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A microbial ecosystem beneath the West Antarctic ice sheet

2014; Nature Portfolio; Volume: 512; Issue: 7514 Linguagem: Inglês

10.1038/nature13667

1476-4687

Brent C. Christner, John C. Priscu, Amanda M. Achberger, Carlo Barbante, Sasha P. Carter, Knut Christianson, Alexander B. Michaud, Jill A. Mikucki, Andrew C. Mitchell, Mark Skidmore, Trista J. Vick‐Majors, W. Peyton Adkins, S. Anandakrishnan, C. G. Barcheck, Lucas Beem, A. Behar, Marci Jillian Beitch, R. Bolsey, C. Branecky, Rodney K. Edwards, A. T. Fisher, H. A. Fricker, Neil Foley, Barry Guthrie, Timothy Hodson, Huw Horgan, R. W. Jacobel, Samuel E. Kelley, Kenneth D. Mankoff, Emily McBryan, Ross D. Powell, Alicia M. Purcell, Daniel E. Sampson, Reed P. Scherer, J. Sherve, Matthew R. Siegfried, Sławek Tulaczyk,

Microbial Community Ecology and Physiology

There has been active debate over microbial life in Antarctic subglacial lakes owing to a paucity of direct observations from beneath the ice sheet and concerns about contamination in the samples that do exist; here the authors present the first geomicrobiological description of pristine water and surficial sediments from Subglacial Lake Whillans, and show that the lake water contains a diverse microbial community, many members of which are closely related to chemolithoautotrophic bacteria and archaea. Whether there is microbial life in subglacial lakes in the Antarctic has been a matter of controversy, as early results were compromised when it was discovered that contamination may have occurred during drilling. Discovered less than a decade ago using satellite data, Lake Whillans lies beneath some 800 metres of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network. In the first study to sample Antarctic subglacial waters directly, analysis of sediments obtained by the WISSARD drilling program shows that Lake Whillans' water contains more than 3,900 different types of bacteria and archaea, including one closely related to the nitrite oxidizing betaproteobacterium 'Candidatus Nitrotoga arctica', which comprised 13% of the sequence data. The lake waters contain a diverse range of metabolically active microorganisms, many of which seem to gain nutrients from the melting ice and from the rock and sediment beneath the ice. Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years1, but only recently have these subglacial aqueous environments been recognized as microbial ecosystems that may influence biogeochemical transformations on a global scale2,3,4. Here we present the first geomicrobiological description of water and surficial sediments obtained from direct sampling of a subglacial Antarctic lake. Subglacial Lake Whillans (SLW) lies beneath approximately 800 m of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network5. The water column of SLW contained metabolically active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic weathering and a minor seawater component. Heterotrophic and autotrophic production data together with small subunit ribosomal RNA gene sequencing and biogeochemical data indicate that SLW is a chemosynthetically driven ecosystem inhabited by a diverse assemblage of bacteria and archaea. Our results confirm that aquatic environments beneath the Antarctic ice sheet support viable microbial ecosystems, corroborating previous reports suggesting that they contain globally relevant pools of carbon and microbes2,4 that can mobilize elements from the lithosphere6 and influence Southern Ocean geochemical and biological systems7.