title: Bioaccumulation and subcellular partitioning of Cr(III) and Cr(VI) in the freshwater green alga Chlamydomonas reinhardtii.
abstract: Chromium occurs in aquatic environments under two main redox forms, namely Cr(III) and Cr(VI), with different geochemical and biochemical properties. Cr(VI) readily crosses biological membranes of living organisms and once inside the cells it undergoes a rapid reduction to Cr(III). The route of entry for the latter form is, however, poorly known. Using the radioactive tracer51Cr we compared the accumulation (absorption and adsorption) of the two Cr forms by the green unicellular alga Chlamydomonas reinhardii after 1h and 72h of exposure to 100nM of either Cr(III) or Cr(VI) at pH 7. Both Cr forms had similar accumulation, with a major part in the extracellular (adsorbed) fraction after 1h and a major part of total accumulated Cr in the intracellular (absorbed) fraction after 72h. We also investigated the intracellular partitioning of Cr using an operational fractionation scheme and found that both Cr forms had similar distributions among fractions: Cr was mostly associated with organelles (23±12% after 1h and 37±7% after 72h) and cytosolic heat-stable proteins and peptides (39±18% after 1h and 35±3% after 72h) fractions. Further investigations using a metallomic approach (SEC-ICP-MS) were performed with the heat-stable proteins and peptides fraction to compare the distribution of the two Cr forms among various biomolecules of this fraction. One Cr-binding biomolecule (∼28kDa) appeared after 1h of exposure for both Cr species. After 72h another biomolecule of lower molecular weight (∼0.7kDa) was involved in binding Cr and higher signal intensities were observed for Cr(VI) than for Cr(III). We show, for the first time, that both Cr(III) and Cr(VI) have similar fate within algal cells, supporting the tenet that a unique redox form occurs within cells.
authors.affiliation: Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360, Université de Lorraine and CNRS, 8 rue du Général Delestraint, 57070 Metz, France.
authors.forename: Imad
authors.initials: I
authors.lastname: Aharchaou
authors.affiliation: Institut National de la Recherche Scientifique, Centre Eau Terre Environnement (INRS-ETE), 490 rue de la Couronne, Québec (Québec) G1K 9A9, Canada.
authors.forename: Maikel
authors.initials: M
authors.lastname: Rosabal
authors.affiliation: Institut National de la Recherche Scientifique, Centre Eau Terre Environnement (INRS-ETE), 490 rue de la Couronne, Québec (Québec) G1K 9A9, Canada.
authors.forename: Fengjie
authors.initials: F
authors.lastname: Liu
authors.affiliation: Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360, Université de Lorraine and CNRS, 8 rue du Général Delestraint, 57070 Metz, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Battaglia
authors.affiliation: Laboratoire Interdisciplinaire des Environnements Continentaux, UMR 7360, Université de Lorraine and CNRS, 8 rue du Général Delestraint, 57070 Metz, France.
authors.forename: Davide A L
authors.initials: DAL
authors.lastname: Vignati
authors.affiliation: Institut National de la Recherche Scientifique, Centre Eau Terre Environnement (INRS-ETE), 490 rue de la Couronne, Québec (Québec) G1K 9A9, Canada. Electronic address: claude.fortin@ete.inrs.ca.
authors.forename: Claude
authors.initials: C
authors.lastname: Fortin
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D002857:Chromium / Q000737:chemistry / Q000378:metabolism*; D004781:Environmental Exposure; D005618:Fresh Water / Q000737:chemistry; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000378:metabolism
chemical_list: D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion
keywords: Hexavalent chromium; SEC-ICP-MS; Subcellular partitioning; Trivalent chromium; Unicellular alga