Fig. 1

Early TEM examinations of VACV and proposed virion assembly. a Brick-shaped morphology of VACV “elementary bodies” first described by Ruska in 1939. b Thin-section TEM images of VACV mature virions (top row) and immature virions containing nucleoids (bottom row). c VACV assembly cycle as proposed by Dales, showing schematic illustration of virion morphology and post-infection time in hours. d TEM image of negatively stained whole VACV mature virion exhibiting characteristic surface tubule decoration. Scale bars are 0.5 μm in (a) and (b), and 0.1 μm in (d). The images are reprinted with permission. Original works are from a Ruska et al., Archiv für die gesamte Virusforschung, 1939, doi: https://doi.org/10.1007/BF01243399, b, c Dales and Siminovitch, The Journal of Biophysical and Biochemical Cytology, 1961, doi: https://doi.org/10.1083/jcb.10.4.475, d Dales, The Journal of Cell Biology, 1962, doi: https://doi.org/10.1083/jcb.13.2.303