Viral diversity of brine and precipitated halite of Tuz Lake, an inland hypersaline lake in Turkey.

The diversity of viral communities in inland hypersaline environments remains largely unexplored. Here, we characterized viral assemblages of the thalassohaline inland hypersaline Tuz Lake (Turkey). To identify viral groups and viral sequences present in multiple samples, brine and precipitated salt samples were analysed using microscopy and metagenomics. Viral assemblages showed an abundance and morphology similar to what is commonly found in hypersaline systems. Despite these similarities, the vast majority of sequences remained unknown with regard to taxonomy and function and could not be characterized, highlighting their novelty. A remarkably high fraction of the viral sequences identified were present in both brine and salt samples, indicating viral stability during salt precipitation and dissolution in the lake, suggesting that Tuz Lake might be of considerable astrobiological interest. Alongside this high level of similarity, read recruitments revealed the presence of some sample-specific viral sequences in the salt sample. Tuz Lake viral assemblages displayed a distinct composition when compared to previously described viral metagenomes and haloviral genomes from hypersaline environments, with the highest similarity to the viral assemblages of the crystallizer ponds in the Bras del Port saltern (Spain).