1
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Khademi SMH, Sahl C, Happonen L, Forsberg Å, Påhlman LI. The twin-arginine translocation system is vital for cell adhesion and uptake of iron in the cystic fibrosis pathogen Achromobacter xylosoxidans. Virulence 2023:2284513. [PMID: 37974335 DOI: 10.1080/21505594.2023.2284513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Accepted: 11/13/2023] [Indexed: 11/19/2023] Open
Abstract
BACKGROUND Achromobacter xylosoxidans is an emerging pathogen that causes airway infections in patients with cystic fibrosis. Knowledge of virulence factors and protein secretion systems in this bacterium is limited. Twin arginine translocation (Tat) is a protein secretion system that transports folded proteins across the inner cell membranes of gram-negative bacteria. Tat has been shown to be important for virulence and cellular processes in many different bacterial species. This study aimed to investigate the role of Tat in iron metabolism and host cell adhesion in A. xylosoxidans. METHODS Putative Tat substrates in A. xylosoxidans were identified using the TatFind, TatP, and PRED-Tat prediction tools. An isogenic tatC deletion mutant (ΔtatC) was generated and phenotypically characterized. The wild-type and ΔtatC A. xylosoxidans were fractionated into cytosolic, membrane, and periplasmic fractions, and the expressed proteome of the different fractions was analyzed using liquid chromatography-mass spectrometry (LC-MS/MS). RESULTS A total of 128 putative Tat substrates were identified in the A. xylosoxidans proteome. The ΔtatC mutant showed attenuated host cell adhesion, growth rate, and iron acquisition. Twenty predicted Tat substrates were identified as expressed proteins in the periplasmic compartment, nine of which were associated with the wild type. CONCLUSION The data indicate that Tat secretion is important for iron acquisition and host cell adhesion in A. xylosoxidans.
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Affiliation(s)
- S M Hossein Khademi
- Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden
| | - Cecilia Sahl
- Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden
| | - Lotta Happonen
- Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden
| | - Åke Forsberg
- Department of Molecular Biology, Umeå University
| | - Lisa I Påhlman
- Department of Clinical Sciences Lund, Division of Infection Medicine, Lund University, Lund, Sweden
- Division of Infectious Diseases, Skåne University Hospital Lund, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Sweden
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2
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Braun V, Hartmann MD, Hantke K. Transcription regulation of iron carrier transport genes by ECF sigma factors through signaling from the cell surface into the cytoplasm. FEMS Microbiol Rev 2022; 46:6524835. [PMID: 35138377 PMCID: PMC9249621 DOI: 10.1093/femsre/fuac010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 01/26/2022] [Accepted: 02/07/2022] [Indexed: 12/02/2022] Open
Abstract
Bacteria are usually iron-deficient because the Fe3+ in their environment is insoluble or is incorporated into proteins. To overcome their natural iron limitation, bacteria have developed sophisticated iron transport and regulation systems. In gram-negative bacteria, these include iron carriers, such as citrate, siderophores, and heme, which when loaded with Fe3+ adsorb with high specificity and affinity to outer membrane proteins. Binding of the iron carriers to the cell surface elicits a signal that initiates transcription of iron carrier transport and synthesis genes, referred to as “cell surface signaling”. Transcriptional regulation is not coupled to transport. Outer membrane proteins with signaling functions contain an additional N-terminal domain that in the periplasm makes contact with an anti-sigma factor regulatory protein that extends from the outer membrane into the cytoplasm. Binding of the iron carriers to the outer membrane receptors elicits proteolysis of the anti-sigma factor by two different proteases, Prc in the periplasm, and RseP in the cytoplasmic membrane, inactivates the anti-sigma function or results in the generation of an N-terminal peptide of ∼50 residues with pro-sigma activity yielding an active extracytoplasmic function (ECF) sigma factor. Signal recognition and signal transmission into the cytoplasm is discussed herein.
