1
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Fong SA, Bouras G, Houtak G, Nepal R, Feizi S, Morales S, Psaltis AJ, Wormald PJ, Vreugde S. Genomic variation in Pseudomonas aeruginosa clinical respiratory isolates with de novo resistance to a bacteriophage cocktail. Microbiol Spectr 2025; 13:e0214924. [PMID: 40162801 PMCID: PMC12054119 DOI: 10.1128/spectrum.02149-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2024] [Accepted: 01/20/2025] [Indexed: 04/02/2025] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that can cause sinus infections and pneumonia in cystic fibrosis (CF) patients. Bacteriophage therapy is being investigated as a treatment for antibiotic-resistant P. aeruginosa infections. Although virulent bacteriophages have shown promise in treating P. aeruginosa infections, the development of bacteriophage-insensitive mutants (BIMs) in the presence of bacteriophages has been described. The aim of this study was to examine the genetic changes associated with the BIM phenotype. Biofilms of three genetically distinct P. aeruginosa strains, including PAO1 (ATCC 15692), and two clinical respiratory isolates (one CF and one non-CF) were grown for 7 days and treated with either a cocktail of four bacteriophages or a vehicle control for 7 consecutive days. BIMs isolated from the biofilms were detected by streak assays, and resistance to the phage cocktail was confirmed using spot test assays. Comparison of whole genome sequencing between the recovered BIMs and their respective vehicle control-treated phage-sensitive isolates revealed structural variants in two strains, and several small variants in all three strains. These variations involved a TonB-dependent outer membrane receptor in one strain, and mutations in lipopolysaccharide synthesis genes in two strains. Prophage deletion and induction were also noted in two strains, as well as mutations in several genes associated with virulence factors. Mutations in genes involved in susceptibility to conventional antibiotics were also identified in BIMs, with both decreased and increased antibiotic sensitivity to various antibiotics being observed. These findings may have implications for future applications of lytic phage therapy.IMPORTANCELytic bacteriophages are viruses that infect and kill bacteria and can be used to treat difficult-to-treat bacterial infections, including biofilm-associated infections and multidrug-resistant bacteria. Pseudomonas aeruginosa is a bacterium that can cause life-threatening infections. Lytic bacteriophage therapy has been trialed in the treatment of P. aeruginosa infections; however, sometimes bacteria develop resistance to the bacteriophages. This study sheds light on the genetic mechanisms of such resistance, and how this might be harnessed to restore the sensitivity of multidrug-resistant P. aeruginosa to conventional antibiotics.
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Affiliation(s)
- Stephanie A. Fong
- Department of Surgery - Otolaryngology Head and Neck Surgery, University of Adelaide, Adelaide, Australia
| | - George Bouras
- Department of Surgery - Otolaryngology Head and Neck Surgery, University of Adelaide, Adelaide, Australia
| | - Ghais Houtak
- Department of Surgery - Otolaryngology Head and Neck Surgery, University of Adelaide, Adelaide, Australia
| | - Roshan Nepal
- Department of Surgery - Otolaryngology Head and Neck Surgery, University of Adelaide, Adelaide, Australia
| | - Sholeh Feizi
- Department of Surgery - Otolaryngology Head and Neck Surgery, University of Adelaide, Adelaide, Australia
| | - Sandra Morales
- AmpliPhi Australia, Brookvale, New South Wales, Australia
| | - Alkis J. Psaltis
- Department of Surgery - Otolaryngology Head and Neck Surgery, University of Adelaide, Adelaide, Australia
| | - Peter-John Wormald
- Department of Surgery - Otolaryngology Head and Neck Surgery, University of Adelaide, Adelaide, Australia
| | - Sarah Vreugde
- Department of Surgery - Otolaryngology Head and Neck Surgery, University of Adelaide, Adelaide, Australia
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2
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Carson DV, Juarez RJ, Do T, Yang Z, James Link A. Antimicrobial Lasso Peptide Cloacaenodin Utilizes a Unique TonB-Dependent Transporter to Access Susceptible Bacteria. ACS Chem Biol 2024; 19:981-991. [PMID: 38527226 PMCID: PMC11031277 DOI: 10.1021/acschembio.4c00009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/27/2024]
Abstract
The development of new antimicrobial agents effective against Gram-negative bacteria remains a major challenge in drug discovery. The lasso peptide cloacaenodin has potent antimicrobial activity against multiple strains in the Enterobacter genus, one of the ESKAPE pathogens. Here, we show that cloacaenodin uses a previously uncharacterized TonB-dependent transporter, which we name CloU, to cross the outer membrane (OM) of susceptible bacteria. Inner membrane transport is mediated by the protein SbmA. CloU is distinct from the known OM transporters (FhuA and PupB) utilized by other antimicrobial lasso peptides and thus offers important insight into the spectrum of activity of cloacaenodin. Using knowledge of the transport pathway to predict other cloacaenodin-susceptible strains, we demonstrate the activity of cloacaenodin against clinical isolates of Enterobacter and of a Kluyvera strain. Further, we use molecular dynamics simulations and mutagenesis of CloU to explain the variation in cloacaenodin susceptibility observed across different strains of Enterobacter. This work expands the currently limited understanding of lasso peptide uptake and advances the potential of cloacaenodin as an antibiotic.
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Affiliation(s)
- Drew V. Carson
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Reecan J. Juarez
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - Truc Do
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
| | - Zhongyue Yang
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, United States
- Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
- Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37235, United States
- Data Science Institute, Vanderbilt University, Nashville, Tennessee 37235, United States
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, United States
| | - A. James Link
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey 08544, United States
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
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3
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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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Peukert C, Gasser V, Orth T, Fritsch S, Normant V, Cunrath O, Schalk IJ, Brönstrup M. Trojan Horse Siderophore Conjugates Induce Pseudomonas aeruginosa Suicide and Qualify the TonB Protein as a Novel Antibiotic Target. J Med Chem 2023; 66:553-576. [PMID: 36548006 PMCID: PMC9841981 DOI: 10.1021/acs.jmedchem.2c01489] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Indexed: 12/24/2022]
Abstract
Rising infection rates with multidrug-resistant pathogens calls for antibiotics with novel modes of action. Herein, we identify the inner membrane protein TonB, a motor of active uptake in Gram-negative bacteria, as a novel target in antimicrobial therapy. The interaction of the TonB box of outer membrane transporters with TonB is crucial for the internalization of essential metabolites. We designed TonB box peptides and coupled them with synthetic siderophores in order to facilitate their uptake into bacteria in up to 32 synthetic steps. Three conjugates repressed the growth of Pseudomonas aeruginosa cells unable to produce their own siderophores, with minimal inhibitory concentrations between 0.1 and 0.5 μM. The transporters mediating uptake of these compounds were identified as PfeA and PirA. The study illustrates a variant of cellular suicide where a transporter imports its own inhibitor and demonstrates that artificial siderophores can import cargo with molecular weights up to 4 kDa.
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Affiliation(s)
- Carsten Peukert
- Department
of Chemical Biology, Helmholtz Centre for
Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany
| | - Véronique Gasser
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Till Orth
- Department
of Chemical Biology, Helmholtz Centre for
Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany
| | - Sarah Fritsch
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Vincent Normant
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Olivier Cunrath
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Isabelle J. Schalk
- CNRS, University
of Strasbourg, UMR7242, ESBS, Boulevard Sébastien Brant, F-67412 Illkirch, Strasbourg, France
| | - Mark Brönstrup
- Department
of Chemical Biology, Helmholtz Centre for
Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany
- German
Center for Infection Research (DZIF), Site Hannover-Braunschweig, 38124 Braunschweig, Germany
- Center for
Biomolecular Drug Research (BMWZ), Schneiderberg 38, 30167 Hannover, Germany
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Eukaryotic catecholamine hormones influence the chemotactic control of Vibrio campbellii by binding to the coupling protein CheW. Proc Natl Acad Sci U S A 2022; 119:e2118227119. [PMID: 35238645 PMCID: PMC8915975 DOI: 10.1073/pnas.2118227119] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Host-emitted stress hormones significantly influence the growth and behavior of various bacterial species; however, their cellular targets have so far remained elusive. Here, we used customized probes and quantitative proteomics to identify the target of epinephrine and the α-adrenoceptor agonist phenylephrine in live cells of the aquatic pathogen Vibrio campbellii. Consequently, we have discovered the coupling protein CheW, which is in the center of the chemotaxis signaling network, as a target of both molecules. We not only demonstrate direct ligand binding to CheW but also elucidate how this affects chemotactic control. These findings are pivotal for further research on hormone-specific effects on bacterial behavior. In addition to their well-known role as stress-associated catecholamine hormones in animals and humans, epinephrine (EPI) and norepinephrine (NE) act as interkingdom signals between eukaryotic hosts and bacteria. However, the molecular basis of their effects on bacteria is not well understood. In initial phenotypic studies utilizing Vibrio campbellii as a model organism, we characterized the bipartite mode of action of catecholamines, which consists of promotion of growth under iron limitation and enhanced colony expansion on soft agar. In order to identify the molecular targets of the hormones, we designed and synthesized tailored probes for chemical proteomic studies. As the catechol group in EPI and NE acts as an iron chelator and is prone to form a reactive quinone moiety, we devised a photoprobe based on the adrenergic agonist phenylephrine (PE), which solely influenced colony expansion. Using this probe, we identified CheW, located at the core of the chemotaxis signaling network, as a major target. In vitro studies confirmed that EPI, NE, PE, and labetalol, a clinically applied antagonist, bind to purified CheW with affinity constants in the submicromolar range. In line with these findings, exposure of V. campbellii to these adrenergic agonists affects the chemotactic control of the bacterium. This study highlights an effect of eukaryotic signaling molecules on bacterial motility.
