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Noszka M, Strzałka A, Muraszko J, Hofreuter D, Abele M, Ludwig C, Stingl K, Zawilak-Pawlik A. CemR atypical response regulator impacts energy conversion in Campylobacteria. mSystems 2024; 9:e0078424. [PMID: 38980050 PMCID: PMC11334517 DOI: 10.1128/msystems.00784-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2024] [Accepted: 06/12/2024] [Indexed: 07/10/2024] Open
Abstract
Campylobacter jejuni and Arcobacter butzleri are microaerobic food-borne human gastrointestinal pathogens that mainly cause diarrheal disease. These related species of the Campylobacteria class face variable atmospheric environments during infection and transmission, ranging from nearly anaerobic to aerobic conditions. Consequently, their lifestyles require that both pathogens need to adjust their metabolism and respiration to the changing oxygen concentrations of the colonization sites. Our transcriptomic and proteomic studies revealed that C. jejuni and A. butzleri, lacking a Campylobacteria-specific regulatory protein, C. jejuni Cj1608, or a homolog, A. butzleri Abu0127, are unable to reprogram tricarboxylic acid cycle or respiration pathways, respectively, to produce ATP efficiently and, in consequence, adjust growth to changing oxygen supply. We propose that these Campylobacteria energy and metabolism regulators (CemRs) are long-sought transcription factors controlling the metabolic shift related to oxygen availability, essential for these bacteria's survival and adaptation to the niches they inhabit. Besides their significant universal role in Campylobacteria, CemRs, as pleiotropic regulators, control the transcription of many genes, often specific to the species, under microaerophilic conditions and in response to oxidative stress. IMPORTANCE C. jejuni and A. butzleri are closely related pathogens that infect the human gastrointestinal tract. In order to infect humans successfully, they need to change their metabolism as nutrient and respiratory conditions change. A regulator called CemR has been identified, which helps them adapt their metabolism to changing conditions, particularly oxygen availability in the gastrointestinal tract so that they can produce enough energy for survival and spread. Without CemR, these bacteria, as well as a related species, Helicobacter pylori, produce less energy, grow more slowly, or, in the case of C. jejuni, do not grow at all. Furthermore, CemR is a global regulator that controls the synthesis of many genes in each species, potentially allowing them to adapt to their ecological niches as well as establish infection. Therefore, the identification of CemR opens new possibilities for studying the pathogenicity of C. jejuni and A. butzleri.
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Affiliation(s)
- Mateusz Noszka
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Agnieszka Strzałka
- Department of Molecular Microbiology, Faculty of Biotechnology, University of Wrocław, Wrocław, Poland
| | - Jakub Muraszko
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
| | - Dirk Hofreuter
- Department of Biological Safety, Unit of Product Hygiene and Disinfection Strategies, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Miriam Abele
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), Technical University of Munich (TUM), Freising, Germany
| | - Christina Ludwig
- Bavarian Center for Biomolecular Mass Spectrometry (BayBioMS), Technical University of Munich (TUM), Freising, Germany
| | - Kerstin Stingl
- Department of Biological Safety, National Reference Laboratory for Campylobacter, German Federal Institute for Risk Assessment, Berlin, Germany
| | - Anna Zawilak-Pawlik
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław, Poland
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2
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Johnston EL, Guy-Von Stieglitz S, Zavan L, Cross J, Greening DW, Hill AF, Kaparakis-Liaskos M. The effect of altered pH growth conditions on the production, composition, and proteomes of Helicobacter pylori outer membrane vesicles. Proteomics 2024; 24:e2300269. [PMID: 37991474 DOI: 10.1002/pmic.202300269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 10/03/2023] [Accepted: 10/16/2023] [Indexed: 11/23/2023]
Abstract
Gram-negative bacteria release outer membrane vesicles (OMVs) that contain cargo derived from their parent bacteria. Helicobacter pylori is a Gram-negative human pathogen that produces urease to increase the pH of the surrounding environment to facilitate colonization of the gastric mucosa. However, the effect of acidic growth conditions on the production and composition of H. pylori OMVs is unknown. In this study, we examined the production, composition, and proteome of H. pylori OMVs produced during acidic and neutral pH growth conditions. H. pylori growth in acidic conditions reduced the quantity and size of OMVs produced. Additionally, OMVs produced during acidic growth conditions had increased protein, DNA, and RNA cargo compared to OMVs produced during neutral conditions. Proteomic analysis comparing the proteomes of OMVs to their parent bacteria demonstrated significant differences in the enrichment of beta-lactamases and outer membrane proteins between bacteria and OMVs, supporting that differing growth conditions impacts OMV composition. We also identified differences in the enrichment of proteins between OMVs produced during different pH growth conditions. Overall, our findings reveal that growth of H. pylori at different pH levels is a factor that alters OMV proteomes, which may affect their subsequent functions.
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Affiliation(s)
- Ella L Johnston
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Bundoora, Australia
- Research Centre for Extracellular Vesicles, La Trobe University, Bundoora, Australia
| | - Sebastian Guy-Von Stieglitz
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Bundoora, Australia
- Research Centre for Extracellular Vesicles, La Trobe University, Bundoora, Australia
| | - Lauren Zavan
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Bundoora, Australia
- Research Centre for Extracellular Vesicles, La Trobe University, Bundoora, Australia
| | - Jonathon Cross
- Baker Heart and Diabetes Institute, Melbourne, Australia
- Baker Department of Cardiometabolic Health, University of Melbourne, Melbourne, Australia
| | - David W Greening
- Research Centre for Extracellular Vesicles, La Trobe University, Bundoora, Australia
- Baker Heart and Diabetes Institute, Melbourne, Australia
- Baker Department of Cardiometabolic Health, University of Melbourne, Melbourne, Australia
| | - Andrew F Hill
- Research Centre for Extracellular Vesicles, La Trobe University, Bundoora, Australia
- Department of Biochemistry and Chemistry, School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, Australia
- Institute for Health and Sport, Victoria University, Melbourne, Victoria, Australia
| | - Maria Kaparakis-Liaskos
- Department of Microbiology, Anatomy, Physiology and Pharmacology, La Trobe University, Bundoora, Australia
- Research Centre for Extracellular Vesicles, La Trobe University, Bundoora, Australia
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3
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Vannini A, Pinatel E, Costantini PE, Pelliciari S, Roncarati D, Puccio S, De Bellis G, Scarlato V, Peano C, Danielli A. (Re)-definition of the holo- and apo-Fur direct regulons of Helicobacter pylori. J Mol Biol 2024; 436:168573. [PMID: 38626867 DOI: 10.1016/j.jmb.2024.168573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 04/09/2024] [Accepted: 04/10/2024] [Indexed: 04/28/2024]
Abstract
Iron homeostasis is a critical process for living organisms because this metal is an essential co-factor for fundamental biochemical activities, like energy production and detoxification, albeit its excess quickly leads to cell intoxication. The protein Fur (ferric uptake regulator) controls iron homeostasis in bacteria by switching from its apo- to holo-form as a function of the cytoplasmic level of ferrous ions, thereby modulating gene expression. The Helicobacter pylori HpFur protein has the rare ability to operate as a transcriptional commutator; apo- and holo-HpFur function as two different repressors with distinct DNA binding recognition properties for specific sets of target genes. Although the regulation of apo- and holo-HpFur in this bacterium has been extensively investigated, we propose a genome-wide redefinition of holo-HpFur direct regulon in H. pylori by integration of RNA-seq and ChIP-seq data, and a large extension of the apo-HpFur direct regulon. We show that in response to iron availability, new coding sequences, non-coding RNAs, toxin-antitoxin systems, and transcripts within open reading frames are directly regulated by apo- or holo-HpFur. These new targets and the more thorough validation and deeper characterization of those already known provide a complete and updated picture of the direct regulons of this two-faced transcriptional regulator.
