1
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Bonvin E, Personne H, Paschoud T, Reusser J, Gan BH, Luscher A, Köhler T, van Delden C, Reymond JL. Antimicrobial Peptide-Peptoid Hybrids with and without Membrane Disruption. ACS Infect Dis 2023; 9:2593-2606. [PMID: 38062792 PMCID: PMC10714400 DOI: 10.1021/acsinfecdis.3c00421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 11/06/2023] [Accepted: 11/06/2023] [Indexed: 12/18/2023]
Abstract
Among synthetic analogues of antimicrobial peptides (AMPs) under investigation to address antimicrobial resistance, peptoids (N-alkylated oligoglycines) have been reported to act both by membrane disruption and on intracellular targets. Here we gradually introduced peptoid units into the membrane-disruptive undecapeptide KKLLKLLKLLL to test a possible transition toward intracellular targeting. We found that selected hybrids containing up to five peptoid units retained the parent AMP's α-helical folding, membrane disruption, and antimicrobial effects against Gram-negative bacteria including multidrug-resistant (MDR) strains of Pseudomonas aeruginosa and Klebsiella pneumoniae while showing reduced hemolysis and cell toxicities. Furthermore, some hybrids containing as few as three peptoid units as well as the full peptoid lost folding, membrane disruption, hemolysis, and cytotoxicity but displayed strong antibacterial activity under dilute medium conditions typical for proline-rich antimicrobial peptides (PrAMPs), pointing to intracellular targeting. These findings parallel previous reports that partially helical amphiphilic peptoids are privileged oligomers for antibiotic development.
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Affiliation(s)
- Etienne Bonvin
- Department
of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Hippolyte Personne
- Department
of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Thierry Paschoud
- Department
of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Jérémie Reusser
- Department
of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Bee-Ha Gan
- Department
of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Alexandre Luscher
- Department
of Microbiology and Molecular Medicine, University of Geneva, CH-1211 Geneva, Switzerland
- Service of
Infectious Diseases, University Hospital
of Geneva, CH-1211 Geneva, Switzerland
| | - Thilo Köhler
- Department
of Microbiology and Molecular Medicine, University of Geneva, CH-1211 Geneva, Switzerland
- Service of
Infectious Diseases, University Hospital
of Geneva, CH-1211 Geneva, Switzerland
| | - Christian van Delden
- Department
of Microbiology and Molecular Medicine, University of Geneva, CH-1211 Geneva, Switzerland
- Service of
Infectious Diseases, University Hospital
of Geneva, CH-1211 Geneva, Switzerland
| | - Jean-Louis Reymond
- Department
of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
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2
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Huber R, Marcourt L, Héritier M, Luscher A, Guebey L, Schnee S, Michellod E, Guerrier S, Wolfender JL, Scapozza L, Köhler T, Gindro K, Queiroz EF. Generation of potent antibacterial compounds through enzymatic and chemical modifications of the trans-δ-viniferin scaffold. Sci Rep 2023; 13:15986. [PMID: 37749179 PMCID: PMC10520035 DOI: 10.1038/s41598-023-43000-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 09/18/2023] [Indexed: 09/27/2023] Open
Abstract
Stilbene dimers are well-known for their diverse biological activities. In particular, previous studies have demonstrated the high antibacterial potential of a series of trans-δ-viniferin-related compounds against gram-positive bacteria such as Staphylococcus aureus. The trans-δ-viniferin scaffold has multiple chemical functions and can therefore be modified in various ways to generate derivatives. Here we report the synthesis of 40 derivatives obtained by light isomerization, O-methylation, halogenation and dimerization of other stilbene monomers. The antibacterial activities of all generated trans-δ-viniferin derivatives were evaluated against S. aureus and information on their structure-activity relationships (SAR) was obtained using a linear regression model. Our results show how several parameters, such as the O-methylation pattern and the presence of halogen atoms at specific positions, can determine the antibacterial activity. Taken together, these results can serve as a starting point for further SAR investigations.
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Affiliation(s)
- Robin Huber
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Laurence Marcourt
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Margaux Héritier
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Alexandre Luscher
- Department of Microbiology and Molecular Medicine, University of Geneva, Rue Michel-Servet 1, 1211, Genève 4, Switzerland
| | - Laurie Guebey
- Department of Microbiology and Molecular Medicine, University of Geneva, Rue Michel-Servet 1, 1211, Genève 4, Switzerland
| | - Sylvain Schnee
- Agroscope, Plant Protection Research Division, Mycology Group, Route de Duillier 50, P.O. Box 1012, 1260, Nyon, Switzerland
| | - Emilie Michellod
- Agroscope, Plant Protection Research Division, Mycology Group, Route de Duillier 50, P.O. Box 1012, 1260, Nyon, Switzerland
| | - Stéphane Guerrier
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
- Geneva School of Economics and Management, University of Geneva, 1205, Geneva, Switzerland
| | - Jean-Luc Wolfender
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Leonardo Scapozza
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Thilo Köhler
- Department of Microbiology and Molecular Medicine, University of Geneva, Rue Michel-Servet 1, 1211, Genève 4, Switzerland
| | - Katia Gindro
- Agroscope, Plant Protection Research Division, Mycology Group, Route de Duillier 50, P.O. Box 1012, 1260, Nyon, Switzerland.
| | - Emerson Ferreira Queiroz
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland.
