VISUALIZATION OF INDIVIDUAL REOVIRUS PARTICLES BY LOW-TEMPERATURE, HIGH-RESOLUTION SCANNING ELECTRON-MICROSCOPY

We used low-temperature, high-resolution scanning electron microscopy (cryo-HRSEM) to visualize surface structures on individual reovirus pa rticles. Both intact virions and two forms of subvirion particles-infe ctious subvirion particles and cores-were examined, and despite some d istortion of particles during specimen preparation and viewing in the microscope, the images obtained by cryo-HRSEM exhibited a level of int erpretable detail not routinely achieved by other methods without imag e averaging. Cryo-HRSEM images of discrete reovirus particles were use d to characterize and confirm features of the outer protein capsid of this virus by comparison with image reconstructions previously derived from cryotransmission electron microscopy. Distinct surface features attributable to each of the four outer-capsid proteins were identified . In addition, cryo-HRSEM images confirmed that significant changes oc cur on the surfaces of individual reovirus particles during disassembl y and entry of cells and that the reovirus outer capsid is organized a s a left-handed T=13 icosahedron. Several unique capabilities and pote ntial uses suggest that cryo-HRSEM has a place alongside other, more e stablished methods for molecular characterizations of virus particles. (C) 1995 Academic Press, Inc.