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Wang W, Xia J, Wang Z, Shao Z. Bacterial cell sensing and signaling pathway for external polycyclic aromatic hydrocarbons (PAHs). iScience 2023; 26:107912. [PMID: 37841585 PMCID: PMC10570129 DOI: 10.1016/j.isci.2023.107912] [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: 03/30/2023] [Revised: 07/19/2023] [Accepted: 09/12/2023] [Indexed: 10/17/2023] Open
Abstract
The mechanism by which a bacterial cell senses external nutrients remains largely unknown. In this study, we identified a bacterial cell sensing system for polycyclic aromatic hydrocarbons (PAHs) in a common marine PAH-using bacterium, Cycloclasticus. It consists of an outer membrane receptor (PahS) and a periplasmic protein (PahP) in combination with a two-component sensing system (TCS) that ensures a rapid response to PAH occurrence by directly controlling serial reactions including chemotactic sensing and movement, PAH uptake and intracellular PAH metabolism. PahS protrudes from the cell and acts as a PAH sensor, transducing the PAH signal across the outer membrane to its periplasmic partner PahP, which in turn transduces the PAH signal across the periplasm to a specialized TCS. This sensing system plays a critical role in sensing and promoting the metabolism of PAHs, which can be scavenged by various hydrocarbon-degrading bacteria.
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Affiliation(s)
- Wanpeng Wang
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
- Key Laboratory of Marine Genetic Resources of Fujian Province, Xiamen, China
| | - Jingyu Xia
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
| | - Zining Wang
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
| | - Zongze Shao
- Key Laboratory of Marine Genetic Resources, Third Institute of Oceanography, Ministry of Natural Resources, Xiamen, China
- Key Laboratory of Marine Genetic Resources of Fujian Province, Xiamen, China
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2
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Abstract
TonB-dependent transporters (TBDTs) are present in all gram-negative bacteria and mediate energy-dependent uptake of molecules that are too scarce or large to be taken up efficiently by outer membrane (OM) diffusion channels. This process requires energy that is derived from the proton motive force and delivered to TBDTs by the TonB-ExbBD motor complex in the inner membrane. Together with the need to preserve the OM permeability barrier, this has led to an extremely complex and fascinating transport mechanism for which the fundamentals, despite decades of research, are still unclear. In this review, we describe our current understanding of the transport mechanism of TBDTs, their potential role in the delivery of novel antibiotics, and the important contributions made by TBDT-associated (lipo)proteins.
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Affiliation(s)
- Augustinas Silale
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom; ,
| | - Bert van den Berg
- Biosciences Institute, The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom; ,
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Tsavea E, Tzika P, Katsivelou E, Adamopoulou A, Nikolaidis M, Amoutzias GD, Mossialos D. Impact of Mt. Olympus Honeys on Virulence Factors Implicated in Pathogenesis Exerted by Pseudomonas aeruginosa. Antibiotics (Basel) 2023; 12:998. [PMID: 37370317 DOI: 10.3390/antibiotics12060998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 05/22/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023] Open
Abstract
The aim of this study was to examine the impact of twenty honey samples, harvested in Mt. Olympus (Greece), on the virulence factors implicated in P. aeruginosa pathogenesis. Six key virulence factors (protease and elastase activity, pyocyanin and pyoverdine concentration, biofilm formation, and swimming motility) were selected in order to assess the effect of the tested honeys compared with Manuka honey. All tested honeys demonstrated a significant inhibition of protease and elastase activity compared with the control. Six and thirteen honeys exerted superior protease (no inhibition zone) and elastase (values lower than 55%) activity, respectively, compared with Manuka honey. Seventeen tested honeys exhibited reduced pyoverdine production compared with the control; all tested honeys, except for one, showed an inhibitory effect on pyocyanin production compared with the control. Regarding swimming motility, nine tested honeys demonstrated significantly higher inhibition compared with Manuka honey. Honey concentrations (6% v/v and 8% v/v) had the most profound impact, as they reduced biofilm formation to less than 20% compared with the control. Overall, our data demonstrate a significant inhibition of the virulence factors in the tested Mt. Olympus honeys, highlighting the strong antimicrobial activity against P. aeruginosa, an antibiotic-resistant pathogen of growing concern, which is implicated in severe nosocomial infections globally.