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Affiliation(s)
- Andrea Vannini
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
| | - Eva Pinatel
- Institute of Biomedical Technologies - National Research Council, Via Fratelli Cervi 93, 20054 Segrate (MI), Italy.
| | - Paolo Emidio Costantini
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
| | - Simone Pelliciari
- Human Genetic Unit, Institute of Genetic and Cancer - University of Edinburgh, Crewe Road, Edinburgh EH4 2XU, UK.
| | - Davide Roncarati
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
| | - Simone Puccio
- Institute of Genetics and Biomedical Research, UoS Milan - National Research Council, Via Manzoni 113, 20089 Rozzano (MI), Italy; Humanitas Clinical and Research Center, Via Manzoni 56, 20089 Rozzano (MI), Italy.
| | - Gianluca De Bellis
- Institute of Biomedical Technologies - National Research Council, Via Fratelli Cervi 93, 20054 Segrate (MI), Italy.
| | - Vincenzo Scarlato
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
| | - Clelia Peano
- Institute of Genetics and Biomedical Research, UoS Milan - National Research Council, Via Manzoni 113, 20089 Rozzano (MI), Italy; Human Technopole, Via Rita Levi Montalcini 1, 20157 Milan, Italy.
| | - Alberto Danielli
- University of Bologna Department of Pharmacy and Biotechnology, Via Selmi 3, 40126 Bologna, Italy.
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4
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Sorokina LV, Phakatkar AH, Rehak PL, Král P, Shokuhfar T, Shahbazian-Yassar R. Nickel as a modifier of calcium oxalate: an in situ liquid cell TEM investigation of nucleation and growth. NANOSCALE 2024; 16:4266-4274. [PMID: 38348770 DOI: 10.1039/d3nr05314h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Despite extensive research on the nucleation and growth of calcium oxalate (CaOx) crystals, there are still several challenges and unknowns that remain. In particular, the role of trace metal elements in the promotion or inhibition of CaOx crystals is not well understood. In the present study, in situ graphene liquid cell transmission electron microscopy (in situ GLC TEM) was used to observe real-time, nanoscale transformations of CaOx crystals in the presence of nickel ions (Ni2+). The results showed that Ni2+ form Ni-water complexes, acting as a shape-directing species, generating a unique morphology and altering growth kinetics. Transient adsorption of Ni-water complexes resulted in a metastable phase formation of calcium oxalate trihydrate. Atomistic molecular dynamics simulations confirmed that Ni2+ acts as a weak inhibitor which slows down the CaOx crystallization, elucidating that Ni2+ impacts small-sized CaOx clusters by bringing more water into the clusters. This work highlighted the intricacies behind the effect of Ni2+ on CaOx biomineralization that were made possible to discern using in situ GLC TEM.
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Affiliation(s)
- Lioudmila V Sorokina
- Department of Civil, Materials, and Environmental Engineering, University of Illinois Chicago, Chicago, IL, 60607, USA.
| | - Abhijit H Phakatkar
- Department of Biomedical Engineering, University of Illinois Chicago, Chicago, IL, 60607, USA
| | - Pavel L Rehak
- Department of Chemistry, University of Illinois Chicago, Chicago, IL, 60607, USA
| | - Petr Král
- Departments of Chemistry, Physics, Pharmaceutical Sciences, and Chemical Engineering, University of Illinois Chicago, Chicago, IL, 60607, USA
| | - Tolou Shokuhfar
- Department of Biomedical Engineering, University of Illinois Chicago, Chicago, IL, 60607, USA
- Department of Mechanical and Industrial Engineering, University of Illinois Chicago, Chicago, IL, 60607, USA
| | - Reza Shahbazian-Yassar
- Department of Civil, Materials, and Environmental Engineering, University of Illinois Chicago, Chicago, IL, 60607, USA.
- Department of Mechanical and Industrial Engineering, University of Illinois Chicago, Chicago, IL, 60607, USA
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5
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Augustine J, Baksh KA, Prosser RS, Zamble DB. Insights into the Allosteric Response to Acidity by the Helicobacter pylori NikR Transcription Factor. Biochemistry 2023; 62:3265-3275. [PMID: 37917856 DOI: 10.1021/acs.biochem.3c00356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
Helicobacter pylori NikR (HpNikR) is a nickel-responsive transcription factor that regulates genes involved in nickel homeostasis, which is essential for the survival of this pathogen within the acidic human stomach. HpNikR also responds to drops in pH and regulates genes controlling acid acclimation of the bacteria, independently of nickel. We previously showed that nickel binding biases the conformational ensemble of HpNikR to the more DNA-binding competent states via an allosteric network of residues encompassing the nickel binding sites and the interface between the metal- and DNA-binding domains. Here, we examine how acidity promotes this response using 19F-NMR, mutagenesis, and DNA-binding studies. 19F-NMR revealed that a drop in pH from 7.6 to 6.0 does little to shift the conformational ensemble of HpNikR to the DNA binding-compatible cis conformer. Nevertheless, DNA-binding affinities of apo-HpNikR at pH 6.0 and Ni(II)-HpNikR at pH 7.6 are comparable for the ureA promoter. Histidine residues of the nickel binding sites were shown to be important for pH-dependent DNA binding and thus likely impart positive charge to the protein, initiating long-range electrostatic interactions with DNA that induce DNA complexation. The results point to a different DNA-binding mechanism in response to acidity compared to the conformational selection mechanism in response to nickel and overall provide new insights into the influence of pH on HpNikR activity, which contributes to H. pylori viability.
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Affiliation(s)
- Jerry Augustine
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Karina A Baksh
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Robert Scott Prosser
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Deborah B Zamble
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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6
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Baksh KA, Augustine J, Sljoka A, Prosser RS, Zamble DB. Mechanistic insights into the nickel-dependent allosteric response of the Helicobacter pylori NikR transcription factor. J Biol Chem 2022; 299:102785. [PMID: 36502919 PMCID: PMC9860126 DOI: 10.1016/j.jbc.2022.102785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 11/30/2022] [Accepted: 12/03/2022] [Indexed: 12/13/2022] Open
Abstract
In Helicobacter pylori, the nickel-responsive NikR transcription factor plays a key role in regulating intracellular nickel concentrations, which is an essential process for survival of this pathogen in the acidic human stomach. Nickel binding to H. pylori NikR (HpNikR) allosterically activates DNA binding to target promoters encoding genes involved in nickel homeostasis and acid adaptation, to either activate or repress their transcription. We previously showed that HpNikR adopts an equilibrium between an open conformation and DNA-binding competent cis and trans states. Nickel binding slows down conformational exchange between these states and shifts the equilibrium toward the binding-competent states. The protein then becomes stabilized in a cis conformation upon binding the ureA promoter. Here, we investigate how nickel binding creates this response and how it is transmitted to the DNA-binding domains. Through mutagenesis, DNA-binding studies, and computational methods, the allosteric response to nickel was found to be propagated from the nickel-binding sites to the DNA-binding domains via the β-sheets of the metal-binding domain and a network of residues at the inter-domain interface. Our computational results suggest that nickel binding increases protein rigidity to slow down the conformational exchange. A thymine base in the ureA promoter sequence, known to be critical for high affinity DNA binding by HpNikR, was also found to be important for the allosteric response, while a modified version of this promoter further highlighted the importance of the DNA sequence in modulating the response. Collectively, our results provide insights into regulation of a key protein for H. pylori survival.
