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Desvaux M, Candela T, Serror P. Surfaceome and Proteosurfaceome in Parietal Monoderm Bacteria: Focus on Protein Cell-Surface Display. Front Microbiol 2018; 9:100. [PMID: 29491848 PMCID: PMC5817068 DOI: 10.3389/fmicb.2018.00100] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 01/16/2018] [Indexed: 12/12/2022] Open
Abstract
The cell envelope of parietal monoderm bacteria (archetypal Gram-positive bacteria) is formed of a cytoplasmic membrane (CM) and a cell wall (CW). While the CM is composed of phospholipids, the CW is composed at least of peptidoglycan (PG) covalently linked to other biopolymers, such as teichoic acids, polysaccharides, and/or polyglutamate. Considering the CW is a porous structure with low selective permeability contrary to the CM, the bacterial cell surface hugs the molecular figure of the CW components as a well of the external side of the CM. While the surfaceome corresponds to the totality of the molecules found at the bacterial cell surface, the proteinaceous complement of the surfaceome is the proteosurfaceome. Once translocated across the CM, secreted proteins can either be released in the extracellular milieu or exposed at the cell surface by associating to the CM or the CW. Following the gene ontology (GO) for cellular components, cell-surface proteins at the CM can either be integral (GO: 0031226), i.e., the integral membrane proteins, or anchored to the membrane (GO: 0046658), i.e., the lipoproteins. At the CW (GO: 0009275), cell-surface proteins can be covalently bound, i.e., the LPXTG-proteins, or bound through weak interactions to the PG or wall polysaccharides, i.e., the cell wall binding proteins. Besides monopolypeptides, some proteins can associate to each other to form supramolecular protein structures of high molecular weight, namely the S-layer, pili, flagella, and cellulosomes. After reviewing the cell envelope components and the different molecular mechanisms involved in protein attachment to the cell envelope, perspectives in investigating the proteosurfaceome in parietal monoderm bacteria are further discussed.
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Affiliation(s)
- Mickaël Desvaux
- Université Clermont Auvergne, INRA, UMR454 MEDiS, Clermont-Ferrand, France
| | - Thomas Candela
- EA4043 Unité Bactéries Pathogènes et Santé, Châtenay-Malabry, France
| | - Pascale Serror
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, Jouy-en-Josas, France
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102
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Bitler A, Dover RS, Shai Y. Fractal properties of cell surface structures: A view from AFM. Semin Cell Dev Biol 2018; 73:64-70. [DOI: 10.1016/j.semcdb.2017.07.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Revised: 07/10/2017] [Accepted: 07/13/2017] [Indexed: 01/08/2023]
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103
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Mielich-Süss B, Wagner RM, Mietrach N, Hertlein T, Marincola G, Ohlsen K, Geibel S, Lopez D. Flotillin scaffold activity contributes to type VII secretion system assembly in Staphylococcus aureus. PLoS Pathog 2017; 13:e1006728. [PMID: 29166667 PMCID: PMC5718613 DOI: 10.1371/journal.ppat.1006728] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Revised: 12/06/2017] [Accepted: 11/02/2017] [Indexed: 12/13/2022] Open
Abstract
Scaffold proteins are ubiquitous chaperones that promote efficient interactions between partners of multi-enzymatic protein complexes; although they are well studied in eukaryotes, their role in prokaryotic systems is poorly understood. Bacterial membranes have functional membrane microdomains (FMM), a structure homologous to eukaryotic lipid rafts. Similar to their eukaryotic counterparts, bacterial FMM harbor a scaffold protein termed flotillin that is thought to promote interactions between proteins spatially confined to the FMM. Here we used biochemical approaches to define the scaffold activity of the flotillin homolog FloA of the human pathogen Staphylococcus aureus, using assembly of interacting protein partners of the type VII secretion system (T7SS) as a case study. Staphylococcus aureus cells that lacked FloA showed reduced T7SS function, and thus reduced secretion of T7SS-related effectors, probably due to the supporting scaffold activity of flotillin. We found that the presence of flotillin mediates intermolecular interactions of T7SS proteins. We tested several small molecules that interfere with flotillin scaffold activity, which perturbed T7SS activity in vitro and in vivo. Our results suggest that flotillin assists in the assembly of S. aureus membrane components that participate in infection and influences the infective potential of this pathogen. The recently discovered functional membrane microdomains (FMM) of prokaryotic cells contain a protein homologous to the scaffold protein flotillin found in eukaryotic lipid rafts. It remains to be elucidated whether, like their eukaryotic counterparts, flotillin homolog proteins have a scaffold function in bacteria. Here we show that the Staphylococcus aureus flotillin FloA acts as a scaffold protein, to promote more efficient assembly of membrane-associated protein interacting partners of multi-enzyme complexes. In a case study, we provide biochemical evidence that FloA participates in assembly of the Type VII secretion system and thus contributes to S. aureus infective potential. Targeted dispersion of FMM-related processes using anti-FMM molecules opens up new perspectives for microbial therapies to treat persistent S. aureus infections.
