Iron transport in Francisella in the absence of a recognizable TonB protein still requires energy generated by the proton motive force.

The mechanism of iron transport in Francisella is still a puzzle since none of the sequenced Francisella strains appears to encode a TonB protein, the energy transducer of the proton motive force necessary to act on the bacterial outer membrane siderophore receptor to allow the internalization of iron. In this work we demonstrate using kinetic experiments of radioactive Fe(3+) utilization, that iron uptake in Francisella novicida, although with no recognizable TonB protein, is indeed dependent on energy generated by the proton motive force. Moreover, mutants of a predicted outer membrane receptor still transport iron and are sensitive to the iron dependent antimicrobial compound streptonigrin.

Complete sequence of virulence plasmid pJM1 from the marine fish pathogen Vibrio anguillarum strain 775.

The virulence plasmid pJM1 enables the fish pathogen Vibrio anguillarum, a gram-negative polarly flagellated comma-shaped rod bacterium, to cause a highly fatal hemorrhagic septicemic disease in salmonids and other fishes, leading to epizootics throughout the world. The pJM1 plasmid 65,009-nucleotide sequence, with an overall G+C content of 42.6%, revealed genes and open reading frames (ORFs) encoding iron transporters, nonribosomal peptide enzymes, and other proteins essential for the biosynthesis of the siderophore anguibactin.

Plasmid-mediated iron uptake and virulence in Vibrio anguillarum.

The plasmid pJM1 of Vibrio anguillarum harbors genes encoding proteins that enable the bacterial cell to survive under iron limiting conditions. A subset of these proteins are involved in the biosynthesis of the siderophore anguibactin and in the internalization of the ferric-siderophore into the cell cytosol. We have identified several genes encoding non-ribosomal peptide synthetases that catalyze the synthesis of anguibactin, these genes are: angB/G, angM, angN, angR, and angT.