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Affiliation(s)
- Karina A. Baksh
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Jerry Augustine
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Adnan Sljoka
- RIKEN Center for Advanced Intelligence Project, RIKEN, Chuo-ku, Tokyo, Japan,For correspondence: R. Scott Prosser; Adnan Sljoka
| | - R. Scott Prosser
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada,Department of Chemistry, University of Toronto, Toronto, Ontario, Canada,For correspondence: R. Scott Prosser; Adnan Sljoka
| | - Deborah B. Zamble
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada,Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
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7
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Insights into the Orchestration of Gene Transcription Regulators in Helicobacter pylori. Int J Mol Sci 2022; 23:ijms232213688. [PMID: 36430169 PMCID: PMC9696931 DOI: 10.3390/ijms232213688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 10/31/2022] [Accepted: 11/04/2022] [Indexed: 11/09/2022] Open
Abstract
Bacterial pathogens employ a general strategy to overcome host defenses by coordinating the virulence gene expression using dedicated regulatory systems that could raise intricate networks. During the last twenty years, many studies of Helicobacter pylori, a human pathogen responsible for various stomach diseases, have mainly focused on elucidating the mechanisms and functions of virulence factors. In parallel, numerous studies have focused on the molecular mechanisms that regulate gene transcription to attempt to understand the physiological changes of the bacterium during infection and adaptation to the environmental conditions it encounters. The number of regulatory proteins deduced from the genome sequence analyses responsible for the correct orchestration of gene transcription appears limited to 14 regulators and three sigma factors. Furthermore, evidence is accumulating for new and complex circuits regulating gene transcription and H. pylori virulence. Here, we focus on the molecular mechanisms used by H. pylori to control gene transcription as a function of the principal environmental changes.
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8
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Freire de Melo F, Marques HS, Fellipe Bueno Lemos F, Silva Luz M, Rocha Pinheiro SL, de Carvalho LS, Souza CL, Oliveira MV. Role of nickel-regulated small RNA in modulation of Helicobacter pylori virulence factors. World J Clin Cases 2022; 10:11283-11291. [PMID: 36387830 PMCID: PMC9649571 DOI: 10.12998/wjcc.v10.i31.11283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/14/2022] [Accepted: 09/06/2022] [Indexed: 02/05/2023] Open
Abstract
Helicobacter pylori (H. pylori) is a Gram-negative bacterium that infects about half of the world's population. H. pylori infection prevails by several mechanisms of adaptation of the bacteria and by its virulence factors including the cytotoxin associated antigen A (CagA). CagA is an oncoprotein that is the protagonist of gastric carcinogenesis associated with prolonged H. pylori infection. In this sense, small regulatory RNAs (sRNAs) are important macromolecules capable of inhibiting and activating gene expression. This function allows sRNAs to act in adjusting to unstable environmental conditions and in responding to cellular stresses in bacterial infections. Recent discoveries have shown that nickel-regulated small RNA (NikS) is a post-transcriptional regulator of virulence properties of H. pylori, including the oncoprotein CagA. Notably, high concentrations of nickel cause the reduction of NikS expression and consequently this increases the levels of CagA. In addition, NikS expression appears to be lower in clinical isolates from patients with gastric cancer when compared to patients without. With that in mind, this minireview approaches, in an accessible way, the most important and current aspects about the role of NikS in the control of virulence factors of H. pylori and the potential clinical repercussions of this modulation.
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Affiliation(s)
- Fabrício Freire de Melo
- Institution Multidisciplinar em Saúde, Universidade Federal da Bahia, Vitória da Conquista 45029-094, Brazil
| | - Hanna Santos Marques
- Campus Vitória da Conquista, Universidade Estadual do Sudoeste da Bahia, Vitória da Conquista 45083-900, Brazil
| | - Fabian Fellipe Bueno Lemos
- Institution Multidisciplinar em Saúde, Universidade Federal da Bahia, Vitória da Conquista 45029-094, Brazil
| | - Marcel Silva Luz
- Institution Multidisciplinar em Saúde, Universidade Federal da Bahia, Vitória da Conquista 45029-094, Brazil
| | - Samuel Luca Rocha Pinheiro
- Institution Multidisciplinar em Saúde, Universidade Federal da Bahia, Vitória da Conquista 45029-094, Brazil
| | - Lorena Sousa de Carvalho
- Institution Multidisciplinar em Saúde, Universidade Federal da Bahia, Vitória da Conquista 45029-094, Brazil
| | - Cláudio Lima Souza
- Institution Multidisciplinar em Saúde, Universidade Federal da Bahia, Vitória da Conquista 45029-094, Brazil
| | - Márcio Vasconcelos Oliveira
- Institution Multidisciplinar em Saúde, Universidade Federal da Bahia, Vitória da Conquista 45029-094, Brazil
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9
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Kumar S, Vinella D, De Reuse H. Nickel, an essential virulence determinant of Helicobacter pylori: Transport and trafficking pathways and their targeting by bismuth. Adv Microb Physiol 2022; 80:1-33. [PMID: 35489790 DOI: 10.1016/bs.ampbs.2022.01.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Metal acquisition and intracellular trafficking are crucial for all cells and metal ions have been recognized as virulence determinants in bacterial pathogens. Nickel is required for the pathogenicity of H. pylori. This bacterial pathogen colonizes the stomach of about half of the human population worldwide and is associated with gastric cancer that is responsible for 800,000 deaths per year. H. pylori possesses two nickel-enzymes that are essential for in vivo colonization, a [NiFe] hydrogenase and an abundant urease responsible for resistance to gastric acidity. Because of these two enzymes, survival of H. pylori relies on an important supply of nickel, implying tight control strategies to avoid its toxic accumulation or deprivation. H. pylori possesses original mechanisms for nickel uptake, distribution, storage and trafficking that will be discussed in this review. During evolution, acquisition of nickel transporters and specific nickel-binding proteins has been a decisive event to allow Helicobacter species to become able to colonize the stomach. Accordingly, many of the factors involved in these mechanisms are required for mouse colonization by H. pylori. These mechanisms are controlled at different levels including protein interaction networks, transcriptional, post-transcriptional and post-translational regulation. Bismuth is another metal used in combination with antibiotics to efficiently treat H. pylori infections. Although the precise mode of action of bismuth is unknown, many targets have been identified in H. pylori and there is growing evidence that bismuth interferes with the essential nickel pathways. Understanding the metal pathways will help improve treatments against H. pylori and other pathogens.
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Affiliation(s)
- Sumith Kumar
- Unité Pathogenèse de Helicobacter, CNRS UMR6047, Département de Microbiologie, Institut Pasteur, Paris, France
| | - Daniel Vinella
- Unité Pathogenèse de Helicobacter, CNRS UMR6047, Département de Microbiologie, Institut Pasteur, Paris, France
| | - Hilde De Reuse
- Unité Pathogenèse de Helicobacter, CNRS UMR6047, Département de Microbiologie, Institut Pasteur, Paris, France.
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10
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Roncarati D, Scarlato V, Vannini A. Targeting of Regulators as a Promising Approach in the Search for Novel Antimicrobial Agents. Microorganisms 2022; 10:microorganisms10010185. [PMID: 35056634 PMCID: PMC8777881 DOI: 10.3390/microorganisms10010185] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 01/12/2022] [Accepted: 01/12/2022] [Indexed: 02/01/2023] Open
Abstract
Since the discovery of penicillin in the first half of the last century, antibiotics have become the pillars of modern medicine for fighting bacterial infections. However, pathogens resistant to antibiotic treatment have increased in recent decades, and efforts to discover new antibiotics have decreased. As a result, it is becoming increasingly difficult to treat bacterial infections successfully, and we look forward to more significant efforts from both governments and the scientific community to research new antibacterial drugs. This perspective article highlights the high potential of bacterial transcriptional and posttranscriptional regulators as targets for developing new drugs. We highlight some recent advances in the search for new compounds that inhibit their biological activity and, as such, appear very promising for treating bacterial infections.
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Affiliation(s)
- Davide Roncarati
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
- Correspondence: (D.R.); (V.S.); (A.V.)
| | - Vincenzo Scarlato
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, 40126 Bologna, Italy
- Correspondence: (D.R.); (V.S.); (A.V.)
| | - Andrea Vannini
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, 40126 Bologna, Italy
- Correspondence: (D.R.); (V.S.); (A.V.)
