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Ellison DW, Clark TR, Sturdevant DE, Virtaneva K, Hackstadt T. Limited transcriptional responses of Rickettsia rickettsii exposed to environmental stimuli. PLoS One 2009; 4:e5612. [PMID: 19440298 PMCID: PMC2680988 DOI: 10.1371/journal.pone.0005612] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Accepted: 04/24/2009] [Indexed: 11/18/2022] Open
Abstract
Rickettsiae are strict obligate intracellular pathogens that alternate between arthropod and mammalian hosts in a zoonotic cycle. Typically, pathogenic bacteria that cycle between environmental sources and mammalian hosts adapt to the respective environments by coordinately regulating gene expression such that genes essential for survival and virulence are expressed only upon infection of mammals. Temperature is a common environmental signal for upregulation of virulence gene expression although other factors may also play a role. We examined the transcriptional responses of Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, to a variety of environmental signals expected to be encountered during its life cycle. R. rickettsii exposed to differences in growth temperature (25 degrees C vs. 37 degrees C), iron limitation, and host cell species displayed nominal changes in gene expression under any of these conditions with only 0, 5, or 7 genes, respectively, changing more than 3-fold in expression levels. R. rickettsii is not totally devoid of ability to respond to temperature shifts as cold shock (37 degrees C vs. 4 degrees C) induced a change greater than 3-fold in up to 56 genes. Rickettsiae continuously occupy a relatively stable environment which is the cytosol of eukaryotic cells. Because of their obligate intracellular character, rickettsiae are believed to be undergoing reductive evolution to a minimal genome. We propose that their relatively constant environmental niche has led to a minimal requirement for R. rickettsii to respond to environmental changes with a consequent deletion of non-essential transcriptional response regulators. A minimal number of predicted transcriptional regulators in the R. rickettsii genome is consistent with this hypothesis.
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Affiliation(s)
- Damon W. Ellison
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infections Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Tina R. Clark
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infections Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Daniel E. Sturdevant
- Genomics Unit, Research Technology Section, Rocky Mountain Laboratories, National Institute of Allergy and Infections Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Kimmo Virtaneva
- Genomics Unit, Research Technology Section, Rocky Mountain Laboratories, National Institute of Allergy and Infections Diseases, National Institutes of Health, Hamilton, Montana, United States of America
| | - Ted Hackstadt
- Laboratory of Intracellular Parasites, Rocky Mountain Laboratories, National Institute of Allergy and Infections Diseases, National Institutes of Health, Hamilton, Montana, United States of America
- * E-mail:
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2
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Abstract
Cyclic AMP is a ubiquitous messenger that integrates many processes of the cell. Diverse families of adenylate cyclases and phosphodiesterases stringently regulate the intracellular concentration of cAMP. Any alteration in the cytosolic concentration of cAMP has a profound effect on the various processes of the cell. Disruption of these cellular processes in vivo is often the most critical event in the pathogenesis of infectious diseases for animals and humans. Many pathogenic bacteria secrete toxins to alter the intracellular concentration of cAMP. These toxins either disrupt the normal regulation of the host cell's adenylate cyclases/phosphodiesterases or they themselves catalyze the synthesis of cAMP in the host cell. The latter are known as the adenylate cyclase toxins. Four such toxins have been identified: the invasive adenylate cyclase of Bordetella pertussis, the edema factor of Bacillus anthracis, ExoY of Pseudomonas aeruginosa, and the adenylate cyclase of Yersinia pestis. These adenylate cyclase toxins enter the eukaryotic host cells and get activated by eukaryotic cofactors, like calmodulin, to trigger the synthesis of cAMP in these cells. By accumulating cAMP in the target cells, these toxins either modulate the cellular function or completely deactivate the cell for further function. The immune effector cells appear to be the primary target of these adenylate cyclase toxins. By accumulating cAMP in the immune effector cells, these adenylate cyclase toxins poison the immune system and thus facilitate the survival of the bacteria in the host.
