Viral Ecogenomics of Arctic Cryopeg Brine and Sea Ice

• Published in: mSystems
• Main Authors: Zhi-Ping Zhong, Josephine Z. Rapp, James M. Wainaina, Natalie E. Solonenko, Heather Maughan, Shelly D. Carpenter, Zachary S. Cooper, Ho Bin Jang, Benjamin Bolduc, Jody W. Deming, Matthew B. Sullivan
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Society for Microbiology 2020
• Subjects: viral communities; extreme environments; virus-host interaction; cold and salt adaption; horizontal gene transfer; Microbiology; QR1-502; Arctic; Ice; permafrost; Sea ice
• Online Access: https://doi.org/10.1128/mSystems.00246-20; https://doaj.org/article/9d37cf666bdd4ac4aac9aa1544dfaf41

ABSTRACT Arctic regions, which are changing rapidly as they warm 2 to 3 times faster than the global average, still retain microbial habitats that serve as natural laboratories for understanding mechanisms of microbial adaptation to extreme conditions. Seawater-derived brines within both sea ice (sea-ice brine) and ancient layers of permafrost (cryopeg brine) support diverse microbes adapted to subzero temperatures and high salinities, yet little is known about viruses in these extreme environments, which, if analogous to other systems, could play important evolutionary and ecosystem roles. Here, we characterized viral communities and their functions in samples of cryopeg brine, sea-ice brine, and melted sea ice. Viral abundance was high in cryopeg brine (1.2 × 108 ml−1) and much lower in sea-ice brine (1.3 × 105 to 2.1 × 105 ml−1), which roughly paralleled the differences in cell concentrations in these samples. Five low-input, quantitative viral metagenomes were sequenced to yield 476 viral populations (i.e., species level; ≥10 kb), only 12% of which could be assigned taxonomy by traditional database approaches, indicating a high degree of novelty. Additional analyses revealed that these viruses: (i) formed communities that differed between sample type and vertically with sea-ice depth; (ii) infected hosts that dominated these extreme ecosystems, including Marinobacter, Glaciecola, and Colwellia; and (iii) encoded fatty acid desaturase (FAD) genes that likely helped their hosts overcome cold and salt stress during infection, as well as mediated horizontal gene transfer of FAD genes between microbes. Together, these findings contribute to understanding viral abundances and communities and how viruses impact their microbial hosts in subzero brines and sea ice. IMPORTANCE This study explores viral community structure and function in remote and extreme Arctic environments, including subzero brines within marine layers of permafrost and sea ice, using a modern viral ecogenomics toolkit for the first time. In ...