rfb Mutations in Vibrio cholerae Do Not Affect Surface Production of Toxin-Coregulated Pili but Still Inhibit Intestinal Colonization

The toxin-coregulated pilus (TCP) of Vibrio cholerae is essential for colonization. It was recently reported that rfb mutations in V. cholerae 569B cause the translocation arrest of the structural subunit of TCP, raising the possibility that the colonization defects of lipopolysaccharide mutants are due to effects on TCP biogenesis. However, an rfbB gene disruption in either V. cholerae O395 or 569B has no apparent effect on surface TCP production as assessed by immunoelectron microscopy and CTX phage transduction, and an rfbD::Tn5lac mutant of O395 also shows no defect in TCP expression. We conclude that the colonization defect associated with rfb mutations is unrelated to defects in TCP assembly.