Functional analysis of the archaea , bacteria , and viruses from 1 a halite endolithic microbial community

23 24 25 The authors declare that there are no competing financial interests in relation to the 26 work described here. 27 28. CC-BY-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not. Abstract 29 Halite endoliths in the Atacama Desert represent one of the most extreme microbial 30 ecosystems on Earth. Here we sequenced and characterized a shotgun metagenome from 31 halite nodules collected in Salar Grande, Chile. The community is dominated by archaea 32 and functional analysis attributed most of the autotrophic CO 2 fixation to a unique 33 cyanobacterium. The assembled 1.1 Mbp genome of a novel nanohaloarchaeon, 34 Candidatus Nanopetramus SG9, revealed a photoheterotrophic life style and a low 35 median isoelectric point (pI) for all predicted proteins, suggesting a " salt-in " strategy for 36 osmotic balance. Predicted proteins of the algae identified in the community also had pI 37 distributions similar to " salt-in " strategists. The Nanopetramus genome contained a 38 unique CRISPR/Cas system with a spacer that matched a partial viral genome from the 39 metagenome. A combination of reference-independent methods identified over 30 40 complete or near complete viral or proviral genomes with diverse genome structure, 41 genome size, gene content, and hosts. Putative hosts included Halobacteriaceae, 42 Nanohaloarchaea, and Cyanobacteria. Despite the dependence of the halite community 43 on deliquescence for liquid water availability, this study exposed an ecosystem spanning 44 three phylogenetic domains, containing a large diversity of viruses, and a predominant 45 " salt-in " strategy to balance the high osmotic pressure of the environment. 46 47. CC-BY-ND 4.0 International license peer-reviewed) is the author/funder. It is made available under a The copyright holder for this preprint (which was not .