Redundant TonB systems which function in iron transport from TonB-dependent ligands have recently been identified in several gram-negative bacteria. We demonstrate here that in addition to the previously described tonB locus, an alternative system exists for the utilization of iron from hemoglobin, transferrin, or lactoferrin in Neisseria meningitidis and Neisseria gonorrhoeae. Following incuba...

In the fish pathogen Vibrio anguillarum the TonB2 protein is essential for the uptake of the indigenous siderophore anguibactin. Here we describe deletion mutants and alanine replacements affecting the final six amino acids of TonB2. Deletions of more than two amino acids of the TonB2 C-terminus abolished ferric-anguibactin transport, whereas replacement of the last three residues resulted in a...

The uropathogenic Escherichia coli strain CFT073 has multiple iron acquisition systems, including heme and siderophore transporters. A tonB mutant derivative of CFT073 failed to use heme as an iron source or to utilize the siderophores enterobactin and aerobactin, indicating that transport of these compounds in CFT073 is TonB dependent. The TonB(-) derivative showed reduced virulence in a mouse...

For the uptake of scarce yet essential organometallic compounds, outer membrane transporters of Gram-negative bacteria work in concert with an energy-generating inner membrane complex, thus spanning the periplasmic space to drive active transport. Here, we examine the interaction of TonB, an inner membrane protein, with an outer membrane transporter based upon a recent crystal structure of a To...

TonB-dependent transport is a mechanism for active uptake across the outer membrane of Gram-negative bacteria. The system promotes transport of rare nutrients and was thought to be restricted to iron complexes and vitamin B12. Recent experimental evidence of TonB-energized transport of nickel and different carbohydrates, in addition to bioinformatic-based predictions, challenges this notion and...

Bartonella quintana is a gram-negative agent of trench fever, chronic bacteremia, endocarditis, and bacillary angiomatosis in humans. B. quintana has the highest known hemin requirement among bacteria, but the mechanisms of hemin acquisition are poorly defined. Genomic analyses revealed a potential locus dedicated to hemin utilization (hut) encoding a putative hemin receptor, HutA; a TonB-like ...

The pectinolytic enterobacterium Erwinia chrysanthemi 3937 causes a systemic disease in its natural host, the African violet (Saintpaulia: ionantha). It produces two structurally unrelated siderophores, chrysobactin and achromobactin. Chrysobactin makes a large contribution to invasive growth of the bacterium in its host. Insertion mutants of a chrysobactin-defective strain were constructed and...

We show that several interacting environmental factors influence the topology of intracellular DNA. Negative supercoiling of DNA in vivo is increased by anaerobic growth and is also influenced by growth phase. The tonB promoter of Escherichia coli and Salmonella typhimurium was found to be highly sensitive to changes in DNA supercoiling. Expression was increased by novobiocin, an inhibitor of D...

The TonB-dependent complex of Gram-negative bacteria couples the inner membrane proton motive force to the active transport of iron.siderophore and vitamin B(12) across the outer membrane. The structural basis of that process has not been described so far in full detail. The crystal structure of the C-terminal domain of TonB from Escherichia coli has now been solved by multiwavelength anomalous...

The nucleotide sequence of a 3.6-kb HindIII-SmaI DNA fragment of Xanthomonas campestris pv. campestris revealed four open reading frames which, based on sequence homologies, were designated tonB, exbB, exbD1, and exbD2. Analysis of translational fusions to alkaline phosphatase and beta-galactosidase confirmed that the TonB, ExbB, ExbD1, and ExbD2 proteins are anchored in the cytoplasmic membran...