A Vibrio T6SS-mediated lethality in a marine animal model

Bacteria belonging to the genus Vibrio include many known and emerging pathogens. Horizontal gene transfer of pathogenicity islands is a major contributor to the emergence of new pathogenic Vibrio strains. In the current report, we use the brine shrimp Artemia salina as a model to show that the marine bacterium Vibrio proteolyticus uses a mobile type VI secretion system, T6SS3, to intoxicate eukaryotic hosts. Two T6SS3 effectors, which were previously shown to induce inflammasome-mediated pyroptotic cell death in mammalian phagocytic cells, contribute to this toxicity. Furthermore, we find a novel, widespread T6SS3 effector that also contributes to the lethality mediated by this system against Artemia salina. Therefore, our results reveal a T6SS that is shared among diverse vibrios and mediates host lethality, indicating that it can lead to the emergence of new pathogenic strains.