Two TonB Systems in Actinobacillus pleuropneumoniae : Their Roles in Iron Acquisition and Virulence

Iron acquisition in vivo by Actinobacillus pleuropneumoniae depends upon a functional TonB system. Tonpitak et al. (W. Tonpitak, S. Thiede, W. Oswald, N. Baltes, and G.-F. Gerlach, Infect. Immun. 68: 1164-1170, 2000) have described one such system, associated with tbpBA encoding the transferrin receptor, and here we report a second, termed tonB2 . This gene cluster ( exbB2 - exbD2 - tonB2 ) is highly homologous to those in other Pasteurellaceae...