacterial diversity by selecting for multiple resistance traits (Koskella and Brockhurst 2014).…”

“…This mechanism, where viral infection causes cell death and thus exerts a control on biomass, would represent a bottom-up control on microbial communities. Detectable phage populations have been demonstrated for extreme environments including hot springs (Breitbart et al 2004), hot deserts , Antarctic lakes (Lo´pez-Bueno et al 2009) and Antarctic hypoliths and surrounding soil (Zablocki et al 2014). Investigations of phage-host interaction, including cell lysis, have yet to be addressed in Antarctica.…”

Ecology and biogeochemistry of cyanobacteria in soils, permafrost, aquatic and cryptic polar habitats

“…Such genome data may be crucial in revealing mechanistic insights of polar cyanobacterial isolates as has been done very recently with other phyla Ferreras et al 2014;Guerrero et al 2014;Ronca et al 2015). There is also a general lack of publicly available cyanobacterial virome data, which may lead to poor representation and potential underestimation of cyanophages in Antarctic environments (Zablocki et al 2014). This deficit negatively affects our understanding of intra-and interspecies interactions.…”

Microbial diversity and functional capacity in polar soils

“…However, very few studies have assessed the diversity of viruses in cold environments, let alone their functional roles. Of these published studies on polar habitats, mostly focus on lacustrine systems [54,55] with only very limited surveys of polar edaphic metaviromes [40,56]. The latter suggests that viruses in cold soil environments are highly diverse but are typically dominated by Mycobacterium phages [56].…”