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Sommerfield AG, Wang M, Mamana J, Darwin AJ. In vivo and in vitro analysis of the role of the Prc protease in inducing mucoidy in Pseudomonas aeruginosa. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.28.596254. [PMID: 38854061 PMCID: PMC11160602 DOI: 10.1101/2024.05.28.596254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
In Pseudomonas aeruginosa, alginate biosynthesis gene expression is inhibited by the transmembrane anti-sigma factor MucA, which sequesters the AlgU sigma factor. Cell envelope stress initiates cleavage of the MucA periplasmic domain by site-1 protease AlgW, followed by further MucA degradation to release AlgU. However, after colonizing the lungs of people with cystic fibrosis, P. aeruginosa converts to a mucoid form that produces alginate constitutively. Mucoid isolates often have mucA mutations, with the most common being mucA22 , which truncates the periplasmic domain. MucA22 is degraded constitutively, and genetic studies suggested that the Prc protease is responsible. Some studies also suggested that Prc contributes to induction in strains with wild type MucA, whereas others suggested the opposite. However, missing from all previous studies is a demonstration that Prc cleaves any protein directly, which leaves open the possibility that the effect of a prc null mutation is indirect. To address the ambiguities and shortfalls, we reevaluated the roles of AlgW and Prc as MucA and MucA22 site-1 proteases. In vivo analyses using three different assays, and two different inducing conditions, all suggested that AlgW is the only site-1 protease for wild type MucA in any condition. In contrast, genetics suggested that AlgW or Prc act as MucA22 site-1 proteases in inducing conditions, whereas Prc is the only MucA22 site-1 protease in non-inducing conditions. For the first time, we also show that Prc is unable to degrade the periplasmic domain of wild type MucA, but does degrade the mutated periplasmic domain of MucA22 directly. IMPORTANCE After colonizing the lungs of individuals with cystic fibrosis, P. aeruginosa undergoes mutagenic conversion to a mucoid form, worsening the prognosis. Most mucoid isolates have a truncated negative regulatory protein MucA, which leads to constitutive production of the extracellular polysaccharide alginate. The protease Prc has been implicated, but not shown, to degrade the most common MucA variant, MucA22, to trigger alginate production. This work provides the first demonstration that the molecular mechanism of Prc involvement is direct degradation of the MucA22 periplasmic domain, and perhaps other truncated MucA variants as well. MucA truncation and degradation by Prc might be the predominant mechanism of mucoid conversion in cystic fibrosis infections, suggesting that Prc activity could be a useful therapeutic target.
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Kang J, Mateu-Borrás M, Monroe HL, Sen-Kilic E, Miller SJ, Dublin SR, Huckaby AB, Yang E, Pyles GM, Nunley MA, Chapman JA, Amin MS, Damron FH, Barbier M. Monoclonal antibodies against lipopolysaccharide protect against Pseudomonas aeruginosa challenge in mice. Front Cell Infect Microbiol 2023; 13:1191806. [PMID: 37424774 PMCID: PMC10326049 DOI: 10.3389/fcimb.2023.1191806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 06/09/2023] [Indexed: 07/11/2023] Open
Abstract
Pseudomonas aeruginosa is a common cause of hospital-acquired infections, including central line-associated bloodstream infections and ventilator-associated pneumonia. Unfortunately, effective control of these infections can be difficult, in part due to the prevalence of multi-drug resistant strains of P. aeruginosa. There remains a need for novel therapeutic interventions against P. aeruginosa, and the use of monoclonal antibodies (mAb) is a promising alternative strategy to current standard of care treatments such as antibiotics. To develop mAbs against P. aeruginosa, we utilized ammonium metavanadate, which induces cell envelope stress responses and upregulates polysaccharide expression. Mice were immunized with P. aeruginosa grown with ammonium metavanadate and we developed two IgG2b mAbs, WVDC-0357 and WVDC-0496, directed against the O-antigen lipopolysaccharide of P. aeruginosa. Functional assays revealed that WVDC-0357 and WVDC-0496 directly reduced the viability of P. aeruginosa and mediated bacterial agglutination. In a lethal sepsis model of infection, prophylactic treatment of mice with WVDC-0357 and WVDC-0496 at doses as low as 15 mg/kg conferred 100% survival against challenge. In both sepsis and acute pneumonia models of infection, treatment with WVDC-0357 and WVDC-0496 significantly reduced bacterial burden and inflammatory cytokine production post-challenge. Furthermore, histopathological examination of the lungs revealed that WVDC-0357 and WVDC-0496 reduced inflammatory cell infiltration. Overall, our results indicate that mAbs directed against lipopolysaccharide are a promising therapy for the treatment and prevention of P. aeruginosa infections.
