Orius sc600a

Samples of selenite-amended culture were treated and analyzed as previously described (25 (link)). The samples were examined in an FEI Tecnai F20 field emission gun (FEG) transmission electron microscope operating at 200 kV and fitted with a Gatan Orius SC600A charge-coupled-device (CCD) camera, an Oxford Instruments XMax SDD energy-dispersive X-ray (EDX) detector, and a high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) detector.
For thin-section analysis, after the ethanol dehydration steps, the cells were embedded in EMbed 812 epoxy resin and cut into thin sections (90 nm, using a diamond knife on a Reichert Ultracut S ultramicrotome). The sections were supported on copper grids and coated with carbon. TEM specimen holders were cleaned by plasma prior to TEM analysis to minimize contamination. Samples were examined with a high-resolution Philips CM 200 transmission electron microscope at an acceleration voltage of 200 kV under standard operating conditions with the liquid nitrogen anticontaminator in place.

Aliquots (either neat, diluted or redispersed in ethanol) of the solid samples were deposited onto holey carbon TEM grids (Agar Scientific), which were transferred into a special anaerobic transfer holder (Gatan 648 Double tilt). This allowed the safe anaerobic transfer of the highly reactive samples to the TEM instrumentation. All samples were freshly synthesized just immediately prior to TEM analyses. The effect of the dilution with ethanol was tested and compared to a nonethanol diluted sample and no changes were observed in the resulting images or spectral and diffraction information.
HR-TEM imaging, selected area electron diffraction and energy dispersive X-ray (EDX) spot analysis were acquired using a Field-Emission-Gun-Transmission-Electron microscope (FEI Tecnai TF20) fitted with a CCD Camera (Gatan Orius SC600A) and an EDX spectrometer (Oxford Instruments 80 mm² X-max). The microscope was operated at 200 kV. To avoid beam damage, the exposure for image collection was limited to maximum 0.25 s. Images were analyzed using the ImageJ software^{37 (link)}. Atomic plane distances were calculated from the fast FFT analyses of several particles from the each acquired high-resolution image and from different areas in each image. The lattice planar distances were then calculated from the reciprocal values of the distance from the spots to the center (Supplementary Table 3).