T6SS-mediated killing of eukaryotic cells such as J774 macrophages and D. discoideum requires the activity of VgrG1 (3). Like the accessory toxin RtxA, VgrG1 carries a C-terminal ACD that, when exposed to a host cytosol, irreversibly cross-links host actin (16). We investigated whether the ACD could confer T6SS-mediated bacterial virulence by targeting MreB, a bacterial actin homolog capable of polymerizing into a protofilament similar to eukaryotic actin (17). Survival of E. coli prey was measured following exposure to V. cholerae predator strains V52, V52ΔvasK, and V52ΔACD in the killing assay, as described in Materials and Methods. V52ΔACD retained wild-type levels of E. coli killing, suggesting that MreB is not targeted in bacterial prey (Fig. 5).