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6
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Functional Diversity of TonB-Like Proteins in the Heterocyst-Forming Cyanobacterium Anabaena sp. PCC 7120. mSphere 2021; 6:e0021421. [PMID: 34787445 PMCID: PMC8597729 DOI: 10.1128/msphere.00214-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The TonB-dependent transport of scarcely available substrates across the outer membrane is a conserved feature in Gram-negative bacteria. The plasma membrane-embedded TonB-ExbB-ExbD accomplishes complex functions as an energy transducer by physically interacting with TonB-dependent outer membrane transporters (TBDTs). TonB mediates structural rearrangements in the substrate-loaded TBDTs that are required for substrate translocation into the periplasm. In the model heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120, four TonB-like proteins have been identified. Out of these TonB3 accomplishes the transport of ferric schizokinen, the siderophore which is secreted by Anabaena to scavenge iron. In contrast, TonB1 (SjdR) is exceptionally short and not involved in schizokinen transport. The proposed function of SjdR in peptidoglycan structuring eliminates the protein from the list of TonB proteins in Anabaena. Compared with the well-characterized properties of SjdR and TonB3, the functions of TonB2 and TonB4 are yet unknown. Here, we examined tonB2 and tonB4 mutants for siderophore transport capacities and other specific phenotypic features. Both mutants were not or only slightly affected in schizokinen transport, whereas they showed decreased nitrogenase activity in apparently normal heterocysts. Moreover, the cellular metal concentrations and pigment contents were altered in the mutants, most pronouncedly in the tonB2 mutant. This strain showed an altered susceptibility toward antibiotics and SDS and formed cell aggregates when grown in liquid culture, a phenotype associated with an elevated lipopolysaccharide (LPS) production. Thus, the TonB-like proteins in Anabaena appear to take over distinct functions, and the mutation of TonB2 strongly influences outer membrane integrity. IMPORTANCE The genomes of many organisms encode more than one TonB protein, and their number does not necessarily correlate with that of TonB-dependent outer membrane transporters. Consequently, specific as well as redundant functions of the different TonB proteins have been identified. In addition to a role in uptake of scarcely available nutrients, including iron complexes, TonB proteins are related to virulence, flagellum assembly, pilus localization, or envelope integrity, including antibiotic resistance. The knowledge about the function of TonB proteins in cyanobacteria is limited. Here, we compare the four TonB proteins of Anabaena sp. strain PCC 7120, providing evidence that their functions are in part distinct, since mutants of these proteins exhibit specific features but also show some common impairments.
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7
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Yoon EJ, Kim HS, Woo H, Choi YJ, Won D, Choi JR, Kim YA, Jeong SH. Trajectory of genetic alterations associated with colistin resistance in Acinetobacter baumannii during an in-hospital outbreak of infection. J Antimicrob Chemother 2021; 77:69-73. [PMID: 34609499 DOI: 10.1093/jac/dkab363] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 09/06/2021] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND As carbapenem-resistant Acinetobacter baumannii is dominant in clinical settings, the old polymyxin antibiotic colistin has been revived as a therapeutic option. The development of colistin resistance during treatment is becoming a growing concern. OBJECTIVES To access low- to mid-level colistin-resistant A. baumannii blood isolates recovered from an outbreak in a tertiary care hospital from a national antimicrobial surveillance study. METHODS The entire bacterial genome was sequenced through long-read sequencing methodology. Quantitative RT-PCR was carried out to determine the level of gene expression. Relative growth rates were determined to estimate fitness costs of each isolate caused by the genetic alterations. RESULTS The A. baumannii isolates belonged to global clone 2 harbouring two intrinsic phosphoethanolamine transferases. Cumulative alterations continuing the colistin resistance were observed. PmrC overproduction caused by the PmrBA226T alteration was identified in A. baumannii isolates with low-level colistin resistance and an additional PmrCR109H substitution led to mid-level colistin resistance. Truncation of the PmrC enzyme by insertion of ISAba59 was compensated by ISAba10-mediated overproduction of EptA and, in the last isolate, the complete PmrAB two-component regulatory system was eliminated to restore the biological cost of the bacterial host. CONCLUSIONS During the in-hospital outbreak, a trajectory of genetic modification in colistin-resistant A. baumannii isolates was observed for survival in the harsh conditions imposed by life-threatening drugs with the clear purpose of maintaining drug resistance above a certain level with a reasonable fitness cost.
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Affiliation(s)
- Eun-Jeong Yoon
- Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, South Korea.,Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, South Korea
| | - Hyun Soo Kim
- Department of Laboratory Medicine, Hallym University Dongtan Sacred Heart Hospital, Hallym University College of Medicine, Hwaseong, South Korea
| | - Heungjeong Woo
- Department of Infectious Diseases, Hallym University Dongtan Sacred Heart Hospital, Hallym University College of Medicine, Hwaseong, South Korea
| | - You Jeong Choi
- Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, South Korea.,Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, South Korea
| | - Dongju Won
- Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, South Korea
| | - Jong Rak Choi
- Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, South Korea
| | - Young Ah Kim
- Department of Laboratory Medicine, National Health Insurance Service Ilsan Hospital, Goyang, South Korea
| | - Seok Hoon Jeong
- Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, South Korea.,Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, South Korea
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8
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Salmonella Typhimurium and Pseudomonas aeruginosa Respond Differently to the Fe Chelator Deferiprone and to Some Novel Deferiprone Derivatives. Int J Mol Sci 2021; 22:ijms221910217. [PMID: 34638558 PMCID: PMC8508819 DOI: 10.3390/ijms221910217] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 09/16/2021] [Accepted: 09/21/2021] [Indexed: 11/16/2022] Open
Abstract
The ability to obtain Fe is critical for pathogens to multiply in their host. For this reason, there is significant interest in the identification of compounds that might interfere with Fe management in bacteria. Here we have tested the response of two Gram-negative pathogens, Salmonella enterica serovar Typhimurium (STM) and Pseudomonas aeruginosa (PAO1), to deferiprone (DFP), a chelating agent already in use for the treatment of thalassemia, and to some DFP derivatives designed to increase its lipophilicity. Our results indicate that DFP effectively inhibits the growth of PAO1, but not STM. Similarly, Fe-dependent genes of the two microorganisms respond differently to this agent. DFP is, however, capable of inhibiting an STM strain unable to synthesize enterochelin, while its effect on PAO1 is not related to the capability to produce siderophores. Using a fluorescent derivative of DFP we have shown that this chelator can penetrate very quickly into PAO1, but not into STM, suggesting that a selective receptor exists in Pseudomonas. Some of the tested derivatives have shown a greater ability to interfere with Fe homeostasis in STM compared to DFP, whereas most, although not all, were less active than DFP against PAO1, possibly due to interference of the added chemical tails with the receptor-mediated recognition process. The results reported in this work indicate that DFP can have different effects on distinct microorganisms, but that it is possible to obtain derivatives with a broader antimicrobial action.
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9
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Slavin YN, Ivanova K, Hoyo J, Perelshtein I, Owen G, Haegert A, Lin YY, LeBihan S, Gedanken A, Häfeli UO, Tzanov T, Bach H. Novel Lignin-Capped Silver Nanoparticles against Multidrug-Resistant Bacteria. ACS APPLIED MATERIALS & INTERFACES 2021; 13:22098-22109. [PMID: 33945683 DOI: 10.1021/acsami.0c16921] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
The emergence of bacteria resistant to antibiotics and the resulting infections are increasingly becoming a public health issue. Multidrug-resistant (MDR) bacteria are responsible for infections leading to increased morbidity and mortality in hospitals, prolonged time of hospitalization, and additional burden to financial costs. Therefore, there is an urgent need for novel antibacterial agents that will both treat MDR infections and outsmart the bacterial evolutionary mechanisms, preventing further resistance development. In this study, a green synthesis employing nontoxic lignin as both reducing and capping agents was adopted to formulate stable and biocompatible silver-lignin nanoparticles (NPs) exhibiting antibacterial activity. The resulting silver-lignin NPs were approximately 20 nm in diameter and did not agglomerate after one year of storage at 4 °C. They were able to inhibit the growth of a panel of MDR clinical isolates, including Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii, at concentrations that did not affect the viability of a monocyte-derived THP-1 human cell line. Furthermore, the exposure of silver-lignin NPs to the THP-1 cells led to a significant increase in the secretion of the anti-inflammatory cytokine IL-10, demonstrating the potential of these particles to act as an antimicrobial and anti-inflammatory agent simultaneously. P. aeruginosa genes linked with efflux, heavy metal resistance, capsular biosynthesis, and quorum sensing were investigated for changes in gene expression upon sublethal exposure to the silver-lignin NPs. Genes encoding for membrane proteins with an efflux function were upregulated. However, all other genes were membrane proteins that did not efflux metals and were downregulated.
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Affiliation(s)
- Yael N Slavin
- Faculty of Medicine, Division of Infectious Diseases, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Kristina Ivanova
- Grup de Biotecnologia Molecular i Industrial, Department of Chemical Engineering, Universitat Politècnica de Catalunya, Terrassa, Barcelona 08222, Spain
| | - Javier Hoyo
- Grup de Biotecnologia Molecular i Industrial, Department of Chemical Engineering, Universitat Politècnica de Catalunya, Terrassa, Barcelona 08222, Spain
| | - Ilana Perelshtein
- Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Gethin Owen
- Department of Dentistry, Centre for High-Throughput Phenogenomics, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Anne Haegert
- Laboratory for Advanced Genome Analysis, Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Yen-Yi Lin
- Laboratory for Advanced Genome Analysis, Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Stephane LeBihan
- Laboratory for Advanced Genome Analysis, Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Aharon Gedanken
- Department of Chemistry, Bar-Ilan University, Ramat Gan 52900, Israel
| | - Urs O Häfeli
- Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Tzanko Tzanov
- Grup de Biotecnologia Molecular i Industrial, Department of Chemical Engineering, Universitat Politècnica de Catalunya, Terrassa, Barcelona 08222, Spain
| | - Horacio Bach
- Faculty of Medicine, Division of Infectious Diseases, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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10
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Pollet RM, Martin LM, Koropatkin NM. TonB-dependent transporters in the Bacteroidetes: Unique domain structures and potential functions. Mol Microbiol 2021; 115:490-501. [PMID: 33448497 DOI: 10.1111/mmi.14683] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/10/2021] [Accepted: 01/11/2021] [Indexed: 12/26/2022]
Abstract
The human gut microbiota endows the host with a wealth of metabolic functions central to health, one of which is the degradation and fermentation of complex carbohydrates. The Bacteroidetes are one of the dominant bacterial phyla of this community and possess an expanded capacity for glycan utilization. This is mediated via the coordinated expression of discrete polysaccharide utilization loci (PUL) that invariantly encode a TonB-dependent transporter (SusC) that works with a glycan-capturing lipoprotein (SusD). More broadly within Gram-negative bacteria, TonB-dependent transporters (TBDTs) are deployed for the uptake of not only sugars, but also more often for essential nutrients such as iron and vitamins. Here, we provide a comprehensive look at the repertoire of TBDTs found in the model gut symbiont Bacteroides thetaiotaomicron and the range of predicted functional domains associated with these transporters and SusD proteins for the uptake of both glycans and other nutrients. This atlas of the B. thetaiotaomicron TBDTs reveals that there are at least three distinct subtypes of these transporters encoded within its genome that are presumably regulated in different ways to tune nutrient uptake.