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11
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Charbonnier M, González-Espinoza G, Kehl-Fie TE, Lalaouna D. Battle for Metals: Regulatory RNAs at the Front Line. Front Cell Infect Microbiol 2022; 12:952948. [PMID: 35865816 PMCID: PMC9294342 DOI: 10.3389/fcimb.2022.952948] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 06/09/2022] [Indexed: 11/13/2022] Open
Abstract
Metal such as iron, zinc, manganese, and nickel are essential elements for bacteria. These nutrients are required in crucial structural and catalytic roles in biological processes, including precursor biosynthesis, DNA replication, transcription, respiration, and oxidative stress responses. While essential, in excess these nutrients can also be toxic. The immune system leverages both of these facets, to limit bacterial proliferation and combat invaders. Metal binding immune proteins reduce the bioavailability of metals at the infection sites starving intruders, while immune cells intoxicate pathogens by providing metals in excess leading to enzyme mismetallation and/or reactive oxygen species generation. In this dynamic metal environment, maintaining metal homeostasis is a critical process that must be precisely coordinated. To achieve this, bacteria utilize diverse metal uptake and efflux systems controlled by metalloregulatory proteins. Recently, small regulatory RNAs (sRNAs) have been revealed to be critical post-transcriptional regulators, working in conjunction with transcription factors to promote rapid adaptation and to fine-tune bacterial adaptation to metal abundance. In this mini review, we discuss the expanding role for sRNAs in iron homeostasis, but also in orchestrating adaptation to the availability of other metals like manganese and nickel. Furthermore, we describe the sRNA-mediated interdependency between metal homeostasis and oxidative stress responses, and how regulatory networks controlled by sRNAs contribute to survival and virulence.
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Affiliation(s)
- Mathilde Charbonnier
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, Strasbourg, France
| | | | - Thomas E Kehl-Fie
- Department of Microbiology, University of Illinois Urbana-Champaign, Urbana IL, United States.,Carl R. Woese Institute for Genomic Biology University of Illinois Urbana-Champaign, Urbana IL, United States
| | - David Lalaouna
- Université de Strasbourg, CNRS, Architecture et Réactivité de l'ARN, UPR9002, Strasbourg, France
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12
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Szczepanowski P, Noszka M, Żyła-Uklejewicz D, Pikuła F, Nowaczyk-Cieszewska M, Krężel A, Stingl K, Zawilak-Pawlik A. HP1021 is a redox switch protein identified in Helicobacter pylori. Nucleic Acids Res 2021; 49:6863-6879. [PMID: 34139017 PMCID: PMC8266642 DOI: 10.1093/nar/gkab440] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 04/26/2021] [Accepted: 05/06/2021] [Indexed: 12/24/2022] Open
Abstract
Helicobacter pylori is a gram-negative, microaerophilic, pathogenic bacterium and a widespread colonizer of humans. H. pylori has developed mechanisms that enable it to overcome the harsh environment of the human stomach, including reactive oxygen species (ROS). Interestingly, up to now no typical regulator dedicated to the oxidative-stress response has been discovered. In this work, we reveal that the inhibitor of replication initiation HP1021 functions as a redox switch protein in H. pylori and plays an important role in response to oxidative stress of the gastric pathogen. Each of the two predicted HP1021 domains contains three cysteine residues. We show that the cysteine residues of HP1021 are sensitive to oxidation both in vitro and in vivo, and we demonstrate that HP1021 DNA-binding activity to oriC depends on the redox state of the protein. Moreover, Zn2+ modulates HP1021 affinity towards oriC template DNA. Transcription analysis of selected H. pylori genes by RT-qPCR indicated that HP1021 is directly involved in the oxygen-dependent control of H. pylori fecA3 and gluP genes, which are implicated in response to oxidative stress. In conclusion, HP1021 is a redox switch protein and could be a target for H. pylori control strategies.
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Affiliation(s)
- Piotr Szczepanowski
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław 53-114, Poland
| | - Mateusz Noszka
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław 53-114, Poland
| | - Dorota Żyła-Uklejewicz
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław 53-114, Poland
| | - Fabian Pikuła
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław 53-114, Poland
| | - Malgorzata Nowaczyk-Cieszewska
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław 53-114, Poland
| | - Artur Krężel
- Department of Chemical Biology, Faculty of Biotechnology, University of Wrocław, Wrocław 50-383, Poland
| | - Kerstin Stingl
- Department of Biological Safety, National Reference Laboratory for Campylobacter, German Federal Institute for Risk Assessment, Berlin 12277, Germany
| | - Anna Zawilak-Pawlik
- Department of Microbiology, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Wrocław 53-114, Poland
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13
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Tejada-Arranz A, De Reuse H. Riboregulation in the Major Gastric Pathogen Helicobacter pylori. Front Microbiol 2021; 12:712804. [PMID: 34335549 PMCID: PMC8322730 DOI: 10.3389/fmicb.2021.712804] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 06/23/2021] [Indexed: 02/05/2023] Open
Abstract
Helicobacter pylori is a Gram-negative bacterial pathogen that colonizes the stomach of about half of the human population worldwide. Infection by H. pylori is generally acquired during childhood and this bacterium rapidly establishes a persistent colonization. H. pylori causes chronic gastritis that, in some cases, progresses into peptic ulcer disease or adenocarcinoma that is responsible for about 800,000 deaths in the world every year. H. pylori has evolved efficient adaptive strategies to colonize the stomach, a particularly hostile acidic environment. Few transcriptional regulators are encoded by the small H. pylori genome and post-transcriptional regulation has been proposed as a major level of control of gene expression in this pathogen. The transcriptome and transcription start sites (TSSs) of H. pylori strain 26695 have been defined at the genome level. This revealed the existence of a total of 1,907 TSSs among which more than 900 TSSs for non-coding RNAs (ncRNAs) including 60 validated small RNAs (sRNAs) and abundant anti-sense RNAs, few of which have been experimentally validated. An RNA degradosome was shown to play a central role in the control of mRNA and antisense RNA decay in H. pylori. Riboregulation, genetic regulation by RNA, has also been revealed and depends both on antisense RNAs and small RNAs. Known examples will be presented in this review. Antisense RNA regulation was reported for some virulence factors and for several type I toxin antitoxin systems, one of which controls the morphological transition of H. pylori spiral shape to round coccoids. Interestingly, the few documented cases of small RNA-based regulation suggest that their mechanisms do not follow the same rules that were well established in the model organism Escherichia coli. First, the genome of H. pylori encodes none of the two well-described RNA chaperones, Hfq and ProQ that are important for riboregulation in several organisms. Second, some of the reported small RNAs target, through "rheostat"-like mechanisms, repeat-rich stretches in the 5'-untranslated region of genes encoding important virulence factors. In conclusion, there are still many unanswered questions about the extent and underlying mechanisms of riboregulation in H. pylori but recent publications highlighted original mechanisms making this important pathogen an interesting study model.
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Affiliation(s)
- Alejandro Tejada-Arranz
- Unité Pathogenèse de Helicobacter, CNRS UMR 2001, Département de Microbiologie, Institut Pasteur, Paris, France
- Université de Paris, Sorbonne Paris Cité, Paris, France
| | - Hilde De Reuse
- Unité Pathogenèse de Helicobacter, CNRS UMR 2001, Département de Microbiologie, Institut Pasteur, Paris, France
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14
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Cunrath O, Palmer JD. An overview of Salmonella enterica metal homeostasis pathways during infection. ACTA ACUST UNITED AC 2021; 2:uqab001. [PMID: 34250489 PMCID: PMC8264917 DOI: 10.1093/femsml/uqab001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/19/2021] [Indexed: 12/14/2022]
Abstract
Nutritional immunity is a powerful strategy at the core of the battlefield between host survival and pathogen proliferation. A host can prevent pathogens from accessing biological metals such as Mg, Fe, Zn, Mn, Cu, Co or Ni, or actively intoxicate them with metal overload. While the importance of metal homeostasis for the enteric pathogen Salmonella enterica Typhimurium was demonstrated many decades ago, inconsistent results across various mouse models, diverse Salmonella genotypes, and differing infection routes challenge aspects of our understanding of this phenomenon. With expanding access to CRISPR-Cas9 for host genome manipulation, it is now pertinent to re-visit past results in the context of specific mouse models, identify gaps and incongruities in current knowledge landscape of Salmonella homeostasis, and recommend a straight path forward towards a more universal understanding of this historic host-microbe relationship.