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Affiliation(s)
- Benjamin Mielich-Süss
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
| | - Rabea M. Wagner
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
- National Center for Biotechnology, Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
| | - Nicole Mietrach
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
- Rudolf Virchow Center - DFG Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Tobias Hertlein
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
| | - Gabriella Marincola
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
| | - Knut Ohlsen
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
| | - Sebastian Geibel
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
- Rudolf Virchow Center - DFG Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany
| | - Daniel Lopez
- Research Center for Infectious Diseases ZINF, University of Würzburg, Würzburg, Germany
- Institute for Molecular Infection Biology IMIB, University of Würzburg, Würzburg, Germany
- National Center for Biotechnology, Consejo Superior de Investigaciones Científicas (CNB-CSIC), Madrid, Spain
- * E-mail:
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104
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García-Fernández E, Koch G, Wagner RM, Fekete A, Stengel ST, Schneider J, Mielich-Süss B, Geibel S, Markert SM, Stigloher C, Lopez D. Membrane Microdomain Disassembly Inhibits MRSA Antibiotic Resistance. Cell 2017; 171:1354-1367.e20. [PMID: 29103614 PMCID: PMC5720476 DOI: 10.1016/j.cell.2017.10.012] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 09/18/2017] [Accepted: 10/06/2017] [Indexed: 12/21/2022]
Abstract
A number of bacterial cell processes are confined functional membrane microdomains (FMMs), structurally and functionally similar to lipid rafts of eukaryotic cells. How bacteria organize these intricate platforms and what their biological significance is remain important questions. Using the pathogen methicillin-resistant Staphylococcus aureus (MRSA), we show here that membrane-carotenoid interaction with the scaffold protein flotillin leads to FMM formation, which can be visualized using super-resolution array tomography. These membrane platforms accumulate multimeric protein complexes, for which flotillin facilitates efficient oligomerization. One of these proteins is PBP2a, responsible for penicillin resistance in MRSA. Flotillin mutants are defective in PBP2a oligomerization. Perturbation of FMM assembly using available drugs interferes with PBP2a oligomerization and disables MRSA penicillin resistance in vitro and in vivo, resulting in MRSA infections that are susceptible to penicillin treatment. Our study demonstrates that bacteria possess sophisticated cell organization programs and defines alternative therapies to fight multidrug-resistant pathogens using conventional antibiotics. Staphyloxanthin and flotillin preferentially interact and accumulate in FMMs FMMs facilitate efficient oligomerization of multimeric protein complexes PBP2a, which confers β-lactam resistance on S. aureus, is harbored within FMMs FMM disruption disables PBP2a oligomerization and thus, S. aureus antibiotic resistance
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Affiliation(s)
- Esther García-Fernández
- National Centre for Biotechnology, Spanish National Research Council (CNB-CSIC), 28049 Madrid, Spain
| | - Gudrun Koch
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, 97080 Würzburg, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Rabea M Wagner
- National Centre for Biotechnology, Spanish National Research Council (CNB-CSIC), 28049 Madrid, Spain; Research Centre for Infectious Diseases (ZINF), University of Würzburg, 97080 Würzburg, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Agnes Fekete
- Julius-von-Sachs-Institute Biocenter, Pharmaceutical Biology, University of Würzburg, 97082 Würzburg, Germany
| | - Stephanie T Stengel
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, 97080 Würzburg, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Johannes Schneider
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, 97080 Würzburg, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Benjamin Mielich-Süss
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, 97080 Würzburg, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Sebastian Geibel
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, 97080 Würzburg, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany
| | - Sebastian M Markert
- Division of Electron Microscopy, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Christian Stigloher
- Division of Electron Microscopy, Biocenter, University of Würzburg, 97074 Würzburg, Germany
| | - Daniel Lopez
- National Centre for Biotechnology, Spanish National Research Council (CNB-CSIC), 28049 Madrid, Spain; Research Centre for Infectious Diseases (ZINF), University of Würzburg, 97080 Würzburg, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, 97080 Würzburg, Germany; National Centre for Biotechnology, Spanish National Research Council (CNB-CSIC), Darwin 3, Campus de Cantoblanco, 28049 Madrid, Spain.