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Affiliation(s)
- Jason Kang
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Margalida Mateu-Borrás
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Hunter L. Monroe
- Department of Pathology, Anatomy, and Laboratory Medicine, West Virginia University, Morgantown, WV, United States
| | - Emel Sen-Kilic
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Sarah Jo Miller
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Spencer R. Dublin
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Annalisa B. Huckaby
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Evita Yang
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Gage M. Pyles
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Mason A. Nunley
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Josh A. Chapman
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Md Shahrier Amin
- Department of Pathology, Anatomy, and Laboratory Medicine, West Virginia University, Morgantown, WV, United States
| | - F. Heath Damron
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
| | - Mariette Barbier
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV, United States
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, WV, United States
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Ma LZ, Wang D, Liu Y, Zhang Z, Wozniak DJ. Regulation of Biofilm Exopolysaccharide Biosynthesis and Degradation in Pseudomonas aeruginosa. Annu Rev Microbiol 2022; 76:413-433. [DOI: 10.1146/annurev-micro-041320-111355] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Microbial communities enmeshed in a matrix of macromolecules, termed as biofilms, are the natural setting of bacteria. Exopolysaccharide is a critical matrix component of biofilms. Here, we focus on biofilm matrix exopolysaccharides in Pseudomonas aeruginosa. This opportunistic pathogen can adapt to a wide range of environments and can form biofilms or aggregates in a variety of surfaces or environments, such as the lungs of people with cystic fibrosis, catheters, wounds, and contact lenses. The ability to synthesize multiple exopolysaccharides is one of the advantages that facilitate bacterial survival in different environments. P. aeruginosa can produce several exopolysaccharides, including alginate, Psl, Pel, and lipopolysaccharide. In this review, we highlight the roles of each exopolysaccharide in P. aeruginosa biofilm development and how bacteria coordinate the biosynthesis of multiple exopolysaccharides and bacterial motility. In addition, we present advances in antibiofilm strategies targeting matrix exopolysaccharides, with a focus on glycoside hydrolases. Expected final online publication date for the Annual Review of Microbiology, Volume 76 is September 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Luyan Z. Ma
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Di Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Yiwei Liu
- Department of Microbial Infection and Immunity and Department of Microbiology, Ohio State University, Columbus, Ohio, USA
| | - Zhenyu Zhang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Daniel J. Wozniak
- Department of Microbial Infection and Immunity and Department of Microbiology, Ohio State University, Columbus, Ohio, USA
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4
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Cell Envelope Stress Response in Pseudomonas aeruginosa. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1386:147-184. [DOI: 10.1007/978-3-031-08491-1_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Overproduction of the AlgT Sigma Factor Is Lethal to Mucoid Pseudomonas aeruginosa. J Bacteriol 2020; 202:JB.00445-20. [PMID: 32747430 DOI: 10.1128/jb.00445-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 07/30/2020] [Indexed: 12/12/2022] Open
Abstract
Pseudomonas aeruginosa isolates from chronic lung infections often overproduce alginate, giving rise to the mucoid phenotype. Isolation of mucoid strains from chronic lung infections correlates with a poor patient outcome. The most common mutation that causes the mucoid phenotype is called mucA22 and results in a truncated form of the anti-sigma factor MucA that is continuously subjected to proteolysis. When a functional MucA is absent, the cognate sigma factor, AlgT, is no longer sequestered and continuously transcribes the alginate biosynthesis operon, leading to alginate overproduction. In this work, we report that in the absence of wild-type MucA, providing exogenous AlgT is toxic. This is intriguing, since mucoid strains endogenously possess high levels of AlgT. Furthermore, we show that suppressors of toxic AlgT production have mutations in mucP, a protease involved in MucA degradation, and provide the first atomistic model of MucP. Based on our findings, we speculate that mutations in mucP stabilize the truncated form of MucA22, rendering it functional and therefore able to reduce toxicity by properly sequestering AlgT.IMPORTANCE Pseudomonas aeruginosa is an opportunistic bacterial pathogen capable of causing chronic lung infections. Phenotypes important for the long-term persistence and adaption to this unique lung ecosystem are largely regulated by the AlgT sigma factor. Chronic infection isolates often contain mutations in the anti-sigma factor mucA, resulting in uncontrolled AlgT and continuous production of alginate in addition to the expression of ∼300 additional genes. Here, we report that in the absence of wild-type MucA, AlgT overproduction is lethal and that suppressors of toxic AlgT production have mutations in the MucA protease, MucP. Since AlgT contributes to the establishment of chronic infections, understanding how AlgT is regulated will provide vital information on how P. aeruginosa is capable of causing long-term infections.
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Wang Y, Garrido-Oter R, Wu J, Winkelmüller TM, Agler M, Colby T, Nobori T, Kemen E, Tsuda K. Site-specific cleavage of bacterial MucD by secreted proteases mediates antibacterial resistance in Arabidopsis. Nat Commun 2019; 10:2853. [PMID: 31253808 PMCID: PMC6599210 DOI: 10.1038/s41467-019-10793-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 06/03/2019] [Indexed: 01/10/2023] Open
Abstract
Plant innate immunity restricts growth of bacterial pathogens that threaten global food security. However, the mechanisms by which plant immunity suppresses bacterial growth remain enigmatic. Here we show that Arabidopsis thaliana secreted aspartic protease 1 and 2 (SAP1 and SAP2) cleave the evolutionarily conserved bacterial protein MucD to redundantly inhibit the growth of the bacterial pathogen Pseudomonas syringae. Antibacterial activity of SAP1 requires its protease activity in planta and in vitro. Plants overexpressing SAP1 exhibit enhanced MucD cleavage and resistance but incur no penalties in growth and reproduction, while sap1 sap2 double mutant plants exhibit compromised MucD cleavage and resistance against P. syringae. P. syringae lacking mucD shows compromised growth in planta and in vitro. Notably, growth of ΔmucD complemented with the non-cleavable MucDF106Y is not affected by SAP activity in planta and in vitro. Our findings identify the genetic factors and biochemical process underlying an antibacterial mechanism in plants. During innate immune responses, plant cells secrete proteases into apoplastic spaces where they contribute to pathogen resistance. Here Wang et al. show that the Arabidopsis SAP1 and SAP2 proteases cleave the bacterial MucD protein to inhibit growth of Pseudomonas syringae.
