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  • 1
    Online Resource
    Online Resource
    American Society for Microbiology ; 2004
    In:  Journal of Bacteriology Vol. 186, No. 4 ( 2004-02-15), p. 938-948
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 186, No. 4 ( 2004-02-15), p. 938-948
    Abstract: The Bordetella pertussis heme utilization gene cluster hurIR bhuRSTUV encodes regulatory and transport functions required for assimilation of iron from heme and hemoproteins. Expression of the bhu genes is iron regulated and heme inducible. The putative extracytoplasmic function (ECF) σ factor, HurI, is required for heme-responsive bhu gene expression. In this study, transcriptional activation of B. pertussis bhu genes in response to heme compounds was shown to be dose dependent and specific for heme; protoporphyrin IX and other heme structural analogs did not activate bhu gene expression. Two promoters controlling expression of the heme utilization genes were mapped by primer extension analysis. The hurI promoter showed similarity to σ 70 -like promoters, and its transcriptional activity was iron regulated and heme independent. A second promoter identified upstream of bhuR exhibited little similarity to previously characterized ECF σ factor-dependent promoters. Expression of bhuR was iron regulated, heme responsive, and hurI dependent in B. pertussis , as shown in a previous study with Bordetella bronchiseptica . Further analyses showed that transcription originating at a distal upstream site and reading through the hurR-bhuR intergenic region contributes to bhuR expression under iron starvation conditions in the absence of heme inducer. The pattern of regulation of the readthrough transcript was consistent with transcription from the hurI promoter. The positions and regulation of the two promoters within the hur-bhu gene cluster influence the production of heme transport machinery so that maximal expression of the bhu genes occurs under iron starvation conditions only in the presence of heme iron sources.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2004
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    American Society for Microbiology ; 2003
    In:  Journal of Bacteriology Vol. 185, No. 3 ( 2003-02), p. 909-917
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 185, No. 3 ( 2003-02), p. 909-917
    Abstract: Bordetella pertussis and Bordetella bronchiseptica , gram-negative respiratory pathogens of mammals, possess a heme iron utilization system encoded by the bhuRSTUV genes. Preliminary evidence suggested that expression of the BhuR heme receptor was stimulated by the presence of heme under iron-limiting conditions. The hurIR (heme uptake regulator) genes were previously identified upstream of the bhuRSTUV gene cluster and are predicted to encode homologs of members of the iron starvation subfamily of extracytoplasmic function (ECF) regulators. In this study, B. pertussis and B. bronchiseptica Δ hurI mutants, predicted to lack an ECF σ factor, were constructed and found to be deficient in the utilization of hemin and hemoglobin. Genetic complementation of Δ hurI strains with plasmid-borne hurI restored wild-type levels of heme utilization. B. bronchiseptica Δ hurI mutant BRM23 was defective in heme-responsive production of the BhuR heme receptor; hurI in trans restored heme-inducible BhuR expression to the mutant and resulted in BhuR overproduction. Transcriptional analyses with bhuR-lacZ fusion plasmids confirmed that bhuR transcription was activated in iron-starved cells in response to heme compounds. Heme-responsive bhuR transcription was not observed in mutant BRM23, indicating that hurI is required for positive regulation of bhu gene expression. Furthermore, bhuR was required for heme-inducible bhu gene activation, supporting the hypothesis that positive regulation of bhuRSTUV occurs by a surface signaling mechanism involving the heme-iron receptor BhuR.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2003
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 3
    Online Resource
    Online Resource
    American Society for Microbiology ; 2001
    In:  Journal of Bacteriology Vol. 183, No. 14 ( 2001-07-15), p. 4278-4287
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 183, No. 14 ( 2001-07-15), p. 4278-4287
    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.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2001
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    American Society for Microbiology ; 2006
    In:  Infection and Immunity Vol. 74, No. 3 ( 2006-03), p. 1741-1744
    In: Infection and Immunity, American Society for Microbiology, Vol. 74, No. 3 ( 2006-03), p. 1741-1744
    Abstract: Bordetella pertussis , the causative agent of whooping cough or pertussis, is an obligate human pathogen with multiple high-affinity iron transport systems. Maximal expression of the dedicated heme utilization functions encoded by the hurIR bhuRSTUV genes requires an iron starvation signal to relieve Fur repression at the hurIR promoter-operator and an inducing signal supplied by heme for HurI-mediated transcriptional activation at the bhuRSTUV promoter. The BhuR outer membrane receptor protein is required for heme uptake and for heme sensing for induction of bhuRSTUV transcription. It was hypothesized that heme utilization contributed to the success of B. pertussis as a pathogen. In this study, virulence attenuation resulting from inactivation of the B. pertussis heme system was assessed using mixed infection competition experiments in a mouse model. As a measure of in vivo fitness, the ability of a B. pertussis heme utilization mutant to colonize and persist was determined relative to that of an isogenic coinfecting wild-type strain. Relative fitness of the mutant strain declined significantly after 7 days postinfection and continued to decline throughout the remainder of the 28-day infection time course. In parallel infections using inocula supplemented with an inducing 2 μM concentration of hemin chloride, hemin coadministration augmented the competitive advantage of the wild-type strain over the mutant. The results confirm that heme utilization contributes to the pathogenesis of B. pertussis in the mouse infection model and indicate that heme utilization may be most important for adaptation to host conditions existing during the later stages of infection.