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Affiliation(s)
- Olivier Cunrath
- Department of Zoology, University of Oxford, Zoology Research and Administration Building, 11a Mansfield Rd, Oxford, UK OX1 3SZ
| | - Jacob D Palmer
- Department of Zoology, University of Oxford, Zoology Research and Administration Building, 11a Mansfield Rd, Oxford, UK OX1 3SZ
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15
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A bacterial small RNA regulates the adaptation of Helicobacter pylori to the host environment. Nat Commun 2021; 12:2085. [PMID: 33837194 PMCID: PMC8035401 DOI: 10.1038/s41467-021-22317-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 03/10/2021] [Indexed: 12/15/2022] Open
Abstract
Long-term infection of the stomach with Helicobacter pylori can cause gastric cancer. However, the mechanisms by which the bacteria adapt to the stomach environment are poorly understood. Here, we show that a small non-coding RNA of H. pylori (HPnc4160, also known as IsoB or NikS) regulates the pathogen’s adaptation to the host environment as well as bacterial oncoprotein production. In a rodent model of H. pylori infection, the genomes of bacteria isolated from the stomach possess an increased number of T-repeats upstream of the HPnc4160-coding region, and this leads to reduced HPnc4160 expression. We use RNA-seq and iTRAQ analyses to identify eight targets of HPnc4160, including genes encoding outer membrane proteins and oncoprotein CagA. Mutant strains with HPnc4160 deficiency display increased colonization ability of the mouse stomach, in comparison with the wild-type strain. Furthermore, HPnc4160 expression is lower in clinical isolates from gastric cancer patients than in isolates derived from non-cancer patients, while the expression of HPnc4160’s targets is higher in the isolates from gastric cancer patients. Therefore, the small RNA HPnc4160 regulates H. pylori adaptation to the host environment and, potentially, gastric carcinogenesis. Long-term infection of the stomach with Helicobacter pylori can cause gastric cancer. Here, Kinoshita-Daitoku et al. show that a small non-coding RNA of H. pylori regulates bacterial adaptation to the stomach environment and bacterial oncoprotein production.
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16
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Matilla MA, Ortega Á, Krell T. The role of solute binding proteins in signal transduction. Comput Struct Biotechnol J 2021; 19:1786-1805. [PMID: 33897981 PMCID: PMC8050422 DOI: 10.1016/j.csbj.2021.03.029] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 03/22/2021] [Accepted: 03/22/2021] [Indexed: 12/13/2022] Open
Abstract
The solute binding proteins (SBPs) of prokaryotes are present in the extracytosolic space. Although their primary function is providing substrates to transporters, SBPs also stimulate different signaling proteins, including chemoreceptors, sensor kinases, diguanylate cyclases/phosphodiesterases and Ser/Thr kinases, thereby causing a wide range of responses. While relatively few such systems have been identified, several pieces of evidence suggest that SBP-mediated receptor activation is a widespread mechanism. (1) These systems have been identified in Gram-positive and Gram-negative bacteria and archaea. (2) There is a structural diversity in the receptor domains that bind SBPs. (3) SBPs belonging to thirteen different families interact with receptor ligand binding domains (LBDs). (4) For the two most abundant receptor LBD families, dCache and four-helix-bundle, there are different modes of interaction with SBPs. (5) SBP-stimulated receptors carry out many different functions. The advantage of SBP-mediated receptor stimulation is attributed to a strict control of SBP levels, which allows a precise adjustment of the systeḿs sensitivity. We have compiled information on the effect of ligands on the transcript/protein levels of their cognate SBPs. In 87 % of the cases analysed, ligands altered SBP expression levels. The nature of the regulatory effect depended on the ligand family. Whereas inorganic ligands typically downregulate SBP expression, an upregulation was observed in response to most sugars and organic acids. A major unknown is the role that SBPs play in signaling and in receptor stimulation. This review attempts to summarize what is known and to present new information to narrow this gap in knowledge.
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Affiliation(s)
- Miguel A Matilla
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Prof. Albareda 1, Granada 18008, Spain
| | - Álvaro Ortega
- Department of Biochemistry and Molecular Biology 'B' and Immunology, Faculty of Chemistry, University of Murcia, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Tino Krell
- Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Prof. Albareda 1, Granada 18008, Spain
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17
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Delineation of the pH-Responsive Regulon Controlled by the Helicobacter pylori ArsRS Two-Component System. Infect Immun 2021; 89:IAI.00597-20. [PMID: 33526561 DOI: 10.1128/iai.00597-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 01/09/2021] [Indexed: 12/22/2022] Open
Abstract
Helicobacter pylori encounters a wide range of pH within the human stomach. In a comparison of H. pylori cultured in vitro under neutral or acidic conditions, about 15% of genes are differentially expressed, and corresponding changes are detectable for many of the encoded proteins. The ArsRS two-component system (TCS), comprised of the sensor kinase ArsS and its cognate response regulator ArsR, has an important role in mediating pH-responsive changes in H. pylori gene expression. In this study, we sought to delineate the pH-responsive ArsRS regulon and further define the role of ArsR in pH-responsive gene expression. We compared H. pylori strains containing an intact ArsRS system with an arsS null mutant or strains containing site-specific mutations of a conserved aspartate residue (D52) in ArsR, which is phosphorylated in response to signals relayed by the cognate sensor kinase ArsS. We identified 178 genes that were pH-responsive in strains containing an intact ArsRS system but not in ΔarsS or arsR mutants. These constituents of the pH-responsive ArsRS regulon include genes involved in acid acclimatization (ureAB, amidases), oxidative stress responses (katA, sodB), transcriptional regulation related to iron or nickel homeostasis (fur, nikR), and genes encoding outer membrane proteins (including sabA, alpA, alpB, hopD [labA], and horA). When comparing H. pylori strains containing an intact ArsRS TCS with arsRS mutants, each cultured at neutral pH, relatively few genes are differentially expressed. Collectively, these data suggest that ArsRS-mediated gene regulation has an important role in H. pylori adaptation to changing pH conditions.
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18
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Kelley BR, Lu J, Haley KP, Gaddy JA, Johnson JG. Metal homeostasis in pathogenic Epsilonproteobacteria: mechanisms of acquisition, efflux, and regulation. Metallomics 2021; 13:mfaa002. [PMID: 33570133 PMCID: PMC8043183 DOI: 10.1093/mtomcs/mfaa002] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 11/25/2020] [Accepted: 12/03/2020] [Indexed: 12/14/2022]
Abstract
Epsilonproteobacteria are a diverse class of eubacteria within the Proteobacteria phylum that includes environmental sulfur-reducing bacteria and the human pathogens, Campylobacter jejuni and Helicobacter pylori. These pathogens infect and proliferate within the gastrointestinal tracts of multiple animal hosts, including humans, and cause a variety of disease outcomes. While infection of these hosts provides nutrients for the pathogenic Epsilonproteobacteria, many hosts have evolved a variety of strategies to either sequester metals from the invading pathogen or exploit the toxicity of metals and drive their accumulation as an antimicrobial strategy. As a result, C. jejuni and H. pylori have developed mechanisms to sense changes in metal availability and regulate their physiology in order to respond to either metal limitation or accumulation. In this review, we will discuss the challenges of metal availability at the host-pathogen interface during infection with C. jejuni and H. pylori and describe what is currently known about how these organisms alter their gene expression and/or deploy bacterial virulence factors in response to these environments.