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105
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Bagam P, Singh DP, Inda ME, Batra S. Unraveling the role of membrane microdomains during microbial infections. Cell Biol Toxicol 2017; 33:429-455. [PMID: 28275881 PMCID: PMC7088210 DOI: 10.1007/s10565-017-9386-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 02/06/2017] [Indexed: 01/06/2023]
Abstract
Infectious diseases pose major socioeconomic and health-related threats to millions of people across the globe. Strategies to combat infectious diseases derive from our understanding of the complex interactions between the host and specific bacterial, viral, and fungal pathogens. Lipid rafts are membrane microdomains that play important role in life cycle of microbes. Interaction of microbial pathogens with host membrane rafts influences not only their initial colonization but also their spread and the induction of inflammation. Therefore, intervention strategies aimed at modulating the assembly of membrane rafts and/or regulating raft-directed signaling pathways are attractive approaches for the. management of infectious diseases. The current review discusses the latest advances in terms of techniques used to study the role of membrane microdomains in various pathological conditions and provides updated information regarding the role of membrane rafts during bacterial, viral and fungal infections.
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Affiliation(s)
- Prathyusha Bagam
- Laboratory of Pulmonary Immuno-Toxicology, Department of Environmental Toxicology, Health Research Center, Southern University and A&M College, Baton Rouge, LA, 70813, USA
| | - Dhirendra P Singh
- Laboratory of Pulmonary Immuno-Toxicology, Department of Environmental Toxicology, Health Research Center, Southern University and A&M College, Baton Rouge, LA, 70813, USA
| | - Maria Eugenia Inda
- Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Suipacha, Rosario, Argentina
| | - Sanjay Batra
- Laboratory of Pulmonary Immuno-Toxicology, Department of Environmental Toxicology, Health Research Center, Southern University and A&M College, Baton Rouge, LA, 70813, USA.
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106
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Abstract
The use of styrene maleic acid lipid particles (SMALPs) for the purification of membrane proteins (MPs) is a rapidly developing technology. The amphiphilic copolymer of styrene and maleic acid (SMA) disrupts biological membranes and can extract membrane proteins in nanodiscs of approximately 10 nm diameter. These discs contain SMA, protein and membrane lipids. There is evidence that MPs in SMALPs retain their native structures and functions, in some cases with enhanced thermal stability. In addition, the method is compatible with biological buffers and a wide variety of biophysical and structural analysis techniques. The use of SMALPs to solubilize and stabilize MPs offers a new approach in our attempts to understand, and influence, the structure and function of MPs and biological membranes. In this review, we critically assess progress with this method, address some of the associated technical challenges, and discuss opportunities for exploiting SMA and SMALPs to expand our understanding of MP biology.
