Archaeal Viruses Multiply: Temporal Screening in a Solar Saltern

Abstract

Hypersaline environments around the world are dominated by archaea and their viruses. To date, very little is known about these viruses and their interaction with the host strains when compared to bacterial and eukaryotic viruses. We performed the first culture-dependent temporal screening of haloarchaeal viruses and their hosts in the saltern of Samut Sakhon, Thailand, during two subsequent years (2009, 2010). Altogether we obtained 36 haloarchaeal virus isolates and 36 archaeal strains, significantly increasing the number of known archaeal virus isolates. Interestingly, the morphological distribution of our temporal isolates (head-tailed, pleomorphic, and icosahedral membrane-containing viruses) was similar to the outcome of our previous spatial survey supporting the observations of a global resemblance of halophilic microorganisms and their viruses. Myoviruses represented the most abundant virus morphotype with strikingly broad host ranges. The other viral morphotypes (siphoviruses, as well as pleomorphic and icosahedral internal membrane-containing viruses) were more host-specific. We also identified a group of Halorubrum strains highly susceptible to numerous different viruses (up to 26). This high virus sensitivity, the abundance of broad host range viruses, and the maintenance of infectivity over a period of one year suggest constant interplay of halophilic microorganisms and their viruses within an extreme environment.

Pleolipoviridae, a newly proposed family comprising archaeal pleomorphic viruses with single-stranded or double-stranded DNA genomes

“…Furthermore, they have a very narrow host range; in most cases they were only able to infect the original isolation strain when representatives from several haloarchaeal genera were tested [3,5,11,24,34]. All current members of the proposed family Pleolipoviridae are nonlytic, and they form hazy plaques on the host lawn [21,24,26,34].…”

“…In addition to the pleolipoviruses described above, three more haloarchaeal pleomorphic viruses, Halorubrum pleomorphic viruses 7 and 8 (HRPV-7 and HRPV-8) and Haloarcula pleomorphic virus 2 (HAPV-2) have recently been isolated [5]. These isolates display characteristics of pleolipoviruses: pleomorphic virion morphotypes observed Fig.…”

“…Archaea and their viruses thrive in extreme environments, and most of archaeal viruses characterized so far infect extremophiles, either hyperhalophiles or hyperthermophiles [4][5][6]29]. Viruses infecting archaea display diverse virion morphotypes, some of which are unique.…”

“…Source of the map: Wikimedia Commons by negative-staining transmission EM, pleolipovirus-like simple structural protein patterns, and hazy plaque morphologies. Moreover, infectivity is affected by the presence of chloroform (at least in the case of HRPV-7 and HAPV-2), suggesting that there is a membrane in the virions [5]. However, the genome sequences of these viruses are not available, and this precludes their further positioning within the pleolipovirus group.…”

Virus‐host interplay in high salt environments

“… Phylogenetic tree based on partial 16S rRNA gene sequences of different Halorubrum strains isolated from spatial (light purple highlight) (Atanasova et al ., ) and temporal (pink highlight) (Atanasova et al ., ) studies. Culture collection Halorubrum strains are not highlighted and from these strains, only Hrr.…”