A look beyond topography: transient phenomena of Escherichia coli cell division captured with high-speed in-line force mapping
Life on the nanoscale has been made accessible in recent decades by the development of techniques that are fast and non-invasive. High-speed atomic force microscopy (HS-AFM) is one such technique that has proven to shed light on elusive mechanisms involving single proteins. Extending HS-AFM to effortlessly incorporate mechanical property mapping while maintaining fast imaging speed allows us to look deeper than topography and reveal more details of the nanoscale mechanisms that govern life. Here, we present high-speed in-line force mapping (HS-iFM), which enables the recording of mechanical properties and topography maps with high spatiotemporal resolution. Employing this method, a detailed study of the dynamic nanoscale mechanical properties of living Escherichia coli bacteria reveals localized stiffening during division, intricate details of the division process, formation and diffusion of pores in the membrane, and the impact of depressurization of a cell. All of these phenomena were recorded with a frame time as low as 15 s and a spatial resolution of 5.5 nm/pixel in topography and 22 nm/pixel in force maps, allowing the capture of transient phenomena on bacterial surfaces in striking detail.