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland.
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3
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Köhler T, Luscher A, Falconnet L, Resch G, McBride R, Mai QA, Simonin JL, Chanson M, Maco B, Galiotto R, Riat A, Civic N, Docquier M, McCallin S, Chan B, van Delden C. Author Correction: Personalized aerosolised bacteriophage treatment of a chronic lung infection due to multidrug-resistant Pseudomonas aeruginosa. Nat Commun 2023; 14:4443. [PMID: 37488101 PMCID: PMC10366089 DOI: 10.1038/s41467-023-40202-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/26/2023] Open
Affiliation(s)
- Thilo Köhler
- Service of Infectious Diseases, Geneva University Hospitals, Geneva, Switzerland.
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland.
| | - Alexandre Luscher
- Service of Infectious Diseases, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Léna Falconnet
- Service of Infectious Diseases, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Grégory Resch
- Center for Research and Innovation in Clinical Pharmaceutical Sciences (CRISP), Lausanne University Hospital (CHUV), Lausanne, Switzerland
| | | | | | - Juliette L Simonin
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Marc Chanson
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Bohumil Maco
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Raphaël Galiotto
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Arnaud Riat
- Diagnostic Bacteriology Laboratory, Geneva University Hospitals, Geneva, Switzerland
| | - Natacha Civic
- iGE3 Genomics Platform, University of Geneva, Geneva, Switzerland
| | - Mylène Docquier
- iGE3 Genomics Platform, University of Geneva, Geneva, Switzerland
| | - Shawna McCallin
- Department of Neuro-Urology Balgrist Hospital, Zurich, Switzerland
| | | | - Christian van Delden
- Service of Infectious Diseases, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
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4
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Köhler T, Luscher A, Falconnet L, Resch G, McBride R, Mai QA, Simonin JL, Chanson M, Maco B, Galiotto R, Riat A, McCallin S, Chan B, van Delden C. Personalized aerosolised bacteriophage treatment of a chronic lung infection due to multidrug-resistant Pseudomonas aeruginosa. Nat Commun 2023; 14:3629. [PMID: 37369702 PMCID: PMC10300124 DOI: 10.1038/s41467-023-39370-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 06/09/2023] [Indexed: 06/29/2023] Open
Abstract
Bacteriophage therapy has been suggested as an alternative or complementary strategy for the treatment of multidrug resistant (MDR) bacterial infections. Here, we report the favourable clinical evolution of a 41-year-old male patient with a Kartagener syndrome complicated by a life-threatening chronic MDR Pseudomonas aeruginosa infection, who is treated successfully with iterative aerosolized phage treatments specifically directed against the patient's isolate. We follow the longitudinal evolution of both phage and bacterial loads during and after phage administration in respiratory samples. Phage titres in consecutive sputum samples indicate in patient phage replication. Phenotypic analysis and whole genome sequencing of sequential bacterial isolates reveals a clonal, but phenotypically diverse population of hypermutator strains. The MDR phenotype in the collected isolates is multifactorial and mainly due to spontaneous chromosomal mutations. All isolates recovered after phage treatment remain phage susceptible. These results demonstrate that clinically significant improvement is achievable by personalised phage therapy even in the absence of complete eradication of P. aeruginosa lung colonization.
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Affiliation(s)
- Thilo Köhler
- Service of Infectious Diseases, Geneva University Hospitals, Geneva, Switzerland.