    Type of Medium: Online Resource
    ISSN: 0019-9567 , 1098-5522
    RVK:
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2006
    detail.hit.zdb_id: 1483247-1
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  • 5
    In: Molecular Microbiology, Wiley, Vol. 112, No. 4 ( 2019-10), p. 1199-1218
    Abstract: Small RNA (sRNA) regulators promote efficient responses to stress, but the mechanisms for prioritizing target mRNA regulation remain poorly understood. This study examines mechanisms underlying hierarchical regulation by the sRNA SgrS, found in enteric bacteria and produced under conditions of metabolic stress. SgrS posttranscriptionally coordinates a nine‐gene regulon to restore growth and homeostasis. An in vivo reporter system quantified SgrS‐dependent regulation of target genes and established that SgrS exhibits a clear target preference. Regulation of some targets is efficient even at low SgrS levels, whereas higher SgrS concentrations are required to regulate other targets. In vivo and in vitro analyses revealed that RNA structure and the number and position of base pairing sites relative to the start of translation impact the efficiency of regulation of SgrS targets. The RNA chaperone Hfq uses distinct modes of binding to different SgrS mRNA targets, which differentially influences positive and negative regulation. The RNA degradosome plays a larger role in regulation of some SgrS targets compared to others. Collectively, our results suggest that sRNA selection of target mRNAs and regulatory hierarchy are influenced by several molecular features and that the combination of these features precisely tunes the efficiency of regulation of multi‐target sRNA regulons.
    Type of Medium: Online Resource
    ISSN: 0950-382X , 1365-2958
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1501537-3
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  • 6
    Online Resource
    Online Resource
    American Society for Microbiology ; 2013
    In:  Journal of Bacteriology Vol. 195, No. 21 ( 2013-11), p. 4804-4815
    In: Journal of Bacteriology, American Society for Microbiology, Vol. 195, No. 21 ( 2013-11), p. 4804-4815
    Abstract: Cells use complex mechanisms to regulate glucose transport and metabolism to achieve optimal energy and biomass production while avoiding accumulation of toxic metabolites. Glucose transport and glycolytic metabolism carry the risk of the buildup of phosphosugars, which can inhibit growth at high concentrations. Many enteric bacteria cope with phosphosugar accumulation and associated stress (i.e., sugar-phosphate stress) by producing a small RNA (sRNA) regulator, SgrS, which decreases phosphosugar accumulation in part by repressing translation of sugar transporter mRNAs ( ptsG and manXYZ ) and enhancing translation of a sugar phosphatase mRNA ( yigL ). Despite a molecular understanding of individual target regulation by SgrS, previously little was known about how coordinated regulation of these multiple targets contributes to the rescue of cell growth during sugar-phosphate stress. This study examines how SgrS regulation of different targets impacts growth under different nutritional conditions when sugar-phosphate stress is induced. The severity of stress-associated growth inhibition depended on nutrient availability. Stress in nutrient-rich media necessitated SgrS regulation of only sugar transporter mRNAs ( ptsG or manXYZ ). However, repression of transporter mRNAs was insufficient for growth rescue during stress in nutrient-poor media; here SgrS regulation of the phosphatase ( yigL ) and as-yet-undefined targets also contributed to growth rescue. The results of this study imply that regulation of only a subset of an sRNA's targets may be important in a given environment. Further, the results suggest that SgrS and perhaps other sRNAs are flexible regulators that modulate expression of multigene regulons to allow cells to adapt to an array of stress conditions.
