title: Selenite transport and its inhibition in the unicellular green alga Chlamydomonas reinhardtii.
abstract: The influence of time, ambient concentration, and medium composition on selenite (Se(IV)) uptake by the unicellular green alga Chlamydomonas reinhardtii has been investigated. The aims of the performed experiments were to describe the kinetics of accumulation, to characterize transport capacities, to identify key nutrients influencing absorption, and to establish links between speciation and bioavailability. Our results suggested that the adsorbed fraction was negligible compared to the absorbed one. Over the short time scale considered, the absorption was linear with time, with an estimated conductance of approximately 0.2 nmol/m2/h/nM. Uptake was proportional to ambient levels in a broad range of intermediate concentrations (from nM to microM). However, conductances were higher at low concentrations (< nM) and then decreased with increasing concentrations (> microM). These results suggested that a specific but rapidly saturated transport system was involved at low concentrations, coupled with a nonspecific one that was only saturated at high ambient concentrations (approximately mM). The latter could involve transporters used by anionic macronutrients, which is supported by the fact that increasing sulfate and nitrate concentrations induced significant inhibition of Se(IV) uptake. Finally, Se(IV) speciation changes caused by varying pH did not significantly affect bioavailability.
authors.affiliation: Laboratoire de Radioécologie et Ecotoxicologie, Institut de Radioprotection et Sûreté Nucléaire, Cadarache, Bat 186, BP 3, 13115 Saint-Paul-lez-Durance, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Morlon
authors.forename: Claude
authors.initials: C
authors.lastname: Fortin
authors.forename: Christelle
authors.initials: C
authors.lastname: Adam
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Garnier-Laplace
mesh_terms: D000818:Animals; D000838:Anions / Q000737:chemistry; D001692:Biological Transport; D016825:Chlamydomonas reinhardtii / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009994:Osmolar Concentration; D012643:Selenium / Q000378:metabolism; D018038:Sodium Selenite / Q000378:metabolism* / Q000494:pharmacology*; D012995:Solubility
chemical_list: D000838:Anions; D012643:Selenium; D018038:Sodium Selenite