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland.
| | - Alexandre Luscher
- Service of Infectious Diseases, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Léna Falconnet
- Service of Infectious Diseases, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Grégory Resch
- Center for Research and Innovation in Clinical Pharmaceutical Sciences (CRISP), Lausanne University Hospital (CHUV), Lausanne, Switzerland
| | | | | | - Juliette L Simonin
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Marc Chanson
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Bohumil Maco
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Raphaël Galiotto
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Arnaud Riat
- Diagnostic Bacteriology Laboratory, Geneva University Hospitals, Geneva, Switzerland
| | - Shawna McCallin
- Department of Neuro-Urology Balgrist Hospital, Zurich, Switzerland
| | | | - Christian van Delden
- Service of Infectious Diseases, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
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5
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Badaoui M, Sobolewski C, Luscher A, Bacchetta M, Köhler T, van Delden C, Foti M, Chanson M. Targeting HuR-Vav3 mRNA interaction prevents Pseudomonas aeruginosa adhesion to the cystic fibrosis airway epithelium. JCI Insight 2023; 8:161961. [PMID: 36602863 PMCID: PMC9977432 DOI: 10.1172/jci.insight.161961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 12/21/2022] [Indexed: 01/06/2023] Open
Abstract
Cystic fibrosis (CF) is characterized by chronic bacterial infections leading to progressive bronchiectasis and respiratory failure. Pseudomonas aeruginosa (Pa) is the predominant opportunistic pathogen infecting the CF airways. The guanine nucleotide exchange factor Vav3 plays a critical role in Pa adhesion to the CF airways by inducing luminal fibronectin deposition that favors bacteria trapping. Here we report that Vav3 overexpression in CF is caused by upregulation of the mRNA-stabilizing protein HuR. We found that HuR accumulates in the cytoplasm of CF airway epithelial cells and that it binds to and stabilizes Vav3 mRNA. Interestingly, disruption of the HuR-Vav3 mRNA interaction improved the CF epithelial integrity, inhibited the formation of the fibronectin-made bacterial docking platforms, and prevented Pa adhesion to the CF airway epithelium. These findings indicate that targeting HuR represents a promising antiadhesive approach in CF that can prevent initial stages of Pa infection in a context of emergence of multidrug-resistant pathogens.
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Affiliation(s)
| | | | - Alexandre Luscher
- Department of Microbiology & Molecular Medicine, Faculty of Medicine, University of Geneva, Switzerland
| | | | - Thilo Köhler
- Department of Microbiology & Molecular Medicine, Faculty of Medicine, University of Geneva, Switzerland
| | - Christian van Delden
- Department of Microbiology & Molecular Medicine, Faculty of Medicine, University of Geneva, Switzerland
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6
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Huber R, Marcourt L, Quiros-Guerrero LM, Luscher A, Schnee S, Michellod E, Ducret V, Kohler T, Perron K, Wolfender JL, Gindro K, Ferreira Queiroz E. Chiral Separation of Stilbene Dimers Generated by Biotransformation for Absolute Configuration Determination and Antibacterial Evaluation. Front Chem 2022; 10:912396. [PMID: 35711965 PMCID: PMC9194554 DOI: 10.3389/fchem.2022.912396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 05/06/2022] [Indexed: 11/13/2022] Open
Abstract
A series of complex stilbene dimers have been generated through biotransformation of resveratrol, pterostilbene, and the mixture of both using the enzymatic secretome of Botrytis cinerea Pers. The process starts with achiral molecules and results in the generation of complex molecules with multiple chiral carbons. So far, we have been studying these compounds in the form of enantiomeric mixtures. In the present study, we isolated the enantiomers to determine their absolute configuration and assess if the stereochemistry could impact their biological properties. Eight compounds were selected for this study, corresponding to the main scaffolds generated (pallidol, leachianol, restrytisol and acyclic dimers) and the most active compounds (trans-δ-viniferin derivatives) against a methicillin-resistant strain of Staphylococcus aureus (MRSA). To isolate these enantiomers and determine their absolute configuration, a chiral HPLC-PDA analysis was performed. The analysis was achieved on a high-performance liquid chromatography system equipped with a chiral column. For each compound, the corresponding enantiomeric pair was obtained with high purity. The absolute configuration of each enantiomer was determined by comparison of experimental and calculated electronic circular dichroism (ECD). The antibacterial activities of the four trans-δ-viniferin derivatives against two S. aureus strains were evaluated.