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Affiliation(s)
- Nidhi Ahuja
- Centre For Biotechnology, Jawaharlal Nehru University, New Delhi, India
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Affiliation(s)
- Peggy A Cotter
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9610, USA.
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4
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Foulongne V, Michaux-Charachon S, O’Callaghan D, Ramuz M. Systèmes de sécrétion des protéines de type IV et virulence bactérienne. Med Sci (Paris) 2002. [DOI: 10.1051/medsci/2002184439] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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von Wintzingerode F, Gerlach G, Schneider B, Gross R. Phylogenetic Relationships and Virulence Evolution in the Genus Bordetella. Curr Top Microbiol Immunol 2002. [DOI: 10.1007/978-3-662-09217-0_10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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6
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Karimova G, Ullmann A, Ladant D. A bacterial two-hybrid system that exploits a cAMP signaling cascade in Escherichia coli. Methods Enzymol 2001; 328:59-73. [PMID: 11075338 DOI: 10.1016/s0076-6879(00)28390-0] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- G Karimova
- Unité de Biochimie Cellulaire, CNRS URA 2185, Institut Pasteur, Paris, France
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Abstract
The genus Bordetella comprises seven species with pathogenic potential for different host organisms. This article attempts to review our current knowledge about the systematics and evolution of this important group of pathogens, their relationship to environmental microorganisms and about molecular mechanisms of host adaptation.
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Affiliation(s)
- G Gerlach
- Lehrstuhl für Mikrobiologie, Theodor-Boveri-Institut, Biozentrum, Universität Würzburg, Am Hubland, D-97074, Würzburg, Germany
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8
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Abstract
Virulence gene expression in most bacteria is a highly regulated phenomenon, affected by a variety of parameters including osmolarity, pH, ion concentration, iron levels, growth phase, and population density. Virulence genes are also regulated by temperature, which acts as an 'on-off' switch in a manner distinct from the more general heat-shock response. Here, we review temperature-responsive expression of virulence genes in four diverse pathogens.
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Affiliation(s)
- M E Konkel
- School of Molecular Biosciences, Washington State University, Pullman, Washington 99164, USA
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9
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Brockmeier SL. Early colonization of the rat upper respiratory tract by temperature modulated Bordetella bronchiseptica. FEMS Microbiol Lett 1999; 174:225-9. [PMID: 10339812 DOI: 10.1111/j.1574-6968.1999.tb13572.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The ability of nonmodulated Bvg+ phase cultures, temperature modulated Bvg- phase cultures, and a Bvg- phase-locked mutant of Bordetella bronchiseptica to colonize the rat upper respiratory tract was investigated. Initially, greater numbers of the temperature modulated Bvg- phase bacteria adhered to the nasal cavity of the rats. The temperature modulated Bvg- phase bacteria appeared to be quickly cleared to levels lower than the Bvg+ phase bacteria by 4 h after inoculation and stayed lower until 48 h after inoculation when colonization levels were equal to the Bvg+ phase bacteria. The level of colonization with the Bvg- phase-locked mutant of B. bronchiseptica was lower than both the nonmodulated Bvg+ phase and temperature modulated Bvg- phase cultures and declined over time during the experiment. These findings suggest that there may be increased adherence from an environmental phase to ensure bacteria survive initial clearance mechanisms until the switch to the Bvg+ phase occurs.
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Affiliation(s)
- S L Brockmeier
- Avian and Swine Respiratory Diseases Research Unit, USDA, Agricultural Research Service, National Animal Disease Center, Ames, IA 50010, USA.
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10
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Abstract
Bordetella pertussis secretes a calmodulin-activated adenylate cyclase toxin (CyaA) that is able to deliver its amino-terminal catalytic domain into the cytosol of eukaryotic cells. The novelty of the structural organization and conformational flexibility of the CyaA catalytic domain has opened up the way for exploiting this protein as a tool for several biological applications, including epitope delivery, protein targeting and characterization of protein-protein interactions.
