title: Cysteine Enhances Bioavailability of Copper to Marine Phytoplankton.
abstract: Emiliania huxleyi, a ubiquitous marine algae, was cultured under replete and Cu-limiting conditions to investigate Cu uptake strategies involving thiols and associated redox reactions; comparisons to a model diatom, Thalassiosira pseudonana, were also drawn. Cu-limitation increased rates of cell surface reduction of Cu(II) to Cu(I) in E. huxleyi but not in T. pseudonana. Furthermore, Cu-limited E. huxleyi cells took up more Cu when cysteine was present compared to when no ligand was added, although a dependence on cysteine concentration was not observed. In contrast, Cu uptake by replete cells was dependent upon the relative abundance of inorganic species [Cu(I)']. We also show that cysteine can increase the bioavailability of Cu to Cu-limited cells, of both species, through the reductive release of Cu(I) from fairly strong Cu(II) ligands such as EDTA. Finally, support for a mechanism involving uptake of a Cys-Cu complex in E. huxleyi is drawn from the observation that Cu-limitation significantly enhances cysteine uptake by transporters that exhibit Michaelis-Menten kinetics. These Cu uptake strategies help explain the presence and distribution of dissolved thiols in surface seawater and have implications for the biogeochemical cycling of Cu in low Cu environments.
authors.affiliation: Cornell University , Biological & Environmental Engineering, Ithaca, New York 14853-5701, United States.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Walsh
authors.affiliation: Cornell University , Biological & Environmental Engineering, Ithaca, New York 14853-5701, United States.
authors.forename: Sarah D
authors.initials: SD
authors.lastname: Goodnow
authors.affiliation: Cornell University , Biological & Environmental Engineering, Ithaca, New York 14853-5701, United States.
authors.forename: Grace E
authors.initials: GE
authors.lastname: Vezeau
authors.affiliation: Cornell University , Biological & Environmental Engineering, Ithaca, New York 14853-5701, United States.
authors.forename: Lubna V
authors.initials: LV
authors.lastname: Richter
authors.affiliation: Cornell University , Biological & Environmental Engineering, Ithaca, New York 14853-5701, United States.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Ahner
mesh_terms: D059001:Aquatic Organisms / Q000378:metabolism*; D001682:Biological Availability; D003300:Copper / Q000493:pharmacokinetics*; D003545:Cysteine / Q000378:metabolism*; D017377:Diatoms / Q000378:metabolism*; D004492:Edetic Acid / Q000737:chemistry; D058087:Haptophyta / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D010084:Oxidation-Reduction; D010839:Phytoplankton / Q000378:metabolism*; D012623:Seawater / Q000737:chemistry
chemical_list: D008024:Ligands; D003300:Copper; D004492:Edetic Acid; D003545:Cysteine