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  • 1. Alonso-Saez, Laura
    et al.
    Waller, Alison S.
    Mende, Daniel R.
    Bakker, Kevin
    Farnelid, Hanna
    Yager, Patricia L.
    Lovejoy, Connie
    Tremblay, Jean-Eric
    Potvin, Marianne
    Heinrich, Friederike
    Estrada, Marta
    Riemann, Lasse
    Bork, Peer
    Pedros-Alio, Carlos
    Bertilsson, Stefan
    Role for urea in nitrification by polar marine Archaea2012In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 44, p. 17989-17994Article in journal (Refereed)
    Abstract [en]

    Despite the high abundance of Archaea in the global ocean, their metabolism and biogeochemical roles remain largely unresolved. We investigated the population dynamics and metabolic activity of Thaumarchaeota in polar environments, where these microorganisms are particularly abundant and exhibit seasonal growth. Thaumarchaeota were more abundant in deep Arctic and Antarctic waters and grew throughout the winter at surface and deeper Arctic halocline waters. However, in situ single-cell activity measurements revealed a low activity of this group in the uptake of both leucine and bicarbonate (<5% Thaumarchaeota cells active), which is inconsistent with known heterotrophic and autotrophic thaumarchaeal lifestyles. These results suggested the existence of alternative sources of carbon and energy. Our analysis of an environmental metagenome from the Arctic winter revealed that Thaumarchaeota had pathways for ammonia oxidation and, unexpectedly, an abundance of genes involved in urea transport and degradation. Quantitative PCR analysis confirmed that most polar Thaumarchaeota had the potential to oxidize ammonia, and a large fraction of them had urease genes, enabling the use of urea to fuel nitrification. Thaumarchaeota from Arctic deep waters had a higher abundance of urease genes than those near the surface suggesting genetic differences between closely related archaeal populations. In situ measurements of urea uptake and concentration in Arctic waters showed that small-sized prokaryotes incorporated the carbon from urea, and the availability of urea was often higher than that of ammonium. Therefore, the degradation of urea may be a relevant pathway for Thaumarchaeota and other microorganisms exposed to the low-energy conditions of dark polar waters.

  • 2. Yager, Patricia L.
    et al.
    Sherrell, Robert M.
    Stammerjohn, Sharon E.
    Alderkamp, Anne-Carlijn
    Schofield, Oscar
    Abrahamsen, E. Povl
    Arrigo, Kevin R.
    Bertilsson, Stefan
    Garay, D. Lollie
    Guerrero, Raul
    Lowry, Kate E.
    Moksnes, Per-Olav
    Ndungu, Kuria
    Post, Anton F.
    Randall-Goodwin, Evan
    Riemann, Lasse
    Severmann, Silke
    Thatje, Sven
    van Dijken, Gert L.
    Wilson, Stephanie
    ASPIRE The Amundsen Sea Polynya International Research Expedition2012In: Oceanography, ISSN 1042-8275, Vol. 25, no 3, p. 40-53Article in journal (Refereed)
    Abstract [en]

    In search of an explanation for some of the greenest waters ever seen in coastal Antarctica and their possible link to some of the fastest melting glaciers and declining summer sea ice, the Amundsen Sea Polynya International Research Expedition (ASPIRE) challenged the capabilities of the US Antarctic Program and RVIB Nathaniel B. Palmer during Austral summer 2010-2011. We were well rewarded by both an extraordinary research platform and a truly remarkable oceanic setting. Here we provide further insights into the key questions that motivated our sampling approach during ASPIRE and present some preliminary findings, while highlighting the value of the Palmer for accomplishing complex, multifaceted oceanographic research in such a challenging environment.

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