3D density of D. radiodurans. (a) Direct volume rendering of the 3D effective mass density of freeze-dried D. radiodurans cells. The coloring indicates densities from 0.8 g/cm3 (blue) to 1.2 g/cm3 (red). (b) Surface rendering obtained by choosing 0.75 g/cm3 as a threshold value. The cells are shown from above and turned upside-down. The presumed position of the substrate is shown as a dotted rectangle at the bottom, where the structure of the cells is nearly flat. (c) Combined direct volume rendering (1.15-1.25 g/cm3) and surface rendering obtained by clipping the dataset with a plane. (d) Histogram of the effective mass density inside the surface shown in (b), corresponding to the volume occupied by the cells. The limits used for direct volume rendering in (a) and (c) are indicated by solid green and dashed red lines, respectively.