    Type of Medium: Online Resource
    ISSN: 0021-9193 , 1098-5530
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2013
    detail.hit.zdb_id: 1481988-0
    SSG: 12
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  • 7
    Online Resource
    Online Resource
    Informa UK Limited ; 2005
    In:  Critical Reviews in Biochemistry and Molecular Biology Vol. 40, No. 2 ( 2005-01), p. 93-113
    In: Critical Reviews in Biochemistry and Molecular Biology, Informa UK Limited, Vol. 40, No. 2 ( 2005-01), p. 93-113
    Type of Medium: Online Resource
    ISSN: 1040-9238 , 1549-7798
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2005
    detail.hit.zdb_id: 2030029-3
    SSG: 12
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  • 8
    Online Resource
    Online Resource
    American Society for Microbiology ; 2018
    In:  Microbiology Spectrum Vol. 6, No. 5 ( 2018-09-07)
    In: Microbiology Spectrum, American Society for Microbiology, Vol. 6, No. 5 ( 2018-09-07)
    Abstract: Bacteria are known to use RNA, either as mRNAs encoding proteins or as noncoding small RNAs (sRNAs), to regulate numerous biological processes. However, a few sRNAs have two functions: they act as base-pairing RNAs and encode a small protein with additional regulatory functions. Thus, these so called “dual-function” sRNAs can serve as both a riboregulator and an mRNA. In some cases, these two functions can act independently within the same pathway, while in other cases, the base-pairing function and protein function act in different pathways. Here, we discuss the five known dual-function sRNAs—SgrS from enteric species, RNAIII and Psm-mec from Staphylococcus aureus , Pel RNA from Streptococcus pyogenes , and SR1 from Bacillus subtilis —and review their mechanisms of action and roles in regulating diverse biological processes. We also discuss the prospect of finding additional dual-function sRNAs and future challenges in studying the overlap and competition between the functions.
    Type of Medium: Online Resource
    ISSN: 2165-0497
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2018
    detail.hit.zdb_id: 2807133-5
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  • 9
    Online Resource
    Online Resource
    Wiley ; 2016
    In:  Molecular Microbiology Vol. 99, No. 2 ( 2016-01), p. 254-273
    In: Molecular Microbiology, Wiley, Vol. 99, No. 2 ( 2016-01), p. 254-273
    Abstract: The E scherichia coli small RNA SgrS controls a metabolic stress response that occurs upon accumulation of certain glycolytic intermediates. SgrS base pairs with and represses translation of pts G and man XYZ m RNA s, which encode sugar transporters, and activates translation of yig L m RNA , encoding a sugar phosphatase. This study defines four new genes as direct targets of E . coli   SgrS . These new targets, asd , adi Y , fol E and pur R , encode transcription factors or enzymes of diverse metabolic pathways, including aspartate semialdehyde dehydrogenase, arginine decarboxylase gene activator, GTP cyclohydrolase I and a repressor of purine biosynthesis, respectively. SgrS represses translation of each of the four target mRNAs via distinct mechanisms. SgrS binding sites overlapping the Shine–Dalgarno sequences of adi Y and fol E m RNA s suggest that SgrS pairing with these targets directly occludes ribosome binding and prevents translation initiation. SgrS binding within the pur R coding sequence recruits the RNA chaperone H fq to directly repress pur R translation. Two separate SgrS binding sites were found on asd m RNA , and both are required for full translational repression. Ectopic overexpression of asd , adi Y and fol E is specifically detrimental to cells experiencing glucose‐phosphate stress, suggesting that SgrS ‐dependent repression of the metabolic functions encoded by these targets promotes recovery from glucose‐phosphate stress.
    Type of Medium: Online Resource
    ISSN: 0950-382X , 1365-2958
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2016
    detail.hit.zdb_id: 1501537-3
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  • 10
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2009
    In:  Nucleic Acids Research Vol. 37, No. 16 ( 2009-9), p. 5465-5476
    In: Nucleic Acids Research, Oxford University Press (OUP), Vol. 37, No. 16 ( 2009-9), p. 5465-5476
    Type of Medium: Online Resource
    ISSN: 1362-4962 , 0305-1048
    RVK:
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2009
    detail.hit.zdb_id: 1472175-2
    SSG: 12
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