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Bacteria stab amoebae with daggers


Researchers from ETH Zurich and the University of Vienna have discovered a type of bacteria that uses tiny daggers to prevent itself from being eaten by amoebae.

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 a team around Mathias Horn from the Department of Microbiology and Ecosystem Science and Research network "Chemistry meets Microbiology". Amoebophilus 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. The scientists also resolved the three-dimensional structure of the mechanism that allows the micro-daggers to be shot quickly.

Böck D, Medeiros JM, Tsao HF, Penz T, Weiss GL, Aistleitner K, Horn M, Pilhofer M: In situ architecture, function and evolution of a contractile injection system. Science, 18 August 2017, DOI: 10.1126/science.aan7904



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A cluster of spring-loaded daggers inside a bacterium. Green in their “loaded” form, red after the dagger has been launched. (Visualisations: Leo Popovich)