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Affiliation(s)
- Eleni Tsavea
- Laboratory of Microbial Biotechnology, Molecular Bacteriology-Virology, Department of Biochemistry & Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Paraskevi Tzika
- Laboratory of Microbial Biotechnology, Molecular Bacteriology-Virology, Department of Biochemistry & Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Eleni Katsivelou
- Laboratory of Microbial Biotechnology, Molecular Bacteriology-Virology, Department of Biochemistry & Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Anna Adamopoulou
- Laboratory of Microbial Biotechnology, Molecular Bacteriology-Virology, Department of Biochemistry & Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Marios Nikolaidis
- Bioinformatics Laboratory, Department of Biochemistry & Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Grigorios D Amoutzias
- Bioinformatics Laboratory, Department of Biochemistry & Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
| | - Dimitris Mossialos
- Laboratory of Microbial Biotechnology, Molecular Bacteriology-Virology, Department of Biochemistry & Biotechnology, School of Health Sciences, University of Thessaly, 41500 Larissa, Greece
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4
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Chan DCK, Josts I, Koteva K, Wright GD, Tidow H, Burrows LL. Interactions of TonB-dependent transporter FoxA with siderophores and antibiotics that affect binding, uptake, and signal transduction. Proc Natl Acad Sci U S A 2023; 120:e2221253120. [PMID: 37043535 PMCID: PMC10120069 DOI: 10.1073/pnas.2221253120] [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: 12/14/2022] [Accepted: 03/07/2023] [Indexed: 04/13/2023] Open
Abstract
The outer membrane of gram-negative bacteria prevents many antibiotics from reaching intracellular targets. However, some antimicrobials can take advantage of iron import transporters to cross this barrier. We showed previously that the thiopeptide antibiotic thiocillin exploits the nocardamine xenosiderophore transporter, FoxA, of the opportunistic pathogen Pseudomonas aeruginosa for uptake. Here, we show that FoxA also transports the xenosiderophore bisucaberin and describe at 2.5 Å resolution the crystal structure of bisucaberin bound to FoxA. Bisucaberin is distinct from other siderophores because it forms a 3:2 rather than 1:1 siderophore-iron complex. Mutations in a single extracellular loop of FoxA differentially affected nocardamine, thiocillin, and bisucaberin binding, uptake, and signal transduction. These results show that in addition to modulating ligand binding, the extracellular loops of siderophore transporters are of fundamental importance for controlling ligand uptake and its regulatory consequences, which have implications for the development of siderophore-antibiotic conjugates to treat difficult infections.
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Affiliation(s)
- Derek C. K. Chan
- David Braley Center for Antibiotic Discovery, McMaster University, Hamilton, ONL8S 4K1, Canada
- Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ONL8S 4K1, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ONL8S 4K1, Canada
| | - Inokentijs Josts
- The Hamburg Advanced Research Center for Bioorganic Chemistry, Hamburg22761, Germany
- Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg22761, Germany
| | - Kalinka Koteva
- David Braley Center for Antibiotic Discovery, McMaster University, Hamilton, ONL8S 4K1, Canada
- Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ONL8S 4K1, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ONL8S 4K1, Canada
| | - Gerard D. Wright
- David Braley Center for Antibiotic Discovery, McMaster University, Hamilton, ONL8S 4K1, Canada
- Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ONL8S 4K1, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ONL8S 4K1, Canada
| | - Henning Tidow
- The Hamburg Advanced Research Center for Bioorganic Chemistry, Hamburg22761, Germany
- Department of Chemistry, Institute for Biochemistry and Molecular Biology, University of Hamburg, Hamburg22761, Germany
| | - Lori L. Burrows
- David Braley Center for Antibiotic Discovery, McMaster University, Hamilton, ONL8S 4K1, Canada
- Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, ONL8S 4K1, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ONL8S 4K1, Canada
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5
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Hamza EH, El-Shawadfy AM, Allam AA, Hassanein WA. Study on pyoverdine and biofilm production with detection of LasR gene in MDR Pseudomonas aeruginosa. Saudi J Biol Sci 2022; 30:103492. [DOI: 10.1016/j.sjbs.2022.103492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 10/08/2022] [Accepted: 11/07/2022] [Indexed: 11/13/2022] Open
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6
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González J, Salvador M, Özkaya Ö, Spick M, Reid K, Costa C, Bailey MJ, Avignone Rossa C, Kümmerli R, Jiménez JI. Loss of a pyoverdine secondary receptor in Pseudomonas aeruginosa results in a fitter strain suitable for population invasion. ISME JOURNAL 2020; 15:1330-1343. [PMID: 33323977 DOI: 10.1038/s41396-020-00853-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 11/03/2020] [Accepted: 11/20/2020] [Indexed: 01/27/2023]
Abstract
The rapid emergence of antibiotic resistant bacterial pathogens constitutes a critical problem in healthcare and requires the development of novel treatments. Potential strategies include the exploitation of microbial social interactions based on public goods, which are produced at a fitness cost by cooperative microorganisms, but can be exploited by cheaters that do not produce these goods. Cheater invasion has been proposed as a 'Trojan horse' approach to infiltrate pathogen populations with strains deploying built-in weaknesses (e.g., sensitiveness to antibiotics). However, previous attempts have been often unsuccessful because population invasion by cheaters was prevented by various mechanisms including the presence of spatial structure (e.g., growth in biofilms), which limits the diffusion and exploitation of public goods. Here we followed an alternative approach and examined whether the manipulation of public good uptake and not its production could result in potential 'Trojan horses' suitable for population invasion. We focused on the siderophore pyoverdine produced by the human pathogen Pseudomonas aeruginosa MPAO1 and manipulated its uptake by deleting and/or overexpressing the pyoverdine primary (FpvA) and secondary (FpvB) receptors. We found that receptor synthesis feeds back on pyoverdine production and uptake rates, which led to strains with altered pyoverdine-associated costs and benefits. Moreover, we found that the receptor FpvB was advantageous under iron-limited conditions but revealed hidden costs in the presence of an antibiotic stressor (gentamicin). As a consequence, FpvB mutants became the fittest strain under gentamicin exposure, displacing the wildtype in liquid cultures, and in biofilms and during infections of the wax moth larvae Galleria mellonella, which both represent structured environments. Our findings reveal that an evolutionary trade-off associated with the costs and benefits of a versatile pyoverdine uptake strategy can be harnessed for devising a Trojan-horse candidate for medical interventions.
