Article Figures & Data
Figures
- FIG. 1.
Distribution of selenium species obtained at different times of exposure of C. metallidurans CH34 cells to 2 mM selenate added in TSM medium containing 0.3 mM sulfate. Selenate was added in the culture medium at the end of the exponential growth phase. Distribution of selenium species was determined from Se K-edge XANES spectra simulated by linear combination from reference spectra of crystallized sodium selenate [Se(VI)] and either the selenodiglutathione organic species, RSSeSR, or red elemental selenium, Se(0).
- FIG. 2.
Se K-edge XANES (A) and EXAFS (B) spectra for bacteria sampled at the beginning (a) and end (b) of exposure to 2 mM selenate in TSM medium containing 0.3 mM sulfate. k2·χ(k), EXAFS function weighted by k2, with k being the wave vector in inverse Angstroms (A−1). Se references are also shown as follows: c, selenate [Se(VI)]; d, methyl-seleno-l-cysteine (RSeR); e, seleno-l-methionine (RSeR); f, selenodiglutathione (RSSeSR); and g, red elemental selenium [Se(0)]. (C) Species distribution obtained with bacteria exposed for 6 days to 2 mM selenate in TSM medium containing 0.3 mM sulfate. Simulations of EXAFS spectra were performed by an LCF of three components: Se(VI), RSeR and RSSeSR, or Se(0). Values below 10% (in italics) were considered not significant.
- FIG. 3.
(Left) TEM images of C. metallidurans CH34 cells after 49 h of exposure to 2 mM selenate in sulfate-limited medium. (Right) EDX spectrum of the electron-dense particles observed in the cytoplasm of the bacteria (X-ray emission lines for selenium would have been at 1.37, 11.22, and 12.49 keV [Lα, Kα, and Kβ rays, respectively]).