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Affiliation(s)
- Brittni R Kelley
- Department of Microbiology, University of Tennessee, Knoxville, TN, USA
| | - Jacky Lu
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, USA
| | - Kathryn P Haley
- Department of Biology, Grand Valley State University, Grand Rapids, MI, USA
| | - Jennifer A Gaddy
- Department of Pathology, Microbiology and Immunology, Vanderbilt University, Nashville, TN, USA
- Tennessee Valley Healthcare Systems, Department of Veterans Affairs, Nashville, TN, USA
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
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19
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Baksh KA, Pichugin D, Prosser RS, Zamble DB. Allosteric regulation of the nickel-responsive NikR transcription factor from Helicobacter pylori. J Biol Chem 2021; 296:100069. [PMID: 33199369 PMCID: PMC7949043 DOI: 10.1074/jbc.ra120.015459] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 11/08/2020] [Accepted: 11/15/2020] [Indexed: 12/20/2022] Open
Abstract
Nickel is essential for the survival of the pathogenic bacteria Helicobacter pylori in the fluctuating pH of the human stomach. Due to its inherent toxicity and limited availability, nickel homeostasis is maintained through a network of pathways that are coordinated by the nickel-responsive transcription factor NikR. Nickel binding to H. pylori NikR (HpNikR) induces an allosteric response favoring a conformation that can bind specific DNA motifs, thereby serving to either activate or repress transcription of specific genes involved in nickel homeostasis and acid adaptation. Here, we examine how nickel induces this response using 19F-NMR, which reveals conformational and dynamic changes associated with nickel-activated DNA complex formation. HpNikR adopts an equilibrium between an open state and DNA-binding competent states regardless of nickel binding, but a higher level of dynamics is observed in the absence of metal. Nickel binding shifts the equilibrium toward the binding-competent states and decreases the mobility of the DNA-binding domains. The nickel-bound protein is then able to adopt a single conformation upon binding a target DNA promoter. Zinc, which does not promote high-affinity DNA binding, is unable to induce the same allosteric response as nickel. We propose that the allosteric mechanism of nickel-activated DNA binding by HpNikR is driven by conformational selection.
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Affiliation(s)
- Karina A Baksh
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Dmitry Pichugin
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Robert Scott Prosser
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.
| | - Deborah B Zamble
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
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20
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Mejía-Almonte C, Busby SJW, Wade JT, van Helden J, Arkin AP, Stormo GD, Eilbeck K, Palsson BO, Galagan JE, Collado-Vides J. Redefining fundamental concepts of transcription initiation in bacteria. Nat Rev Genet 2020; 21:699-714. [PMID: 32665585 PMCID: PMC7990032 DOI: 10.1038/s41576-020-0254-8] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/29/2020] [Indexed: 12/15/2022]
Abstract
Despite enormous progress in understanding the fundamentals of bacterial gene regulation, our knowledge remains limited when compared with the number of bacterial genomes and regulatory systems to be discovered. Derived from a small number of initial studies, classic definitions for concepts of gene regulation have evolved as the number of characterized promoters has increased. Together with discoveries made using new technologies, this knowledge has led to revised generalizations and principles. In this Expert Recommendation, we suggest precise, updated definitions that support a logical, consistent conceptual framework of bacterial gene regulation, focusing on transcription initiation. The resulting concepts can be formalized by ontologies for computational modelling, laying the foundation for improved bioinformatics tools, knowledge-based resources and scientific communication. Thus, this work will help researchers construct better predictive models, with different formalisms, that will be useful in engineering, synthetic biology, microbiology and genetics.
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Affiliation(s)
- Citlalli Mejía-Almonte
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Morelos, Cuernavaca, México
| | | | - Joseph T Wade
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Jacques van Helden
- Aix-Marseille University, INSERM UMR S 1090, Theory and Approaches of Genome Complexity (TAGC), Marseille, France
- CNRS, Institut Français de Bioinformatique, IFB-core, UMS 3601, Evry, France
| | - Adam P Arkin
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA, USA
| | - Gary D Stormo
- Department of Genetics, Washington University School of Medicine, St Louis, MO, USA
| | - Karen Eilbeck
- Department of Biomedical Informatics, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Bernhard O Palsson
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - James E Galagan
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - Julio Collado-Vides
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Morelos, Cuernavaca, México.
- Department of Biomedical Engineering, Boston University, Boston, MA, USA.
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21
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Eisenbart SK, Alzheimer M, Pernitzsch SR, Dietrich S, Stahl S, Sharma CM. A Repeat-Associated Small RNA Controls the Major Virulence Factors of Helicobacter pylori. Mol Cell 2020; 80:210-226.e7. [PMID: 33002424 DOI: 10.1016/j.molcel.2020.09.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Revised: 07/29/2020] [Accepted: 09/04/2020] [Indexed: 12/12/2022]
Abstract
Many bacterial pathogens regulate their virulence genes via phase variation, whereby length-variable simple sequence repeats control the transcription or coding potential of those genes. Here, we have exploited this relationship between DNA structure and physiological function to discover a globally acting small RNA (sRNA) regulator of virulence in the gastric pathogen Helicobacter pylori. Our study reports the first sRNA whose expression is affected by a variable thymine (T) stretch in its promoter. We show the sRNA post-transcriptionally represses multiple major pathogenicity factors of H. pylori, including CagA and VacA, by base pairing to their mRNAs. We further demonstrate transcription of the sRNA is regulated by the nickel-responsive transcriptional regulator NikR (thus named NikS for nickel-regulated sRNA), thereby linking virulence factor regulation to nickel concentrations. Using in-vitro infection experiments, we demonstrate NikS affects host cell internalization and epithelial barrier disruption. Together, our results show NikS is a phase-variable, post-transcriptional global regulator of virulence properties in H. pylori.
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Affiliation(s)
- Sara K Eisenbart
- Chair of Molecular Infection Biology II, Institute of Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Mona Alzheimer
- Chair of Molecular Infection Biology II, Institute of Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Sandy R Pernitzsch
- Chair of Molecular Infection Biology II, Institute of Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Sascha Dietrich
- Core Unit Systems Medicine, Interdisciplinary Center for Clinical Research (IZKF) of the University Hospital Würzburg, 97080 Würzburg, Germany
| | - Stephanie Stahl
- Chair of Molecular Infection Biology II, Institute of Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Cynthia M Sharma
- Chair of Molecular Infection Biology II, Institute of Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany.
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22
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Bakare OO, Fadaka AO, Klein A, Pretorius A. Dietary effects of antimicrobial peptides in therapeutics. ALL LIFE 2020. [DOI: 10.1080/26895293.2020.1726826] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Affiliation(s)
- Olalekan Olanrewaju Bakare
- Department of Biotechnology, Faculty of Natural Sciences, University of the Western Cape, Cape Town, South Africa
| | - Adewale Oluwaseun Fadaka
- Department of Biotechnology, Faculty of Natural Sciences, University of the Western Cape, Cape Town, South Africa
| | - Ashwil Klein
- Department of Biotechnology, Faculty of Natural Sciences, University of the Western Cape, Cape Town, South Africa
| | - Ashley Pretorius
- Department of Biotechnology, Faculty of Natural Sciences, University of the Western Cape, Cape Town, South Africa
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23
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Baksh KA, Zamble DB. Allosteric control of metal-responsive transcriptional regulators in bacteria. J Biol Chem 2020; 295:1673-1684. [PMID: 31857375 PMCID: PMC7008368 DOI: 10.1074/jbc.rev119.011444] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Many transition metals are essential trace nutrients for living organisms, but they are also cytotoxic in high concentrations. Bacteria maintain the delicate balance between metal starvation and toxicity through a complex network of metal homeostasis pathways. These systems are coordinated by the activities of metal-responsive transcription factors-also known as metal-sensor proteins or metalloregulators-that are tuned to sense the bioavailability of specific metals in the cell in order to regulate the expression of genes encoding proteins that contribute to metal homeostasis. Metal binding to a metalloregulator allosterically influences its ability to bind specific DNA sequences through a variety of intricate mechanisms that lie on a continuum between large conformational changes and subtle changes in internal dynamics. This review summarizes recent advances in our understanding of how metal sensor proteins respond to intracellular metal concentrations. In particular, we highlight the allosteric mechanisms used for metal-responsive regulation of several prokaryotic single-component metalloregulators, and we briefly discuss current open questions of how metalloregulators function in bacterial cells. Understanding the regulation and function of metal-responsive transcription factors is a fundamental aspect of metallobiochemistry and is important for gaining insights into bacterial growth and virulence.
