Listeria monocytogenes uses an actin tail to project itself into neighboring cells. This process allows the bacterium to cross the placental and blood-brain barriers and causes spontaneous abortion and meningitis, respectively, but it has only been documented in a few static electron micrographs. Now Robbins et al. (page 1333) observe intercellular Listeria movement in real time, and suggest that it may take advantage of a conserved host cell engulfment process.
Once a Listerium has formed an intercellular protrusion averaging 8.5 μm in length, the bacterium continues an erratic motility that Robbins et al. term “fitful movement.” This ceases after ∼20 min, presumably when the donor cell's membrane is sealed, cutting off the supply of ATP. Another ∼20 min later, the second (host cell) membrane fuses, and the protrusion shrinks to a roughly spherical double membrane vacuole. Within 5 min...
