It has long been speculated that V. cholerae has evolved mechanisms to kill bacterial competitors. Chakrabarty et al. identified 11 diffusible bacteriocins with toxicity toward the enteric bacteria Escherichia coli, Shigella sonnei, and Shigella flexneri (15). However, expression of such bacteriocins and mechanisms underlying their antimicrobial properties are not well understood. Thus, we investigated whether the T6SS contributes to the antimicrobial properties of V. cholerae. Interbacterial virulence was determined by exposing bacterial prey (the organism that is attacked) to a bacterial predator (a V. cholerae strain that is attacking) and measuring the survival of bacterial prey. Here, we present experimental evidence to demonstrate the antimicrobial properties of the V. cholerae T6SS. We propose that interbacterial toxicity
promotes V. cholerae survival in the environment and/or during colonization of a host.