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Affiliation(s)
- D Ladant
- Dept of Biochemistry and Molecular Genetics, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cedex 15, France
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11
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Wilson DR, Siebers A, Finlay BB. Antigenic analysis of Bordetella pertussis filamentous hemagglutinin with phage display libraries and rabbit anti-filamentous hemagglutinin polyclonal antibodies. Infect Immun 1998; 66:4884-94. [PMID: 9746593 PMCID: PMC108604 DOI: 10.1128/iai.66.10.4884-4894.1998] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/1998] [Accepted: 07/24/1998] [Indexed: 11/20/2022] Open
Abstract
Although substantial advancements have been made in the development of efficacious acellular vaccines against Bordetella pertussis, continued progress requires better understanding of the antigenic makeup of B. pertussis virulence factors, including filamentous hemagglutinin (FHA). To identify antigenic regions of FHA, phage display libraries constructed by using random fragments of the 10-kbp EcoRI fragment of B. pertussis fhaB were affinity selected with rabbit anti-FHA polyclonal antibodies. Characterization of antibody-reactive clones displaying FHA-derived peptides identified 14 antigenic regions, each containing one or more epitopes. A number of clones mapped within regions containing known or putative FHA adhesin domains and may be relevant for the generation of protective antibodies. The immunogenic potential of the phage-displayed peptides was assessed indirectly by comparing their recognition by antibodies elicited by sodium dodecyl sulfate (SDS)-denatured and native FHA and by measuring the inhibition of this recognition by purified FHA. FHA residues 1929 to 2019 may contain the most dominant linear epitope of FHA. Clones mapping to this region accounted for ca. 20% of clones recovered from the initial library selection and screening procedures. They are strongly recognized by sera against both SDS-denatured and native FHA, and this recognition is readily inhibited by purified FHA. Given also that this region includes a factor X homolog (J. Sandros and E. Tuomanen, Trends Microbiol. 1:192-196, 1993) and that the single FHA epitope (residues 2001 to 2015) was unequivocally defined in a comparable study by E. Leininger et al. (J. Infect. Dis. 175:1423-1431, 1997), peptides derived from residues of 1929 to 2019 of FHA are strong candidates for future protection studies.
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Affiliation(s)
- D R Wilson
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
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12
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Register KB, Ackermann MR. A highly adherent phenotype associated with virulent Bvg+-phase swine isolates of Bordetella bronchiseptica grown under modulating conditions. Infect Immun 1997; 65:5295-300. [PMID: 9393829 PMCID: PMC175762 DOI: 10.1128/iai.65.12.5295-5300.1997] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The ability of Bvg(-)-phase and Bvg(+)-phase Bordetella bronchiseptica swine isolates, grown under modulating or nonmodulating conditions, to adhere to swine ciliated nasal epithelial cells was determined. When virulent strains were cultivated at 37 degrees C in the Bvg+ phase, numerous adherent bacteria (approximately eight per cell, depending on the strain used) were observed. However, when such strains were grown under modulating conditions (23 degrees C), a significant increase in the level of attachment was seen, suggesting that B. bronchiseptica produces a Bvg-repressed adhesin under these conditions. bvg mutant strains, including an isogenic bvgS mutant, adhered minimally. Western blots indicated that two putative B. bronchiseptica adhesins, filamentous hemagglutinin and pertactin, were not detectable in cultures displaying the highly adherent phenotype. Several proteins apparent in Western blots obtained by using bacterial extracts enriched in outer membrane proteins derived from B. bronchiseptica grown at 23 degrees C were not present in similar extracts prepared from an isogenic bvgS mutant grown at 23 degrees C or from the parent strain grown at 37 degrees C. Adherence of bacteria cultivated at 23 degrees C was almost completely abolished by pretreatment of organisms at 60 degrees C; adherence was reduced by 57% when bacteria were pretreated with pronase E. Temperature shift experiments revealed that the heightened level of adhesion that occurs following growth at 23 degrees C was maintained for up to 18 h when bacteria were subsequently incubated at 37 degrees C. We propose that a Bvg-repressed adhesin, expressed only by modulated bvg+ strains of B. bronchiseptica, may play a key role in the initial colonization of naturally infected swine.
