Regulation of the T6SS in V. cholerae is poorly understood. We recently identified the T6SS regulator VasH, predicted to encode a transcriptional regulator and activator of the alternate σ-factor σ54, essential for Hcp production (3). In pandemic strains, expression of T6SS genes remains undetected under laboratory conditions. In contrast, the O37 serogroup strain V52 constitutively expresses the T6SS and serves as our experimental model system for studying T6SS-mediated virulence (3).