title: Interactions of core-shell quantum dots with metal resistant bacterium Cupriavidus metallidurans: consequences for Cu and Pb removal.
abstract: In the present study we address the interactions of carboxyl-CdSe/ZnS core/shell quantum dots (QDs), as a model of water dispersible engineered nanoparticles, and metal resistant bacteria Cupriavidus metallidurans, largely used in metal decontamination. The results demonstrate that QDs with average hydrodynamic size of 12.9 nm adhere to C. metallidurans. The percentage of bacterial cells displaying QD-fluorescence increased proportionally with contact time and QD concentration in bacterial medium demonstrating the association of QDs with the metal resistant bacteria. No evidence of QD internalization into bacterial cytoplasm was found by transmission electron microscopy with energy dispersive X-ray spectrometry, however QD clusters of sizes between 20 and 50 nm were observed on the bacterial surface and in the bacterial periplasmic compartment; observations consistent with the losses of membrane integrity induced by QDs. The presence of 20 nM QDs induced about 2-fold increase in Cu and Pb uptake fluxes by C. metallidurans exposed to 500 nM Pb or Cu, respectively. Overall, the results of this work suggest that when present in mixture with Cu and Pb, low levels of QDs originating from possible incidental release or QD disposal could increase metal accumulation in metal resistant bacterium.
authors.affiliation: Environmental Biogeochemistry and Ecotoxicology, Institute F.-A. Forel, Earth and Environment Science, Faculty of Sciences, University of Geneva, 10, route de Suisse, 1290 Versoix, Switzerland. Electronic address: vera.slaveykova@unige.ch.
authors.forename: Vera I
authors.initials: VI
authors.lastname: Slaveykova
authors.forename: José Paulo
authors.initials: JP
authors.lastname: Pinheiro
authors.forename: Magali
authors.initials: M
authors.lastname: Floriani
authors.forename: Miguel
authors.initials: M
authors.lastname: Garcia
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D003300:Copper / Q000737:chemistry / Q000378:metabolism*; D049921:Cupriavidus / Q000254:growth & development / Q000378:metabolism*; D007854:Lead / Q000737:chemistry / Q000378:metabolism*; D045663:Quantum Dots / Q000737:chemistry; D018036:Selenium Compounds / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; D007854:Lead; D003300:Copper; C058667:cadmium selenide; C031238:zinc sulfide
keywords: Bacteria; Bioremediation; Metal uptake; Quantum dots