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Affiliation(s)
- K B Register
- National Animal Disease Center, Agricultural Research Service, U.S. Department of Agriculture, Ames, Iowa 50010, USA.
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Kenny B, Abe A, Stein M, Finlay BB. Enteropathogenic Escherichia coli protein secretion is induced in response to conditions similar to those in the gastrointestinal tract. Infect Immun 1997; 65:2606-12. [PMID: 9199427 PMCID: PMC175369 DOI: 10.1128/iai.65.7.2606-2612.1997] [Citation(s) in RCA: 196] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The pathogenicity of enteropathogenic Escherichia coli (EPEC) is associated with the expression and secretion of specific bacterial factors. EspB is one such secreted protein which is required to trigger host signaling pathways resulting in effacement of microvilli and cytoskeletal rearrangements. These events presumably contribute to the ensuing diarrhea associated with EPEC infections. EPEC encounters several environmental changes and stimuli during its passage from the external environment into the host gastrointestinal tract. In this paper we show that the secretion of EspB is subject to environmental regulation, and maximal secretion occurs under conditions reminiscent of those in the gastrointestinal tract. Thus, secretion is maximal at 37 degrees C, pH 7, and physiological osmolarity. In addition, maximal secretion requires the presence of sodium bicarbonate and calcium and is stimulated by millimolar concentrations of Fe(NO3)3. The secretion of the four other EPEC-secreted proteins appears to be modulated in a manner similar to that of EspB. Our results also show that secretion is not dependent on CO2, as originally reported by Haigh et al. (FEMS Microbiol. Lett. 129: 63-67, 1995), but that CO2 more likely acts as a component of the medium buffering system, since CO2 dependence was abolished by the use of alternative buffers.
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Affiliation(s)
- B Kenny
- Biotechnology Laboratory, University of British Columbia, Vancouver, Canada
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14
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DeShazer D, Wood GE, Friedman RL. Identification of a Bordetella pertussis regulatory factor required for transcription of the pertussis toxin operon in Escherichia coli. J Bacteriol 1995; 177:3801-7. [PMID: 7601846 PMCID: PMC177099 DOI: 10.1128/jb.177.13.3801-3807.1995] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Transcription of the pertussis toxin operon (ptx) is positively regulated in Bordetella pertussis by the bvgAS locus. However, a ptx-lacZ transcriptional fusion in Escherichia coli cannot be activated by bvgAS in trans. This suggests that an additional factor(s) is required for transcription of ptx. A gene encoding a Bvg accessory factor (Baf) was identified by its ability to activate an E. coli ptx-lacZ fusion in the presence of bvgAS. The expression of ptx-lacZ was decreased by the addition of 40 mM MgSO4, a compound that also modulates ptx expression in B. pertussis. Baf alone did not activate expression of an E. coli fhaB-lacZ fusion, nor did it increase expression of fhaB-lacZ in trans with bvgAS. The gene encoding Baf was localized, sequenced, and found to produce a novel 28-kDa protein. Sequences homologous to B. pertussis baf were identified in Bordetella bronchiseptica and Bordetella parapertussis but not in Bordetella avium. When an additional copy of baf was integrated into the chromosome of BC75, a B. pertussis mutant that produces a low level of pertussis toxin, pertussis toxin production was partially complemented in the cointegrate strain.