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Affiliation(s)
- Volkmar Braun
- Max Planck Institute for Biology, Department of Protein Evolution, Max Planck Ring 5, 72076 Tübingen, Germany
| | - Marcus D Hartmann
- Max Planck Institute for Biology, Department of Protein Evolution, Max Planck Ring 5, 72076 Tübingen, Germany
| | - Klaus Hantke
- IMIT Institute, University of Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
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3
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Casas Garcia GP, Perugini MA, Lamont IL, Maher MJ. The purification of the σ FpvI/FpvR 20 and σ PvdS/FpvR 20 protein complexes is facilitated at room temperature. Protein Expr Purif 2019; 160:11-18. [PMID: 30878602 DOI: 10.1016/j.pep.2019.03.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 03/07/2019] [Accepted: 03/11/2019] [Indexed: 10/27/2022]
Abstract
Bacteria contain sigma (σ) factors that control gene expression in response to various environmental stimuli. The alternative sigma factors σFpvI and σPvdS bind specifically to the antisigma factor FpvR. These proteins are an essential component of the pyoverdine-based system for iron uptake in Pseudomonas aeruginosa. Due to the uniqueness of this system, where the activities of both the σFpvI and σPvdS sigma factors are regulated by the same antisigma factor, the interactions between the antisigma protein FpvR20 and the σFpvI and σPvdS proteins have been widely studied in vivo. However, difficulties in obtaining soluble, recombinant preparations of the σFpvI and σPvdS proteins have limited their biochemical and structural characterizations. In this study, we describe a purification protocol that resulted in the production of soluble, recombinant His6-σFpvI/FpvR1-67, His6-σFpvI/FpvR1-89, His6-σPvdS/FpvR1-67 and His6-σPvdS/FpvR1-89 protein complexes (where FpvR1-67 and FpvR1-89 are truncated versions of FpvR20) at high purities and concentrations, appropriate for biophysical analyses by circular dichroism spectroscopy and analytical ultracentrifugation. These results showed the proteins to be folded in solution and led to the determination of the affinities of the protein-protein interactions within the His6-σFpvI/FpvR1-67 and His6-σPvdS/FpvR1-67 complexes. A comparison of these values with those previously reported for the His6-σFpvI/FpvR1-89 and His6-σPvdS/FpvR1-89 complexes is made.
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Affiliation(s)
- G Patricia Casas Garcia
- 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
| | - Iain L Lamont
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Megan J Maher
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.
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4
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Albelda-Berenguer M, Monachon M, Joseph E. Siderophores: From natural roles to potential applications. ADVANCES IN APPLIED MICROBIOLOGY 2019; 106:193-225. [PMID: 30798803 DOI: 10.1016/bs.aambs.2018.12.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Siderophores are secondary metabolites produced by different organisms in order to scavenge iron from their surrounding environment making this essential element available to the cell. Presenting high affinity for ferric iron, siderophores are secreted out to form soluble ferric complexes that can be taken up by the organisms. Siderophores present complex chemistry that allows them to form the strongest iron-chelating complexes. Interest in this field is always up to date and new siderophores are found with new roles and applications. For example, siderophores participate to the mobilization of iron and other elements and are involved in virulence processes. Recently, a strong relation between siderophores and oxidative stress tolerance has been also highlighted. Their application in medicine has been widely studied as well as in agriculture. However, new fields are paying attention to the use of siderophores as green-iron chelators. In particular, siderophores have been proposed for the preservation of cultural heritage.
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Affiliation(s)
- Magdalena Albelda-Berenguer
- Laboratory of Technologies for Heritage Materials, Institute of Chemistry, University of Neuchâtel, Neuchâtel, Switzerland
| | - Mathilde Monachon
- Laboratory of Technologies for Heritage Materials, Institute of Chemistry, University of Neuchâtel, Neuchâtel, Switzerland
| | - Edith Joseph
- Laboratory of Technologies for Heritage Materials, Institute of Chemistry, University of Neuchâtel, Neuchâtel, Switzerland; Haute Ecole Arc Conservation-Restauration, Neuchâtel, Switzerland.
