Extended Data Figure 7: Electron cryotomography of H. volcanii.

Cells growing in Hv-YPC + 4 mM Trp were frozen in vitreous ice to maintain native structure, and then tomographic data were acquired with a 300 kV cryo-transmission electron microscope. A 10 nm section from the tomographic reconstruction of the whole cell is shown for each. a, H98+pTA962 (wild-type) cell, showing cell envelope layers with some structural detail of the outer S-layer visible, a dense granule, particles consistent with ribosomes visible in the outer ∼25% of the cytoplasmic region, and fibres that may be seen underlying the cell envelope. b, Wild-type cell, with detail of the cell envelope region (inset as per Fig. 4f). c, Cells overproducing CetZ1(E218A) (H98+pTA962-cetZ1(E218A)), show extensive sections of the envelope with underlying fibres (inset as per Fig. 4f). (Supplementary Video 5 shows a segment image series through a cell, showing the sheet-like structure of the extra layer.) d, Example showing subtle ruffling of the cell envelope associated with the additional envelope fibres in a cell producing CetZ1(E218A). Scale bars, 100 nm for all panels, and 50 nm for all insets.