ABSTRACT
The SARS-CoV-2 pandemic has had a global impact and has put scientific endeavour in the spotlight, perhaps more than any previous viral outbreak. SARS-CoV-2 also emerged at the inflection point of a technological revolution in macromolecular imaging by cryo-electron microscopy (cryo-EM), fuelled by a confluence of major technological advances in sample preparation, optics, detectors and image processing software, that complemented pre-existing techniques. Electron microscopy samples must be imaged in a vacuum to prevent scattering of the electron beam, thus making it impossible to study the dynamics of biological processes in living specimens. By contrast, light microscopy can be performed on live cells, allowing for example, tracking of fluorescently labelled viruses in real-time as they travel through the cell. Individual viral RNAs with branched secondary structures were observed and viral proteins were found at sites with increased membrane curvature in the cryo-ET reconstructions, representing nascent virus particles captured at intermediate assembly steps.