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5
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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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6
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Inglis RF, Scanlan P, Buckling A. Iron availability shapes the evolution of bacteriocin resistance in Pseudomonas aeruginosa. THE ISME JOURNAL 2016; 10:2060-6. [PMID: 26905630 PMCID: PMC4883653 DOI: 10.1038/ismej.2016.15] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 12/18/2015] [Accepted: 01/04/2016] [Indexed: 11/08/2022]
Abstract
The evolution of bacterial resistance to conventional antimicrobials is a widely documented phenomenon with gravely important consequences for public health. However, bacteria also produce a vast repertoire of natural antimicrobials, presumably in order to kill competing species. Bacteriocins are a common class of protein-based antimicrobials that have been shown to have an important role in the ecology and evolution of bacterial communities. Relative to the evolution of antibiotic resistance, little is known about how novel resistance to these toxic compounds evolves. In this study, we present results illustrating that, although resistance is able to evolve, it remains critically dependent on the environmental context. Resistance to bacteriocins, in particular the pyocin S2, evolves readily when iron is present but less so when iron is limiting, because the receptor for this pyocin is also required for iron uptake during iron limitation. This suggests that although resistance to bacteriocins can easily evolve, environmental conditions will determine how and when resistance occurs.
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Affiliation(s)
- R Fredrik Inglis
- Department of Biology, Washington University in St Louis, St Louis, MO, USA
| | | | - Angus Buckling
- ESI and CEC, Biosciences, University of Exeter, Penryn, Cornwall, UK
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7
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Bastiaansen KC, van Ulsen P, Wijtmans M, Bitter W, Llamas MA. Self-cleavage of the Pseudomonas aeruginosa Cell-surface Signaling Anti-sigma Factor FoxR Occurs through an N-O Acyl Rearrangement. J Biol Chem 2015; 290:12237-46. [PMID: 25809487 DOI: 10.1074/jbc.m115.643098] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Indexed: 11/06/2022] Open
Abstract
The Fox system of Pseudomonas aeruginosa is a cell-surface signaling (CSS) pathway employed by the bacterium to sense and respond to the presence of the heterologous siderophore ferrioxamine in the environment. This regulatory pathway controls the transcription of the foxA ferrioxamine receptor gene through the extracytoplasmic function sigma factor σ(FoxI). In the absence of ferrioxamine, the activity of σ(FoxI) is inhibited by the transmembrane anti-sigma factor FoxR. Upon binding of ferrioxamine by the FoxA receptor, FoxR is processed by a complex proteolytic cascade leading to the release and activation of σ(FoxI). Interestingly, we have recently shown that FoxR undergoes self-cleavage between the periplasmic Gly-191 and Thr-192 residues independent of the perception of ferrioxamine. This autoproteolytic event, which is widespread among CSS anti-sigma factors, produces two distinct domains that interact and function together to transduce the presence of the signal. In this work, we provide evidence that the self-cleavage of FoxR is not an enzyme-dependent process but is induced by an N-O acyl rearrangement. Mutation analysis showed that the nucleophilic side chain of the Thr-192 residue at +1 of the cleavage site is required for an attack on the preceding Gly-191, after which the resulting ester bond is likely hydrolyzed. Because the cleavage site is well preserved and the hydrolysis of periplasmic CSS anti-sigma factors is widely observed, we hypothesize that cleavage via an N-O acyl rearrangement is a conserved feature of these proteins.