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Affiliation(s)
- Yiming Wang
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany
| | - Ruben Garrido-Oter
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany.,Cluster of Excellence on Plant Sciences, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
| | - Jingni Wu
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany.,Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 200032, Shanghai, China
| | - Thomas M Winkelmüller
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany
| | - Matthew Agler
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany.,Plant Microbiosis Lab, Institute of Microbiology, Friedrich-Schiller University Jena, Neugasse 23, 07743, Jena, Germany
| | - Thomas Colby
- Plant Proteomics Group, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany.,Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Strasse 9B, 50931, Cologne, Germany
| | - Tatsuya Nobori
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany
| | - Eric Kemen
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany.,Center for Plant Molecular Biology, Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Auf der Morgenstelle 32, 72076, Tübingen, Germany
| | - Kenichi Tsuda
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, 50829, Cologne, Germany.
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Pandey S, Delgado C, Kumari H, Florez L, Mathee K. Outer-membrane protein LptD (PA0595) plays a role in the regulation of alginate synthesis in Pseudomonas aeruginosa. J Med Microbiol 2018; 67:1139-1156. [PMID: 29923820 DOI: 10.1099/jmm.0.000752] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
PURPOSE The presence of alginate-overproducing (Alg+) strains of Pseudomonas aeruginosa in cystic fibrosis patients is indicative of chronic infection. The Alg+ phenotype is generally due to a mutation in the mucA gene, encoding an innermembrane protein that sequesters AlgT/U, the alginate-specific sigma factor. AlgT/U release from the anti-sigma factor MucA is orchestrated via a complex cascade called regulated intramembrane proteolysis. The goal of this study is to identify new players involved in the regulation of alginate production. METHODOLOGY Previously, a mutant with a second-site suppressor of alginate production (sap), sap27, was isolated from the constitutively Alg+ PDO300 that harbours the mucA22 allele. A cosmid from a P. aeruginosa minimum tiling path library was identified via en masse complementation of sap27. The cosmid was transposon mutagenized to map the contributing gene involved in the alginate production. The identified gene was sequenced in sap27 along with algT/U, mucA, algO and mucP. The role of the novel gene was explored using precise in-frame algO and algW deletion mutants of PAO1 and PDO300.Results/Key findings. The gene responsible for restoring the mucoid phenotype was mapped to lptD encoding an outer-membrane protein. However, the sequencing of sap27 revealed a mutation in algO, but not in lptD. In addition, we demonstrate that lipopolysaccharide transport protein D (LptD)-dependent alginate production requires AlgW in PAO1 and AlgO in PDO300. CONCLUSION LptD plays a specific role in alginate production. Our findings suggest that there are two pathways for the production of alginate in P. aeruginosa, one involving AlgW in the wild-type, and one involving AlgO in the mucA22 mutant.
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Affiliation(s)
- Sundar Pandey
- 1Department of Biological Sciences, College of Arts Sciences and Education, Florida International University, Miami, FL, USA
| | - Camila Delgado
- 2Department of Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA.,†Present address: Langone Medical Center, New York University School of Medicine, New York, USA
| | - Hansi Kumari
- 2Department of Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA.,3Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Laura Florez
- 2Department of Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
| | - Kalai Mathee
- 4Biomolecular Sciences Institute, Florida International University, Miami, FL, USA.,2Department of Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA.,3Department of Human and Molecular Genetics, Herbert Wertheim College of Medicine, Florida International University, Miami, FL, USA
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Strempel N, Nusser M, Neidig A, Brenner-Weiss G, Overhage J. The Oxidative Stress Agent Hypochlorite Stimulates c-di-GMP Synthesis and Biofilm Formation in Pseudomonas aeruginosa. Front Microbiol 2017; 8:2311. [PMID: 29213262 PMCID: PMC5702645 DOI: 10.3389/fmicb.2017.02311] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 11/08/2017] [Indexed: 01/25/2023] Open
Abstract
The opportunistic human pathogen Pseudomonas aeruginosa is able to survive under a variety of often harmful environmental conditions due to a multitude of intrinsic and adaptive resistance mechanisms, including biofilm formation as one important survival strategy. Here, we investigated the adaptation of P. aeruginosa PAO1 to hypochlorite (HClO), a phagocyte-derived host defense compound and frequently used disinfectant. In static biofilm assays, we observed a significant enhancement in initial cell attachment in the presence of sublethal HClO concentrations. Subsequent LC-MS analyses revealed a strong increase in cyclic-di-GMP (c-di-GMP) levels suggesting a key role of this second messenger in HClO-induced biofilm development. Using DNA microarrays, we identified a 26-fold upregulation of ORF PA3177 coding for a putative diguanylate cyclase (DGC), which catalyzes the synthesis of the second messenger c-di-GMP – an important regulator of bacterial motility, sessility and persistence. This DGC PA3177 was further characterized in more detail demonstrating its impact on P. aeruginosa motility and biofilm formation. In addition, cell culture assays attested a role for PA3177 in the response of P. aeruginosa to human phagocytes. Using a subset of different mutants, we were able to show that both Pel and Psl exopolysaccharides are effectors in the PA3177-dependent c-di-GMP network.