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Affiliation(s)
- Robin Huber
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Laurence Marcourt
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Luis-Manuel Quiros-Guerrero
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Alexandre Luscher
- Departement of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Sylvain Schnee
- Mycology Group, Plant Protection Research Division, Agroscope, Nyon, Switzerland
| | - Emilie Michellod
- Mycology Group, Plant Protection Research Division, Agroscope, Nyon, Switzerland
| | - Verena Ducret
- Microbiological Analysis Platform, Microbiology Unit, Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland
| | - Thilo Kohler
- Departement of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Karl Perron
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Microbiological Analysis Platform, Microbiology Unit, Department of Botany and Plant Biology, University of Geneva, Geneva, Switzerland
| | - Jean-Luc Wolfender
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
| | - Katia Gindro
- Mycology Group, Plant Protection Research Division, Agroscope, Nyon, Switzerland
- *Correspondence: Katia Gindro, ; Emerson Ferreira Queiroz,
| | - Emerson Ferreira Queiroz
- School of Pharmaceutical Sciences, University of Geneva, CMU, Geneva, Switzerland
- Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, CMU, Geneva, Switzerland
- *Correspondence: Katia Gindro, ; Emerson Ferreira Queiroz,
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7
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Simonin JL, Luscher A, Losa D, Badaoui M, van Delden C, Köhler T, Chanson M. Surface Hydration Protects Cystic Fibrosis Airways from Infection by Restoring Junctional Networks. Cells 2022; 11:cells11091587. [PMID: 35563895 PMCID: PMC9105190 DOI: 10.3390/cells11091587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 04/20/2022] [Accepted: 05/06/2022] [Indexed: 02/01/2023] Open
Abstract
Defective hydration of airway surface mucosa is associated with recurrent lung infection in cystic fibrosis (CF), a disease caused by CF transmembrane conductance regulator (CFTR) gene mutations. Whether the composition and/or presence of an airway surface liquid (ASL) is sufficient to prevent infection remains unclear. The susceptibility to infection of polarized wild type and CFTR knockdown (CFTR-KD) airway epithelial cells was determined in the presence or absence of a healthy ASL or physiological saline. CFTR-KD epithelia exhibited strong ASL volume reduction, enhanced susceptibility to infection, and reduced junctional integrity. Interestingly, the presence of an apical physiological saline alleviated disruption of the airway epithelial barrier by stimulating essential junctional protein expression. Thus, rehydrated CFTR-KD cells were protected from infection despite normally intense bacterial growth. This study indicates that an epithelial integrity gatekeeper is modulated by the presence of an apical liquid volume, irrespective of the liquid's composition and of expression of a functional CFTR.
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Affiliation(s)
- Juliette L. Simonin
- Department of Cell Physiology & Metabolism, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; (J.L.S.); (D.L.); (M.B.)
| | - Alexandre Luscher
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; (A.L.); (C.v.D.); (T.K.)
| | - Davide Losa
- Department of Cell Physiology & Metabolism, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; (J.L.S.); (D.L.); (M.B.)
| | - Mehdi Badaoui
- Department of Cell Physiology & Metabolism, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; (J.L.S.); (D.L.); (M.B.)
| | - Christian van Delden
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; (A.L.); (C.v.D.); (T.K.)
- Department of Medicine Specialties, Division of Infectious Diseases, Geneva University Hospitals, 1211 Geneva, Switzerland
| | - Thilo Köhler
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; (A.L.); (C.v.D.); (T.K.)
| | - Marc Chanson
- Department of Cell Physiology & Metabolism, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland; (J.L.S.); (D.L.); (M.B.)
- Correspondence: ; Tel./Fax: +41-22-37-95-206
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8
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Jafari P, Luscher A, Siriwardena T, Michetti M, Que YA, Rahme LG, Reymond JL, Raffoul W, Van Delden C, Applegate LA, Köhler T. Antimicrobial Peptide Dendrimers and Quorum-Sensing Inhibitors in Formulating Next-Generation Anti-Infection Cell Therapy Dressings for Burns. Molecules 2021; 26:molecules26133839. [PMID: 34202446 PMCID: PMC8270311 DOI: 10.3390/molecules26133839] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 06/02/2021] [Accepted: 06/12/2021] [Indexed: 12/21/2022] Open
Abstract
Multidrug resistance infections are the main cause of failure in the pro-regenerative cell-mediated therapy of burn wounds. The collagen-based matrices for delivery of cells could be potential substrates to support bacterial growth and subsequent lysis of the collagen leading to a cell therapy loss. In this article, we report the development of a new generation of cell therapy formulations with the capacity to resist infections through the bactericidal effect of antimicrobial peptide dendrimers and the anti-virulence effect of anti-quorum sensing MvfR (PqsR) system compounds, which are incorporated into their formulation. Anti-quorum sensing compounds limit the pathogenicity and antibiotic tolerance of pathogenic bacteria involved in the burn wound infections, by inhibiting their virulence pathways. For the first time, we report a biological cell therapy dressing incorporating live progenitor cells, antimicrobial peptide dendrimers, and anti-MvfR compounds, which exhibit bactericidal and anti-virulence properties without compromising the viability of the progenitor cells.
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Affiliation(s)
- Paris Jafari
- Regenerative Therapy Unit (UTR), Department of Musculoskeletal Medicine DAL, Lausanne University Hospital, 1011 Lausanne, Switzerland; (P.J.); (M.M.)
