Single-Molecule and Superresolution Imaging in Live Bacteria Cells

Single-molecule imaging enables biophysical measurements devoid of ensemble averaging, gives enhanced spatial resolution beyond the diffraction limit, and permits superresolution reconstructions. Here, single-molecule and superresolution imaging are applied to the study of proteins in live Caulobacter crescentus cells to illustrate the power of these methods in bacterial imaging. Based on these techniques, the diffusion coefficient and dynamics of the histidine protein kinase PleC, the localization behavior of the polar protein PopZ, and the treadmilling behavior and protein superstructure of the structural protein MreB are investigated with sub-40-nm spatial resolution, all in live cells. Since its advent 20 years ago, single-moleculefluorescence imaging has given rise to a host of exciting experiments (Ambrose andMoerner 1991). Beyond enabling fundamental investi-gations of the physics of emissive molecules, one main advantage of this technique is its use in biologically relevant, live-cell experiments. Optical fluorescence microscopy is an impor