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Affiliation(s)
| | - Lauryn M Martin
- Department of Biology, Alcorn State University, Alcorn, MS, USA
| | - Nicole M Koropatkin
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI, USA
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11
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Shao X, Xie Y, Zhang Y, Liu J, Ding Y, Wu M, Wang X, Deng X. Novel therapeutic strategies for treating Pseudomonas aeruginosa infection. Expert Opin Drug Discov 2020; 15:1403-1423. [PMID: 32880507 DOI: 10.1080/17460441.2020.1803274] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
INTRODUCTION Persistent infections caused by the superbug Pseudomonas aeruginosa and its resistance to multiple antimicrobial agents are huge threats to patients with cystic fibrosis as well as those with compromised immune systems. Multidrug-resistant P. aeruginosa has posed a major challenge to conventional antibiotics and therapeutic approaches, which show limited efficacy and cause serious side effects. The public demand for new antibiotics is enormous; yet, drug development pipelines have started to run dry with limited targets available for inventing new antibacterial drugs. Consequently, it is important to uncover potential therapeutic targets. AREAS COVERED The authors review the current state of drug development strategies that are promising in terms of the development of novel and potent drugs to treat P. aeruginosa infection. EXPERT OPINION The prevention of P. aeruginosa infection is increasingly challenging. Furthermore, targeting key virulence regulators has great potential for developing novel anti-P. aeruginosa drugs. Additional promising strategies include bacteriophage therapy, immunotherapies, and antimicrobial peptides. Additionally, the authors believe that in the coming years, the overall network of molecular regulatory mechanism of P. aeruginosa virulence will be fully elucidated, which will provide more novel and promising drug targets for treating P. aeruginosa infections.
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Affiliation(s)
- Xiaolong Shao
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Yingpeng Xie
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Yingchao Zhang
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Jingui Liu
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Yiqing Ding
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Min Wu
- Department of Biomedical Sciences, University of North Dakota , Grand Forks, North Dakota, USA
| | - Xin Wang
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China
| | - Xin Deng
- Department of Biomedical Sciences, City University of Hong Kong , Hong Kong SAR, China.,Shenzhen Research Institute, City University of Hong Kong , Shenzhen, China
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12
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Iatsenko I, Marra A, Boquete JP, Peña J, Lemaitre B. Iron sequestration by transferrin 1 mediates nutritional immunity in Drosophila melanogaster. Proc Natl Acad Sci U S A 2020; 117:7317-7325. [PMID: 32188787 PMCID: PMC7132258 DOI: 10.1073/pnas.1914830117] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Iron sequestration is a recognized innate immune mechanism against invading pathogens mediated by iron-binding proteins called transferrins. Despite many studies on antimicrobial activity of transferrins in vitro, their specific in vivo functions are poorly understood. Here we use Drosophila melanogaster as an in vivo model to investigate the role of transferrins in host defense. We find that systemic infections with a variety of pathogens trigger a hypoferremic response in flies, namely, iron withdrawal from the hemolymph and accumulation in the fat body. Notably, this hypoferremia to infection requires Drosophila nuclear factor κB (NF-κB) immune pathways, Toll and Imd, revealing that these pathways also mediate nutritional immunity in flies. Next, we show that the iron transporter Tsf1 is induced by infections downstream of the Toll and Imd pathways and is necessary for iron relocation from the hemolymph to the fat body. Consistent with elevated iron levels in the hemolymph, Tsf1 mutants exhibited increased susceptibility to Pseudomonas bacteria and Mucorales fungi, which could be rescued by chemical chelation of iron. Furthermore, using siderophore-deficient Pseudomonas aeruginosa, we discover that the siderophore pyoverdine is necessary for pathogenesis in wild-type flies, but it becomes dispensable in Tsf1 mutants due to excessive iron present in the hemolymph of these flies. As such, our study reveals that, similar to mammals, Drosophila uses iron limitation as an immune defense mechanism mediated by conserved iron-transporting proteins transferrins. Our in vivo work, together with accumulating in vitro studies, supports the immune role of insect transferrins against infections via an iron withholding strategy.
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Affiliation(s)
- Igor Iatsenko
- Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland;
| | - Alice Marra
- Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Jean-Philippe Boquete
- Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Jasquelin Peña
- Institute of Earth Surface Dynamics, University of Lausanne, 1015 Lausanne, Switzerland
| | - Bruno Lemaitre
- Global Health Institute, School of Life Sciences, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland;
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Behrens HM, Lowe ED, Gault J, Housden NG, Kaminska R, Weber TM, Thompson CMA, Mislin GLA, Schalk IJ, Walker D, Robinson CV, Kleanthous C. Pyocin S5 Import into Pseudomonas aeruginosa Reveals a Generic Mode of Bacteriocin Transport. mBio 2020; 11:e03230-19. [PMID: 32156826 PMCID: PMC7064778 DOI: 10.1128/mbio.03230-19] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 01/28/2020] [Indexed: 11/20/2022] Open
Abstract
Pyocin S5 (PyoS5) is a potent protein bacteriocin that eradicates the human pathogen Pseudomonas aeruginosa in animal infection models, but its import mechanism is poorly understood. Here, using crystallography, biophysical and biochemical analyses, and live-cell imaging, we define the entry process of PyoS5 and reveal links to the transport mechanisms of other bacteriocins. In addition to its C-terminal pore-forming domain, elongated PyoS5 comprises two novel tandemly repeated kinked 3-helix bundle domains that structure-based alignments identify as key import domains in other pyocins. The central domain binds the lipid-bound common polysaccharide antigen, allowing the pyocin to accumulate on the cell surface. The N-terminal domain binds the ferric pyochelin transporter FptA while its associated disordered region binds the inner membrane protein TonB1, which together drive import of the bacteriocin across the outer membrane. Finally, we identify the minimal requirements for sensitizing Escherichia coli toward PyoS5, as well as other pyocins, and suggest that a generic pathway likely underpins the import of all TonB-dependent bacteriocins across the outer membrane of Gram-negative bacteria.IMPORTANCE Bacteriocins are toxic polypeptides made by bacteria to kill their competitors, making them interesting as potential antibiotics. Here, we reveal unsuspected commonalities in bacteriocin uptake pathways, through molecular and cellular dissection of the import pathway for the pore-forming bacteriocin pyocin S5 (PyoS5), which targets Pseudomonas aeruginosa In addition to its C-terminal pore-forming domain, PyoS5 is composed of two tandemly repeated helical domains that we also identify in other pyocins. Functional analyses demonstrate that they have distinct roles in the import process. One recognizes conserved sugars projected from the surface, while the other recognizes a specific outer membrane siderophore transporter, FptA, in the case of PyoS5. Through engineering of Escherichia coli cells, we show that pyocins can be readily repurposed to kill other species. This suggests basic ground rules for the outer membrane translocation step that likely apply to many bacteriocins targeting Gram-negative bacteria.
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Affiliation(s)
- Hannah M Behrens
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Edward D Lowe
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Joseph Gault
- Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom
| | - Nicholas G Housden
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Renata Kaminska
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - T Moritz Weber
- Institute of Bioorganic Chemistry, Heinrich Heine University Düsseldorf, Forschungszentrum Jülich, Jülich, Germany
| | - Catriona M A Thompson
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Gaëtan L A Mislin
- UMR 7242, Biotechnologie et Signalisation Cellulaire, ESBS, Illkirch, France
| | - Isabelle J Schalk
- UMR 7242, Biotechnologie et Signalisation Cellulaire, ESBS, Illkirch, France
| | - Daniel Walker
- Institute of Infection, Immunity, and Inflammation, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Carol V Robinson
- Chemistry Research Laboratory, University of Oxford, Oxford, United Kingdom
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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14
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Ronnebaum TA, Gupta K, Christianson DW. Higher-order oligomerization of a chimeric αβγ bifunctional diterpene synthase with prenyltransferase and class II cyclase activities is concentration-dependent. J Struct Biol 2020; 210:107463. [PMID: 31978464 DOI: 10.1016/j.jsb.2020.107463] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 01/03/2020] [Accepted: 01/15/2020] [Indexed: 12/11/2022]
Abstract
The unusual diterpene (C20) synthase copalyl diphosphate synthase from Penicillium verruculosum (PvCPS) is the first bifunctional terpene synthase identified with both prenyltransferase and class II cyclase activities in a single polypeptide chain with αβγ domain architecture. The C-terminal prenyltransferase α domain generates geranylgeranyl diphosphate which is then cyclized to form copalyl diphosphate at the N-terminal βγ domain interface. We now demonstrate that PvCPS exists as a hexamer at high concentrations - a unique quaternary structure for known αβγ terpene synthases. Hexamer assembly is corroborated by a 2.41 Å-resolution crystal structure of the α domain prenyltransferase obtained from limited proteolysis of full-length PvCPS, as well as the ab initio model of full-length PvCPS derived from small-angle X-ray scattering data. Hexamerization of the prenyltransferase α domain appears to drive the hexamerization of full-length PvCPS. The PvCPS hexamer dissociates into lower-order species at lower concentrations, as evidenced by size-exclusion chromatography in-line with multiangle light scattering, sedimentation velocity analytical ultracentrifugation, and native polyacrylamide gel electrophoresis experiments, suggesting that oligomerization is concentration dependent. Even so, PvCPS oligomer assembly does not affect prenyltransferase activity in vitro.
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Affiliation(s)
- Trey A Ronnebaum
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA
| | - Kushol Gupta
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - David W Christianson
- Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA.
