Figure shows electron tomography of experimental and control cells. Panel A shows 75 of 340 slices through an E. coli cell expressing FtsZ-cSeNP, grown in 2 mM SeO3 2-. Two features are readily apparent: (1) The outer membrane (OM) and portions of the inner membrane (IM); (2) Punctate densities interpreted as CuSeNPs arising from cSeNPs (blue arrows mark 3 of the 22 punctate densities in this image). The cellular preparation process made the inner-membrane difficult to discern; Membranes also distort during fixation.[cite] Panel B shows a magnified view of the boxed area panel A, with the OM manually segmented in blue. The CuSeNPs (cSeNP) particles have sufficient contrast for automatic segmentation. Panel C shows an isosurface rendering of the boxed section of panel A, except rendering the full X-slice tomogram. The isosurface rendering gives a pink color to all voxels with intensities below a threshold level. Importantly, automatic segmentation of CuSeNPs removes the human bias in their identification. Automatic segmentation CuSeNPs in whole cells is also accomplished with the BeadFinder program of the IMOD software package. Panel D of Figure shows manual membrane and automatic CuSeNP segmentation for the entire 250 nm thick tomogram. Panel E shows a magnified image of the boxed area of Panel D.