A bacterial shield that works in reverse — and could sharpen tomorrow's gene-editing tools

Bacteria carry tiny built-in defenses called retrons that sacrifice an infected cell to save the colony. A Gladstone Institutes team in San Francisco has now mapped a kind called type VI that does everything backwards: instead of keeping a toxin ready-made, it only starts building its DNA trigger after a virus invades, which then switches the toxin on. Published in Molecular Cell, the backwards design is already inspiring new sensors, switches and possible germ-fighting therapies.