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Affiliation(s)
- Karlijn C Bastiaansen
- From the Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada E-18008, Spain and Section of Molecular Microbiology, Department of Molecular Cell Biology and
| | - Peter van Ulsen
- Section of Molecular Microbiology, Department of Molecular Cell Biology and
| | - Maikel Wijtmans
- Division of Medicinal Chemistry, Department of Chemistry and Pharmaceutical Sciences, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands
| | - Wilbert Bitter
- Section of Molecular Microbiology, Department of Molecular Cell Biology and
| | - María A Llamas
- From the Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada E-18008, Spain and
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8
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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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9
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Malki I, Simenel C, Wojtowicz H, Cardoso de Amorim G, Prochnicka-Chalufour A, Hoos S, Raynal B, England P, Chaffotte A, Delepierre M, Delepelaire P, Izadi-Pruneyre N. Interaction of a partially disordered antisigma factor with its partner, the signaling domain of the TonB-dependent transporter HasR. PLoS One 2014; 9:e89502. [PMID: 24727671 PMCID: PMC3984077 DOI: 10.1371/journal.pone.0089502] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 01/21/2014] [Indexed: 11/21/2022] Open
Abstract
Bacteria use diverse signaling pathways to control gene expression in response to external stimuli. In Gram-negative bacteria, the binding of a nutrient is sensed by an outer membrane transporter. This signal is then transmitted to an antisigma factor and subsequently to the cytoplasm where an ECF sigma factor induces expression of genes related to the acquisition of this nutrient. The molecular interactions involved in this transmembrane signaling are poorly understood and structural data on this family of antisigma factor are rare. Here, we present the first structural study of the periplasmic domain of an antisigma factor and its interaction with the transporter. The study concerns the signaling in the heme acquisition system (Has) of Serratia marcescens. Our data support unprecedented partially disordered periplasmic domain of an anti-sigma factor HasS in contact with a membrane-mimicking environment. We solved the 3D structure of the signaling domain of HasR transporter and identified the residues at the HasS-HasR interface. Their conservation in several bacteria suggests wider significance of the proposed model for the understanding of bacterial transmembrane signaling.
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Affiliation(s)
- Idir Malki
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
- Université Pierre et Marie Curie, Cellule Pasteur UPMC, Paris, France
| | - Catherine Simenel
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Halina Wojtowicz
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Gisele Cardoso de Amorim
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Ada Prochnicka-Chalufour
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Sylviane Hoos
- Institut Pasteur, Plate-forme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, Paris, France
| | - Bertrand Raynal
- Institut Pasteur, Plate-forme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, Paris, France
| | - Patrick England
- Institut Pasteur, Plate-forme de Biophysique des Macromolécules et de leurs Interactions, Département de Biologie Structurale et Chimie, Paris, France
| | - Alain Chaffotte
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Muriel Delepierre
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
| | - Philippe Delepelaire
- Institut de Biologie Physico-Chimique, CNRS Université Paris-Diderot UMR 7099, Paris, France
| | - Nadia Izadi-Pruneyre
- Institut Pasteur, Unité de RMN des Biomolécules, Département de Biologie Structurale et Chimie, Paris, France
- CNRS, UMR 3528, Paris, France
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10
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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: 13] [Impact Index Per Article: 1.2] [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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11
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Cell-cell contacts confine public goods diffusion inside Pseudomonas aeruginosa clonal microcolonies. Proc Natl Acad Sci U S A 2013; 110:12577-82. [PMID: 23858453 DOI: 10.1073/pnas.1301428110] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The maintenance of cooperation in populations where public goods are equally accessible to all but inflict a fitness cost on individual producers is a long-standing puzzle of evolutionary biology. An example of such a scenario is the secretion of siderophores by bacteria into their environment to fetch soluble iron. In a planktonic culture, these molecules diffuse rapidly, such that the same concentration is experienced by all bacteria. However, on solid substrates, bacteria form dense and packed colonies that may alter the diffusion dynamics through cell-cell contact interactions. In Pseudomonas aeruginosa microcolonies growing on solid substrate, we found that the concentration of pyoverdine, a secreted iron chelator, is heterogeneous, with a maximum at the center of the colony. We quantitatively explain the formation of this gradient by local exchange between contacting cells rather than by global diffusion of pyoverdine. In addition, we show that this local trafficking modulates the growth rate of individual cells. Taken together, these data provide a physical basis that explains the stability of public goods production in packed colonies.