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Affiliation(s)
- Jaime González
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Manuel Salvador
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Özhan Özkaya
- Department of Quantitative Medicine, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Matt Spick
- Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Kate Reid
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Catia Costa
- Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Melanie J Bailey
- Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | | | - Rolf Kümmerli
- Department of Quantitative Medicine, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - José I Jiménez
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, GU2 7XH, UK. .,Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK.
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7
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Nicolafrancesco C, Porcaro F, Pis I, Nappini S, Simonelli L, Marini C, Frangipani E, Visaggio D, Visca P, Mobilio S, Meneghini C, Fratoddi I, Iucci G, Battocchio C. Gallium- and Iron-Pyoverdine Coordination Compounds Investigated by X-ray Photoelectron Spectroscopy and X-ray Absorption Spectroscopy. Inorg Chem 2019; 58:4935-4944. [DOI: 10.1021/acs.inorgchem.8b03574] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Chiara Nicolafrancesco
- Department of Science, Roma Tre University, Via della Vasca Navale 79, 00146 Rome, Italy
| | - Francesco Porcaro
- University of Bordeaux, CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan, France
| | - Igor Pis
- Elettra-Sincrotrone Trieste S.C.p.A., SS 14, km 163,5 Basovizza, I-34149 Trieste, Italy
| | - Silvia Nappini
- IOM-CNR Laboratorio TASC, SS 14, Km 163,5 Basovizza, I-34149 Trieste, Italy
| | - Laura Simonelli
- CELLS—ALBA Synchrotron Radiation Facility, Carrer de la Llum 2-26, 08290 Cerdanyola del Vallès, Barcelona, Spain
| | - Carlo Marini
- CELLS—ALBA Synchrotron Radiation Facility, Carrer de la Llum 2-26, 08290 Cerdanyola del Vallès, Barcelona, Spain
| | - Emanuela Frangipani
- Department of Science, Roma Tre University, Via della Vasca Navale 79, 00146 Rome, Italy
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, Urbino, 61029 Province of Pesaro and Urbino, Italy
| | - Daniela Visaggio
- Department of Science, Roma Tre University, Via della Vasca Navale 79, 00146 Rome, Italy
| | - Paolo Visca
- Department of Science, Roma Tre University, Via della Vasca Navale 79, 00146 Rome, Italy
| | - Settimio Mobilio
- Department of Science, Roma Tre University, Via della Vasca Navale 79, 00146 Rome, Italy
| | - Carlo Meneghini
- Department of Science, Roma Tre University, Via della Vasca Navale 79, 00146 Rome, Italy
| | | | - Giovanna Iucci
- Department of Science, Roma Tre University, Via della Vasca Navale 79, 00146 Rome, Italy
| | - Chiara Battocchio
- Department of Science, Roma Tre University, Via della Vasca Navale 79, 00146 Rome, Italy
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8
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Ringel MT, Brüser T. The biosynthesis of pyoverdines. MICROBIAL CELL (GRAZ, AUSTRIA) 2018; 5:424-437. [PMID: 30386787 PMCID: PMC6206403 DOI: 10.15698/mic2018.10.649] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 07/03/2018] [Indexed: 01/11/2023]
Abstract
Pyoverdines are fluorescent siderophores of pseudomonads that play important roles for growth under iron-limiting conditions. The production of pyoverdines by fluorescent pseudomonads permits their colonization of hosts ranging from humans to plants. Prominent examples include pathogenic or non-pathogenic species such as Pseudomonas aeruginosa, P. putida, P. syringae, or P. fluorescens. Many distinct pyoverdines have been identified, all of which have a dihydroxyquinoline fluorophore in common, derived from oxidative cyclizations of non-ribosomal peptides. These serve as precursor of pyoverdines and are commonly known as ferribactins. Ferribactins of distinct species or even strains often differ in their sequence, resulting in a large variety of pyoverdines. However, synthesis of all ferribactins begins with an L-Glu/D-Tyr/L-Dab sequence, and the fluorophore is generated from the D-Tyr/L-Dab residues. In addition, the initial L-Glu residue is modified to various acids and amides that are responsible for the range of distinguishable pyoverdines in individual strains. While ferribactin synthesis is a cytoplasmic process, the maturation to the fluorescent pyoverdine as well as the tailoring of the initial glutamate are exclusively periplasmic processes that have been a mystery until recently. Here we review the current knowledge of pyoverdine biosynthesis with a focus on the recent advancements regarding the periplasmic maturation and tailoring reactions.
