Probing changes in Hg(II) coordination during its bacterial uptake

[摘要] We present XAFS data collected at the Hg LIII-edge for bacterial cells of Escherichia coli that have been exposed to 500 and 50 nano-molar Hg2+in aqueous solution, which corresponds to ∼30 and ∼3μg Hg per g cells (wet weight). These concentrations are respectively 1 and 2 orders of magnitude lower than what has been previously reported for Hg-bacteria XAFS experiments. The cells were metabolically active while exposed to Hg(II), providing coordination information that can be directly compared to Hg(II) biouptake experiments. At these amounts of total dissolved metal, Hg(II) binds primarily to thiol moieties that are either present at the cell membrane or localized in the cytoplasm. We show that in this case the Hg binding environment is a mixture of 2- and 4-fold coordination to thiols. This information can be inferred from XANES spectra but the EXAFS provides a more quantitative answer.

[发布机构] Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston; IL; 60208-3109, United States^1;DND-CAT Synchrotron Research Center, APS/ANL Building 432A, 9700 S. Cass Ave., Argonne; IL; 60439-4857, United States^2

[关键词] Bacterial cells;Bacterial uptake;Biouptake;Dissolved metals;Exposed to;Orders of magnitude;Wet weight;XANES spectra