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Affiliation(s)
- Karina A Baksh
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Deborah B Zamble
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada; Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
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24
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Pohl D, Keller PM, Bordier V, Wagner K. Review of current diagnostic methods and advances in Helicobacter pylori diagnostics in the era of next generation sequencing. World J Gastroenterol 2019; 25:4629-4660. [PMID: 31528091 PMCID: PMC6718044 DOI: 10.3748/wjg.v25.i32.4629] [Citation(s) in RCA: 68] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 06/25/2019] [Accepted: 07/19/2019] [Indexed: 02/06/2023] Open
Abstract
Helicobacter pylori (H. pylori) infection is highly prevalent in the human population and may lead to severe gastrointestinal pathology including gastric and duodenal ulcers, mucosa associated tissue lymphoma and gastric adenocarcinoma. In recent years, an alarming increase in antimicrobial resistance and subsequently failing empiric H. pylori eradication therapies have been noted worldwide, also in many European countries. Therefore, rapid and accurate determination of H. pylori’s antibiotic susceptibility prior to the administration of eradication regimens becomes ever more important. Traditionally, detection of H. pylori and its antimicrobial resistance is done by culture and phenotypic drug susceptibility testing that are cumbersome with a long turn-around-time. Recent advances in diagnostics provide new tools, like real-time polymerase chain reaction (PCR) and line probe assays, to diagnose H. pylori infection and antimicrobial resistance to certain antibiotics, directly from clinical specimens. Moreover, high-throughput whole genome sequencing technologies allow the rapid analysis of the pathogen’s genome, thereby allowing identification of resistance mutations and associated antibiotic resistance. In the first part of this review, we will give an overview on currently available diagnostic methods for detection of H. pylori and its drug resistance and their implementation in H. pylori management. The second part of the review focusses on the use of next generation sequencing technology in H. pylori research. To this end, we conducted a literature search for original research articles in English using the terms “Helicobacter”, “transcriptomic”, “transcriptome”, “next generation sequencing” and “whole genome sequencing”. This review is aimed to bridge the gap between current diagnostic practice (histology, rapid urease test, H. pylori culture, PCR and line probe assays) and new sequencing technologies and their potential implementation in diagnostic laboratory settings in order to complement the currently recommended H. pylori management guidelines and subsequently improve public health.
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Affiliation(s)
- Daniel Pohl
- Division of Gastroenterology, University Hospital of Zurich, Zurich 8006, Switzerland
| | - Peter M Keller
- Institute for Infectious Diseases, University of Bern, Bern 3010, Switzerland
| | - Valentine Bordier
- Division of Gastroenterology, University Hospital of Zurich, Zurich 8006, Switzerland
| | - Karoline Wagner
- Institute of Medical Microbiology, University of Zurich, Zurich 8006, Switzerland
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25
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Abstract
Nickel is essential for the survival of many pathogenic bacteria. E. coli and H. pylori require nickel for [NiFe]-hydrogenases. H. pylori also requires nickel for urease. At high concentrations nickel can be toxic to the cell, therefore, nickel concentrations are tightly regulated. Metalloregulators help to maintain nickel concentration in the cell by regulating the expression of the genes associated with nickel import and export. Nickel import into the cell, delivery of nickel to target proteins, and export of nickel from the cell is a very intricate and well-choreographed process. The delivery of nickel to [NiFe]-hydrogenase and urease is complex and involves several chaperones and accessory proteins. A combination of biochemical, crystallographic, and spectroscopic techniques has been utilized to study the structures of these proteins, as well as protein-protein interactions resulting in an expansion of our knowledge regarding how these proteins sense and bind nickel. In this review, recent advances in the field will be discussed, focusing on the metal site structures of nickel bound to metalloregulators and chaperones.
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26
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Fagoonee S, Pellicano R. Helicobacter pylori: molecular basis for colonization and survival in gastric environment and resistance to antibiotics. A short review. Infect Dis (Lond) 2019; 51:399-408. [PMID: 30907202 DOI: 10.1080/23744235.2019.1588472] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Helicobacter pylori is a human-specific pathogen with a strict tropism for the gastric mucosa. This bacterium infects around half of the world population and is the main responsible for gastritis, peptic ulcer and, in some cases, for the pathogenesis of gastric cancer. Nevertheless, disease development in infected subjects depends not only on the bacterium, but also on the host genetic predisposition and on environmental factors. The fascinating question of how the bacterium can survive in the gastric environment has stimulated research in this field. It is now clear that H. pylori is able to colonize and adhere to the gastric epithelium through several mechanisms, including the breakdown of urea with production of the cell-toxic ammonia. The resulting raise in pH neutralizes acidity of the stomach, thereby allowing the bacterium to safely cross the mucus layer to the epithelial surface. Current challenges regard understanding the mechanisms of antibiotic resistance and how to overcome it. Lately, an increasing H. pylori resistance rate to antibiotics has been reported and several molecular bases for this phenomenon described. In this review, we highlight the current knowledge on mechanisms supporting H. pylori resistance to gastric environment and to therapy.
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Affiliation(s)
- Sharmila Fagoonee
- a Institute for Biostructure and Bioimaging (CNR) c/o Molecular Biotechnology Center , Turin , Italy
| | - Rinaldo Pellicano
- b Unit of Gastroenterology , Molinette-SGAS Hospital , Turin , Italy
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27
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Jones MD, Li Y, Zamble DB. Acid-responsive activity of the Helicobacter pylori metalloregulator NikR. Proc Natl Acad Sci U S A 2018; 115:8966-8971. [PMID: 30126985 PMCID: PMC6130374 DOI: 10.1073/pnas.1808393115] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Helicobacter pylori is a human pathogen that infects the stomach, where it experiences variable pH. To survive the acidic gastric conditions, H. pylori produces large quantities of urease, a nickel enzyme that hydrolyzes urea to ammonia, which neutralizes the local environment. One of the regulators of urease expression in H. pylori is HpNikR, a nickel-responsive transcription factor. Here we show that HpNikR also regulates urease expression in response to changes in pH, linking acid adaptation and nickel homeostasis. Upon measuring the cytosolic pH of H. pylori exposed to an external pH of 2, similar to the acidic shock conditions that occur in the human stomach, a significant drop in internal pH was observed. This decrease in internal pH resulted in HpNikR-dependent activation of ureA transcription. Furthermore, analysis of a slate of H. pylori genes encoding other acid adaptation or nickel homeostasis components revealed HpNikR-dependent regulation in response to acid shock. This regulation was consistent with pH-dependent DNA binding to the corresponding promoter sequences observed in vitro with purified HpNikR. These results demonstrate that HpNikR can directly respond to changes in cytosolic pH during acid acclimation and illustrate the exquisitely coordinated regulatory networks that support H. pylori infections in the harsh environment of the human stomach.