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15
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Impact of FiuA Outer Membrane Receptor Polymorphism on the Resistance of Pseudomonas aeruginosa toward Peptidoglycan Lipid II-Targeting PaeM Pyocins. J Bacteriol 2019; 201:JB.00164-19. [PMID: 30988031 DOI: 10.1128/jb.00164-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Accepted: 04/04/2019] [Indexed: 12/29/2022] Open
Abstract
Certain Pseudomonas aeruginosa strains produce a homolog of colicin M, namely, PaeM, that specifically inhibits peptidoglycan biosynthesis of susceptible P. aeruginosa strains by hydrolyzing the lipid II intermediate precursor. Two variants of this pyocin were identified whose sequences mainly differed in the N-terminal protein moiety, i.e., the region involved in the binding to the FiuA outer membrane receptor and translocation into the periplasm. The antibacterial activity of these two variants, PaeM1 and PaeM2, was tested against various P. aeruginosa strains comprising reference strains PAO1 and PA14, PaeM-producing strains, and 60 clinical isolates. Seven of these strains, including PAO1, were susceptible to only one variant (2 to PaeM1 and 5 to PaeM2), and 11 were affected by both. The remaining strains, including PA14 and four PaeM1 producers, were resistant to both variants. The differences in the antibacterial spectra of the two PaeM homologs prompted us to investigate the molecular determinants allowing their internalization into P. aeruginosa cells, taking the PAO1 strain that is susceptible to PaeM2 but resistant to PaeM1 as the indicator strain. Heterologous expression of fiuA gene orthologs from different strains into PAO1, site-directed mutagenesis experiments, and construction of PaeM chimeric proteins provided evidence that the cell susceptibility and discrimination differences between the PaeM variants resulted from a polymorphism of both the pyocin and the outer membrane receptor FiuA. Moreover, we found that a third component, TonB1, a protein involved in iron transport in P. aeruginosa, working together with FiuA and the ExbB/ExbD complex, was directly implicated in this discrimination.IMPORTANCE Bacterial antibiotic resistance constitutes a threat to human health, imposing the need for identification of new targets and development of new strategies to fight multiresistant pathogens. Bacteriocins and other weapons that bacteria have themselves developed to kill competitors are therefore of great interest and a valuable source of inspiration for us. Attention was paid here to two variants of a colicin M homolog (PaeM) produced by certain strains of P. aeruginosa that inhibit the growth of their congeners by blocking cell wall peptidoglycan synthesis. Molecular determinants allowing recognition of these pyocins by the outer membrane receptor FiuA were identified, and a receptor polymorphism affecting the susceptibility of P. aeruginosa clinical strains was highlighted, providing new insights into the potential use of these pyocins as an alternative to antibiotics.
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16
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Lysocins: Bioengineered Antimicrobials That Deliver Lysins across the Outer Membrane of Gram-Negative Bacteria. Antimicrob Agents Chemother 2019; 63:AAC.00342-19. [PMID: 30962344 DOI: 10.1128/aac.00342-19] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 04/03/2019] [Indexed: 11/20/2022] Open
Abstract
The prevalence of multidrug-resistant Pseudomonas aeruginosa has stimulated development of alternative therapeutics. Bacteriophage peptidoglycan hydrolases, termed lysins, represent an emerging antimicrobial option for targeting Gram-positive bacteria. However, lysins against Gram-negatives are generally deterred by the outer membrane and their inability to work in serum. One solution involves exploiting evolved delivery systems used by colicin-like bacteriocins (e.g., S-type pyocins of P. aeruginosa) to translocate through the outer membrane. Following surface receptor binding, colicin-like bacteriocins form Tol- or TonB-dependent translocons to actively import bactericidal domains through outer membrane protein channels. With this understanding, we developed lysocins, which are bioengineered lysin-bacteriocin fusion molecules capable of periplasmic import. In our proof-of-concept studies, components from the P. aeruginosa bacteriocin pyocin S2 (PyS2) responsible for surface receptor binding and outer membrane translocation were fused to the GN4 lysin to generate the PyS2-GN4 lysocin. PyS2-GN4 delivered the GN4 lysin to the periplasm to induce peptidoglycan cleavage and log-fold killing of P. aeruginosa with minimal endotoxin release. While displaying narrow-spectrum antipseudomonal activity in human serum, PyS2-GN4 also efficiently disrupted biofilms, outperformed standard-of-care antibiotics, exhibited no cytotoxicity toward eukaryotic cells, and protected mice from P. aeruginosa challenge in a bacteremia model. In addition to targeting P. aeruginosa, lysocins can be constructed to target other prominent Gram-negative bacterial pathogens.
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17
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Planckaert S, Jourdan S, Francis IM, Deflandre B, Rigali S, Devreese B. Proteomic Response to Thaxtomin Phytotoxin Elicitor Cellobiose and to Deletion of Cellulose Utilization Regulator CebR in Streptomyces scabies. J Proteome Res 2018; 17:3837-3852. [DOI: 10.1021/acs.jproteome.8b00528] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sören Planckaert
- Laboratory for Microbiology, Department of Biochemistry and Microbiology, Ghent University, B-9000 Ghent, Belgium
| | - Samuel Jourdan
- InBioS − Center for Protein Engineering, University of Liège, Institut de Chimie, B-4000 Liège, Belgium
| | - Isolde M. Francis
- Department of Biology, California State University Bakersfield, Bakersfield, California 93311-1022, United States
| | - Benoit Deflandre
- InBioS − Center for Protein Engineering, University of Liège, Institut de Chimie, B-4000 Liège, Belgium
| | - Sébastien Rigali
- InBioS − Center for Protein Engineering, University of Liège, Institut de Chimie, B-4000 Liège, Belgium
| | - Bart Devreese
- Laboratory for Microbiology, Department of Biochemistry and Microbiology, Ghent University, B-9000 Ghent, Belgium
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18
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Rosenberg T, Salam BB, Burdman S. Association Between Loss of Type IV Pilus Synthesis Ability and Phenotypic Variation in the Cucurbit Pathogenic Bacterium Acidovorax citrulli. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:548-559. [PMID: 29298127 DOI: 10.1094/mpmi-12-17-0324-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Acidovorax citrulli is the causal agent of bacterial fruit blotch of cucurbits. We have shown that functional type IV pili (T4P) are required for full virulence of this bacterium. To identify A. citrulli genes required for T4P activity, we screened a library of about 10,000 transposon mutants of A. citrulli M6 for altered T4P-mediated twitching motility. This screen led to the identification of 50 mutants impaired in twitching ability due to transposon insertions into 20 different genes. Representative mutants with disruptions in these genes were further characterized. All mutants were compromised in their virulence in seed transmission and stem inoculation assays and had reduced biofilm formation ability relative to wild-type M6. When grown on nutrient agar, most mutants produced colonies with a translucent and fuzzy appearance, in contrast to the opaque and smooth appearance of wild-type colonies. The colony morphology of these mutants was identical to that of previously reported phenotypic variants of strain M6. The exceptions were M6 mutants disrupted in genes tonB, pilT, pilW, and pilX that exhibited typical wild-type colony morphology, although lacking twitching haloes surrounding the colony. Transmission electron microscopy revealed that most mutants lacked the ability to produce T4P. The exceptions were mutants with disruptions in tonB, pilT, pilW, and pilX genes that were shown to produce these appendages. These findings support the idea that colony phenotypic variation in A. citrulli is determined by the lack of ability to synthesize T4P but not by lack of T4P functionality.
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Affiliation(s)
- Tally Rosenberg
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Bolaji Babajide Salam
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Saul Burdman
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel
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19
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The Pseudomonas aeruginosa PrrF1 and PrrF2 Small Regulatory RNAs Promote 2-Alkyl-4-Quinolone Production through Redundant Regulation of the antR mRNA. J Bacteriol 2018; 200:JB.00704-17. [PMID: 29507088 DOI: 10.1128/jb.00704-17] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 03/01/2018] [Indexed: 01/10/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that requires iron for growth and virulence. Under low-iron conditions, P. aeruginosa transcribes two highly identical (95%) small regulatory RNAs (sRNAs), PrrF1 and PrrF2, which are required for virulence in acute murine lung infection models. The PrrF sRNAs promote the production of 2-akyl-4(1H)-quinolone metabolites (AQs) that mediate a range of biological activities, including quorum sensing and polymicrobial interactions. Here, we show that the PrrF1 and PrrF2 sRNAs promote AQ production by redundantly inhibiting translation of antR, which encodes a transcriptional activator of the anthranilate degradation genes. A combination of genetic and biophysical analyses was used to define the sequence requirements for PrrF regulation of antR, demonstrating that the PrrF sRNAs interact with the antR 5' untranslated region (UTR) at sequences overlapping the translational start site of this mRNA. The P. aeruginosa Hfq protein interacted with UA-rich sequences in both PrrF sRNAs (Kd [dissociation constant] = 50 nM and 70 nM). Hfq bound with lower affinity to the antR mRNA (0.3 μM), and PrrF was able to bind to antR mRNA in the absence of Hfq. Nevertheless, Hfq increased the rate of PrrF annealing to the antR UTR by 10-fold. These studies provide a mechanistic description of how the PrrF1 and PrrF2 sRNAs mediate virulence traits, such as AQ production, in P. aeruginosaIMPORTANCE The iron-responsive PrrF sRNAs play a central role in regulating P. aeruginosa iron homeostasis and pathogenesis, yet the molecular mechanisms by which PrrF regulates gene expression are largely unknown. In this study, we used genetic and biophysical analyses to define the interactions of the PrrF sRNAs with Hfq, an RNA annealer, and the antR mRNA, which has downstream effects on quorum sensing and virulence factor production. These studies provide a comprehensive mechanistic analysis of how the PrrF sRNAs regulate virulence trait production through a key mRNA target in P. aeruginosa.
