Type Three Secretion System Island-Encoded Proteins Required for Colonization by Non-O1/Non-O139 Serogroup Vibrio cholerae

Abstract

ABSTRACT Vibrio cholerae is a genetically diverse species, and pathogenic strains can encode different virulence factors that mediate colonization and secretory diarrhea. Although the toxin-coregulated pilus (TCP) is the primary colonization factor in epidemic-causing V. cholerae strains, other strains do not encode the TCP and instead promote colonization via the activity of a type 3 secretion system (T3SS). Using the infant mouse model and T3SS-positive O39 serogroup strain AM-19226, we sought to determine which of 12 previously identified, T3SS-translocated proteins (Vops) are important for host colonization. We constructed in-frame deletions in each of the 12 loci in strain AM-19226 and identified five Vop deletion strains, including ΔVopM, which were severely attenuated for colonization. Interestingly, a subset of deletion strains was also incompetent for effector protein transport. Our collective data therefore suggest that several translocated proteins may also function as components of the structural apparatus or translocation machinery and indicate that while VopM is critical for establishing an infection, the combined activities of other effectors may also contribute to the ability of T3SS-positive strains to colonize host epithelial cell surfaces.