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Affiliation(s)
- Michael D Jones
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
| | - Yanjie Li
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
| | - Deborah B Zamble
- Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada;
- Department of Biochemistry, University of Toronto, Toronto, ON M5S 1A8, Canada
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28
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Abstract
In this review, we highlight progress in the last year in characterizing known virulence factors like flagella and the Cag type IV secretion system with sophisticated structural and biochemical approaches to yield new insight on the assembly and functions of these critical virulence determinants. Several aspects of Helicobacter pylori physiology were newly explored this year and evaluated for their functions during stomach colonization, including a fascinating role for the essential protease HtrA in allowing access of H. pylori to the basolateral side of the gastric epithelium through cleavage of the tight junction protein E-cadherin to facilitate CagA delivery. Molecular biology tools standard in model bacteria, including regulated gene expression during animal infection and fluorescent reporter gene fusions, were newly applied to H. pylori to explore functions for urease beyond initial colonization and establish high salt consumption as a mediator of gene expression changes. New sequencing technologies enabled validation of long postulated roles for DNA methylation in regulating H. pylori gene expression. On the cell biology side, elegant work using lineage tracing in the murine model and organoid primary cell culture systems has provided new insights into how H. pylori manipulates gastric tissue functions, locally and at a distance, to promote its survival in the stomach and induce pathologic changes. Finally, new work has bolstered the case for genomic variation as an important mechanism to generate phenotypic diversity during changing environmental conditions in the context of diet manipulation in animal infection models and during human experimental infection after vaccination.
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Affiliation(s)
- Langgeng Agung Waskito
- Faculty of Medicine, Department of Environmental and Preventive Medicine, Oita University, Yufu-City, Oita, Japan.,Institute of Tropical Disease, Universitas Airlangga, Surabaya, Indonesia
| | - Nina R Salama
- Human Biology Division, Fred Hutchinson Cancer Research Center, Seattle, Washington
| | - Yoshio Yamaoka
- Faculty of Medicine, Department of Environmental and Preventive Medicine, Oita University, Yufu-City, Oita, Japan.,Department of Medicine, Gastroenterology and Hepatology Section, Baylor College of Medicine, Houston, Texas
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29
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Pepe S, Pinatel E, Fiore E, Puccio S, Peano C, Brignoli T, Vannini A, Danielli A, Scarlato V, Roncarati D. The Helicobacter pylori Heat-Shock Repressor HspR: Definition of Its Direct Regulon and Characterization of the Cooperative DNA-Binding Mechanism on Its Own Promoter. Front Microbiol 2018; 9:1887. [PMID: 30154784 PMCID: PMC6102357 DOI: 10.3389/fmicb.2018.01887] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 07/27/2018] [Indexed: 12/12/2022] Open
Abstract
The ability of pathogens to perceive environmental conditions and modulate gene expression accordingly is a crucial feature for bacterial survival. In this respect, the heat-shock response, a universal cellular response, allows cells to adapt to hostile environmental conditions and to survive during stress. In the major human pathogen Helicobacter pylori the expression of chaperone-encoding operons is under control of two auto-regulated transcriptional repressors, HrcA and HspR, with the latter acting as the master regulator of the regulatory circuit. To further characterize the HspR regulon in H. pylori, we used global transcriptome analysis (RNA-sequencing) in combination with Chromatin Immunoprecipitation coupled with deep sequencing (ChIP-sequencing) of HspR genomic binding sites. Intriguingly, these analyses showed that HspR is involved in the regulation of different crucial cellular functions through a limited number of genomic binding sites. Moreover, we further characterized HspR-DNA interactions through hydroxyl-radical footprinting assays. This analysis in combination with a nucleotide sequence alignment of HspR binding sites, revealed a peculiar pattern of DNA protection and highlighted sequence conservation with the HAIR motif (an HspR-associated inverted repeat of Streptomyces spp.). Site-directed mutagenesis demonstrated that the HAIR motif is fundamental for HspR binding and that additional nucleotide determinants flanking the HAIR motif are required for complete binding of HspR to its operator sequence spanning over 70 bp of DNA. This finding is compatible with a model in which possibly a dimer of HspR recognizes the HAIR motif overlapping its promoter for binding and in turn cooperatively recruits two additional dimers on both sides of the HAIR motif.
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Affiliation(s)
- Simona Pepe
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Bologna, Italy
| | - Eva Pinatel
- Institute of Biomedical Technologies, National Research Council, Milan, Italy
| | - Elisabetta Fiore
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Bologna, Italy
| | - Simone Puccio
- Institute of Biomedical Technologies, National Research Council, Milan, Italy.,Humanitas Clinical and Research Center, Milan, Italy
| | - Clelia Peano
- Institute of Biomedical Technologies, National Research Council, Milan, Italy.,Humanitas Clinical and Research Center, Milan, Italy.,Institute of Genetic and Biomedical Research, National Research Council, Milan, Italy
| | - Tarcisio Brignoli
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Bologna, Italy
| | - Andrea Vannini
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Bologna, Italy
| | - Alberto Danielli
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Bologna, Italy
| | - Vincenzo Scarlato
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Bologna, Italy
| | - Davide Roncarati
- Department of Pharmacy and Biotechnology (FaBiT), University of Bologna, Bologna, Italy
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30
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Saylor Z, Maier R. Helicobacter pylori nickel storage proteins: recognition and modulation of diverse metabolic targets. Microbiology (Reading) 2018; 164:1059-1068. [DOI: 10.1099/mic.0.000680] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Affiliation(s)
- Zachary Saylor
- Department of Microbiology and Center for Metalloprotein Studies, University of Georgia, Athens, GA, USA
| | - Robert Maier
- Department of Microbiology and Center for Metalloprotein Studies, University of Georgia, Athens, GA, USA
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31
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Abstract
As Helicobacter pylori infects half the world's population and displays an extensive intraspecies diversity, genomics is a powerful tool to understand evolution and disease, to identify factors that confer higher risk of severe sequelae, and to find new approaches for therapy both among bacterial and host targets. In line with these objectives, this review article summarizes the major findings in Helicobacter genomics in papers published between April 2016 and March 2017.
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Affiliation(s)
- Kaisa Thorell
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institute, Stockholm, Sweden
| | - Philippe Lehours
- INSERM, Univ. Bordeaux, UMR1053 Bordeaux Research In Translational Oncology, BaRITOn, Bordeaux, France
| | - Filipa F Vale
- Faculty of Pharmacy, Host-Pathogen Interactions Unit, Research Institute for Medicines (iMed-ULisboa), Universidade de Lisboa, Lisbon, Portugal
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32
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Abstract
Helicobacter pylori is responsible for the most commonly found infection in the world's population. It is the major risk factor for gastric cancer development. Numerous studies published over the last year provide new insights into the strategies employed by H. pylori to adapt to the extreme acidic conditions of the gastric environment, to establish persistent infection and to deregulate host functions, leading to gastric pathogenesis and cancer. In this review, we report recent data on the mechanisms involved in chemotaxis, on the essential role of nickel in acid resistance and gastric colonization, on the importance of adhesins and Hop proteins and on the role of CagPAI-components and CagA. Among the host functions, a special focus has been made on the escape from immune response, the ability of bacteria to induce genetic instability and modulate telomeres, the mechanism of autophagy and the deregulation of micro RNAs.
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Affiliation(s)
- Vania Camilo
- Pasteur Institute, Department of Microbiology, Helicobacter Pathogenesis Unit, Paris Cedex 15, France.,INSERM U1173, Faculty of Health Sciences Simone Veil, Université Versailles-Saint-Quentin, Saint Quentin en Yvelines, France
| | - Toshiro Sugiyama
- Graduate School of Medicine and Pharmaceutical Sciences, Department of Gastroenterology, University of Toyama, Sugitani, Toyama, Japan
| | - Eliette Touati
- Pasteur Institute, Department of Microbiology, Helicobacter Pathogenesis Unit, Paris Cedex 15, France
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