Several cellular activities such as phagocytosis and cell migration are intimately dependent on a spatially-and temporally-regulated remodelling of the actin cytoskeleton. Because these processes are characterised by a complex series of events that are interconnected with each other, the molecular mechanisms that operate during these cellular processes could not be easily investigated using traditional biochemical and genetic approaches. A simplified system for better understanding actin-based events was provided by the realisation, more than a decade ago, that the gram-positive bacterium Listeria monocytogenes has the ability to subvert the actin cytoskeleton of cells it has infected and use the host