| Abstract: | The structural organization of Ectromelia virus DNA in infected mouse liver cells has been studied by using thin sections stained with the Feulgen-like osmium-ammine reaction. We found that in the cytoplasmic factories, free viral DNA was structured into completely extended filaments 2-3 nm thick. Viral DNA in immature virions, however, appeared to have a structural organization that superimposed that of eukaryotic chromatin. This was constituted by roundish subunits, with a diameter of 11-13 nm, composed of a DNA ring encircling an unstained inner core. The mature virion was composed of the same type of subunits, which were arranged in threads twisted into a figure 8 configuration. The distribution of basic proteins was also investigated with the acrolein silver-methenamine technique. In the viral particles only nucleoids were stained; a uniformly distributed positive reaction was observed in the cytoplasmic factories. |