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12
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Brillet K, Ruffenach F, Adams H, Journet L, Gasser V, Hoegy F, Guillon L, Hannauer M, Page A, Schalk IJ. An ABC transporter with two periplasmic binding proteins involved in iron acquisition in Pseudomonas aeruginosa. ACS Chem Biol 2012; 7:2036-45. [PMID: 23009327 DOI: 10.1021/cb300330v] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pyoverdine I is the main siderophore secreted byPseudomonas aeruginosa PAO1 to obtain access to iron. After extracellular iron chelation, pyoverdine-Fe uptake into the bacteria involves a specific outer-membrane transporter, FpvA. Iron is then released in the periplasm by a mechanism involving no siderophore modification but probably iron reduction. The proteins involved in this dissociation step are currently unknown. The pyoverdine locus contains the fpvCDEF operon, which contains four genes. These genes encode an ABC transporter of unknown function with the distinguishing characteristic of encompassing two periplasmic binding proteins, FpvC and FpvF, associated with the ATPase, FpvE, and the permease, FpvD. Deletion of these four genes partially inhibited cytoplasmic uptake of (55)Fe in the presence of pyoverdine and markedly slowed down the in vivo kinetics of iron release from the siderophore. This transporter is therefore involved in iron acquisition by pyoverdine in P. aeruginosa. Sequence alignments clearly showed that FpvC and FpvF belong to two different subgroups of periplasmic binding proteins. FpvC appears to be a metal-binding protein, whereas FpvF has homology with ferrisiderophore binding proteins. In vivo cross-linking assays and incubation of purified FpvC and FpvF proteins showed formation of complexes between both proteins. These complexes were able to bind in vitro PVDI-Fe, PVDI-Ga, or apo PVDI. This is the first example of an ABC transporter involved in iron acquisition via siderophores, with two periplasmic binding proteins interacting with the ferrisiderophore. The possible roles of FpvCDEF in iron uptake by the PVDI pathway are discussed.
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Affiliation(s)
- Karl Brillet
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant,
F-67412 Illkirch, Strasbourg, France
| | - Frank Ruffenach
- Institut de Génétique et de Biologie Moléculaire
et Cellulaire (IGBMC), INSERM Unité 964/UMR 7104 CNRS, Université de Strasbourg, 1, rue Laurent Fries,
67404 Illkirch, France
| | - Hendrik Adams
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant,
F-67412 Illkirch, Strasbourg, France
| | - Laure Journet
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant,
F-67412 Illkirch, Strasbourg, France
| | - Véronique Gasser
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant,
F-67412 Illkirch, Strasbourg, France
| | - Francoise Hoegy
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant,
F-67412 Illkirch, Strasbourg, France
| | - Laurent Guillon
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant,
F-67412 Illkirch, Strasbourg, France
| | - Mélissa Hannauer
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant,
F-67412 Illkirch, Strasbourg, France
| | - Adeline Page
- Institut de Génétique et de Biologie Moléculaire
et Cellulaire (IGBMC), INSERM Unité 964/UMR 7104 CNRS, Université de Strasbourg, 1, rue Laurent Fries,
67404 Illkirch, France
| | - Isabelle J. Schalk
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant,
F-67412 Illkirch, Strasbourg, France
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13
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Ferric-pyoverdine recognition by Fpv outer membrane proteins of Pseudomonas protegens Pf-5. J Bacteriol 2012; 195:765-76. [PMID: 23222724 DOI: 10.1128/jb.01639-12] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The soil bacterium Pseudomonas protegens Pf-5 (previously called P. fluorescens Pf-5) produces two siderophores, enantio-pyochelin and a compound in the large and diverse pyoverdine family. Using high-resolution mass spectroscopy, we determined the structure of the pyoverdine produced by Pf-5. In addition to producing its own siderophores, Pf-5 also utilizes ferric complexes of some pyoverdines produced by other strains of Pseudomonas spp. as sources of iron. Previously, phylogenetic analysis of the 45 TonB-dependent outer membrane proteins in Pf-5 indicated that six are in a well-supported clade with ferric-pyoverdine receptors (Fpvs) from other Pseudomonas spp. We used a combination of phylogenetics, bioinformatics, mutagenesis, pyoverdine structural determinations, and cross-feeding bioassays to assign specific ferric-pyoverdine substrates to each of the six Fpvs of Pf-5. We identified at least one ferric-pyoverdine that was taken up by each of the six Fpvs of Pf-5. Functional redundancy of the Pf-5 Fpvs was also apparent, with some ferric-pyoverdines taken up by all mutants with a single Fpv deletion but not by a mutant having deletions in two of the Fpv-encoding genes. Finally, we demonstrated that phylogenetically related Fpvs take up ferric complexes of structurally related pyoverdines, thereby establishing structure-function relationships that can be employed in the future to predict the pyoverdine substrates of Fpvs in other Pseudomonas spp.
