title: The Bordetella bhu locus is required for heme iron utilization.
abstract: Bordetella pertussis and Bordetella bronchiseptica are capable of obtaining iron from hemin and hemoglobin. Genes encoding a putative bacterial heme iron acquisition system (bhu, for Bordetella heme utilization) were identified in a B. pertussis genomic sequence database, and the corresponding DNA was isolated from a virulent strain of B. pertussis. A B. pertussis bhuR mutant, predicted to lack the heme outer membrane receptor, was generated by allelic exchange. In contrast to the wild-type strain, bhuR mutant PM5 was incapable of acquiring iron from hemin and hemoglobin; genetic complementation of PM5 with the cloned bhuRSTUV genes restored heme utilization to wild-type levels. In parallel studies, B. bronchiseptica bhu sequences were also identified and a B. bronchiseptica bhuR mutant was constructed and confirmed to be defective in heme iron acquisition. The wild-type B. bronchiseptica parent strain grown under low-iron conditions produced the presumptive BhuR protein, which was absent in the bhuR mutant. Furthermore, production of BhuR by iron-starved B. bronchiseptica was markedly enhanced by culture in hemin-supplemented medium, suggesting that these organisms sense and respond to heme in the environment. Analysis of the genetic region upstream of the bhu cluster identified open reading frames predicted to encode homologs of the Escherichia coli ferric citrate uptake regulators FecI and FecR. These putative Bordetella regulators may mediate heme-responsive positive transcriptional control of the bhu genes.
authors: Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455-0312, USA.
authors: C K
authors: CK
authors: Vanderpool
authors: S K
authors: SK
authors: Armstrong
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001886:Bordetella pertussis / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D015870:Gene Expression; D005798:Genes, Bacterial; D006418:Heme / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016366:Open Reading Frames; D010641:Phenotype; D011956:Receptors, Cell Surface; D012097:Repressor Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D012808:Sigma Factor / Q000235:genetics
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C431916:BhuR protein, Bordetella pertussis; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C490539:FecI protein, E coli; C093541:FecR protein, E coli; D026901:Membrane Transport Proteins; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; D012808:Sigma Factor; C068477:ferric uptake regulating proteins, bacterial; D006418:Heme; D007501:Iron