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Affiliation(s)
- D DeShazer
- Department of Microbiology and Immunology, University of Arizona, Tucson 85724, USA
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15
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Scarlato V, Aricò B, Goyard S, Ricci S, Manetti R, Prugnola A, Manetti R, Polverino-De-Laureto P, Ullmann A, Rappuoli R. A novel chromatin-forming histone H1 homologue is encoded by a dispensable and growth-regulated gene in Bordetella pertussis. Mol Microbiol 1995; 15:871-81. [PMID: 7596289 DOI: 10.1111/j.1365-2958.1995.tb02357.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We report the identification of a protein homologous to a histone H1 in Bordetella pertussis. The B. pertussis histone homologue, BpH1, varies in size in different strains from 182 to 206 amino acids. The variability of the size of the protein is due to gene variability by insertion or deletion of DNA modules. Insertion of a kanamycin cassette into the bpH1 gene generates a BpH1 null mutant with phenotypic properties and growth rate similar to those of the wild-type strain, showing that this gene is dispensable. In vitro, the BpH1 protein prevents chromosomal DNA degradation from DNase I and constrains supercoiled DNA. Transcription of the bpH1 gene is activated during exponential growth of the bacteria, whereas it is repressed during the stationary phase of growth. It is proposed that BpH1 plays a role in chromatin formation and condensation during DNA replication and that repression of transcription depends upon a reduced rate of DNA replication.
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Affiliation(s)
- V Scarlato
- Immunobiological Research Institute Siena (IRIS), Siena, Italy
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Manetti R, Aricò B, Rappuoli R, Scarlato V. Mutations in the linker region of BvgS abolish response to environmental signals for the regulation of the virulence factors in Bordetella pertussis. Gene 1994; 150:123-7. [PMID: 7959037 DOI: 10.1016/0378-1119(94)90870-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Expression of virulence factors of Bordetella pertussis is coordinately regulated by the products of the bvg locus, which codes for a sensory protein (BvgS) and a positive regulator of transcription (BvgA), a pair in the family of bacterial 'two-component' regulators. Transcription of the bvg-regulated promoters is repressed by modulating environmental factors such as 50 mM MgSO4, 10 mM nicotinic acid (NA) or low temperature (25 degrees C). We have isolated a spontaneous mutant (SK170) which expresses virulence genes at either 25 degrees C, or in the presence of 1-5 mM NA, or 10-50 mM MgSO4. Virulence factors in strain SK170 are still repressed by higher concentrations of NA (10 mM), or by a combination of low temperature (25 degrees C) and one of the other modulating agents. From this strain, we have isolated a second mutant (SK180) that showed constitutive synthesis of the virulence factors under any growth regime. Nucleotide (nt) and deduced amino acid (aa) sequence analysis showed that SK170 contains a substitution at aa570 of BvgS and SK180 contains an additional substitution at aa680. These substitutions are confined to a 161-aa sequence that links the transmembrane (TM) and kinase domains of BvgS. These mutations also alter the transcriptional autoregulation of the P1 and P2 promoters of the bvg locus. P1, which in the wild-type (wt) strain is repressed by modulating agents, is constitutively active in the mutant strains. On the contrary, P2, which is normally induced by all three modulating agents, is active in strain SK170 only in the presence of MgSO4 or NA, while in strain SK180 this promoter is repressed by modulating agents. The mutants exhibit elevated levels of the BvgA regulatory protein and have a virulent phenotype also in the presence of modulating agents.
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Affiliation(s)
- R Manetti
- Immunobiological Research Institute Siena (IRIS), Italy
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17
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Abstract
We have characterized a new virulence factor in Bordetella pertussis: serum resistance. Compared with Escherichia coli HB101, wild-type B. pertussis was relatively resistant to classical-pathway, complement-dependent killing by normal human serum. However, a mutant of B. pertussis (BPM2041) which is less virulent in mice and which has Tn5 lac inserted in a previously uncharacterized bvg-regulated gene was found to be at least 10-fold more susceptible to serum killing than the wild type. We have named this locus brk, for Bordetella resistance to killing. We have cloned and sequenced the brk locus, and it encodes two divergently transcribed open reading frames (ORFs), termed BrkA and BrkB. Both ORFs are necessary for serum resistance. Within the 300 bases which separate the two ORFs and upstream of each ORF are putative sites for BvgA binding. BrkA shows 29% identity to pertactin and has two RGD motifs in addition to a conserved proteolytic processing site and an outer membrane targeting signal. Like pertactin, BrkA is involved in adherence and invasion. Despite the similarities, a pertactin mutant was found to be not as sensitive to serum killing as the BrkA or BrkB mutants. BrkB is similar to ORFs in E. coli and Mycobacterium leprae and displays domains of homology to various transporters. On the basis of its hydropathy profile, BrkB is predicted to be a cytoplasmic membrane protein. By Southern blot, brk sequences were found in Bordetella bronchiseptica and Bordetella parapertussis but not in Bordetella avium.
