COPPER-UPTAKE KINETICS OF COASTAL AND OCEANIC DIATOMS

Authors

  • Jian Guo,

    1. Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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  • Amber L. Annett,

    1. Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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    • Present address: School of GeoSciences, Grant Institute, University of Edinburgh, The King’s Buildings, West Mains Road, Edinburgh, EH9 3JW, UK.

  • Rebecca L. Taylor,

    1. Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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  • Suzanne Lapi,

    1. Chemistry Department, Simon Fraser University, Vancouver, British Columbia, V6T 1Z4, Canada
      Tri-University Meson Facility (TRIUMF), Life Sciences Division, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada
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    • Present address: Mallinkrodt Institute of Radiology, Washington University, St. Louis, Missouri, USA.

  • Thomas J. Ruth,

    1. Chemistry Department, Simon Fraser University, Vancouver, British Columbia, V6T 1Z4, Canada
      Tri-University Meson Facility (TRIUMF), Life Sciences Division, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3, Canada
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  • Maria T. Maldonado

    1. Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
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  • Received 11 September 2009. Accepted 30 June 2010.

Abstract

We investigated copper (Cu) acquisition mechanisms and uptake kinetics of the marine diatoms Thalassiosira oceanica Hasle, an oceanic strain, and Thalassiosira pseudonana Hasle et Heimdal, a coastal strain, grown under replete and limiting iron (Fe) and Cu availabilities. The Cu-uptake kinetics of these two diatoms followed classical Michaelis–Menten kinetics. Biphasic uptake kinetics as a function of Cu concentration were observed, suggesting the presence of both high- and low-affinity Cu-transport systems. The half-saturation constants (Km) and the maximum Cu-uptake rates (Vmax) of the high-affinity Cu-transport systems (∼7–350 nM and 1.5–17 zmol · μm−2 · h−1, respectively) were significantly lower than those of the low-affinity systems (>800 nM and 30–250 zmol · μm−2 · h−1, respectively). The two Cu-transport systems were controlled differently by low Fe and/or Cu. The high-affinity Cu-transport system of both diatoms was down-regulated under Fe limitation. Under optimal-Fe and low-Cu growth conditions, the Km of the high-affinity transport system of T. oceanica was lower (7.3 nM) than that of T. pseudonana (373 nM), indicating that T. oceanica had a better ability to acquire Cu at subsaturating concentrations. When Fe was sufficient, the low-affinity Cu-transport system of T. oceanica saturated at 2,000 nM Cu, while that of T. pseudonana did not saturate, indicating different Cu-transport regulation by these two diatoms. Using CuEDTA as a model organic complex, our results also suggest that diatoms might be able to access Cu bound within organic Cu complexes.

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