- Service of Plastic, Reconstructive & Hand Surgery, Lausanne University Hospital, 1011 Lausanne, Switzerland;
- Department of Pharmaceutics and Pharmaceutical Chemistry, College of Pharmacy, University of Utah, Salt Lake City, UT 84112, USA
| | - Alexandre Luscher
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva, Switzerland; (A.L.); (C.V.D.)
| | - Thissa Siriwardena
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, 3012 Bern, Switzerland; (T.S.); (J.-L.R.)
| | - Murielle Michetti
- Regenerative Therapy Unit (UTR), Department of Musculoskeletal Medicine DAL, Lausanne University Hospital, 1011 Lausanne, Switzerland; (P.J.); (M.M.)
- Service of Plastic, Reconstructive & Hand Surgery, Lausanne University Hospital, 1011 Lausanne, Switzerland;
| | - Yok-Ai Que
- Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, 3010 Bern, Switzerland;
| | - Laurence G. Rahme
- Department of Surgery, Harvard Medical School and Massachusetts General Hospital, Boston, MA 02114, USA;
- Shriners Hospitals for Children Boston, Boston, MA 02114, USA
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Jean-Louis Reymond
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, 3012 Bern, Switzerland; (T.S.); (J.-L.R.)
| | - Wassim Raffoul
- Service of Plastic, Reconstructive & Hand Surgery, Lausanne University Hospital, 1011 Lausanne, Switzerland;
| | - Christian Van Delden
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva, Switzerland; (A.L.); (C.V.D.)
- Division on Infectious Disease and Transplantation, University Hospital of Geneva, 1205 Geneva, Switzerland
| | - Lee Ann Applegate
- Regenerative Therapy Unit (UTR), Department of Musculoskeletal Medicine DAL, Lausanne University Hospital, 1011 Lausanne, Switzerland; (P.J.); (M.M.)
- Service of Plastic, Reconstructive & Hand Surgery, Lausanne University Hospital, 1011 Lausanne, Switzerland;
- Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Winterthurerstrasse 260, 8057 Zurich, Switzerland
- Oxford OSCAR Suzhou Center, Oxford University, Suzhou 215028, China
- Correspondence: (L.A.A.); (T.K.); Tel.: +41-21-314-3510 (L.A.A.); +41-22-379-5571 (T.K.)
| | - Thilo Köhler
- Department of Microbiology and Molecular Medicine, University of Geneva, 1211 Geneva, Switzerland; (A.L.); (C.V.D.)
- Division on Infectious Disease and Transplantation, University Hospital of Geneva, 1205 Geneva, Switzerland
- Correspondence: (L.A.A.); (T.K.); Tel.: +41-21-314-3510 (L.A.A.); +41-22-379-5571 (T.K.)
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9
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Luscher A, Simonin J, Falconnet L, Valot B, Hocquet D, Chanson M, Resch G, Köhler T, van Delden C. Combined Bacteriophage and Antibiotic Treatment Prevents Pseudomonas aeruginosa Infection of Wild Type and cftr- Epithelial Cells. Front Microbiol 2020; 11:1947. [PMID: 32983005 PMCID: PMC7479825 DOI: 10.3389/fmicb.2020.01947] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 07/23/2020] [Indexed: 12/21/2022] Open
Abstract
With the increase of infections due to multidrug resistant bacterial pathogens and the shortage of antimicrobial molecules with novel targets, interest in bacteriophages as a therapeutic option has regained much attraction. Before the launch of future clinical trials, in vitro studies are required to better evaluate the efficacies and potential pitfalls of such therapies. Here we studied in an ex vivo human airway epithelial cell line model the efficacy of phage and ciprofloxacin alone and in combination to treat infection by Pseudomonas aeruginosa. The Calu-3 cell line and the isogenic CFTR knock down cell line (cftr-) infected apically with P. aeruginosa strain PAO1 showed a progressive reduction in transepithelial resistance during 24 h. Administration at 6 h p.i. of single phage, phage cocktails or ciprofloxacin alone prevented epithelial layer destruction at 24 h p.i. Bacterial regrowth, due to phage resistant mutants harboring mutations in LPS synthesis genes, occurred thereafter both in vitro and ex vivo. However, co-administration of two phages combined with ciprofloxacin efficiently prevented PAO1 regrowth and maintained epithelial cell integrity at 72 p.i. The phage/ciprofloxacin treatment did not induce an inflammatory response in the tested cell lines as determined by nanoString® gene expression analysis. We conclude that combination of phage and ciprofloxacin efficiently protects wild type and cftr- epithelial cells from infection by P. aeruginosa and emergence of phage resistant mutants without inducing an inflammatory response. Hence, phage-antibiotic combination should be a safe and promising anti-Pseudomonas therapy for future clinical trials potentially including cystic fibrosis patients.