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Affiliation(s)
- R C Fernandez
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati, Ohio 45267
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Goyard S, Bellalou J, Mireau H, Ullmann A. Mutations in the Bordetella pertussis bvgS gene that confer altered expression of the fhaB gene in Escherichia coli. J Bacteriol 1994; 176:5163-6. [PMID: 8051035 PMCID: PMC196362 DOI: 10.1128/jb.176.16.5163-5166.1994] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The bvg locus of Bordetella pertussis, required for coordinate regulation of virulence genes in response to environmental signals, encodes two proteins, BvgS and BvgA, that belong to the bacterial two-component signal transduction systems. We have isolated spontaneous mutations of the bvg locus in Escherichia coli and analyzed their effects on the expression of fhaB::lacZY transcriptional fusions. The mutations, localized in the linker and transmitter domain of BvgS, result in increased activation of fhaB and/or in insensitivity to a modulating agent, nicotinic acid.
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Affiliation(s)
- S Goyard
- Unité de Biochimie des Régulations Cellulaires, Institut Pasteur, Paris, France
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Scarlato V, Aricò B, Rappuoli R. DNA topology affects transcriptional regulation of the pertussis toxin gene of Bordetella pertussis in Escherichia coli and in vitro. J Bacteriol 1993; 175:4764-71. [PMID: 8393006 PMCID: PMC204928 DOI: 10.1128/jb.175.15.4764-4771.1993] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The bvg locus of Bordetella pertussis encodes an environmentally inducible operon essential for the expression of virulence genes. We show that in Escherichia coli, the PTOX promoter cloned in cis of the bvg locus is activated and environmentally regulated. Cotransformation of E. coli with the bvg locus cloned in a low-copy-number plasmid and with the PTOX promoter cloned in a high-copy-number plasmid can give rise to two different results. If the PTOX promoter is cloned in the pGem-3 vector, transcription is absent. If the PTOX promoter is cloned in the plasmid pKK232, containing the PTOX promoter between two ribosomal gene terminators of transcription, transcription occurs, although regulation of transcription is abolished. Under these conditions, the intracellular amount of RNA transcripts is increased by adding to the culture medium novobiocin, an inhibitor of bacterial gyrases. In vitro, the transcription of the PTOX promoter is activated on E. coli RNA polymerase supplemented with cell extracts from wild-type B. pertussis. Addition of DNA gyrase to the mixture dramatically reduces the amount of RNA synthesized. Our data show that the products of the bvg locus, BvgA and BvgS, are directly involved in the regulation of the PTOX promoter in E. coli and that DNA topology may play a role in the induction of transcription.
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MESH Headings
- Bordetella pertussis/genetics
- DNA Topoisomerases, Type II/metabolism
- DNA, Bacterial/genetics
- DNA, Bacterial/physiology
- Escherichia coli
- Gene Expression Regulation, Bacterial/physiology
- Genes, Bacterial/genetics
- Genes, Bacterial/physiology
- Pertussis Toxin
- Plasmids/genetics
- Plasmids/physiology
- Promoter Regions, Genetic/genetics
- Promoter Regions, Genetic/physiology
- Transcription, Genetic/genetics
- Transcription, Genetic/physiology
- Virulence Factors, Bordetella/genetics
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Affiliation(s)
- V Scarlato
- Immunobiological Research Institute Siena, Italy
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