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20
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Liang D, Robinson E, Hom K, Yu W, Nguyen N, Li Y, Zong Q, Wilks A, Xue F. Structure-based design and biological evaluation of inhibitors of the pseudomonas aeruginosa heme oxygenase (pa-HemO). Bioorg Med Chem Lett 2018; 28:1024-1029. [PMID: 29459206 DOI: 10.1016/j.bmcl.2018.02.027] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 02/03/2018] [Accepted: 02/13/2018] [Indexed: 02/03/2023]
Affiliation(s)
- Dongdong Liang
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, United States
| | - Elizabeth Robinson
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, United States
| | - Kellie Hom
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, United States
| | - Wenbo Yu
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, United States
| | - Nam Nguyen
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, United States
| | - Yue Li
- Department of Chemistry and Biochemistry, University of Maryland College Park, College Park 20740, United States
| | - Qianshou Zong
- College of Biological and Chemical Sciences and Engineering, Jiaxing University, Jiaxing City, Zhejiang 314001, People's Republic of China
| | - Angela Wilks
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, United States.
| | - Fengtian Xue
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, United States.
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21
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The Pseudomonas aeruginosa PrrF Small RNAs Regulate Iron Homeostasis during Acute Murine Lung Infection. Infect Immun 2017; 85:IAI.00764-16. [PMID: 28289146 DOI: 10.1128/iai.00764-16] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 03/06/2017] [Indexed: 12/20/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that requires iron for virulence. Iron homeostasis is maintained in part by the PrrF1 and PrrF2 small RNAs (sRNAs), which block the expression of iron-containing proteins under iron-depleted conditions. The PrrF sRNAs also promote the production of the Pseudomonas quinolone signal (PQS), a quorum sensing molecule that activates the expression of several virulence genes. The tandem arrangement of the prrF genes allows for expression of a third sRNA, PrrH, which is predicted to regulate gene expression through its unique sequence derived from the prrF1-prrF2 intergenic (IG) sequence (the PrrHIG sequence). Previous studies showed that the prrF locus is required for acute lung infection. However, the individual functions of the PrrF and PrrH sRNAs were not determined. Here, we describe a system for differentiating PrrF and PrrH functions by deleting the PrrHIG sequence [prrF(ΔHIG)]. Our analyses of this construct indicate that the PrrF sRNAs, but not PrrH, are required for acute lung infection by P. aeruginosa Moreover, we show that the virulence defect of the ΔprrF1-prrF2 mutant is due to decreased bacterial burden during acute lung infection. In vivo analysis of gene expression in lung homogenates shows that PrrF-mediated regulation of genes for iron-containing proteins is disrupted in the ΔprrF1-prrF2 mutant during infection, while the expression of genes that mediate PrrF-regulated PQS production are not affected by prrF deletion in vivo Combined, these studies demonstrate that regulation of iron utilization plays a critical role in P. aeruginosa's ability to survive during infection.
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22
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Reinhart AA, Oglesby-Sherrouse AG. Regulation of Pseudomonas aeruginosa Virulence by Distinct Iron Sources. Genes (Basel) 2016; 7:genes7120126. [PMID: 27983658 PMCID: PMC5192502 DOI: 10.3390/genes7120126] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 12/02/2016] [Accepted: 12/05/2016] [Indexed: 02/06/2023] Open
Abstract
Pseudomonas aeruginosa is a ubiquitous environmental bacterium and versatile opportunistic pathogen. Like most other organisms, P. aeruginosa requires iron for survival, yet iron rapidly reacts with oxygen and water to form stable ferric (FeIII) oxides and hydroxides, limiting its availability to living organisms. During infection, iron is also sequestered by the host innate immune system, further limiting its availability. P. aeruginosa’s capacity to cause disease in diverse host environments is due to its ability to scavenge iron from a variety of host iron sources. Work over the past two decades has further shown that different iron sources can affect the expression of distinct virulence traits. This review discusses how the individual components of P. aeruginosa’s iron regulatory network allow this opportunist to adapt to a multitude of host environments during infection.
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Affiliation(s)
- Alexandria A Reinhart
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
| | - Amanda G Oglesby-Sherrouse
- Department of Pharmaceutical Sciences, School of Pharmacy, and Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA.
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23
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Ottman N, Huuskonen L, Reunanen J, Boeren S, Klievink J, Smidt H, Belzer C, de Vos WM. Characterization of Outer Membrane Proteome of Akkermansia muciniphila Reveals Sets of Novel Proteins Exposed to the Human Intestine. Front Microbiol 2016; 7:1157. [PMID: 27507967 PMCID: PMC4960237 DOI: 10.3389/fmicb.2016.01157] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 07/12/2016] [Indexed: 12/26/2022] Open
Abstract
Akkermansia muciniphila is a common member of the human gut microbiota and belongs to the Planctomycetes-Verrucomicrobia-Chlamydiae superphylum. Decreased levels of A. muciniphila have been associated with many diseases, and thus it is considered to be a beneficial resident of the intestinal mucus layer. Surface-exposed molecules produced by this organism likely play important roles in colonization and communication with other microbes and the host, but the protein composition of the outer membrane (OM) has not been characterized thus far. Herein we set out to identify and characterize A. muciniphila proteins using an integrated approach of proteomics and computational analysis. Sarkosyl extraction and sucrose density-gradient centrifugation methods were used to enrich and fractionate the OM proteome of A. muciniphila. Proteins from these fractions were identified by LC-MS/MS and candidates for OM proteins derived from the experimental approach were subjected to computational screening to verify their location in the cell. In total we identified 79 putative OM and membrane-associated extracellular proteins, and 23 of those were found to differ in abundance between cells of A. muciniphila grown on the natural substrate, mucin, and those grown on the non-mucus sugar, glucose. The identified OM proteins included highly abundant proteins involved in secretion and transport, as well as proteins predicted to take part in formation of the pili-like structures observed in A. muciniphila. The most abundant OM protein was a 95-kD protein, termed PilQ, annotated as a type IV pili secretin and predicted to be involved in the production of pili in A. muciniphila. To verify its location we purified the His-Tag labeled N-terminal domain of PilQ and generated rabbit polyclonal antibodies. Immunoelectron microscopy of thin sections immunolabeled with these antibodies demonstrated the OM localization of PilQ, testifying for its predicted function as a type IV pili secretin in A. muciniphila. As pili structures are known to be involved in the modulation of host immune responses, this provides support for the involvement of OM proteins in the host interaction of A. muciniphila. In conclusion, the characterization of A. muciniphila OM proteome provides valuable information that can be used for further functional and immunological studies.
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Affiliation(s)
- Noora Ottman
- Laboratory of Microbiology, Wageningen UniversityWageningen, Netherlands; Metapopulation Research Centre, University of HelsinkiHelsinki, Finland
| | - Laura Huuskonen
- Department of Veterinary Biosciences, University of Helsinki Helsinki, Finland
| | - Justus Reunanen
- Department of Veterinary Biosciences, University of HelsinkiHelsinki, Finland; Microbiology and Biotechnology, Department of Food and Environmental Sciences, University of HelsinkiHelsinki, Finland
| | - Sjef Boeren
- Laboratory of Biochemistry, Wageningen University Wageningen, Netherlands
| | - Judith Klievink
- Immunobiology, Department of Bacteriology and Immunology, and Research Programs Unit, University of Helsinki Helsinki, Finland
| | - Hauke Smidt
- Laboratory of Microbiology, Wageningen University Wageningen, Netherlands
| | - Clara Belzer
- Laboratory of Microbiology, Wageningen University Wageningen, Netherlands
| | - Willem M de Vos
- Laboratory of Microbiology, Wageningen UniversityWageningen, Netherlands; Department of Veterinary Biosciences, University of HelsinkiHelsinki, Finland; Immunobiology, Department of Bacteriology and Immunology, and Research Programs Unit, University of HelsinkiHelsinki, Finland
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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: 160] [Impact Index Per Article: 17.8] [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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A novel siderophore system is essential for the growth of Pseudomonas aeruginosa in airway mucus. Sci Rep 2015; 5:14644. [PMID: 26446565 PMCID: PMC4597187 DOI: 10.1038/srep14644] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 09/02/2015] [Indexed: 12/25/2022] Open
Abstract
Pseudomonas aeruginosa establishes airway infections in Cystic Fibrosis patients. Here, we investigate the molecular interactions between P. aeruginosa and airway mucus secretions (AMS) derived from the primary cultures of normal human tracheal epithelial (NHTE) cells. PAO1, a prototype strain of P. aeruginosa, was capable of proliferating during incubation with AMS, while all other tested bacterial species perished. A PAO1 mutant lacking PA4834 gene became susceptible to AMS treatment. The ΔPA4834 mutant was grown in AMS supplemented with 100 μM ferric iron, suggesting that the PA4834 gene product is involved in iron metabolism. Consistently, intracellular iron content was decreased in the mutant, but not in PAO1 after the AMS treatment. Importantly, a PAO1 mutant unable to produce both pyoverdine and pyochelin remained viable, suggesting that these two major siderophore molecules are dispensable for maintaining viability during incubation with AMS. The ΔPA4834 mutant was regrown in AMS amended with 100 μM nicotianamine, a phytosiderophore whose production is predicted to be mediated by the PA4836 gene. Infectivity of the ΔPA4834 mutant was also significantly compromised in vivo. Together, our results identify a genetic element encoding a novel iron acquisition system that plays a previously undiscovered role in P. aeruginosa airway infection.