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Schalk IJ, Guillon L. Pyoverdine biosynthesis and secretion in Pseudomonas aeruginosa: implications for metal homeostasis. Environ Microbiol 2012; 15:1661-73. [PMID: 23126435 DOI: 10.1111/1462-2920.12013] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 09/17/2012] [Accepted: 09/26/2012] [Indexed: 02/03/2023]
Abstract
Pyoverdines are siderophores produced by fluorescent Pseudomonads to acquire iron. At least 60 different pyoverdines produced by diverse strains have been chemically characterized. They all consist of a dihydroquinoline-type chromophore linked to a peptide. These peptides are of various lengths and the sequences are strain specific. Pyoverdine biosynthesis in Pseudomonas aeruginosa and fluorescent Pseudomonads is a complex process involving at least 12 different proteins, starting in the cytoplasm and ending in the periplasm. The cellular localization of pyoverdine precursors was recently shown to be consistent with their biosynthetic enzymes. In the cytoplasm, pyoverdine appears to be assembled at the inner membrane and particularly at the old cell pole of the bacterium. Mature pyoverdine is uniformly distributed throughout the periplasm, like the periplasmic enzyme PvdQ. Secretion of pyoverdine involves a recently identified ATP-dependent efflux pump, PvdRT-OpmQ. This efflux system does not only secrete newly synthesized pyoverdine but also pyoverdine that already transported iron into the bacterial periplasm and any pyoverdine-metal complex other than ferri-pyoverdine present in the periplasm. This review considers how these new insights into pyoverdine biosynthesis and secretion contribute to our understanding of the role of pyoverdine in iron and metal homeostasis in fluorescent Pseudomonads.
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Affiliation(s)
- Isabelle J Schalk
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brant, F-67413 Illkirch, Strasbourg, France.
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Saha R, Saha N, Donofrio RS, Bestervelt LL. Microbial siderophores: a mini review. J Basic Microbiol 2012; 53:303-17. [PMID: 22733623 DOI: 10.1002/jobm.201100552] [Citation(s) in RCA: 215] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Accepted: 01/20/2012] [Indexed: 01/22/2023]
Abstract
Iron is one of the major limiting factors and essential nutrients of microbial life. Since in nature it is not readily available in the preferred form, microorganisms produce small high affinity chelating molecules called siderophores for its acquisition. Microorganisms produce a wide variety of siderophores controlled at the molecular level by different genes to accumulate, mobilize and transport iron for metabolism. Siderophores also play a critical role in the expression of virulence and development of biofilms by different microbes. Apart from maintaining microbial life, siderophores can be harnessed for the sustainability of human, animals and plants. With the advent of modern molecular tools, a major breakthrough is taking place in the understanding of the multifaceted role of siderophores in nature. This mini review is intended to provide a general overview on siderophore along with its role and applications.
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Affiliation(s)
- Ratul Saha
- Department of Microbiology and Molecular Biology, NSF International, Ann Arbor, MI, USA.
