The dangerous food-borne pathogen Listeria monocytogenes (the specks of green) enters the body via the gut, specifically at the tips of tiny finger-like projections that line the intestine, called villi (red, seen here from above). Cells at the villi tips are regularly shed, which exposes a protein that the bacteria use to get inside the cells. The E-cadherin protein sticks cells together like grout between tiles. How Listeria manage to reach that grout had long perplexed scientists but they now know that it is the continuous replacement of the cellular tiles at the villi tips that gives the bugs the perfect opportunity.
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