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).