Toward sub-second correlative light and electron microscopy of Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae is a model organism widely used to study cell biological processes because of its easy genomic manipulation and its close relatedness to higher eukaryotes. For electron microscopy, the good freezing properties and the small size of yeast cells make it a nearly ideal specimen for the development of cryopreparation techniques. Here we report on the development of a method to correlate yeast cells by live-fluorescence and electron microscopy with the potential to achieve sub-second correlation times. This is possible by plunge-freezing of an optically transparent sample sandwich, so that the temporal resolution is only determined by the transfer speed from the fluorescence microscope to the freezing device. While direct correlation was not yet achieved, the system already offers the possibility to verify the state of the identical population of cells by fluorescence microscopy immediately before freezing and processing for transmission electron microscopy.