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Affiliation(s)
- Nikola Strempel
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Michael Nusser
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Anke Neidig
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Gerald Brenner-Weiss
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Joerg Overhage
- Institute of Functional Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany.,Department of Health Sciences, Carleton University, Ottawa, ON, Canada
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Harvey DJ. Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012. MASS SPECTROMETRY REVIEWS 2017; 36:255-422. [PMID: 26270629 DOI: 10.1002/mas.21471] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Accepted: 01/15/2015] [Indexed: 06/04/2023]
Abstract
This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.
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Affiliation(s)
- David J Harvey
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, Oxford, OX1 3QU, UK
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10
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Pseudomonas aeruginosa AmrZ Binds to Four Sites in the algD Promoter, Inducing DNA-AmrZ Complex Formation and Transcriptional Activation. J Bacteriol 2016; 198:2673-81. [PMID: 27185826 DOI: 10.1128/jb.00259-16] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 05/09/2016] [Indexed: 11/20/2022] Open
Abstract
During late stages of cystic fibrosis pulmonary infections, Pseudomonas aeruginosa often overproduces the exopolysaccharide alginate, protecting the bacterial community from host immunity and antimicrobials. The transcription of the alginate biosynthesis operon is under tight control by a number of factors, including AmrZ, the focus of this study. Interestingly, multiple transcription factors interact with the far-upstream region of this promoter (PalgD), in which one AmrZ binding site has been identified previously. The mechanisms of AmrZ binding and subsequent activation remain unclear and require more-detailed investigation. In this study, in-depth examinations elucidated four AmrZ binding sites, and their disruption eliminated AmrZ binding and promoter activation. Furthermore, our in vitro fluorescence resonance energy transfer experiments suggest that AmrZ holds together multiple binding sites in PalgD and thereafter induces the formation of higher-order DNA-AmrZ complexes. To determine the importance of interactions between those AmrZ oligomers in the cell, a DNA phasing experiment was performed. PalgD transcription was significantly impaired when the relative phase between AmrZ binding sites was reversed (5 bp), while a full-DNA-turn insertion (10 bp) restored promoter activity. Taken together, the investigations presented here provide a deeper mechanistic understanding of AmrZ-mediated binding to PalgD IMPORTANCE: Overproduction of the exopolysaccharide alginate provides protection to Pseudomonas aeruginosa against antimicrobial treatments and is associated with chronic P. aeruginosa infections in the lungs of cystic fibrosis patients. In this study, we combined a variety of microbiological, genetic, biochemical, and biophysical approaches to investigate the activation of the alginate biosynthesis operon promoter by a key transcription factor named AmrZ. This study has provided important new information on the mechanism of activation of this extremely complex promoter.
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D'Orazio M, Mastropasqua MC, Cerasi M, Pacello F, Consalvo A, Chirullo B, Mortensen B, Skaar EP, Ciavardelli D, Pasquali P, Battistoni A. The capability of Pseudomonas aeruginosa to recruit zinc under conditions of limited metal availability is affected by inactivation of the ZnuABC transporter. Metallomics 2016; 7:1023-35. [PMID: 25751674 DOI: 10.1039/c5mt00017c] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ability of a large number of bacterial pathogens to multiply in the infected host and cause disease is dependent on their ability to express high affinity zinc importers. In many bacteria, ZnuABC, a transporter of the ABC family, plays a central role in the process of zinc uptake in zinc poor environments, including the tissues of the infected host. To initiate an investigation into the relevance of the zinc uptake apparatus for Pseudomonas aeruginosa pathogenicity, we have generated a znuA mutant in the PA14 strain. We have found that this mutant strain displays a limited growth defect in zinc depleted media. The znuA mutant strain is more sensitive than the wild type strain to calprotectin-mediated growth inhibition, but both the strains are highly resistant to this zinc sequestering antimicrobial protein. Moreover, intracellular zinc content is not evidently affected by inactivation of the ZnuABC transporter. These findings suggest that P. aeruginosa is equipped with redundant mechanisms for the acquisition of zinc that might favor P. aeruginosa colonization of environments containing low levels of this metal. Nonetheless, deletion of znuA affects alginate production, reduces the activity of extracellular zinc-containing proteases, including LasA, LasB and protease IV, and decreases the ability of P. aeruginosa to disseminate during systemic infections. These results indicate that efficient zinc acquisition is critical for the expression of various virulence features typical of P. aeruginosa and that ZnuABC also plays an important role in zinc homeostasis in this microorganism.
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Affiliation(s)
- Melania D'Orazio
- Department of Biology, University of Rome Tor Vergata, 00133 Roma, Italy.