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Affiliation(s)
- Michael T. Ringel
- Institute of Microbiology, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
| | - Thomas Brüser
- Institute of Microbiology, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany
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9
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Bishop TF, Martin LW, Lamont IL. Activation of a Cell Surface Signaling Pathway in Pseudomonas aeruginosa Requires ClpP Protease and New Sigma Factor Synthesis. Front Microbiol 2017; 8:2442. [PMID: 29312164 PMCID: PMC5733041 DOI: 10.3389/fmicb.2017.02442] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Accepted: 11/24/2017] [Indexed: 11/13/2022] Open
Abstract
Extracytoplasmic function (ECF) sigma factors control expression of large numbers of genes in bacteria. Most ECF sigma factors are inhibited by antisigma proteins, with inhibition being relieved by environmental signals that lead to inactivation of the antisigma protein and consequent sigma factor activity. In cell surface signaling (CSS) systems in Gram negative bacteria antisigma activity is controlled by an outer membrane protein receptor and its ligand. In Pseudomonas aeruginosa one such system controls expression of genes for secretion and uptake of a siderophore, pyoverdine. In this system the activities of two sigma factors σFpvI and σPvdS are inhibited by antisigma protein FpvR20 that binds to the sigma factors, preventing their interaction with core RNA polymerase. Transport of ferripyoverdine by its outer membrane receptor FpvA causes proteolytic degradation of FpvR20, inducing expression of σFpvI- and σPvdS-dependent target genes. Here we show that degradation of FpvR20 and induction of target gene expression was initiated within 1 min of addition of pyoverdine. FpvR20 was only partially degraded in a mutant lacking the intracellular ClpP protease, resulting in an FpvR20 subfragment (FpvR12) that inhibited σFpvI and σPvdS. The translation inhibitor chloramphenicol did not prevent induction of an σFpvI-dependent gene, showing that degradation of FpvR20 released pre-existing σFpvI in an active form. However, chloramphenicol inhibited induction of σPvdS-dependent genes showing that active σPvdS is not released when FpvR20 is degraded and instead, σPvdS must be synthesized in the absence of FpvR20 to be active. These findings show that sigma factor activation occurs rapidly following addition of the inducing signal in a CSS pathway and requires ClpP protease. Induction of gene expression that can arise from release of active sigma from an antisigma protein but can also require new sigma factor synthesis.
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Affiliation(s)
- Thomas F Bishop
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Lois W Martin
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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10
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Edgar RJ, Hampton GE, Garcia GPC, Maher MJ, Perugini MA, Ackerley DF, Lamont IL. Integrated activities of two alternative sigma factors coordinate iron acquisition and uptake by Pseudomonas aeruginosa. Mol Microbiol 2017; 106:891-904. [PMID: 28971540 DOI: 10.1111/mmi.13855] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/27/2017] [Indexed: 11/28/2022]
Abstract
Alternative sigma (σ) factors govern expression of bacterial genes in response to diverse environmental signals. In Pseudomonas aeruginosa σPvdS directs expression of genes for production of a siderophore, pyoverdine, as well as a toxin and a protease. σFpvI directs expression of a receptor for ferripyoverdine import. Expression of the genes encoding σPvdS and σFpvI is iron-regulated and an antisigma protein, FpvR20 , post-translationally controls the activities of the sigma factors in response to the amount of ferripyoverdine present. Here we show that iron represses synthesis of σPvdS to a far greater extent than σFpvI . In contrast ferripyoverdine exerts similar effects on the activities of both sigma factors. Using a combination of in vivo and in vitro assays we show that σFpvI and σPvdS have comparable affinities for, and are equally inhibited by, FpvR20 . Importantly, in the absence of ferripyoverdine the amount of FpvR20 per cell is lower than the amount of σFpvI and σPvdS , allowing basal expression of target genes that is required to activate the signalling pathway when ferripyoverdine is present. This complex interplay of transcriptional and post-translational regulation enables a co-ordinated response to ferripyoverdine but distinct responses to iron.
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Affiliation(s)
- Rebecca J Edgar
- Department of Biochemistry, University of Otago, Dunedin, New Zealand.,School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | | | - G Patricia Casas Garcia
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Megan J Maher
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - Matthew A Perugini
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia
| | - David F Ackerley
- School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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11
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Role of Iron Uptake Systems in Pseudomonas aeruginosa Virulence and Airway Infection. Infect Immun 2016; 84:2324-2335. [PMID: 27271740 DOI: 10.1128/iai.00098-16] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 05/26/2016] [Indexed: 12/24/2022] Open
Abstract
Pseudomonas aeruginosa is a leading cause of hospital-acquired pneumonia and chronic lung infections in cystic fibrosis patients. Iron is essential for bacterial growth, and P. aeruginosa expresses multiple iron uptake systems, whose role in lung infection deserves further investigation. P. aeruginosa Fe(3+) uptake systems include the pyoverdine and pyochelin siderophores and two systems for heme uptake, all of which are dependent on the TonB energy transducer. P. aeruginosa also has the FeoB transporter for Fe(2+) acquisition. To assess the roles of individual iron uptake systems in P. aeruginosa lung infection, single and double deletion mutants were generated in P. aeruginosa PAO1 and characterized in vitro, using iron-poor media and human serum, and in vivo, using a mouse model of lung infection. The iron uptake-null mutant (tonB1 feoB) and the Fe(3+) transport mutant (tonB1) did not grow aerobically under low-iron conditions and were avirulent in the mouse model. Conversely, the wild type and the feoB, hasR phuR (heme uptake), and pchD (pyochelin) mutants grew in vitro and caused 60 to 90% mortality in mice. The pyoverdine mutant (pvdA) and the siderophore-null mutant (pvdA pchD) grew aerobically in iron-poor media but not in human serum, and they caused low mortality in mice (10 to 20%). To differentiate the roles of pyoverdine in iron uptake and virulence regulation, a pvdA fpvR double mutant defective in pyoverdine production but expressing wild-type levels of pyoverdine-regulated virulence factors was generated. Deletion of fpvR in the pvdA background partially restored the lethal phenotype, indicating that pyoverdine contributes to the pathogenesis of P. aeruginosa lung infection by combining iron transport and virulence-inducing capabilities.
