Live Imaging of Ions in Cells Infected with Chlamydia trachomatis

This chapter describes methodological approaches for studying intracellular ion dynamics during Chlamydia trachomatis infection. It emphasizes the requirement for live-cell imaging to capture active and compartmentalized ion fluxes in infected cells precluded by fixed-cell techniques. Specifically, we present step-by-step protocols for labeling Chlamydia-infected cells with a fluorescent potassium ion (K⁺)-sensitive probe for performing live imaging with confocal microscopy or spinning disc confocal microscopy for higher resolution and procedures for image processing and quantification. We also describe time-lapse microscopy to monitor K⁺ dynamics over the extended time course of the infection. These advanced microscopy methods have the potential to visualize ion transport in real time at the host-pathogen interface.