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Flores-Kim J, Darwin AJ. Regulation of bacterial virulence gene expression by cell envelope stress responses. Virulence 2015; 5:835-51. [PMID: 25603429 DOI: 10.4161/21505594.2014.965580] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The bacterial cytoplasm lies within a multilayered envelope that must be protected from internal and external hazards. This protection is provided by cell envelope stress responses (ESRs), which detect threats and reprogram gene expression to ensure survival. Pathogens frequently need these ESRs to survive inside the host, where their envelopes face dangerous environmental changes and attack from antimicrobial molecules. In addition, some virulence genes have become integrated into ESR regulons. This might be because these genes can protect the cell envelope from damage by host molecules, or it might help ESRs to reduce stress by moderating the assembly of virulence factors within the envelope. Alternatively, it could simply be a mechanism to coordinate the induction of virulence gene expression with entry into the host. Here, we briefly describe some of the bacterial ESRs, followed by examples where they control virulence gene expression in both Gram-negative and Gram-positive pathogens.
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Key Words
- BFP, bundle-forming pilus
- CAMP, cationic antimicrobial peptide
- CF, cystic fibrosis
- ECF, extracytoplasmic function
- EPEC, enteropathogenic E. coli
- ESR, envelope stress response
- HMV, hypermucoviscosity
- IM, inner membrane
- LPS, lipopolysaccharide
- LTA, lipoteichoic acids
- OM, outer membrane
- OMP, outer membrane protein
- PG, phosphatidylglycerol
- T(2/3/4)SS, type II/III/IV secretion system
- UPEC, uropathogenic E. coli
- WTA, wall teichoic acids
- antimicrobial peptide
- bacterial pathogens
- cell envelope
- gene regulation
- peptidoglycan
- phospholipid
- stress response
- teichoic acid
- virulence gene
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Affiliation(s)
- Josué Flores-Kim
- a Department of Microbiology ; New York University School of Medicine ; New York , NY USA
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Whitfield GB, Marmont LS, Howell PL. Enzymatic modifications of exopolysaccharides enhance bacterial persistence. Front Microbiol 2015; 6:471. [PMID: 26029200 PMCID: PMC4432689 DOI: 10.3389/fmicb.2015.00471] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 04/29/2015] [Indexed: 12/25/2022] Open
Abstract
Biofilms are surface-attached communities of bacterial cells embedded in a self-produced matrix that are found ubiquitously in nature. The biofilm matrix is composed of various extracellular polymeric substances, which confer advantages to the encapsulated bacteria by protecting them from eradication. The matrix composition varies between species and is dependent on the environmental niche that the bacteria inhabit. Exopolysaccharides (EPS) play a variety of important roles in biofilm formation in numerous bacterial species. The ability of bacteria to thrive in a broad range of environmental settings is reflected in part by the structural diversity of the EPS produced both within individual bacterial strains as well as by different species. This variability is achieved through polymerization of distinct sugar moieties into homo- or hetero-polymers, as well as post-polymerization modification of the polysaccharide. Specific enzymes that are unique to the production of each polymer can transfer or remove non-carbohydrate moieties, or in other cases, epimerize the sugar units. These modifications alter the physicochemical properties of the polymer, which in turn can affect bacterial pathogenicity, virulence, and environmental adaptability. Herein, we review the diversity of modifications that the EPS alginate, the Pel polysaccharide, Vibrio polysaccharide, cepacian, glycosaminoglycans, and poly-N-acetyl-glucosamine undergo during biosynthesis. These are EPS produced by human pathogenic bacteria for which studies have begun to unravel the effect modifications have on their physicochemical and biological properties. The biological advantages these polymer modifications confer to the bacteria that produce them will be discussed. The expanding list of identified modifications will allow future efforts to focus on linking these modifications to specific biosynthetic genes and biofilm phenotypes.
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Affiliation(s)
- Gregory B Whitfield
- Program in Molecular Structure and Function, Research Institute, The Hospital for Sick Children Toronto, ON, Canada ; Department of Biochemistry, Faculty of Medicine, University of Toronto Toronto, ON, Canada
| | - Lindsey S Marmont
- Program in Molecular Structure and Function, Research Institute, The Hospital for Sick Children Toronto, ON, Canada ; Department of Biochemistry, Faculty of Medicine, University of Toronto Toronto, ON, Canada
| | - P Lynne Howell
- Program in Molecular Structure and Function, Research Institute, The Hospital for Sick Children Toronto, ON, Canada ; Department of Biochemistry, Faculty of Medicine, University of Toronto Toronto, ON, Canada
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14
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Kumari H, Murugapiran SK, Balasubramanian D, Schneper L, Merighi M, Sarracino D, Lory S, Mathee K. LTQ-XL mass spectrometry proteome analysis expands the Pseudomonas aeruginosa AmpR regulon to include cyclic di-GMP phosphodiesterases and phosphoproteins, and identifies novel open reading frames. J Proteomics 2013; 96:328-342. [PMID: 24291602 DOI: 10.1016/j.jprot.2013.11.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 11/12/2013] [Accepted: 11/18/2013] [Indexed: 12/23/2022]
Abstract
UNLABELLED Pseudomonas aeruginosa is well known for its antibiotic resistance and intricate regulatory network, contributing to its success as an opportunistic pathogen. This study is an extension of our transcriptomic analyses (microarray and RNA-Seq) to understand the global changes in PAO1 upon deleting a gene encoding a transcriptional regulator AmpR, in the presence and absence of β-lactam antibiotic. This study was performed under identical conditions to explore the proteome profile of the ampR deletion mutant (PAOΔampR) using LTQ-XL mass spectrometry. The proteomic data identified ~53% of total PAO1 proteins and expanded the master regulatory role of AmpR in determining antibiotic resistance and multiple virulence phenotypes in P. aeruginosa. AmpR proteome analysis identified 853 AmpR-dependent proteins, which include 102 transcriptional regulators and 21 two-component system proteins. AmpR also regulates cyclic di-GMP phosphodiesterases (PA4367, PA4969, PA4781) possibly affecting major virulence systems. Phosphoproteome analysis also suggests a significant role for AmpR in Ser, Thr and Tyr phosphorylation. These novel mechanisms of gene regulation were previously not associated with AmpR. The proteome analysis also identified many unannotated and misannotated ORFs in the P. aeruginosa genome. Thus, our data sheds light on important virulence regulatory pathways that can potentially be exploited to deal with P. aeruginosa infections. BIOLOGICAL SIGNIFICANCE The AmpR proteome data not only confirmed the role of AmpR in virulence and resistance to multiple antibiotics, but also expanded the perimeter of AmpR regulon. The data presented here points to the role of AmpR in regulating cyclic di-GMP levels and phosphorylation of Ser, Thr and Tyr, adding another dimension to the regulatory functions of AmpR. We also identify some previously unannotated/misannotated ORFs in the P. aeruginosa genome, indicating the limitations of existing ORF analyses software. This study will contribute towards understanding complex genetic organization of P. aeruginosa. Whole genome proteomic picture of regulators at higher nodal positions in the regulatory network will not only help us link various virulence phenotypes but also design novel therapeutic strategies.