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12
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Pyoverdine and proteases affect the response of Pseudomonas aeruginosa to gallium in human serum. Antimicrob Agents Chemother 2015; 59:5641-6. [PMID: 26149986 DOI: 10.1128/aac.01097-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 06/26/2015] [Indexed: 11/20/2022] Open
Abstract
Gallium is an iron mimetic which has recently been repurposed as an antibacterial agent due to its capability to disrupt bacterial iron metabolism. In this study, the antibacterial activity of gallium nitrate [Ga(NO3)3] was investigated in complement-free human serum (HS) on 55 Pseudomonas aeruginosa clinical isolates from cystic fibrosis and non-cystic fibrosis patients. The susceptibility of P. aeruginosa to Ga(NO3)3 in HS was dependent on the bacterial ability to acquire iron from serum binding proteins (i.e., transferrin). The extent of serum protein degradation correlated well with P. aeruginosa growth in HS, while pyoverdine production did not. However, pyoverdine-deficient P. aeruginosa strains were unable to grow in HS and overcome iron restriction, albeit capable of releasing proteases. Predigestion of HS with proteinase K promoted the growth of all strains, irrespective of their ability to produce proteases and/or pyoverdine. The MICs of Ga(NO3)3 were higher in HS than in an iron-poor Casamino Acids medium, where proteolysis does not affect iron availability. Coherently, strains displaying high proteolytic activity were less susceptible to Ga(NO3)3 in HS. Our data support a model in which both pyoverdine and proteases affect the response of P. aeruginosa to Ga(NO3)3 in HS. The relatively high Ga(NO3)3 concentration required to inhibit the growth of highly proteolytic P. aeruginosa isolates in HS poses a limitation to the potential of Ga(NO3)3 in the treatment of P. aeruginosa bloodstream infections.
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13
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Edgar RJ, Xu X, Shirley M, Konings AF, Martin LW, Ackerley DF, Lamont IL. Interactions between an anti-sigma protein and two sigma factors that regulate the pyoverdine signaling pathway in Pseudomonas aeruginosa. BMC Microbiol 2014; 14:287. [PMID: 25433393 PMCID: PMC4256889 DOI: 10.1186/s12866-014-0287-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 11/06/2014] [Indexed: 12/03/2022] Open
Abstract
Background Synthesis and uptake of pyoverdine, the primary siderophore of the opportunistic pathogen Pseudomonas aeruginosa, is dependent on two extra-cytoplasmic function (ECF) sigma factors, FpvI and PvdS. FpvI and PvdS are required for expression of the ferri-pyoverdine receptor gene fpvA and of pyoverdine synthesis genes respectively. In the absence of pyoverdine the anti-sigma factor FpvR that spans the cytoplasmic membrane inhibits the activities of both FpvI and PvdS, despite the two sigma factors having low sequence identity. Results To investigate the interactions of FpvR with FpvI and PvdS, we first used a tandem affinity purification system to demonstrate binding of PvdS by the cytoplasmic region of FpvR in P. aeruginosa at physiological levels. The cytoplasmic region of FpvR bound to and inhibited both FpvI and PvdS when the proteins were co-expressed in Escherichia coli. Each sigma factor was then subjected to error prone PCR and site-directed mutagenesis to identify mutations that increased sigma factor activity in the presence of FpvR. In FpvI, the amino acid changes clustered around conserved region four of the protein and are likely to disrupt interactions with FpvR. Deletion of five amino acids from the C-terminal end of FpvI also disrupted interactions with FpvR. Mutations in PvdS were present in conserved regions two and four. Most of these mutations as well as deletion of thirteen amino acids from the C-terminal end of PvdS increased sigma factor activity independent of whether FpvR was present, suggesting that they increase either the stability of PvdS or its affinity for core RNA polymerase. Conclusions These data show that FpvR binds to PvdS in both P. aeruginosa and E. coli, inhibiting its activity. FpvR also binds to and inhibits FpvI and binding of FpvI is likely to involve conserved region four of the sigma factor protein. Electronic supplementary material The online version of this article (doi:10.1186/s12866-014-0287-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Rebecca J Edgar
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand. .,School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
| | - Xin Xu
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
| | - Matt Shirley
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
| | - Anna F Konings
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
| | - Lois W Martin
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
| | - David F Ackerley
- School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
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Llamas MA, Imperi F, Visca P, Lamont IL. Cell-surface signaling inPseudomonas: stress responses, iron transport, and pathogenicity. FEMS Microbiol Rev 2014; 38:569-97. [DOI: 10.1111/1574-6976.12078] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Revised: 05/20/2014] [Accepted: 05/27/2014] [Indexed: 01/06/2023] Open
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Guillon L, Altenburger S, Graumann PL, Schalk IJ. Deciphering protein dynamics of the siderophore pyoverdine pathway in Pseudomonas aeruginosa. PLoS One 2013; 8:e79111. [PMID: 24205369 PMCID: PMC3813593 DOI: 10.1371/journal.pone.0079111] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 09/26/2013] [Indexed: 11/24/2022] Open
Abstract
Pseudomonas aeruginosa produces the siderophore, pyoverdine (PVD), to obtain iron. Siderophore pathways involve complex mechanisms, and the machineries responsible for biosynthesis, secretion and uptake of the ferri-siderophore span both membranes of Gram-negative bacteria. Most proteins involved in the PVD pathway have been identified and characterized but the way the system functions as a whole remains unknown. By generating strains expressing fluorescent fusion proteins, we show that most of the proteins are homogeneously distributed throughout the bacterial cell. We also studied the dynamics of these proteins using fluorescence recovery after photobleaching (FRAP). This led to the first diffusion coefficients ever determined in P. aeruginosa. Cytoplasmic and periplamic diffusion appeared to be slower than in Escherichia coli but membrane proteins seemed to behave similarly in the two species. The diffusion of cytoplasmic and periplasmic tagged proteins involved in the PVD pathway was dependent on the interaction network to which they belong. Importantly, the TonB protein, motor of the PVD-Fe uptake process, was mostly immobile but its mobility increased substantially in the presence of PVD-Fe.