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Lopez-Medina E, Fan D, Coughlin LA, Ho EX, Lamont IL, Reimmann C, Hooper LV, Koh AY. Candida albicans Inhibits Pseudomonas aeruginosa Virulence through Suppression of Pyochelin and Pyoverdine Biosynthesis. PLoS Pathog 2015; 11:e1005129. [PMID: 26313907 PMCID: PMC4552174 DOI: 10.1371/journal.ppat.1005129] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 08/04/2015] [Indexed: 01/09/2023] Open
Abstract
Bacterial-fungal interactions have important physiologic and medical ramifications, but the mechanisms of these interactions are poorly understood. The gut is host to trillions of microorganisms, and bacterial-fungal interactions are likely to be important. Using a neutropenic mouse model of microbial gastrointestinal colonization and dissemination, we show that the fungus Candida albicans inhibits the virulence of the bacterium Pseudomonas aeruginosa by inhibiting P. aeruginosa pyochelin and pyoverdine gene expression, which plays a critical role in iron acquisition and virulence. Accordingly, deletion of both P. aeruginosa pyochelin and pyoverdine genes attenuates P. aeruginosa virulence. Heat-killed C. albicans has no effect on P. aeruginosa, whereas C. albicans secreted proteins directly suppress P. aeruginosa pyoverdine and pyochelin expression and inhibit P. aeruginosa virulence in mice. Interestingly, suppression or deletion of pyochelin and pyoverdine genes has no effect on P. aeruginosa’s ability to colonize the GI tract but does decrease P. aeruginosa’s cytotoxic effect on cultured colonocytes. Finally, oral iron supplementation restores P. aeruginosa virulence in P. aeruginosa and C. albicans colonized mice. Together, our findings provide insight into how a bacterial-fungal interaction can modulate bacterial virulence in the intestine. Previously described bacterial-fungal antagonistic interactions have focused on growth inhibition or colonization inhibition/modulation, yet here we describe a novel observation of fungal-inhibition of bacterial effectors critical for virulence but not important for colonization. These findings validate the use of a mammalian model system to explore the complexities of polymicrobial, polykingdom infections in order to identify new therapeutic targets for preventing microbial disease. Pseudomonas aeruginosa and Candida albicans are two medically important human pathogens that often co-infect or co-colonize the same human niches, such as the gut. In a normal healthy host, P. aeruginosa and C. albicans can colonize the gut without any significant pathologic sequelae. But in immunocompromised hosts, both pathogens can escape the gut and cause life-threatening disseminated infections. Yet the mechanisms and pathogenic consequences of interactions between these two pathogens within a living mammalian host are not well understood. Here, we use a mouse model of P. aeruginosa and C. albicans gut co-infection to better understand the mechanisms by which C. albicans inhibits P. aeruginosa infection. C. albicans inhibits the expression of P. aeruginosa genes that are vital for iron acquisition. Accordingly, deleting these iron acquisition genes in P. aeruginosa prevents infection. Understanding how microbes interact and antagonize each other may help us identify new potential therapeutic targets for preventing or treating infections.
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Affiliation(s)
- Eduardo Lopez-Medina
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Di Fan
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Laura A. Coughlin
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Evi X. Ho
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Iain L. Lamont
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Cornelia Reimmann
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Lora V. Hooper
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- The Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Center for Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
| | - Andrew Y. Koh
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America
- * E-mail:
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Spoils of war: iron at the crux of clinical and ecological fitness of Pseudomonas aeruginosa. Biometals 2015; 28:433-43. [DOI: 10.1007/s10534-015-9848-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 03/13/2015] [Indexed: 01/07/2023]
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The prrF-encoded small regulatory RNAs are required for iron homeostasis and virulence of Pseudomonas aeruginosa. Infect Immun 2014; 83:863-75. [PMID: 25510881 DOI: 10.1128/iai.02707-14] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that requires iron to cause infection, but it also must regulate the uptake of iron to avoid iron toxicity. The iron-responsive PrrF1 and PrrF2 small regulatory RNAs (sRNAs) are part of P. aeruginosa's iron regulatory network and affect the expression of at least 50 genes encoding iron-containing proteins. The genes encoding the PrrF1 and PrrF2 sRNAs are encoded in tandem in P. aeruginosa, allowing for the expression of a distinct, heme-responsive sRNA named PrrH that appears to regulate genes involved in heme metabolism. Using a combination of growth, mass spectrometry, and gene expression analysis, we showed that the ΔprrF1,2 mutant, which lacks expression of the PrrF and PrrH sRNAs, is defective for both iron and heme homeostasis. We also identified phuS, encoding a heme binding protein involved in heme acquisition, and vreR, encoding a previously identified regulator of P. aeruginosa virulence genes, as novel targets of prrF-mediated heme regulation. Finally, we showed that the prrF locus encoding the PrrF and PrrH sRNAs is required for P. aeruginosa virulence in a murine model of acute lung infection. Moreover, we showed that inoculation with a ΔprrF1,2 deletion mutant protects against future challenge with wild-type P. aeruginosa. Combined, these data demonstrate that the prrF-encoded sRNAs are critical regulators of P. aeruginosa virulence.
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Osborne J, Djapgne L, Tran BQ, Goo YA, Oglesby-Sherrouse AG. A method for in vivo identification of bacterial small RNA-binding proteins. Microbiologyopen 2014; 3:950-60. [PMID: 25351924 PMCID: PMC4263517 DOI: 10.1002/mbo3.220] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 09/30/2014] [Accepted: 10/06/2014] [Indexed: 11/07/2022] Open
Abstract
Small bacterial regulatory RNAs (sRNAs) have gained immense appreciation over the last decade for their roles in mediating posttranscriptional gene regulation of numerous physiological processes. Several proteins contribute to sRNA stability and regulation, most notably the Hfq RNA-binding protein. However, not all sRNAs rely on Hfq for their stability. It is therefore likely that other proteins contribute to the stability and function of certain bacterial sRNAs. Here, we describe a methodology for identifying in vivo-binding proteins of sRNAs, developed using the iron-responsive PrrF and PrrH sRNAs of Pseudomonas aeruginosa. RNA was isolated from iron-depleted cultures, which were irradiated to cross-link nucleoprotein complexes. Subsequently, PrrF- and PrrH-protein complexes were enriched using cDNA "bait", and enriched RNA-protein complexes were analyzed by tandem mass spectrometry to identify PrrF and PrrH associated proteins. This method identified Hfq as a potential PrrF- and PrrH-binding protein. Interestingly, Hfq was identified more often in samples probed with the PrrF cDNA "bait" as compared to the PrrH cDNA "bait", suggesting Hfq has a stronger binding affinity for the PrrF sRNAs in vivo. Hfq binding to the PrrF and PrrH sRNAs was validated by electrophoretic mobility shift assays with purified Hfq protein from P. aeruginosa. As such, this study demonstrates that in vivo cross-linking coupled with sequence-specific affinity chromatography and tandem mass spectrometry (SSAC-MS/MS) is an effective methodology for unbiased identification of bacterial sRNA-binding proteins.
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Affiliation(s)
- Jonathan Osborne
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland
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Fur is the master regulator of the extraintestinal pathogenic Escherichia coli response to serum. mBio 2014; 5:mBio.01460-14. [PMID: 25118243 PMCID: PMC4145685 DOI: 10.1128/mbio.01460-14] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
UNLABELLED Drug-resistant extraintestinal pathogenic Escherichia coli (ExPEC) strains are the major cause of colisepticemia (colibacillosis), a condition that has become an increasing public health problem in recent years. ExPEC strains are characterized by high resistance to serum, which is otherwise highly toxic to most bacteria. To understand how these bacteria survive and grow in serum, we performed system-wide analyses of their response to serum, making a clear distinction between the responses to nutritional immunity and innate immunity. Thus, mild heat inactivation of serum destroys the immune complement and abolishes the bactericidal effect of serum (inactive serum), making it possible to examine nutritional immunity. We used a combination of deep RNA sequencing and proteomics in order to characterize ExPEC genes whose expression is affected by the nutritional stress of serum and by the immune complement. The major change in gene expression induced by serum-active and inactive-involved metabolic genes. In particular, the serum metabolic response is coordinated by three transcriptional regulators, Fur, BasR, and CysB. Fur alone was responsible for more than 80% of the serum-induced transcriptional response. Consistent with its role as a major serum response regulator, deletion of Fur renders the bacteria completely serum sensitive. These results highlight the role of metabolic adaptation in colisepticemia and virulence. IMPORTANCE Drug-resistant extraintestinal pathogenic Escherichia coli (ExPEC) strains have emerged as major pathogens, especially in community- and hospital-acquired infections. These bacteria cause a large spectrum of syndromes, the most serious of which is septicemia, a condition with a high mortality rate. These bacterial strains are characterized by high resistance to serum, otherwise highly toxic to most bacteria. To understand the basis of this resistance, we carried out system-wide analyses of the response of ExPEC strains to serum by using proteomics and deep RNA sequencing. The major changes in gene expression induced by exposure to serum involved metabolic genes, not necessarily implicated in relation to virulence. One metabolic regulator-Fur-involved in iron metabolism was responsible for more than 80% of the serum-induced response, and its deletion renders the bacteria completely serum sensitive. These results highlight the role of metabolic adaptation in virulence.
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Bonchi C, Imperi F, Minandri F, Visca P, Frangipani E. Repurposing of gallium-based drugs for antibacterial therapy. Biofactors 2014; 40:303-12. [PMID: 24532037 DOI: 10.1002/biof.1159] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 01/16/2014] [Accepted: 01/19/2014] [Indexed: 12/21/2022]
Abstract
While the occurrence and spread of antibiotic resistance in bacterial pathogens is vanishing current anti-infective therapies, the antibiotic discovery pipeline is drying up. In the last years, the repurposing of existing drugs for new clinical applications has become a major research area in drug discovery, also in the field of anti-infectives. This review discusses the potential of repurposing previously approved gallium formulations in antibacterial chemotherapy. Gallium has no proven function in biological systems, but it can act as an iron-mimetic in both prokaryotic and eukaryotic cells. The activity of gallium mostly relies on its ability to replace iron in redox enzymes, thus impairing their function and ultimately hampering cell growth. Cancer cells and bacteria are preferential gallium targets due to their active metabolism and fast growth. The wealth of knowledge on the pharmacological properties of gallium has opened the door to the repurposing of gallium-based drugs for the treatment of infections sustained by antibiotic-resistant bacterial pathogens, such as Acinetobacter baumannii or Pseudomonas aeruginosa, and for suppression of Mycobacterium tuberculosis growth. The promising antibacterial activity of gallium both in vitro and in different animal models of infection raises the hope that gallium will confirm its efficacy in clinical trials, and will become a valuable therapeutic option to cure otherwise untreatable bacterial infections.