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Schalk IJ, Mislin GLA, Brillet K. Structure, function and binding selectivity and stereoselectivity of siderophore-iron outer membrane transporters. CURRENT TOPICS IN MEMBRANES 2012; 69:37-66. [PMID: 23046646 DOI: 10.1016/b978-0-12-394390-3.00002-1] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
To get access to iron, microorganisms produce and release into their environment small organic metal chelators called siderophores. In parallel, they produce siderophore-iron outer membrane transporters (also called TonB-Dependent Transporters or TBDT) embedded in the outer membrane; these proteins actively reabsorb the siderophore loaded with iron from the extracellular medium. This active uptake requires energy in the form of the proton motive force transferred from the inner membrane to the outer membrane transporter via the inner membrane TonB complex. Siderophores produced by microorganisms are structurally very diverse with molecular weights of 150 up to 2000Da. Siderophore-iron uptake from the extracellular medium by TBDTs is a highly selective and sometimes even stereoselective process, with each siderophore having a specific TBDT. Unlike the siderophores, all TBDTs have similar structures and belong to the outer membrane β-barrel protein superfamily. The way in which the siderophore-iron complex passes through the TBDT is still unclear. In some bacteria, TBDTs are also partners of signaling cascades regulating the expression of proteins involved in siderophore biosynthesis and siderophore-iron acquisition.
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Affiliation(s)
- Isabelle J Schalk
- UMR 7242, Université de Strasbourg-CNRS, ESBS, Boulevard Sébastien Brant, Strasbourg, France.
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Hannauer M, Braud A, Hoegy F, Ronot P, Boos A, Schalk IJ. The PvdRT-OpmQ efflux pump controls the metal selectivity of the iron uptake pathway mediated by the siderophore pyoverdine in Pseudomonas aeruginosa. Environ Microbiol 2011; 14:1696-708. [PMID: 22187978 DOI: 10.1111/j.1462-2920.2011.02674.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pyoverdine (PVD) is the major siderophore produced by Pseudomonas aeruginosa for iron acquisition. PvdRT-OpmQ is an ATP-dependent efflux pump involved in the secretion of newly synthesized pyoverdine (PVD) and of PVD that has transported and released its iron into the bacterium from the periplasm into the extracellular medium. This iron uptake pathway also involves an outer membrane transporter, FpvA, for PVD-Fe uptake from the extracellular medium into the periplasm. In binding assays, FpvA bound PVD in complex with many different metals, with affinities from 2.9 nM for PVD-Fe to 13 µM for PVD-Al. Uptake assays with various FpvA and PvdRT-OpmQ mutants, monitored by inductively coupled plasma-atomic emission spectrometry (ICP-AES) for metal detection, and by fluorescence for PVD detection, showed that both metals and PVD accumulated in P. aeruginosa, due to the uptake of these compounds via the FpvA/PVD pathway. Higher levels of accumulation were observed in the absence of PvdRT-OpmQ expression. Thus, FpvA has a broad metal specificity for both the binding and uptake of PVD-metal complexes, and the PvdRT-OpmQ efflux pump exports unwanted metals complexed with PVD from the bacterium. This study provides the first evidence of efflux pump involvement in the export of unwanted siderophore-metal complexes and insight into the molecular mechanisms involved controlling the metal selectivity of siderophore-mediated iron uptake pathways.
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Affiliation(s)
- Mélissa Hannauer
- Université de Strasbourg-CNRS, Blvd Sébastien Brant, Illkirch, Strasbourg, France
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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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Schalk IJ, Hannauer M, Braud A. New roles for bacterial siderophores in metal transport and tolerance. Environ Microbiol 2011; 13:2844-54. [PMID: 21883800 DOI: 10.1111/j.1462-2920.2011.02556.x] [Citation(s) in RCA: 286] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Siderophores are chelators with extremely strong affinity for ferric iron and are best known for their capacity to feed microorganisms with this metal. Despite their preference for iron, they can also chelate numerous other metals with variable affinities. There is also increasing evidence that metals other than iron can activate the production of siderophores by bacteria, thereby implicating siderophores in the homeostasis of metals other than iron and especially heavy metal tolerance. This article considers this new concept that siderophores play a role in protecting bacteria against metal toxicity and discusses the possible contribution of these chelators to the transport of biological relevant metals in addition to iron.