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Affiliation(s)
| | - Stephan Altenburger
- SYMMIKRO, LOEWE Center for Synthetic Microbiology, and Department of Chemistry, University of Marburg, Marburg, Germany
| | - Peter L. Graumann
- SYMMIKRO, LOEWE Center for Synthetic Microbiology, and Department of Chemistry, University of Marburg, Marburg, Germany
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Ponraj P, Shankar M, Ilakkiam D, Rajendhran J, Gunasekaran P. Influence of periplasmic oxidation of glucose on pyoverdine synthesis in Pseudomonas putida S11. Appl Microbiol Biotechnol 2013; 97:5027-41. [DOI: 10.1007/s00253-013-4737-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 12/27/2012] [Accepted: 01/23/2013] [Indexed: 11/25/2022]
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17
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Draper RC, Martin LW, Beare PA, Lamont IL. Differential proteolysis of sigma regulators controls cell-surface signalling in Pseudomonas aeruginosa. Mol Microbiol 2011; 82:1444-53. [DOI: 10.1111/j.1365-2958.2011.07901.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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18
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Mettrick KA, Lamont IL. Different roles for anti-sigma factors in siderophore signalling pathways of Pseudomonas aeruginosa. Mol Microbiol 2009; 74:1257-71. [PMID: 19889096 DOI: 10.1111/j.1365-2958.2009.06932.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Group IV (extracytoplasmic function) sigma factors direct the expression of a large number of regulons in bacteria. The activities of many Group IV sigma factors are inhibited by members of a family of anti-sigma factor proteins, with appropriate environmental signals causing the sigma factor to be released for interaction with core RNA polymerase and consequent transcription of target genes. One subgroup of Group IV sigmas directs expression of genes for uptake of siderophores (iron-chelating compounds) by Gram-negative bacteria. The activities of these sigma factors are controlled by anti-sigma factors that span the cytoplasmic membrane. Binding of siderophore by a receptor protein in the outer membrane results in signal transduction from the periplasmic portion to the cytoplasmic portion of the appropriate anti-sigma factor, with consequent activity of the cognate sigma factor and upregulation of the gene encoding the receptor protein. We have investigated receptor/anti-sigma/sigma factor signalling pathways for uptake of the siderophores ferrichrome and desferrioxamine by Pseudomonas aeruginosa. In these pathways the 'anti-sigma' proteins are normally required for sigma factor activity and the cytoplasmic parts of the 'anti-sigmas' have 'pro-sigma' activity. We suggest that the family of anti-sigma factor proteins may be better considered as 'sigma regulators'.
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Affiliation(s)
- Karla A Mettrick
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin, New Zealand.
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19
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Abstract
Pyoverdines are siderophores secreted by Pseudomonas aeruginosa. Uptake of ferripyoverdine in P. aeruginosa PAO1 occurs via the FpvA receptor protein and requires the energy-transducing protein TonB1. Interaction of (ferri)pyoverdine with FpvA activates pyoverdine gene expression in a signaling process involving the cytoplasmic-membrane-spanning anti-sigma factor FpvR and the sigma factor PvdS. Here, we show that mutation of a region of FpvA that interacts with TonB1 (the TonB box) prevents this signaling process, as well as inhibiting bacterial growth in the presence of the iron-chelating compound ethylenediamine-di(o-hydroxy-phenylacetic acid). Signaling via wild-type FpvA was also eliminated in strains lacking TonB1 but was unaffected in strains lacking either (or both) of two other TonB proteins in P. aeruginosa, TonB2 and TonB3. An absence of pyoverdine-mediated signaling corresponded with proteolysis of PvdS. These data show that interactions between FpvA and TonB1 are required for (ferri)pyoverdine signal transduction, as well as for ferripyoverdine transport, consistent with a mechanistic link between the signaling and transport functions of FpvA.
