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Expression of the putative siderophore receptor gene bfrZ is controlled by the extracytoplasmic-function sigma factor BupI in Bordetella bronchiseptica.

ABSTRACT: A new gene from Bordetella bronchiseptica, bfrZ encoding a putative siderophore receptor, was identified in a Fur-repressor titration assay. A bfrZ null mutant was constructed by allelic exchange. The protein profile of this mutant is similar to that of the wild-type parent strain. The BfrZ(-)-BfrZ(+) isogenic pair was tested for utilization of 132 different siderophores as iron sources. None of these iron sources acted as a ligand for BfrZ. Translational bfrZ::phoA and transcriptional bfrZ::lacZ fusions were introduced into the B. bronchiseptica bfrZ locus. No alkaline phosphatase or beta-galactosidase activity was detected. Sequence analysis of the bfrZ upstream region revealed the presence of two tightly linked genes, bupI and bupR. Both of these genes are located downstream from a Fur-binding sequence. BupI is homologous to Escherichia coli FecI and Pseudomonas putida PupI and belongs to the family of extracytoplasmic-function sigma factors involved in transcription of genes with extracytoplasmic functions. BupR is homologous to the FecR and PupR antisigma factors and is predicted to be localized in the inner membrane. Similar to the surface signaling receptors FecA and PupB, BfrZ bears an N-terminal extension. We found that bfrZ is not transcribed when bupI and bupR are expressed at the same level. However, overexpression of bupI from a multicopy plasmid triggers bfrZ transcription, and under these conditions BfrZ was detected in membrane fractions. By analogy with the FecI-FecR-FecA and PupI-PupR-PupB systems, our data suggest that bfrZ expression is inducible by binding of the cognate ligand to BfrZ and transduction of a signal through the envelope.

SUBMITTER: Pradel E

PROVIDER: S-EPMC99509 | biostudies-literature | 2001 May

REPOSITORIES: biostudies-literature

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Expression of the putative siderophore receptor gene bfrZ is controlled by the extracytoplasmic-function sigma factor BupI in Bordetella bronchiseptica.

Pradel E E Locht C C

Journal of bacteriology 20010501 9

A new gene from Bordetella bronchiseptica, bfrZ encoding a putative siderophore receptor, was identified in a Fur-repressor titration assay. A bfrZ null mutant was constructed by allelic exchange. The protein profile of this mutant is similar to that of the wild-type parent strain. The BfrZ(-)-BfrZ(+) isogenic pair was tested for utilization of 132 different siderophores as iron sources. None of these iron sources acted as a ligand for BfrZ. Translational bfrZ::phoA and transcriptional bfrZ::lac ...[more]

PMID: 11292812

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Project description:Bordetella pertussis, B. parapertussis, and B. bronchiseptica cause respiratory infections, many of which are characterized by coughing of the infected hosts. The pathogenesis of the coughing remains to be analyzed, mainly because there were no convenient infection models of small animals that replicate coughing after Bordetella infection. Here, we present a coughing model of rats infected with B. bronchiseptica Rats, which are one of natural hosts of B. bronchiseptica, were readily infected with the organisms and showed frequent coughing. B. pertussis also caused coughing in rats, which is consistent with previous reports, but the cough response was less apparent than the B. bronchiseptica-induced cough. By using the rat model, we demonstrated that adenylate cyclase toxin, dermonecrotic toxin, and the type III secretion system are not involved in cough production, but BspR/BtrA (different names for the same protein), an anti-σ factor, regulates the production of unknown factor(s) to cause coughing. Rat coughing was observed by inoculation of not only the living bacteria but also the bacterial lysates. Infection with bspR (btrA)-deficient strains caused significantly less frequent coughing than the wild type; however, intranasal inoculation of the lysates from a bspR (btrA)-deficient strain caused coughing similarly to the wild type, suggesting that BspR/BtrA regulates the production of the cough factor(s) only when the bacteria colonize host bodies. Moreover, the cough factor(s) was found to be heat labile and produced by B. bronchiseptica in the Bvg+ phase. We consider that our rat model provides insight into the pathogenesis of cough induced by the Bordetella infection.IMPORTANCE Whooping cough is a contagious respiratory disease caused by Bordetella pertussis This disease is characterized by severe paroxysmal coughing, which becomes a heavy burden for patients and occasionally results in death; however, its pathogenesis remains largely unknown. The major obstacle to analyzing Bordetella-induced coughing is the lack of conventional animal models that replicate coughing. As Bordetella pertussis is highly adapted to humans, infection models in experimental animals are not considered to be well established. In the present study, we examined coughing in rats infected with B. bronchiseptica, which shares many virulence factors with B. pertussis Using this rat model, we demonstrated that some of the major virulence factors of Bordetella are not involved in cough production, but an anti-σ factor, BspR/BtrA, of B. bronchiseptica regulates the production of unknown cough-causing bacterial factor(s). Our results provide important clues to understand the mechanism by which Bordetella induces cough.

Project description:A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) at an extremely low concentration triggers streptomycin production and aerial mycelium formation in Streptomyces griseus. A-factor induces the expression of an A-factor-dependent transcriptional activator, AdpA, essential for both morphological and physiological differentiation by binding to the A-factor receptor protein ArpA, which has bound and repressed the adpA promoter, and dissociating it from the promoter. Nine DNA fragments that were specifically recognized and bound by histidine-tagged AdpA were isolated by cycles of a gel mobility shift-PCR method. One of them was located in front of a gene encoding an extracytoplasmic function sigma factor belonging to a subgroup of the primary sigma(70) family. The cloned gene was named AdpA-dependent sigma factor gene (adsA), and the gene product was named sigma(AdsA). Transcription of adsA depended on A-factor and AdpA, since adsA was transcribed at a very low and constant level in an A-factor-deficient mutant strain or in an adpA-disrupted strain. Consistent with this, transcription of adsA was greatly enhanced at or near the timing of aerial hyphae formation, as determined by low-resolution S1 nuclease mapping. High-resolution S1 mapping determined the transcriptional start point 82 nucleotides upstream of the translational start codon. DNase I footprinting showed that AdpA bound both strands symmetrically between the transcriptional start point and the translational start codon; AdpA protected the antisense strand from positions +7 to +41 with respect to the transcriptional start point and the sense strand from positions +12 to +46. A weak palindrome was found in the AdpA-binding site. The unusual position bound by AdpA as a transcriptional activator, in relation to the promoter, suggested the presence of a mechanism by which AdpA activates transcription of adsA in some unknown way. Disruption of the chromosomal adsA gene resulted in loss of aerial hyphae formation but not streptomycin or yellow pigment production, indicating that sigma(AdsA) is involved only in morphological development and not in secondary metabolic function. The presence of a single copy in each of the Streptomyces species examined by Southern hybridization suggests a common role in morphogenesis in this genus.

Dataset Information

Expression of the putative siderophore receptor gene bfrZ is controlled by the extracytoplasmic-function sigma factor BupI in Bordetella bronchiseptica.

Publications

Expression of the putative siderophore receptor gene bfrZ is controlled by the extracytoplasmic-function sigma factor BupI in Bordetella bronchiseptica.

Similar Datasets

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