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Affiliation(s)
- Hansi Kumari
- Department of Molecular Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL
| | - Senthil K Murugapiran
- Department of Molecular Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL
| | - Deepak Balasubramanian
- Department of Biological Sciences, College of Arts and Sciences, Florida International University, Miami, FL United States
| | - Lisa Schneper
- Department of Molecular Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL
| | - Massimo Merighi
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA
| | - David Sarracino
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA
| | - Stephen Lory
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA
| | - Kalai Mathee
- Department of Molecular Microbiology and Infectious Diseases, Herbert Wertheim College of Medicine, Florida International University, Miami, FL
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15
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Yin Y, Damron FH, Withers TR, Pritchett CL, Wang X, Schurr MJ, Yu HD. Expression of mucoid induction factor MucE is dependent upon the alternate sigma factor AlgU in Pseudomonas aeruginosa. BMC Microbiol 2013; 13:232. [PMID: 24138584 PMCID: PMC3819740 DOI: 10.1186/1471-2180-13-232] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 10/09/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Alginate overproduction in P. aeruginosa, also referred to as mucoidy, is a poor prognostic marker for patients with cystic fibrosis (CF). We previously reported the construction of a unique mucoid strain which overexpresses a small envelope protein MucE leading to activation of the protease AlgW. AlgW then degrades the anti-sigma factor MucA thus releasing the alternative sigma factor AlgU/T (σ(22)) to initiate transcription of the alginate biosynthetic operon. RESULTS In the current study, we mapped the mucE transcriptional start site, and determined that P(mucE) activity was dependent on AlgU. Additionally, the presence of triclosan and sodium dodecyl sulfate was shown to cause an increase in P(mucE) activity. It was observed that mucE-mediated mucoidy in CF isolates was dependent on both the size of MucA and the genotype of algU. We also performed shotgun proteomic analysis with cell lysates from the strains PAO1, VE2 (PAO1 with constitutive expression of mucE) and VE2ΔalgU (VE2 with in-frame deletion of algU). As a result, we identified nine algU-dependent and two algU-independent proteins that were affected by overexpression of MucE. CONCLUSIONS Our data indicates there is a positive feedback regulation between MucE and AlgU. Furthermore, it seems likely that MucE may be part of the signal transduction system that senses certain types of cell wall stress to P. aeruginosa.
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Affiliation(s)
| | | | | | | | | | | | - Hongwei D Yu
- Department of Biochemistry and Microbiology, Joan C, Edwards School of Medicine at Marshall University, Huntington, WV 25755, USA.
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16
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Yin Y, Withers TR, Wang X, Yu HD. Evidence for sigma factor competition in the regulation of alginate production by Pseudomonas aeruginosa. PLoS One 2013; 8:e72329. [PMID: 23991093 PMCID: PMC3750012 DOI: 10.1371/journal.pone.0072329] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 07/08/2013] [Indexed: 11/18/2022] Open
Abstract
Alginate overproduction, or mucoidy, plays an important role in the pathogenesis of P. aeruginosa lung infection in cystic fibrosis (CF). Mucoid strains with mucA mutations predominantly populate in chronically-infected patients. However, the mucoid strains can revert to nonmucoidy in vitro through suppressor mutations. We screened a mariner transposon library using CF149, a non-mucoid clinical isolate with a misssense mutation in algU (AlgUA61V). The wild type AlgU is a stress-related sigma factor that activates transcription of alginate biosynthesis. Three mucoid mutants were identified with transposon insertions that caused 1) an overexpression of AlgUA61V, 2) an overexpression of the stringent starvation protein A (SspA), and 3) a reduced expression of the major sigma factor RpoD (σ70). Induction of AlgUA61Vin trans caused conversion to mucoidy in CF149 and PAO1DalgU, suggesting that AlgUA61V is functional in activating alginate production. Furthermore, the level of AlgUA61V was increased in all three mutants relative to CF149. However, compared to the wild type AlgU, AlgUA61V had a reduced activity in promoting alginate production in PAO1ΔalgU. SspA and three other anti-σ70 orthologues, P. aeruginosa AlgQ, E. coli Rsd, and T4 phage AsiA, all induced mucoidy, suggesting that reducing activity of RpoD is linked to mucoid conversion in CF149. Conversely, RpoD overexpression resulted in suppression of mucoidy in all mucoid strains tested, indicating that sigma factor competition can regulate mucoidy. Additionally, an RpoD-dependent promoter (PssrA) was more active in non-mucoid strains than in isogenic mucoid variants. Altogether, our results indicate that the anti-σ70 factors can induce conversion to mucoidy in P. aeruginosa CF149 with algU-suppressor mutation via modulation of RpoD.
