The Type VI secretion system (T6SS) is a macromolecular machine anchored to the bacterial envelope that is widespread in Gram negative bacteria. This machine is one of the key players in the bacterial warfare by delivering anti-bacterial effectors directly into competitor cells. The T6SS consists of a membrane complex anchored in the bacterial envelope that recruits a platform assembly for a contractile tail structure. The tail is a tube wrapped by a sheath and topped by a needle spike. Effectors are loaded onto the spike or confined into the tube. Upon contact, the contraction of the sheath propels the inner tube and the spike toward target cells, hence delivering the toxin effectors. Our aim is to identify and determine the mode of action of T6SS effector toxins, using pathogenic Escherichia coli strains as a model. We also want to understand how T6SS effectors are loaded on the T6SS machine for delivery. We used a multidisciplinary approach using biochemistry, deletion mutagenesis, functional assays, fluorescence microscopy and cryo-Electron Microscopy to reveal how a phospholipase toxin binds the T6SS spike of enteroaggregative E. coli for delivery into target cells.​

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