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20
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Structure-function relationships in the bifunctional ferrisiderophore FpvA receptor from Pseudomonas aeruginosa. Biometals 2009; 22:671-8. [PMID: 19153809 DOI: 10.1007/s10534-008-9203-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Accepted: 12/29/2008] [Indexed: 10/21/2022]
Abstract
FpvA is the primary outer membrane transporter required for iron acquisition via the siderophore pyoverdine (Pvd) in Pseudomonas aeruginosa. FpvA, like other ferrisiderophore transporters, consists of a membrane-spanning beta-barrel occluded by a plug domain. The beta-strands of the barrel are connected by large extracellular loops and periplasmic turns. Like some other TonB-dependent transporters, FpvA has a periplasmic domain involved in a signalling cascade that regulates expression of genes required for ferrisiderophore transport. Here, the structures of FpvA in different loading states are analysed in light of mutagenesis data. This analysis highlights the roles of different protein domains in Pvd-Fe uptake and the signalling cascade and reveals a strong correlation between Pvd-Fe transport and activation of the signalling cascade. It is likely that conclusions drawn for FpvA will be relevant to other TonB-dependent ferrisiderophore transport and signalling proteins.
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21
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Role of cell surface signaling in proteolysis of an alternative sigma factor in Pseudomonas aeruginosa. J Bacteriol 2008; 190:4865-9. [PMID: 18502853 DOI: 10.1128/jb.01998-07] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alternative sigma factor proteins enable transcription of specific sets of genes in bacterial cells. Their activities can be controlled by posttranslational mechanisms including inhibition by antisigma proteins and proteolytic degradation. PvdS is an alternative sigma factor that is required for expression of genes involved in synthesis of a siderophore, pyoverdine, by Pseudomonas aeruginosa. In the absence of pyoverdine, the activity of PvdS is inhibited by a membrane-spanning antisigma factor, FpvR. Inhibition is relieved by a cell surface signaling pathway. In this pathway, a combination of pyoverdine and a cell surface receptor protein, FpvA, suppresses the antisigma activity of FpvR, enabling transcription of PvdS-dependent genes. In this research, we investigated proteolytic degradation of PvdS in response to the signaling pathway. Proteolysis of PvdS was observed in strains of P. aeruginosa in which FpvR had anti-sigma factor activity due to the absence of pyoverdine or the FpvA receptor protein or overproduction of FpvR. Suppression of antisigma activity by addition of pyoverdine or through the absence of FpvR prevented detectable proteolysis of PvdS. The amounts of PvdS were less in bacteria in which proteolysis was observed, and reporter gene assays showed that this reduction was not due to decreased expression of PvdS. In wild-type bacteria, there was an average of 730 molecules of PvdS per cell in late exponential growth phase. Our results show that proteolysis and amounts of PvdS are affected by the antisigma factor FpvR and that this activity of FpvR is controlled by the cell surface signaling pathway.
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22
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Jones AM, Lindow SE, Wildermuth MC. Salicylic acid, yersiniabactin, and pyoverdin production by the model phytopathogen Pseudomonas syringae pv. tomato DC3000: synthesis, regulation, and impact on tomato and Arabidopsis host plants. J Bacteriol 2007; 189:6773-86. [PMID: 17660289 PMCID: PMC2045226 DOI: 10.1128/jb.00827-07] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2007] [Accepted: 07/16/2007] [Indexed: 01/07/2023] Open
Abstract
A genetically tractable model plant pathosystem, Pseudomonas syringae pv. tomato DC3000 on tomato and Arabidopsis thaliana hosts, was used to investigate the role of salicylic acid (SA) and iron acquisition via siderophores in bacterial virulence. Pathogen-induced SA accumulation mediates defense in these plants, and DC3000 contains the genes required for the synthesis of SA, the SA-incorporated siderophore yersiniabactin (Ybt), and the fluorescent siderophore pyoverdin (Pvd). We found that DC3000 synthesizes SA, Ybt, and Pvd under iron-limiting conditions in culture. Synthesis of SA and Ybt by DC3000 requires pchA, an isochorismate synthase gene in the Ybt genomic cluster, and exogenous SA can restore Ybt production by the pchA mutant. Ybt was also produced by DC3000 in planta, suggesting that Ybt plays a role in DC3000 pathogenesis. However, the pchA mutant did not exhibit any growth defect or altered virulence in plants. This lack of phenotype was not attributable to plant-produced SA restoring Ybt production, as the pchA mutant grew similarly to DC3000 in an Arabidopsis SA biosynthetic mutant, and in planta Ybt was not detected in pchA-infected wild-type plants. In culture, no growth defect was observed for the pchA mutant versus DC3000 for any condition tested. Instead, enhanced growth of the pchA mutant was observed under stringent iron limitation and additional stresses. This suggests that SA and Ybt production by DC3000 is costly and that Pvd is sufficient for iron acquisition. Further exploration of the comparative synthesis and utility of Ybt versus Pvd production by DC3000 found siderophore-dependent amplification of ybt gene expression to be absent, suggesting that Ybt may play a yet unknown role in DC3000 pathogenesis.