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Affiliation(s)
- Isabelle J Schalk
- UMR7242, University of Strasbourg-CNRS, ESBS, Blvd Sébastien Brant, F-67413 Illkirch, Strasbourg, France.
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Hare NJ, Scott NE, Shin EHH, Connolly AM, Larsen MR, Palmisano G, Cordwell SJ. Proteomics of the oxidative stress response induced by hydrogen peroxide and paraquat reveals a novel AhpC-like protein in Pseudomonas aeruginosa. Proteomics 2011; 11:3056-69. [DOI: 10.1002/pmic.201000807] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 03/01/2011] [Accepted: 03/07/2011] [Indexed: 12/26/2022]
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Nader M, Journet L, Meksem A, Guillon L, Schalk IJ. Mechanism of Ferripyoverdine Uptake by Pseudomonas aeruginosa Outer Membrane Transporter FpvA: No Diffusion Channel Formed at Any Time during Ferrisiderophore Uptake. Biochemistry 2011; 50:2530-40. [DOI: 10.1021/bi101821n] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mirella Nader
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
| | - Laure Journet
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
| | - Ahmed Meksem
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
| | - Laurent Guillon
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
| | - Isabelle J. Schalk
- UMR7242, Université de Strasbourg-CNRS, ESBS, Blvd Sébastien Brandt, F-67513 Illkirch, France
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Legionella pneumophila LbtU acts as a novel, TonB-independent receptor for the legiobactin siderophore. J Bacteriol 2011; 193:1563-75. [PMID: 21278293 DOI: 10.1128/jb.01111-10] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gram-negative Legionella pneumophila produces a siderophore (legiobactin) that promotes lung infection. We previously determined that lbtA and lbtB are required for the synthesis and secretion of legiobactin. DNA sequence and reverse transcription-PCR (RT-PCR) analyses now reveal the presence of an iron-repressed gene (lbtU) directly upstream of the lbtAB-containing operon. In silico analysis predicted that LbtU is an outer membrane protein consisting of a 16-stranded transmembrane β-barrel, multiple extracellular domains, and short periplasmic tails. Immunoblot analysis of cell fractions confirmed an outer membrane location for LbtU. Although replicating normally in standard media, lbtU mutants, like lbtA mutants, were impaired for growth on iron-depleted agar media. While producing typical levels of legiobactin, lbtU mutants were unable to use supplied legiobactin to stimulate growth on iron-depleted media and displayed an inability to take up iron. Complemented lbtU mutants behaved as the wild type did. The lbtU mutants were also impaired for infection in a legiobactin-dependent manner. Together, these data indicate that LbtU is involved in the uptake of legiobactin and, based upon its location, is most likely the Legionella siderophore receptor. The sequence and predicted two-dimensional (2D) and 3D structures of LbtU were distinct from those of all known siderophore receptors, which generally contain a 22-stranded β-barrel and an extended N terminus that binds TonB in order to transduce energy from the inner membrane. This observation coupled with the fact that L. pneumophila does not encode TonB suggests that LbtU is a new type of receptor that participates in a form of iron uptake that is mechanistically distinct from the existing paradigm.
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Abstract
Siderophores are compounds produced by bacteria, fungi and graminaceous plants for scavenging iron from the environment. They are low-molecular-weight compounds (500-1500 daltons) possessing a high affinity for iron(III) (Kf > 1030), the biosynthesis of which is regulated by iron levels and the function of which is to supply iron to the cell. This article briefly describes the classification and chemical properties of siderophores, before outlining research on siderophore biosynthesis and transport. Clinically important siderophores and the therapeutic potential of siderophore design are described. Appendix 1 provides a comprehensive list of siderophore structures.
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Affiliation(s)
- Robert C Hider
- Division of Pharmaceutical Science, King's College, London, SE1 9NH, UK.
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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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