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Affiliation(s)
- Yeshi Yin
- Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia, United States of America
- Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - T. Ryan Withers
- Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia, United States of America
| | - Xin Wang
- Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Hongwei D. Yu
- Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia, United States of America
- Department of Pediatrics, Joan C. Edwards School of Medicine at Marshall University, Huntington, West Virginia, United States of America
- Progenesis Technologies, LLC, Huntington, West Virginia, United States of America
- * E-mail:
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17
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Genes required for and effects of alginate overproduction induced by growth of Pseudomonas aeruginosa on Pseudomonas isolation agar supplemented with ammonium metavanadate. J Bacteriol 2013; 195:4020-36. [PMID: 23794622 DOI: 10.1128/jb.00534-13] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that can adapt to changing environments and can secrete an exopolysaccharide known as alginate as a protection response, resulting in a colony morphology and phenotype referred to as mucoid. However, how P. aeruginosa senses its environment and activates alginate overproduction is not fully understood. Previously, we showed that Pseudomonas isolation agar supplemented with ammonium metavanadate (PIAAMV) induces P. aeruginosa to overproduce alginate. Vanadate is a phosphate mimic and causes protein misfolding by disruption of disulfide bonds. Here we used PIAAMV to characterize the pathways involved in inducible alginate production and tested the global effects of P. aeruginosa growth on PIAAMV by a mutant library screen, by transcriptomics, and in a murine acute virulence model. The PA14 nonredundant mutant library was screened on PIAAMV to identify new genes that are required for the inducible alginate stress response. A functionally diverse set of genes encoding products involved in cell envelope biogenesis, peptidoglycan remodeling, uptake of phosphate and iron, phenazine biosynthesis, and other processes were identified as positive regulators of the mucoid phenotype on PIAAMV. Transcriptome analysis of P. aeruginosa cultures growing in the presence of vanadate showed differential expression of genes involved in virulence, envelope biogenesis, and cell stress pathways. In this study, it was observed that growth on PIAAMV attenuates P. aeruginosa in a mouse pneumonia model. Induction of alginate overproduction occurs as a stress response to protect P. aeruginosa, but it may be possible to modulate and inhibit these pathways based on the new genes identified in this study.
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18
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Construction of mobilizable mini-Tn7 vectors for bioluminescent detection of gram-negative bacteria and single-copy promoter lux reporter analysis. Appl Environ Microbiol 2013; 79:4149-53. [PMID: 23584769 DOI: 10.1128/aem.00640-13] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We describe the construction of mini-Tn7-based broad-host-range vectors encoding lux genes as bioluminescent reporters. These constructs can be mobilized into the desired host(s) by conjugation for chromosomal mini-Tn7-lux integration and are useful for localization of bacteria during infections or for characterizing regulation of promoters of interest in Gram-negative bacteria.
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Identification of the mutation responsible for the temperature-sensitive lipopolysaccharide O-antigen defect in the Pseudomonas aeruginosa cystic fibrosis isolate 2192. J Bacteriol 2013; 195:1504-14. [PMID: 23354750 DOI: 10.1128/jb.01999-12] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Pseudomonas aeruginosa in the lungs of cystic fibrosis (CF) patients is characterized by a series of genotypic and phenotypic changes that reflect the transition from acute to chronic infection. These include the overproduction of the exopolysaccharide alginate and the loss of complete lipopolysaccharide (LPS). LPS is a major component of the Gram-negative outer membrane and is composed of lipid A, core oligosaccharide, and O antigen. In this report, we show that the LPS defect of the P. aeruginosa chronic infection isolate 2192 is temperature sensitive. When grown at 25°C, 2192 expresses serotype O1 LPS with a moderate chain length and in reduced amounts relative to those of a wild-type serotype O1 laboratory strain (stO1). In contrast, 2192 expresses no LPS O antigen when grown at 37°C. This is the first time that a temperature-sensitive defect in O-antigen production has been reported. Using complementation analyses with a constructed wbpM deletion mutant of stO1, we demonstrate that the temperature-sensitive O-antigen production defect in 2192 is due to a mutation in wbpM, which encodes a UDP-4,6-GlcNAc dehydratase involved in O-antigen synthesis. The mutation, a deletion of a single amino acid (V636) from the extreme C terminus of WbpM, renders the protein less stable than its wild-type counterpart. This residue of WbpM, which is critical for stability and function, is located outside of the recognized domains of the protein and may provide insight into the structure-function relationship of this enzyme, which is found in all 20 serotypes of P. aeruginosa. We also identify a promoter of wbpM, map a transcriptional start site of wbpM, and show that mucoidy plays a role in the loss of expression of high-molecular-weight LPS in this CF isolate.
