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Why Does Cysteine Enhance Metal Uptake by Phytoplankton in Seawater but Not in Freshwater?


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Liu, Fengjie, Tan, Qiao-Guo, Fortin, Claude ORCID: https://orcid.org/0000-0002-2479-1869 et Campbell, Peter G. C. (2019). Why Does Cysteine Enhance Metal Uptake by Phytoplankton in Seawater but Not in Freshwater? Environmental Science & Technology , vol. 53 , nº 11. p. 6511-6519. DOI: 10.1021/acs.est.9b00571.

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Low-molecular-weight weak ligands such as cysteine have been shown to enhance metal uptake by marine phytoplankton in the presence of strong ligands, but the effect is not observed in freshwater. We hypothesized that these contrasting results might be caused by local cysteine degradation and a Ca effect on metal–ligand exchange kinetics in the boundary layer surrounding the algal cells; newly liberated free metal ions cannot be immediately complexed in seawater by Ca-bound strong ligands but can be rapidly complexed by free ligands at low-Ca levels. The present results consistently support this hypothesis. At constant bulk Cd²⁺ concentrations, buffered by strong ligands: (1) at 50 mM Ca, cysteine addition significantly enhanced Cd uptake in high-Ca preacclimated euryhaline Chlamydomonas reinhardtii (cultured with cysteine as a nitrogen source to enhance local Cd²⁺ liberation via cysteine degradation); (2) at 0.07 mM Ca, this enhancement was not observed in the algae; (3) at 50 mM Ca, the enhancement disappeared when C. reinhardtii were cultured with ammonium (to inhibit cysteine degradation and local Cd²⁺ liberation); (4) cysteine addition did not enhance Cd uptake by cysteine-cultured marine Thalassiosira weissflogii when the concentration of immediately reacting strong ligands was sufficient to complex local Cd²⁺ liberation.

Type de document: Article
Mots-clés libres: amino acids; boundary layers; cadmium; marine biology; metal ions; phytoplankton; seawater effects
Centre: Centre Eau Terre Environnement
Date de dépôt: 29 nov. 2019 14:15
Dernière modification: 08 févr. 2022 20:02
URI: https://espace.inrs.ca/id/eprint/9563

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