staphyloferrin-a and Staphylococcal-Infections

Siderophores, iron-scavenging small molecules, are fundamental to bacterial nutrient metal acquisition and enable pathogens to overcome challenges imposed by nutritional immunity. Multimodal imaging mass spectrometry allows visualization of host-pathogen iron competition, by mapping siderophores within infected tissue. We have observed heterogeneous distributions of

Topics: Abscess; Animals; Citrates; Host-Pathogen Interactions; Iron; Mice; Ornithine; Siderophores; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Staphylococcal Infections; Staphylococcus aureus

The siderophores staphyloferrin A (SA) and staphyloferrin B (SB) of

Topics: A549 Cells; Abscess; Animals; Bacterial Proteins; Citrates; Epithelial Cells; Gene Expression Regulation, Bacterial; Genetic Complementation Test; Genetic Fitness; Humans; Iron; Membrane Transport Proteins; Mice; Mutation; Ornithine; Plasmids; Siderophores; Staphylococcal Infections; Staphylococcus aureus

To obtain host iron, Staphylococcus aureus secretes siderophores staphyloferrin A (SA) or staphyloferrin B (SB), and accesses heme iron through use of iron-regulated surface determinant proteins. While iron transport in S. aureus is well documented, there is scant information about proteins required to access iron from complexes in the cytoplasm. In vitro studies identified a pyridine nucleotide-disulfide oxidoreductase, named IruO, as an electron donor for the heme monooxygenases IsdG and IsdI, promoting heme degradation. Here, we show that an iruO mutant was not debilitated for growth on heme, suggesting involvement of another reductase. NtrA is an iron-regulated nitroreductase and, as with the iruO mutant, a ntrA mutant grew on heme comparable with wild type (WT). In contrast, a iruO ntrA double mutant was severely debilitated for growth on heme, a phenotype that was complemented by expression of either iruO or ntrA in trans, demonstrating their overlapping role in heme-iron utilization. Contrasting the involvement of multiple reductases for heme iron utilization, ntrA was shown essential for iron utilization using SA, although not SB or other siderophores tested, and an iruO mutant was incapable of deferoxamine-mediated growth. Accordingly, virulence of WT S. aureus, but not an iruO mutant, was enhanced in mice receiving deferoxamine.

Topics: Animals; Citrates; Female; Heme; Iron; Mice; Mice, Inbred BALB C; Nitroreductases; Ornithine; Oxidoreductases Acting on Sulfur Group Donors; Siderophores; Staphylococcal Infections; Staphylococcus aureus; Virulence

Bacteria need to scavenge iron from their environment, and this is no less important for bacterial pathogens while attempting to survive in the mammalian host. One key strategy is the synthesis of small iron chelators known as siderophores. The study of siderophore biosynthesis systems over the past several years has shed light on novel enzymology and, as such, has identified new therapeutic targets. Staphylococcus aureus, a noted human and animal pathogen, produces two citrate-based siderophores, termed staphyloferrin A and staphyloferrin B. The iron-regulated gene cluster for the biosynthesis of staphyloferrin B, sbnA-I, contains several yet uncharacterized genes. Here, we report on the identification of an enzyme, SbnG, which is annotated in the genome sequence as a metal-dependent class II aldolase. In contrast to this prediction, we report that, instead, SbnG has evolved to catalyze metal-independent citrate synthase activity using oxaloacetate and acetyl-CoA as substrates. We describe an in vitro assay to synthesize biologically active staphyloferrin B from purified enzymes and substrates, and identify several SbnG inhibitors, including metals such as calcium and magnesium.

Topics: Citrate (si)-Synthase; Citrates; Fructose-Bisphosphate Aldolase; Genes, Bacterial; Humans; Iron; Multigene Family; Ornithine; Protein Multimerization; Staphylococcal Infections; Staphylococcus aureus

Staphylococcus aureus is a frequent cause of bloodstream, respiratory tract, and skin and soft tissue infections. In the bloodstream, the iron-binding glycoprotein transferrin circulates to provide iron to cells throughout the body, but its iron-binding properties make it an important component of innate immunity. It is well established that siderophores, with their high affinity for iron, in many instances can remove iron from transferrin as a means to promote proliferation of bacterial pathogens. It is also established that catecholamine hormones can interfere with the iron-binding properties of transferrin, thus allowing infectious bacteria access to this iron pool. The present study demonstrates that S. aureus can use either of two carboxylate-type siderophores, staphyloferrin A and staphyloferrin B, via the transporters Hts and Sir, respectively, to access the transferrin iron pool. Growth of staphyloferrin-producing S. aureus in serum or in the presence of holotransferrin was not enhanced in the presence of catecholamines. However, catecholamines significantly enhanced the growth of staphyloferrin-deficient S. aureus in human serum or in the presence of human holotransferrin. It was further demonstrated that the Sst transporter was essential for this activity as well as for the utilization of bacterial catechol siderophores. The substrate binding protein SstD was shown to interact with ferrated catecholamines and catechol siderophores, with low to submicromolar affinities. Experiments involving mice challenged intravenously with wild-type S. aureus and isogenic mutants demonstrated that the combination of Hts, Sir, and Sst transport systems was required for full virulence of S. aureus.

Topics: Animals; Blotting, Western; Citrates; Epinephrine; Female; Genes, Bacterial; Humans; Iron; Mice; Mice, Inbred BALB C; Norepinephrine; Ornithine; Siderophores; Staphylococcal Infections; Staphylococcus aureus; Transferrin