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Affiliation(s)
- Alexandre Luscher
- Transplant Infectious Diseases Unit, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Juliette Simonin
- Department of Pediatrics, Gynecology and Obstetrics, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Léna Falconnet
- Transplant Infectious Diseases Unit, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Benoît Valot
- UMR CNRS 6249 Chrono-Environnement, University of Franche-Comté-Bourgogne, Besançon, France
- Bioinformatique et Big Data au Service de la Santé, UFR Santé, Université de Bourgogne Franche-Comté, Besançon, France
| | - Didier Hocquet
- UMR CNRS 6249 Chrono-Environnement, University of Franche-Comté-Bourgogne, Besançon, France
- Bioinformatique et Big Data au Service de la Santé, UFR Santé, Université de Bourgogne Franche-Comté, Besançon, France
- Department of Infection Control, University Hospital of Besançon, Besançon, France
| | - Marc Chanson
- Department of Pediatrics, Gynecology and Obstetrics, Geneva University Hospitals and University of Geneva, Geneva, Switzerland
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Grégory Resch
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
| | - Thilo Köhler
- Transplant Infectious Diseases Unit, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Christian van Delden
- Transplant Infectious Diseases Unit, Geneva University Hospitals, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
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10
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Luscher A, Fröhlich F, Barisch C, Littlewood C, Metcalfe J, Leuba F, Palma A, Pirruccello M, Cesareni G, Stagi M, Walther TC, Soldati T, De Camilli P, Swan LE. Lowe syndrome-linked endocytic adaptors direct membrane cycling kinetics with OCRL in Dictyostelium discoideum. Mol Biol Cell 2019; 30:2268-2282. [PMID: 31216233 PMCID: PMC6743453 DOI: 10.1091/mbc.e18-08-0510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Mutations of the inositol 5-phosphatase OCRL cause Lowe syndrome (LS), characterized by congenital cataract, low IQ, and defective kidney proximal tubule resorption. A key subset of LS mutants abolishes OCRL’s interactions with endocytic adaptors containing F&H peptide motifs. Converging unbiased methods examining human peptides and the unicellular phagocytic organism Dictyostelium discoideum reveal that, like OCRL, the Dictyostelium OCRL orthologue Dd5P4 binds two proteins closely related to the F&H proteins APPL1 and Ses1/2 (also referred to as IPIP27A/B). In addition, a novel conserved F&H interactor was identified, GxcU (in Dictyostelium) and the Cdc42-GEF FGD1-related F-actin binding protein (Frabin) (in human cells). Examining these proteins in D. discoideum, we find that, like OCRL, Dd5P4 acts at well-conserved and physically distinct endocytic stations. Dd5P4 functions in coordination with F&H proteins to control membrane deformation at multiple stages of endocytosis and suppresses GxcU-mediated activity during fluid-phase micropinocytosis. We also reveal that OCRL/Dd5P4 acts at the contractile vacuole, an exocytic osmoregulatory organelle. We propose F&H peptide-containing proteins may be key modifiers of LS phenotypes.
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Affiliation(s)
- Alexandre Luscher
- Department of Biochemistry, Faculty of Science, University of Geneva, 1211 Geneva-4, Switzerland
| | - Florian Fröhlich
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510.,Department of Genetics and Complex Diseases, Harvard School of Public Health, and Department of Cell Biology, Harvard Medical School, Howard Hughes Medical Institute, Boston, MA 02115
| | - Caroline Barisch
- Department of Biochemistry, Faculty of Science, University of Geneva, 1211 Geneva-4, Switzerland
| | - Clare Littlewood
- Department of Cellular and Molecular Physiology, University of Liverpool, L69 3BX Liverpool, United Kingdom
| | - Joe Metcalfe
- Department of Cellular and Molecular Physiology, University of Liverpool, L69 3BX Liverpool, United Kingdom
| | - Florence Leuba
- Department of Biochemistry, Faculty of Science, University of Geneva, 1211 Geneva-4, Switzerland
| | - Anita Palma
- Department of Biology, University of Rome, 00133 Rome, Italy
| | - Michelle Pirruccello
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510.,Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510
| | - Gianni Cesareni
- Department of Biology, University of Rome, 00133 Rome, Italy
| | - Massimiliano Stagi
- Department of Cellular and Molecular Physiology, University of Liverpool, L69 3BX Liverpool, United Kingdom
| | - Tobias C Walther
- Department of Genetics and Complex Diseases, Harvard School of Public Health, and Department of Cell Biology, Harvard Medical School, Howard Hughes Medical Institute, Boston, MA 02115
| | - Thierry Soldati
- Department of Biochemistry, Faculty of Science, University of Geneva, 1211 Geneva-4, Switzerland
| | - Pietro De Camilli
