In the mid 1990s, scientists discovered the oral pathogen Porphyromonas gingivalis can invade and survive within the outer, or epithelial, cells of the gingiva. Subsequent work established this oral bacterium also can replicate within these cells and infect nearby gingival epithelial cells, suggesting a possible route of infection in causing periodontal disease. In the January issue of the journal Infection and Immunity, NIDCR grantees report how P. gingivalis might spread from one cell to the next. Rather than releasing into the extracellular space as might be expected, the bacterium “translocates,” directly into neighboring cells. They found it may do so via a protrusion of the cell membrane that appears to be composed of the filament-like actin protein. In this way, P. gingivalis can colonize oral issues without exposing itself to antibody-producing immune cells.