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Affiliation(s)
- Alexander M Jones
- Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102, USA
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23
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Vasil ML. How we learnt about iron acquisition in Pseudomonas aeruginosa: a series of very fortunate events. Biometals 2006; 20:587-601. [PMID: 17186376 DOI: 10.1007/s10534-006-9067-2] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Accepted: 11/28/2006] [Indexed: 11/29/2022]
Abstract
The ferric uptake repressor (Fur) of Pseudomonas aeruginosa, and a wide assortment of other prokaryotic organisms, has been mostly regarded as a negative regulator (repressor) of genes involved in iron acquisition (e.g., expression and utilization of siderophores) or of iron-regulated genes involved in virulence (e.g., toxins). However, there is an emerging picture of an even broader role for this protein in basic bacterial biology. Evidence has now accumulated indicating that Fur acts in a positive manner as well, and that it has a considerably wider impact on gene expression than originally perceived. We discovered that in P. aeruginosa Fur directly (i.e., negatively) regulates the expression of two, nearly identical tandem small (<200nt) RNA transcripts (sRNA). Our initial experiments showed that these Fur-regulated sRNAs (PrrF) affected expression of certain genes we initially thought might be directly, but positively, regulated by Fur. However, with discovery of the Fur-regulated sRNAs, first in Escherichia coli and then in P. aeruginosa, it became clear that Fur, in at least some cases, exerts its positive regulatory effect on gene expression by repressing the expression a negative regulatory factor (i.e., PrrF), which acts at the posttranscriptional level. While a clear picture was already available regarding the function of genes (see above) that are directly repressed by Fur (negative regulation), the functional classes of genes that are influenced by Fur-repressed sRNAs (positive regulation) had not been identified for P. aeruginosa. Accordingly we established a set of rigorous criteria, based on microarray experimental data, to identify the cohort of genes that are likely to be directly influenced by Fur-regulated PrrFs. More than 60 genes that fulfilled these strict criteria were identified. These include genes encoding proteins required for the sequestration of iron (e.g., bacterioferritins) and genes encoding enzymes (superoxide dismutase) vital to defense against iron catalyzed oxidative stress. More notably however, we identified more than 30 genes encoding proteins involved in carbon catabolism and aerobic or anaerobic respiration that are regulated by PrrFs. A significant number of genes encoding enzymes (e.g., aconitase, citrate synthase) involved in the TCA cycle are controlled by the PrrFs however, in quite a few instances there are genes encoding proteins with redundant functions (i.e., aconitase, citrate synthase) that do not appear to be influenced in any way by PrrFs. Based on our microarray experiments, as well as on phenotypic data, we propose that the Fur regulated sRNAs (i.e., PrrFs) exert a powerful regulatory influence that permits the sparing of vital metabolic compounds (e.g., citrate) during periods of iron limitation. These and other data to be presented indicate that Fur controlled gene expression in bacteria like P. aeruginosa is considerably more imperative and intricate than previously appreciated.
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Affiliation(s)
- Michael L Vasil
- University of Colorado at Denver and Health Sciences Center, 12800 E. 19th Avenue RC-1 North P18-9127, Microbiology Mail Stop 8333, P.O. Box 6511, Aurora, CO 80045, USA.
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Cwerman H, Wandersman C, Biville F. Heme and a five-amino-acid hemophore region form the bipartite stimulus triggering the has signaling cascade. J Bacteriol 2006; 188:3357-64. [PMID: 16621830 PMCID: PMC1447456 DOI: 10.1128/jb.188.9.3357-3364.2006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Accepted: 02/10/2006] [Indexed: 11/20/2022] Open
Abstract
Bacterial cells sense the extracellular environment and adapt to that environment by activating gene regulation circuits, often by means of signaling molecules. The Serratia marcescens hemophore is a signaling molecule that acts as an extracellular heme-scavenging protein. The heme-loaded hemophore interacts with its cognate receptor (HasR), triggering transmembrane signaling and turning on transcription of hemophore-dependent heme uptake genes. We investigated the features of the holo-hemophore, the only HasR ligand known to act as an inducer. We used a hemophore mutant that does not deliver its heme and a HasR mutant that does not bind heme, and we showed that heme transfer from the hemophore to the receptor is necessary for induction. Using a hemophore mutant that does not bind heme and that blocks heme transport, we demonstrated that two molecules that do not interact (heme and the mutant hemophore) may nonetheless induce this system. These findings suggest that hemophore-mediated induction and heme transport involve different mechanisms. The hemophore region important for induction was precisely localized to amino acids 50 to 55, which lie in one of the two HasR-binding hemophore regions. This bipartite stimulus probably corresponds to a physiological process because heme is transferred to the receptor before apo-hemophore release. This bipartite regulation mechanism may allow the bacterium to adjust its heme transport mechanism to the perceived environmental heme concentration.
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Affiliation(s)
- Hélène Cwerman
- Unité des Membranes Bactériennes, Institut Pasteur, 25, Rue du Dr. Roux, 75024 Paris Cedex 15, France
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Shen JS, Geoffroy V, Neshat S, Jia Z, Meldrum A, Meyer JM, Poole K. FpvA-mediated ferric pyoverdine uptake in Pseudomonas aeruginosa: identification of aromatic residues in FpvA implicated in ferric pyoverdine binding and transport. J Bacteriol 2006; 187:8511-5. [PMID: 16321958 PMCID: PMC1317021 DOI: 10.1128/jb.187.24.8511-8515.2005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A number of aromatic residues were seen to cluster in the upper portion of the three-dimensional structure of the FpvA ferric pyoverdine receptor of Pseudomonas aeruginosa, reminiscent of the aromatic binding pocket for ferrichrome in the FhuA receptor of Escherichia coli. Alanine substitutions in three of these, W362, W391, and F795, markedly compromised ferric pyoverdine binding and transport, consistent with a role of FpvA in ferric pyoverdine recognition.
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Affiliation(s)
- Jiang-Sheng Shen
- Department of Microbiology and Immunology, Queen's University, Kingston, Ontario K7L 3N6, Canada
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