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Affiliation(s)
- Carlo Bonchi
- Department of Sciences, University "Roma Tre,", Rome, Italy
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Adaptation of iron homeostasis pathways by a Pseudomonas aeruginosa pyoverdine mutant in the cystic fibrosis lung. J Bacteriol 2014; 196:2265-76. [PMID: 24727222 DOI: 10.1128/jb.01491-14] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Cystic fibrosis (CF) patients suffer from chronic bacterial lung infections, most notably by Pseudomonas aeruginosa, which persists for decades in the lungs and undergoes extensive evolution. P. aeruginosa requires iron for virulence and uses the fluorescent siderophore pyoverdine to scavenge and solubilize ferric iron during acute infections. Pyoverdine mutants accumulate in the lungs of some CF patients, however, suggesting that the heme and ferrous iron acquisition pathways of P. aeruginosa are more important in this environment. Here, we sought to determine how evolution of P. aeruginosa in the CF lung affects iron acquisition and regulatory pathways through the use of longitudinal CF isolates. These analyses demonstrated a significant reduction of siderophore production during the course of CF lung infection in nearly all strains tested. Mass spectrometry analysis of one of these strains showed that the later CF isolate has streamlined the metabolic flux of extracellular heme through the HemO heme oxygenase, resulting in more-efficient heme utilization. Moreover, gene expression analysis shows that iron regulation via the PrrF small RNAs (sRNAs) is enhanced in the later CF isolate. Finally, analysis of P. aeruginosa gene expression in the lungs of various CF patients demonstrates that both PrrF and HemO are consistently expressed in the CF lung environment. Combined, these results suggest that heme is a critical source of iron during prolonged infection of the CF lung and that changes in iron and heme regulatory pathways play a crucial role in adaptation of P. aeruginosa to this ever-changing host environment.
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Oglesby-Sherrouse AG, Djapgne L, Nguyen AT, Vasil AI, Vasil ML. The complex interplay of iron, biofilm formation, and mucoidy affecting antimicrobial resistance of Pseudomonas aeruginosa. Pathog Dis 2014; 70:307-20. [PMID: 24436170 DOI: 10.1111/2049-632x.12132] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 12/20/2013] [Accepted: 01/02/2014] [Indexed: 11/29/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic bacterial pathogen that is refractory to a variety of current antimicrobial therapeutic regimens. Complicating treatment for such infections is the ability of P. aeruginosa to form biofilms, as well as several innate and acquired resistance mechanisms. Previous studies suggest iron plays a role in resistance to antimicrobial therapy, including the efficacy of an FDA-approved iron chelator, deferasirox (DSX), or Gallium, an iron analog, in potentiating antibiotic-dependent killing of P. aeruginosa biofilms. Here, we show that iron-replete conditions enhance resistance of P. aeruginosa nonbiofilm growth against tobramycin and tigecycline. Interestingly, the mechanism of iron-enhanced resistance to each of these antibiotics is distinct. Whereas pyoverdine-mediated iron uptake is important for optimal resistance to tigecycline, it does not enhance tobramycin resistance. In contrast, heme supplementation results in increased tobramycin resistance, while having no significant effect on tigecycline resistance. Thus, nonsiderophore bound iron plays an important role in resistance to tobramycin, while pyoverdine increases the ability of P. aeruginosa to resist tigecycline treatment. Lastly, we show that iron increases the minimal concentration of tobramycin, but not tigecycline, required to eradicate P. aeruginosa biofilms. Moreover, iron depletion blocks the previous observed induction of biofilm formation by subinhibitory concentrations of tobramycin, suggesting iron and tobramycin signal through overlapping regulatory pathways to affect biofilm formation. These data further support the role of iron in P. aeruginosa antibiotic resistance, providing yet another compelling case for targeting iron acquisition for future antimicrobial drug development.
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Affiliation(s)
- Amanda G Oglesby-Sherrouse
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD, USA; Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, MD, USA
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Cornelis P, Dingemans J. Pseudomonas aeruginosa adapts its iron uptake strategies in function of the type of infections. Front Cell Infect Microbiol 2013; 3:75. [PMID: 24294593 PMCID: PMC3827675 DOI: 10.3389/fcimb.2013.00075] [Citation(s) in RCA: 248] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 10/22/2013] [Indexed: 11/13/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative γ-Proteobacterium which is known for its capacity to colonize various niches, including some invertebrate and vertebrate hosts, making it one of the most frequent bacteria causing opportunistic infections. P. aeruginosa is able to cause acute as well as chronic infections and it uses different colonization and virulence factors to do so. Infections range from septicemia, urinary infections, burn wound colonization, and chronic colonization of the lungs of cystic fibrosis patients. Like the vast majority of organisms, P. aeruginosa needs iron to sustain growth. P. aeruginosa utilizes different strategies to take up iron, depending on the type of infection it causes. Two siderophores are produced by this bacterium, pyoverdine and pyochelin, characterized by high and low affinities for iron respectively. P. aeruginosa is also able to utilize different siderophores from other microorganisms (siderophore piracy). It can also take up heme from hemoproteins via two different systems. Under microaerobic or anaerobic conditions, P. aeruginosa is also able to take up ferrous iron via its Feo system using redox-cycling phenazines. Depending on the type of infection, P. aeruginosa can therefore adapt by switching from one iron uptake system to another as we will describe in this short review.
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Affiliation(s)
- Pierre Cornelis
- Research Group Microbiology, Department of Bioengineering Sciences, Vrije Universiteit BrusselBrussels, Belgium
- Department Structural Biology, VIB, Vrije Universiteit BrusselBrussels, Belgium
| | - Jozef Dingemans
- Research Group Microbiology, Department of Bioengineering Sciences, Vrije Universiteit BrusselBrussels, Belgium
- Department Structural Biology, VIB, Vrije Universiteit BrusselBrussels, Belgium
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35
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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: 1.1] [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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Cyclic voltammetric, fluorescence and biological analysis of purified aeruginosin A, a secreted red pigment of Pseudomonas aeruginosa PAO1. Microbiology (Reading) 2013; 159:1736-1747. [DOI: 10.1099/mic.0.065235-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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37
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Functional features of TonB energy transduction systems of Acinetobacter baumannii. Infect Immun 2013; 81:3382-94. [PMID: 23817614 DOI: 10.1128/iai.00540-13] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Acinetobacter baumannii is an opportunistic pathogen that causes severe nosocomial infections. Strain ATCC 19606(T) utilizes the siderophore acinetobactin to acquire iron under iron-limiting conditions encountered in the host. Accordingly, the genome of this strain has three tonB genes encoding proteins for energy transduction functions needed for the active transport of nutrients, including iron, through the outer membrane. Phylogenetic analysis indicates that these tonB genes, which are present in the genomes of all sequenced A. baumannii strains, were acquired from different sources. Two of these genes occur as components of tonB-exbB-exbD operons and one as a monocistronic copy; all are actively transcribed in ATCC 19606(T). The abilities of components of these TonB systems to complement the growth defect of Escherichia coli W3110 mutants KP1344 (tonB) and RA1051 (exbBD) under iron-chelated conditions further support the roles of these TonB systems in iron acquisition. Mutagenesis analysis of ATCC 19606(T) tonB1 (subscripted numbers represent different copies of genes or proteins) and tonB2 supports this hypothesis: their inactivation results in growth defects in iron-chelated media, without affecting acinetobactin biosynthesis or the production of the acinetobactin outer membrane receptor protein BauA. In vivo assays using Galleria mellonella show that each TonB protein is involved in, but not essential for, bacterial virulence in this infection model. Furthermore, we observed that TonB2 plays a role in the ability of bacteria to bind to fibronectin and to adhere to A549 cells by uncharacterized mechanisms. Taken together, these results indicate that A. baumannii ATCC 19606(T) produces three independent TonB proteins, which appear to provide the energy-transducing functions needed for iron acquisition and cellular processes that play a role in the virulence of this pathogen.
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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: 228] [Impact Index Per Article: 17.5] [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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39
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Holden KM, Browning GF, Noormohammadi AH, Markham PF, Marenda MS. TonB is essential for virulence in avian pathogenic Escherichia coli. Comp Immunol Microbiol Infect Dis 2012; 35:129-38. [DOI: 10.1016/j.cimid.2011.12.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 12/05/2011] [Accepted: 12/06/2011] [Indexed: 11/25/2022]
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40
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Noël S, Gasser V, Pesset B, Hoegy F, Rognan D, Schalk IJ, Mislin GLA. Synthesis and biological properties of conjugates between fluoroquinolones and a N3''-functionalized pyochelin. Org Biomol Chem 2011; 9:8288-300. [PMID: 22052022 DOI: 10.1039/c1ob06250f] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Pyochelin is a siderophore common to Pseudomonas aeruginosa and several other pathogenic bacteria. A pyochelin functionalized at the N3'' position with a propyl-amine extension was previously synthesized. In the present work we proved that this analog binds FptA, the pyochelin outer membrane receptor, and transports iron(III) efficiently into bacteria. This functionalized pyochelin seemed to be a good candidate for antibiotic vectorization in the framework of a Trojan horse prodrug strategy. In this context, conjugates between pyochelin and three fluoroquinolones (norfloxacin, ciprofloxacin and N-desmethyl-ofloxacin) were synthesized with a spacer arm that was either stable or hydrolyzable in vivo. Some pyochelin-fluoroquinolone conjugates had antibacterial activities in growth inhibition experiments on several P. aeruginosa strains. However, these activities were weaker than those of the antibiotic alone. These properties appeared to be related to both the solubility and bioavailability of conjugates and to the stability of the spacer arm used.
