Avian Reoviruses V. Studies of Ultrastructural Morphology by Electron Microscopy

The ultrastructural morphology of avian reoviruses 24, 25, and 59 was studied by electron microscopy utilizing both negative-staining and thin-sectioning techniques. Viruses 24 and 25 had an average diameter of 62 nm in negatively stained preparation. In thin sections the average respective diameters of viruses 24 and 25 were 56 and 61 nm. The virus particles had cubic symmetry and a double capsid structure, as is true of all other reoviruses. They were without an envelope. Virus 59 had average respective diameters of 77 and 76 nm in negatively stained preparations and thin sections. The particles were nonenveloped. Reoviruses 24 and 25 differed from 59 in size besides the other characteristics reported previously. The present morphological observations support earlier classification of reoviruses 24, 25 and 59 as avian members of the reovirus group.