Our innate immune system, made up mainly of phagocytes, protects our body by exterminating bacteria. To do this, it uses two mechanisms. The first kills foreign bodies within the phagocyte itself. The second kills them outside the cell. These two strategies were already known to researchers, but only in humans and other higher animals. Microbiologists from the University of Geneva (UNIGE), Switzerland, have just discovered that a social amoeba, a unicellular microorganism living in the soils of temperate forests, also uses both these mechanisms, and has done so for over a billion years.