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510.,Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510.,Department of Neuroscience and Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06510
| | - Laura E Swan
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510.,Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT 06510.,Department of Cellular and Molecular Physiology, University of Liverpool, L69 3BX Liverpool, United Kingdom
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11
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Tognon M, Köhler T, Luscher A, van Delden C. Transcriptional profiling of Pseudomonas aeruginosa and Staphylococcus aureus during in vitro co-culture. BMC Genomics 2019; 20:30. [PMID: 30630428 PMCID: PMC6327441 DOI: 10.1186/s12864-018-5398-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 12/19/2018] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND Co-colonization by Pseudomonas aeruginosa and Staphylococcus aureus is frequent in cystic fibrosis patients. Polymicrobial infections involve both detrimental and beneficial interactions between different bacterial species. Such interactions potentially indirectly impact the human host through virulence, antibiosis and immunomodulation. RESULTS Here we explored the responses triggered by the encounter of these two pathogens to identify early processes that are important for survival when facing a potential competitor. Transcriptional profiles of both bacteria were obtained after 3 h co-culture and compared to the respective mono-culture using RNAseq. Global responses in both bacteria included competition for nitrogen sources, amino acids and increased tRNA levels. Both organisms also induced lysogenic mechanisms related to prophage induction (S. aureus) and R- and F- pyocin synthesis (P. aeruginosa), possibly as a response to stress resulting from nutrient limitation or cell damage. Specific responses in S. aureus included increased expression of de novo and salvation pathways for purine and pyrimidine synthesis, a switch to glucose fermentation, and decreased expression of major virulence factors and global regulators. CONCLUSIONS Taken together, transcriptomic data indicate that early responses between P. aeruginosa and S. aureus involve competition for resources and metabolic adaptations, rather than the expression of bacteria- or host-directed virulence factors.
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Affiliation(s)
- Mikaël Tognon
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Geneva, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, 1, rue Michel Servet, CH-1211, Genève 4, Switzerland
| | - Thilo Köhler
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Geneva, Switzerland. .,Department of Microbiology and Molecular Medicine, University of Geneva, 1, rue Michel Servet, CH-1211, Genève 4, Switzerland.
| | - Alexandre Luscher
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Geneva, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, 1, rue Michel Servet, CH-1211, Genève 4, Switzerland
| | - Christian van Delden
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Geneva, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, 1, rue Michel Servet, CH-1211, Genève 4, Switzerland
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12
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Luscher A, Moynié L, Auguste PS, Bumann D, Mazza L, Pletzer D, Naismith JH, Köhler T. TonB-Dependent Receptor Repertoire of Pseudomonas aeruginosa for Uptake of Siderophore-Drug Conjugates. Antimicrob Agents Chemother 2018; 62:e00097-18. [PMID: 29555629 PMCID: PMC5971595 DOI: 10.1128/aac.00097-18] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/12/2018] [Indexed: 12/22/2022] Open
Abstract
The conjugation of siderophores to antimicrobial molecules is an attractive strategy to overcome the low outer membrane permeability of Gram-negative bacteria. In this Trojan horse approach, the transport of drug conjugates is redirected via TonB-dependent receptors (TBDR), which are involved in the uptake of essential nutrients, including iron. Previous reports have demonstrated the involvement of the TBDRs PiuA and PirA from Pseudomonas aeruginosa and their orthologues in Acinetobacter baumannii in the uptake of siderophore-beta-lactam drug conjugates. By in silico screening, we further identified a PiuA orthologue, termed PiuD, present in clinical isolates, including strain LESB58. The piuD gene in LESB58 is located at the same genetic locus as piuA in strain PAO1. PiuD has a similar crystal structure as PiuA and is involved in the transport of the siderophore-drug conjugates BAL30072, MC-1, and cefiderocol in strain LESB58. To screen for additional siderophore-drug uptake systems, we overexpressed 28 of the 34 TBDRs of strain PAO1 and identified PfuA, OptE, OptJ, and the pyochelin receptor FptA as novel TBDRs conferring increased susceptibility to siderophore-drug conjugates. The existence of a TBDR repertoire in P. aeruginosa able to transport siderophore-drug molecules potentially decreases the likelihood of resistance emergence during therapy.
