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The role of trace metals in controlling structure and function of microbial communities in contemporary oceans
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A reduction-dependent copper uptake pathway in an oceanic diatom
Tuesday 8th @ 1050-1110, Conference Room 1
Liangliang Kong* , McGill University, Montreal, Canada
Neil M. Price, McGill University, Montreal, Canada
Presenter Email: kongliangl@gmail.com |
| Conventional models of metal uptake by phytoplankton describe the dependence of uptake on the concentration of hydrated metal ions or kinetically labile species (Morel and Hering 1993). Chemical speciation of metals in the environment thus strongly influences metal accumulation by biota and their physiological and ecological effects. Some of the earliest work in the field showed how Cu toxicity in diatoms and dinoflagellates depended on the concentration of free cupric ions (Sunda and Guillard 1976; Anderson and Morel 1978). Studies that are more recent suggest that organically complexed Cu may also be bioavailable and that, for these forms of Cu, a cell surface reduction step may be required before Cu is transported (Hudson 1998; Quigg et al. 2006; Semeniuk et al. 2015; Walsh et al. 2015). We studied Cu reduction and uptake in a model oceanic diatom, Thalassiosira oceanica, a species that has an elevated Cu requirement for growth compared to related coastal species (Peers and Price 2006). Inorganic Cu and Cu complexed by EDTA were reduced extracellularly by T. oceanica and reduction rate was up-regulated in Cu-limited compared to Cu-replete cells. Addition of a Cu reductase inhibitor, oxidized platinum salt (K2PtCl6), and a Cu(I) trapping agent, bathocuproinedisulfonic acid (BCDS), decreased Cu uptake rate by 97% and 75%, respectively. Addition of BCDS also inhibited cell growth at low Cu concentration (1 nM) and significantly reduced cellular Cu quota by 75% in short-term growth assays. Thus at low and high Cu, a cell surface reduction step was part of the Cu uptake mechanism. The results show that a cell surface Cu reduction step precedes Cu uptake in T. oceanica and provide further support for the presence of a Cu(I) uptake pathway in this oceanic diatom. |
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