Bacterium-host interactions monitored by time-lapse photography

Any experimental system for measuring bacterial virulence has two parts: The bacterium itself and the host analog. Although animal models are the gold standard of research on bacterial virulence mechanisms, animals present a complex system in which many variables cannot be controlled. To study individual steps in the infection process, such as adherence and invasion, one must usually resort to cell cultures as model systems. Cultured mammalian cells are commonly used to provide a simpler, more easily controlled model for investigating host--bacterium interactions. We present a new technique, time-lapse photography, which is used to monitor interactions between the human gastric pathogen Helicobacter pylori and cultured epithelial cells. With this technique, we could visually establish the bacterium--host interaction in vitro with a more dynamic method than electron microscopy. The technique has many applications and may be suitable for measuring specific steps in colonization by other pathogenic bacteria.