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Affiliation(s)
- Alexandre Luscher
- Service of Infectious Diseases, University Hospital Geneva, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | - Lucile Moynié
- School of Chemistry and Biomedical Sciences Research Complex, University of St Andrews, Fife, Scotland, United Kingdom
| | | | - Dirk Bumann
- Biozentrum, University of Basel, Basel, Switzerland
| | - Lena Mazza
- Service of Infectious Diseases, University Hospital Geneva, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
| | | | - James H Naismith
- School of Chemistry and Biomedical Sciences Research Complex, University of St Andrews, Fife, Scotland, United Kingdom
| | - Thilo Köhler
- Service of Infectious Diseases, University Hospital Geneva, Geneva, Switzerland
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
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13
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Tognon M, Köhler T, Gdaniec BG, Hao Y, Lam JS, Beaume M, Luscher A, Buckling A, van Delden C. Co-evolution with Staphylococcus aureus leads to lipopolysaccharide alterations in Pseudomonas aeruginosa. ISME J 2017; 11:2233-2243. [PMID: 28548661 DOI: 10.1038/ismej.2017.83] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Revised: 03/24/2017] [Accepted: 04/19/2017] [Indexed: 02/07/2023]
Abstract
Detrimental and beneficial interactions between co-colonizing bacteria may influence the course of infections. In cystic fibrosis (CF) airways, Staphylococcus aureus prevails in childhood, whereas Pseudomonas aeruginosa progressively predominates thereafter. While a range of interactions has been identified, it is unclear if these represent specific adaptations or correlated responses to other aspects of the environment. Here, we investigate how P. aeruginosa adapts to S. aureus by evolving P. aeruginosa in the presence and absence of S. aureus. P. aeruginosa populations that evolved for 150 generations were sequenced and compared to the ancestor strain. Mutations in the Wsp signaling system were identified in both treatments and likely occurred because of low oxygen availability. Despite showing increased killing activity, wsp mutants were less fit in the presence of S. aureus. In contrast, mutations in lipopolysaccharide (LPS) biosynthesis occurred exclusively in co-cultures with S. aureus and conferred a fitness gain in its presence. Moreover, they increased resistance towards beta-lactam antibiotics. Strikingly, both mutations in wsp and LPS genes are observed in clinical isolates from CF-patients. Our results suggest that P. aeruginosa LPS mutations are a direct consequence of S. aureus imposed selection in vitro.
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Affiliation(s)
- Mikael Tognon
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Genève, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, Genève, Switzerland
| | - Thilo Köhler
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Genève, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, Genève, Switzerland
| | - Bartosz G Gdaniec
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Genève, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, Genève, Switzerland
| | - Youai Hao
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| | - Joseph S Lam
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
| | - Marie Beaume
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Genève, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, Genève, Switzerland
| | - Alexandre Luscher
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Genève, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, Genève, Switzerland
| | - Angus Buckling
- Environment and Sustainability Institute, University of Exeter, Penryn, UK
| | - Christian van Delden
- Transplant Infectious Diseases Unit, University Hospitals of Geneva, Genève, Switzerland.,Department of Microbiology and Molecular Medicine, University of Geneva, Genève, Switzerland
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14
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Luscher A. Size-dependent discrimination of mating partners in the simultaneous hermaphroditic cestode Schistocephalus solidus. Behav Ecol 2002. [DOI: 10.1093/beheco/13.2.254] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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15
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Zanetti S, Hartwig UA, Luscher A, Hebeisen T, Frehner M, Fischer BU, Hendrey GR, Blum H, Nosberger J. Stimulation of Symbiotic N2 Fixation in Trifolium repens L. under Elevated Atmospheric pCO2 in a Grassland Ecosystem. Plant Physiol 1996; 112:575-583. [PMID: 12226411 PMCID: PMC157980 DOI: 10.1104/pp.112.2.575] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Symbiotic N2 fixation is one of the main processes that introduces N into terrestrial ecosystems. As such, it may be crucial for the sequestration of the extra C available in a world of continuously increasing atmospheric CO2 partial pressure (pCO2). The effect of elevated pCO2 (60 Pa) on symbiotic N2 fixation (15N-isotope dilution method) was investigated using Free-Air-CO2-Enrichment technology over a period of 3 years. Trifolium repens was cultivated either alone or together with Lolium perenne (a nonfixing reference crop) in mixed swards. Two different N fertilization levels and defoliation frequencies were applied. The total N yield increased consistently and the percentage of plant N derived from symbiotic N2 fixation increased significantly in T. repens under elevated pCO2. All additionally assimilated N was derived from symbiotic N2 fixation, not from the soil. In the mixtures exposed to elevated pCO2, an increased amount of symbiotically fixed N (+7.8, 8.2, and 6.2 g m-2 a-1 in 1993, 1994, and 1995, respectively) was introduced into the system. Increased N2 fixation is a competitive advantage for T. repens in mixed swards with pasture grasses and may be a crucial factor in maintaining the C:N ratio in the ecosystem as a whole.
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Affiliation(s)
- S. Zanetti
- Institute of Plant Sciences, Swiss Federal Institute of Technology, 8092 Zurich, Switzerland
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