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Barbier M, Martínez-Ramos I, Townsend P, Albertí S. Surfactant protein A blocks recognition of Pseudomonas aeruginosa by CKAP4/P63 on airway epithelial cells. J Infect Dis 2012; 206:1753-62. [PMID: 22966120 DOI: 10.1093/infdis/jis587] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We used isogenic mutant strains that were deficient or over-expressed capsule to study the function of the alginate exopolysaccharide in the interaction of Pseudomonas aeruginosa with the human airway epithelial cells (AEC) in the presence or absence of surfactant protein A (SP-A). SP-A prevented the invasion of AEC by alginate-producing P. aeruginosa strains because of a direct effect on the AEC. Monoclonal antibodies to CKAP4/P63, the principal SP-A-binding receptor on AEC, or inhibition of its expression using specific siRNA reduced the invasion of both highly encapsulated and poorly encapsulated strains, but not the invasion of the acapsular mutant. Treatment of AEC with SP-A, monoclonal antibodies to CKAP4/P63, or CKAP4/P63-specific siRNA decreased the binding of purified alginate exopolysaccharide to AEC. Alginate binding to AEC reduced SP-A release by these cells. Because the alginate exopolysaccharide is surface-exposed, levels of SP-A may be crucial to modulate the interaction of P. aeruginosa with AEC.
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Affiliation(s)
- Mariette Barbier
- Instituto Universitario de Investigaciones en Ciencias de la Salud, Universidad de las Islas Baleares, Palma de Mallorca, Spain
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21
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Damron FH, Goldberg JB. Proteolytic regulation of alginate overproduction in Pseudomonas aeruginosa. Mol Microbiol 2012; 84:595-607. [PMID: 22497280 DOI: 10.1111/j.1365-2958.2012.08049.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Pseudomonas aeruginosa, a Gram-negative bacterium, is a significant opportunistic pathogen associated with skin and soft tissue infections, nosocomial pneumonia and sepsis. In addition, it can chronically colonize the lungs of cystic fibrosis (CF) patients. Overproduction of the exopolysaccharide called alginate provides P. aeruginosa with a selective advantage and facilitates survival in the CF lung. The in vitro phenotype of alginate overproduction observed on solid culture media is referred to as mucoid. Expression of the alginate machinery and biosynthetic enzymes are controlled by the extracytoplasmic sigma factor, σ(22) (AlgU/T). The key negative regulator of both σ(22) activity and the mucoid phenotype is the cognate anti-sigma factor MucA. MucA sequesters σ(22) to the inner membrane inhibiting the sigma factor's transcriptional activity. The well-studied mechanism for transition to the mucoid phenotype is mutation of mucA, leading to loss of MucA function and therefore activation of σ(22) . Recently, regulated intramembrane proteolysis (RIP) has been recognized as a mechanism whereby proteolysis of the anti-sigma factor MucA leads to active σ(22) allowing P. aeruginosa to respond to environmental stress conditions by overproduction of alginate. The goal of this review is to illuminate the pathways leading to RIP that have been identified and proposed.
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Affiliation(s)
- F Heath Damron
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia Health System, Charlottesville, VA, USA
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22
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Analysis of the Pseudomonas aeruginosa regulon controlled by the sensor kinase KinB and sigma factor RpoN. J Bacteriol 2011; 194:1317-30. [PMID: 22210761 DOI: 10.1128/jb.06105-11] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alginate overproduction by Pseudomonas aeruginosa, also known as mucoidy, is associated with chronic endobronchial infections in cystic fibrosis. Alginate biosynthesis is initiated by the extracytoplasmic function sigma factor (σ(22); AlgU/AlgT). In the wild-type (wt) nonmucoid strains, such as PAO1, AlgU is sequestered to the cytoplasmic membrane by the anti-sigma factor MucA that inhibits alginate production. One mechanism underlying the conversion to mucoidy is mutation of mucA. However, the mucoid conversion can occur in wt mucA strains via the degradation of MucA by activated intramembrane proteases AlgW and/or MucP. Previously, we reported that the deletion of the sensor kinase KinB in PAO1 induces an AlgW-dependent proteolysis of MucA, resulting in alginate overproduction. This type of mucoid induction requires the alternate sigma factor RpoN (σ(54)). To determine the RpoN-dependent KinB regulon, microarray and proteomic analyses were performed on a mucoid kinB mutant and an isogenic nonmucoid kinB rpoN double mutant. In the kinB mutant of PAO1, RpoN controlled the expression of approximately 20% of the genome. In addition to alginate biosynthetic and regulatory genes, KinB and RpoN also control a large number of genes including those involved in carbohydrate metabolism, quorum sensing, iron regulation, rhamnolipid production, and motility. In an acute pneumonia murine infection model, BALB/c mice exhibited increased survival when challenged with the kinB mutant relative to survival with PAO1 challenge. Together, these data strongly suggest that KinB regulates virulence factors important for the development of acute pneumonia and conversion to mucoidy.
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