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Issue 42, 2016
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The role of extracellular DNA in uranium precipitation and biomineralisation

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Bacterial extra polymeric substances (EPS) have been associated with the extracellular precipitation of uranium. Here we report findings on the biomineralisation of uranium, with extracellular DNA (eDNA) used as a model biomolecule representative of EPS. The complexation and precipitation of eDNA with uranium were investigated as a function of pH, ionic strength and varying concentrations of reactants. The role of phosphate moieties in the biomineralisation mechanism was studied by enzymatically releasing phosphate (ePO4) from eDNA compared to abiotic phosphate (aPO4). The eDNA–uranium precipitates and uranium minerals obtained were characterised by Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FT-IR) spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-Ray analysis (SEM-EDX), X-Ray Powder Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS). ATR-FT-IR showed that at pH 5, the eDNA–uranium precipitation mechanism was predominantly mediated by interactions with phosphate moieties from eDNA. At pH 2, the uranium interactions with eDNA occur mainly through phosphate. The solubility equilibrium was dependent on pH with the formation of precipitate reduced as the pH increased. The XRD data confirmed the formation of a uranium phosphate precipitate when synthesised using ePO4. XPS and SEM-EDX studies showed the incorporation of carbon and nitrogen groups from the enzymatic orthophosphate hydrolysis on the obtained precipitated. These results suggested that the removal of uranium from solution occurs via two mechanisms: complexation by eDNA molecules and precipitation of a uranium phosphate mineral of the type (UO2HPO4xH2O by enzymatic orthophosphate hydrolysis. This demonstrated that eDNA from bacterial EPS is a key contributor to uranium biomineralisation.

Graphical abstract: The role of extracellular DNA in uranium precipitation and biomineralisation

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Publication details

The article was received on 12 May 2016, accepted on 22 Sep 2016 and first published on 27 Sep 2016

Article type: Paper
DOI: 10.1039/C6CP03239G
Citation: Phys. Chem. Chem. Phys., 2016,18, 29101-29112
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    The role of extracellular DNA in uranium precipitation and biomineralisation

    J. Hufton, J. H. Harding and M. E. Romero-González, Phys. Chem. Chem. Phys., 2016, 18, 29101
    DOI: 10.1039/C6CP03239G

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