The TonB systems of V. vulnificus and their homology to other bacterial species. (A) The three TonB systems of V. vulnificus are depicted. The percentages of identity of the V. vulnificus proteins to the V. parahaemolyticus, V. alginolyticus, V. cholerae, and V. anguillarum proteins are shown. The percentage of identity is listed below each protein being compared. NA represents the lack of that system in the bacterium. (B) The TtpC2-TonB2 system of V. vulnificus, V. parahaemolyticus, and V. alginolyticus is compared to the TtpC3-TonB3 system from the same species. The percentage of identity is listed below each protein being compared. (C) The TonB system of E. coli is compared against the TonB1 systems of V. vulnificus, V. parahaemolyticus, V. alginolyticus, V. cholerae, and V. anguillarum. The percentage of identity is listed below each protein being compared.