Bacteria stab amoebae with micro-daggers

Bacteria have to watch out for amoeba. Hungry amoebae hunt them: they catch them with their pseudopodia and then absorb and digest them.

However, some bacteria know how to defend themselves. One of these is Amoebophilus, which was discovered by researchers at the University of Vienna a few years ago. This bacterium cannot only survive inside amoebae, but also thrive: the amoeba has become its favourite habitat.

Together with the Viennese discoverers of the bacterium, scientists from ETH Zurich have now found a mechanism that they assume is crucial for the survival of Amoebophilus inside the amoeba. The bacterium has devices to shoot micro-daggers. It can use the daggers to pierce the amoeba from inside and thus escape digestion.

Escape from the amoeba's gut

The shooting mechanism consists of a sheath attached to the bacterium's inner membrane by a baseplate and an anchoring platform. João Medeiros, a doctoral student in Professor Martin Pilhofer's group at ETH, explains the mechanism: "The sheath is spring-loaded and the micro-dagger lies inside it. When the sheath contracts, the dagger is shot outwards extremely quickly through the bacterial membrane."

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