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Affiliation(s)
- Sabrina Noël
- Team Transports Membranaires Bactériens, UMR 7242 Université de Strasbourg-CNRS, Boulevard Sébastien Brant, 67400 Illkirch, France
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Yang B, Hoegy F, Mislin GL, Mesini PJ, Schalk IJ. Terbium, a fluorescent probe for investigation of siderophore pyochelin interactions with its outer membrane transporter FptA. J Inorg Biochem 2011; 105:1293-8. [DOI: 10.1016/j.jinorgbio.2011.03.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 03/02/2011] [Accepted: 03/24/2011] [Indexed: 11/29/2022]
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Oglesby-Sherrouse AG, Vasil ML. Characterization of a heme-regulated non-coding RNA encoded by the prrF locus of Pseudomonas aeruginosa. PLoS One 2010; 5:e9930. [PMID: 20386693 PMCID: PMC2851614 DOI: 10.1371/journal.pone.0009930] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2009] [Accepted: 03/09/2010] [Indexed: 11/18/2022] Open
Abstract
Pseudomonas aeruginosa, an opportunistic pathogen, requires iron for virulence and can obtain this nutrient via the acquisition of heme, an abundant source of iron in the human body. A surplus of either iron or heme can lead to oxidative stress; thus, the Fur (ferric uptake regulator) protein blocks expression of genes required for iron and heme uptake in iron-replete environments. Fur also represses expression of two nearly identical genes encoding the 116- and 114-nucleotide (nt) long PrrF1 and PrrF2 RNAs, respectively. While other Pseudomonads encode for the two PrrF RNAs at separate genomic loci, PrrF1 and PrrF2 are encoded in tandem in all sequenced strains of P. aeruginosa. In this report we characterize a third longer transcript encoded by the prrF locus, PrrH, which is repressed by heme as well as iron. We mapped the PrrH RNA in PA01 using 5′ rapid amplification of cDNA ends (RACE) and northern analysis, demonstrating the PrrH RNA is 325 nt in length. Accordingly, transcription of PrrH initiates at the 5′ end of prrF1, proceeds through the prrF1 terminator and prrF1-prrF2 intergenic sequence (95 nt), and terminates at the 3′ end of the prrF2 gene. We also present evidence that repression of PrrH by heme causes increased expression of previously identified PrrF-regulated genes, as well as newly identified iron- and heme-activated genes. Thus, the PrrH RNA appears to impart a novel heme regulatory mechanism to P. aeruginosa.
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Affiliation(s)
- Amanda G Oglesby-Sherrouse
- Department of Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America.
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The ferrichrome uptake pathway in Pseudomonas aeruginosa involves an iron release mechanism with acylation of the siderophore and recycling of the modified desferrichrome. J Bacteriol 2010; 192:1212-20. [PMID: 20047910 DOI: 10.1128/jb.01539-09] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The uptake of iron into Pseudomonas aeruginosa is mediated by two major siderophores produced by the bacterium, pyoverdine and pyochelin. The bacterium is also able of utilize several heterologous siderophores of bacterial or fungal origin. In this work, we have investigated the iron uptake in P. aeruginosa PAO1 by the heterologous ferrichrome siderophore. (55)Fe uptake assays showed that ferrichrome is transported across the outer membrane primarily (80%) by the FiuA receptor and to a lesser extent (20%) by a secondary transporter. Moreover, we demonstrate that like in the uptake of ferripyoverdine and ferripyochelin, the energy required for both pathways of ferrichrome uptake is provided by the inner membrane protein TonB1. Desferrichrome-(55)Fe uptake in P. aeruginosa was also dependent on the expression of the permease FiuB, suggesting that this protein is the inner membrane transporter of the ferrisiderophore. A biomimetic fluorescent analogue of ferrichrome, RL1194, was used in vivo to monitor the kinetics of iron release from ferrichrome in P. aeruginosa in real time. This dissociation involves acylation of ferrichrome and its biomimetic analogue RL1194 and recycling of both modified siderophores into the extracellular medium. FiuC, an N-acetyltransferase, is certainly involved in this mechanism of iron release, since its mutation abolished desferrichrome-(55)Fe uptake. The acetylated derivative reacts with iron in the extracellular medium and is able to be taken up again by the cells. All these observations are discussed in light of the current knowledge concerning ferrichrome uptake in P. aeruginosa and in Escherichia coli.
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Molecular basis of pyoverdine siderophore recycling in Pseudomonas aeruginosa. Proc Natl Acad Sci U S A 2009; 106:20440-5. [PMID: 19906986 DOI: 10.1073/pnas.0908760106] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The siderophore pyoverdine (PVD) is a primary virulence factor of the human pathogenic bacterium Pseudomonas aeruginosa, acting as both an iron carrier and a virulence-related signal molecule. By exploring a number of P. aeruginosa candidate systems for PVD secretion, we identified a tripartite ATP-binding cassette efflux transporter, here named PvdRT-OpmQ, which translocates PVD from the periplasmic space to the extracellular milieu. We show this system to be responsible for recycling of PVD upon internalization by the cognate outer-membrane receptor FpvA, thus making PVD virtually available for new cycles of iron uptake. Our data exclude the involvement of PvdRT-OpmQ in secretion of de novo synthesized PVD, indicating alternative pathways for PVD export and recycling. The PvdRT-OpmQ transporter is one of the few secretion systems for which substrate recognition and extrusion occur in the periplasm. Homologs of the PvdRT-OpmQ system are present in genomes of all fluorescent pseudomonads sequenced so far, suggesting that PVD recycling represents a general energy-saving strategy adopted by natural Pseudomonas populations.
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Susceptibility of Pseudomonas aeruginosa to catechol-substituted cephalosporin is unrelated to the pyochelin–Fe transporter FptA. Amino Acids 2009; 38:1627-9. [DOI: 10.1007/s00726-009-0353-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 09/12/2009] [Indexed: 10/20/2022]
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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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Abstract
Serratia marcescens possesses two functional TonB paralogs, TonB(Sm) and HasB, for energizing TonB-dependent transport receptors (TBDT). Previous work had shown that HasB is specific to heme uptake in the natural host and in Escherichia coli expressing the S. marcescens TBDT receptor HasR, whereas the S. marcescens TonB and E. coli TonB proteins function equally well with various TBDT receptors for heme and siderophores. This has raised the question of the target of this specificity. HasB could be specific either to heme TBDT receptors or only to HasR. To resolve this question, we have cloned in E. coli another S. marcescens heme receptor, HemR, and we show here that this receptor is TonB dependent and does not work with HasB. This demonstrates that HasB is not dedicated to heme TBDT receptors but rather forms a specific pair with HasR. This is the first reported case of a specific TonB protein working with only one TBDT receptor in one given species. We discuss the occurrence, possible molecular mechanisms, and selective advantages of such dedicated TonB paralogs.
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Abbas A, Adams C, Scully N, Glennon J, O'Gara F. A role for TonB1 in biofilm formation and quorum sensing inPseudomonas aeruginosa. FEMS Microbiol Lett 2007; 274:269-78. [PMID: 17623027 DOI: 10.1111/j.1574-6968.2007.00845.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
This study revealed that a Pseudomonas aeruginosa tonB1 mutant was unable to produce a mature biofilm and showed reduced swarming and twitching motilities compared with the parent strain. The tonB1 mutant was also found to produce significantly lower cell-free and cell-associated levels of the quorum sensing (QS) signal molecule 3-oxo-C12-AHL. Altered biofilm and motility phenotypes were restored to wildtype with the addition of exogenous N-acylhomoserine lactones. These functions were independent of the role of TonB1 in iron uptake. This is the first time that a link has been established between TonB1 activity and QS.
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Affiliation(s)
- Abdelhamid Abbas
- Microbiology Department, National University of Ireland, Cork, Ireland
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Wu Q, Jiang Z, Liao J, Chen Z, Li H, Mei M, Zhang LH. Identification of genetic markers to distinguish the virulent and avirulent subspecies of Pantoea stewartii by comparative proteomics and genetic analysis. Appl Microbiol Biotechnol 2007; 74:186-93. [PMID: 17086414 DOI: 10.1007/s00253-006-0656-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Revised: 09/01/2006] [Accepted: 09/04/2006] [Indexed: 11/30/2022]
Abstract
Pantoea stewartii subsp. stewartii (Pnss), the causal agent of Stewart's bacterial wilt and leaf blight of maize and sweet corn, is one of the quarantine pathogens in many countries and regions. In contrast, P. stewartii subsp. indologenes (Pnsi), the closely related subspecies of Pnss, is avirulent on these plants. In this study, the protein expression profiles of these two subspecies were compared using two-dimensional gel electrophoresis analysis. Twenty-one unique protein spots consistently detected in Pnss but not in Pnsi were analyzed by mass spectrometry. Some of these Pnss-specific proteins are known to be essential for virulence and survival in host, such as FoxR and HrcJ, which are the key components of iron uptake and Type III secretion systems, respectively. For further genetic analysis, six Pnss-specific proteins were characterized by peptide sequencing. Southern and Northern blot analyses revealed that the differences in protein expression profiles of the two subspecies were either due to the discrepancy at genome level or because of the variations in transcriptional expression. The results provide novel genetic markers to distinguish the two closely related subspecies and may also serve as useful clues for investigation of the genetic basis accounting for their sharp difference in virulence.
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Affiliation(s)
- Qiong Wu
- Institute of Molecular and Cell Biology, 61 Biopolis Drive, Singapore 138673, Singapore
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Adams H, Zeder-Lutz G, Schalk I, Pattus F, Celia H. Interaction of TonB with the outer membrane receptor FpvA of Pseudomonas aeruginosa. J Bacteriol 2006; 188:5752-61. [PMID: 16885443 PMCID: PMC1540090 DOI: 10.1128/jb.00435-06] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pyoverdine-mediated iron uptake by the FpvA receptor in the outer membrane of Pseudomonas aeruginosa is dependent on the inner membrane protein TonB1. This energy transducer couples the proton-electrochemical potential of the inner membrane to the transport event. To shed more light upon this process, a recombinant TonB1 protein lacking the N-terminal inner membrane anchor (TonB(pp)) was constructed. This protein was, after expression in Escherichia coli, purified from the soluble fraction of lysed cells by means of an N-terminal hexahistidine or glutathione S-transferase (GST) tag. Purified GST-TonB(pp) was able to capture detergent-solubilized FpvA, regardless of the presence of pyoverdine or pyoverdine-Fe. Targeting of the TonB1 fragment to the periplasm of P. aeruginosa inhibited the transport of ferric pyoverdine by FpvA in vivo, indicating an interference with endogenous TonB1, presumably caused by competition for binding sites at the transporter or by formation of nonfunctional TonB heterodimers. Surface plasmon resonance experiments demonstrated that the FpvA-TonB(pp) interactions have apparent affinities in the micromolar range. The binding of pyoverdine or ferric pyoverdine to FpvA did not modulate this affinity. Apparently, the presence of either iron or pyoverdine is not essential for the formation of the FpvA-TonB complex in vitro.
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Affiliation(s)
- Hendrik Adams
- ESBS UMR7175, Récepteurs et Protéines Membranaires, Rue Sebastien Brant, BP 10413 F-67412 Illkirch Cedex, France
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