Two tonB systems function in iron transport in Vibrio anguillarum, but only one is essential for virulence

We have identified two functional tonB systems in the marine fish pathogen Vibrio anguillarum, tonB1 and tonB2. Each of the tonB genes is transcribed in an operon with the cognate exbB and exbD genes in response to iron limitation. Only tonB2 is essential for transport of ferric anguibactin and virulence.