Abundant dissolved genetic material in Arctic sea ice Part I: Extracellular DNA
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The porous medium of sea ice, a surface-rich environment characterized by low temperature and high salinity, has been proposed as a favorable site for horizontal gene transfer, but few measurements are available to assess the possibility of this mode of evolution in ice. Here, we report the first measurements of dissolved DNA in sea ice, measured by fluorescent dye staining of centrifugal-filter-concentrated samples of melted ice. Newly formed landfast and pack ice on the Canadian Arctic Shelf (ca. 71°N, 125°W) contained higher concentrations (scaled to volume of brine) of the major components of dissolved DNA—extracellular DNA and viruses—than the underlying seawater. Dissolved DNA was dominated by extracellular DNA in surface seawater (up to 95%), with viruses making up relatively larger fractions at depths below 100 m (up to 27%) and in thick sea ice (66–78 cm; up to 100%). Extracellular DNA was heterogeneously distributed, with concentrations up to 135 μg DNA L−1 brine detected in landfast sea ice, higher than previously reported from any marine environment. Additionally, extracellular DNA was significantly highly enriched at the base of ice of medium thickness (33–37 cm), suggestive of in situ production. Relative to underlying seawater, higher concentrations of extracellular DNA, viruses, and bacteria, and the availability of numerous surfaces for attachment within the ice matrix suggest that sea ice may be a hotspot for HGT in the marine environment.
KeywordsArctic Sea ice Extracellular DNA Bacteria Viruses Horizontal gene transfer
We thank the captain, crew, and scientific party of the CCGS Amundsen for a successful cruise. We gratefully acknowledge M. Pucko, W. Walkusz, P. Galand, B. Else, N. Sutherland, and M. Gupta for field assistance, C. Marrasé for assistance with chlorophyll a measurements, J. Islefson, D. Barber and CFL Team 2 for ice microstructure data and the use of ice-coring equipment, and S. Carpenter for help with laboratory analyses. We thank the three referees, whose contributions improved the manuscript.
- Collins RE, Deming JW (2011) Abundant dissolved genetic material in Arctic sea ice Part II: Viral dynamics during autumn freeze-up. Polar Biol. doi: 10.1007/s00300-011-1008-z
- Cox GFN, Weeks WF (1983) Equations for determining the gas and brine volumes in sea-ice samples. J Glaciol 29:306–316Google Scholar
- Cox GFN, Weeks WF (1986) Changes in the salinity and porosity of sea-ice samples during shipping and storage. J Glaciol 32:371–375Google Scholar
- Dell’Anno A, Fabiano M, Duineveld GCA, Kok A, Danovaro R (1998) Nucleic acid (DNA, RNA) quantification and RNA/DNA ratio determination in marine sediments: comparison of spectrophotometric, fluorometric, and high performance liquid chromatography methods and estimation of detrital DNA. Appl Environ Microbiol 64:3238–3245PubMedGoogle Scholar
- Frischer ME, Thurmond JM, Paul JH (1993) Factors affecting competence in a high-frequency of transformation marine Vibrio. J Gen Microbiol 139:753–761Google Scholar
- Kiko R (2010) Acquisition of freeze protection in a sea-ice crustacean through horizontal gene transfer? Polar Biol 33:543–556Google Scholar
- Kokjohn T (1989) Transduction: mechanism and potential for gene transfer in the environment. In: Levy S, Miller R (eds) Gene transfer in the environment. McGraw-Hill Publishing Co., New York, pp 73–97Google Scholar
- Lawrence JG, Hendrickson H (2003) Lateral gene transfer: when will adolescence end? Mol Microbiol 50:739–749Google Scholar
- Lorenz MG, Wackernagel W (1992) DNA binding to various clay inerals and retarded enzymatic degradation of DNA in a sand/clay microcosm. In: Gauthier MJ (eds) Gene transfers and environment. Springer-Verlag KG, Berlin, pp 103–113Google Scholar
- Parsons TR, Maita Y, Lalli CM (1984) A manual of chemical and biological methods for seawater analysis. Pergamon, New YorkGoogle Scholar
- R Development Core Team (2011) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. ISBN 3-900051-07-0Google Scholar