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National Academy of Sciences, Proceedings of the National Academy of Sciences, 14(108), p. 5649-5654, 2011

DOI: 10.1073/pnas.1015744108

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Diatoms respire nitrate to survive dark and anoxic conditions

Journal article published in 2011 by Anja Kamp, Dirk de Beer ORCID, Jana L. Nitsch, Gaute Lavik, Peter Stief
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Diatoms survive in dark, anoxic sediment layers for months to decades. Our investigation reveals a correlation between the dark survival potential of marine diatoms and their ability to accumulate NO 3 intracellularly. Axenic strains of benthic and pelagic diatoms that stored 11–274 mM NO 3 in their cells survived for 6–28 wk. After sudden shifts to dark, anoxic conditions, the benthic diatom Amphora coffeaeformis consumed 84–87% of its intracellular NO 3 pool within 1 d. A stable-isotope labeling experiment proved that 15 NO 3 consumption was accompanied by the production and release of 15 NH 4 + , indicating dissimilatory nitrate reduction to ammonium (DNRA). DNRA is an anaerobic respiration process that is known mainly from prokaryotic organisms, and here shown as dissimilatory nitrate reduction pathway used by a eukaryotic phototroph. Similar to large sulfur bacteria and benthic foraminifera, diatoms may respire intracellular NO 3 in sediment layers without O 2 and NO 3 . The rapid depletion of the intracellular NO 3 storage, however, implies that diatoms use DNRA to enter a resting stage for long-term survival. Assuming that pelagic diatoms are also capable of DNRA, senescing diatoms that sink through oxygen-deficient water layers may be a significant NH 4 + source for anammox, the prevalent nitrogen loss pathway of oceanic oxygen minimum zones.