Shigella flexneri invading embryonic stem cell

Shigella flexneri is the causative agent of human shigellosis via the faecal-oral route, typically resulting in dysentery. Shigella invades through microfold (M) cells in the host gut in humans and primates solely. This scanning electron micrograph was produced as part of a research project using genetically modified embryonic stem cells to study Shigella-host interactions. The image demonstrates that after long filopodia from the host cell establish contact with the bacteria, actin-rich cell membrane ruffles are formed which envelope and engulf the Shigella. This process is actively orchestrated by the bacterium itself using the type III secretion system. The Shigella cell in center is 5µm long.