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107
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Koch G, Wermser C, Acosta IC, Kricks L, Stengel ST, Yepes A, Lopez D. Attenuating Staphylococcus aureus Virulence by Targeting Flotillin Protein Scaffold Activity. Cell Chem Biol 2017; 24:845-857.e6. [PMID: 28669526 DOI: 10.1016/j.chembiol.2017.05.027] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 04/11/2017] [Accepted: 05/30/2017] [Indexed: 01/13/2023]
Abstract
Scaffold proteins are ubiquitous chaperones that bind proteins and facilitate physical interaction of multi-enzyme complexes. Here we used a biochemical approach to dissect the scaffold activity of the flotillin-homolog protein FloA of the multi-drug-resistant human pathogen Staphylococcus aureus. We show that FloA promotes oligomerization of membrane protein complexes, such as the membrane-associated RNase Rny, which forms part of the RNA-degradation machinery called the degradosome. Cells lacking FloA had reduced Rny function and a consequent increase in the targeted sRNA transcripts that negatively regulate S. aureus toxin expression. Small molecules that altered FloA oligomerization also reduced Rny function and decreased the virulence potential of S. aureus in vitro, as well as in vivo, using invertebrate and murine infection models. Our results suggest that flotillin assists in the assembly of protein complexes involved in S. aureus virulence, and could thus be an attractive target for the development of new antimicrobial therapies.
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Affiliation(s)
- Gudrun Koch
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
| | - Charlotte Wermser
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
| | - Ivan C Acosta
- National Centre for Biotechnology (CNB), Spanish Research Council (CSIC), Darwin 3, Madrid 28049, Spain
| | - Lara Kricks
- National Centre for Biotechnology (CNB), Spanish Research Council (CSIC), Darwin 3, Madrid 28049, Spain
| | - Stephanie T Stengel
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
| | - Ana Yepes
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
| | - Daniel Lopez
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany; National Centre for Biotechnology (CNB), Spanish Research Council (CSIC), Darwin 3, Madrid 28049, Spain.
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108
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Hutton ML, D'Costa K, Rossiter AE, Wang L, Turner L, Steer DL, Masters SL, Croker BA, Kaparakis-Liaskos M, Ferrero RL. A Helicobacter pylori Homolog of Eukaryotic Flotillin Is Involved in Cholesterol Accumulation, Epithelial Cell Responses and Host Colonization. Front Cell Infect Microbiol 2017; 7:219. [PMID: 28634572 PMCID: PMC5460342 DOI: 10.3389/fcimb.2017.00219] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Accepted: 05/11/2017] [Indexed: 12/12/2022] Open
Abstract
The human pathogen Helicobacter pylori acquires cholesterol from membrane raft domains in eukaryotic cells, commonly known as "lipid rafts." Incorporation of this cholesterol into the H. pylori cell membrane allows the bacterium to avoid clearance by the host immune system and to resist the effects of antibiotics and antimicrobial peptides. The presence of cholesterol in H. pylori bacteria suggested that this pathogen may have cholesterol-enriched domains within its membrane. Consistent with this suggestion, we identified a hypothetical H. pylori protein (HP0248) with homology to the flotillin proteins normally found in the cholesterol-enriched domains of eukaryotic cells. As shown for eukaryotic flotillin proteins, HP0248 was detected in detergent-resistant membrane fractions of H. pylori. Importantly, H. pylori HP0248 mutants contained lower levels of cholesterol than wild-type bacteria (P < 0.01). HP0248 mutant bacteria also exhibited defects in type IV secretion functions, as indicated by reduced IL-8 responses and CagA translocation in epithelial cells (P < 0.05), and were less able to establish a chronic infection in mice than wild-type bacteria (P < 0.05). Thus, we have identified an H. pylori flotillin protein and shown its importance for bacterial virulence. Taken together, the data demonstrate important roles for H. pylori flotillin in host-pathogen interactions. We propose that H. pylori flotillin may be required for the organization of virulence proteins into membrane raft-like structures in this pathogen.
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Affiliation(s)
- Melanie L. Hutton
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical ResearchMelbourne, VIC, Australia
| | - Kimberley D'Costa
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical ResearchMelbourne, VIC, Australia
| | - Amanda E. Rossiter
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical ResearchMelbourne, VIC, Australia
| | - Lin Wang
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical ResearchMelbourne, VIC, Australia
| | - Lorinda Turner
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical ResearchMelbourne, VIC, Australia
| | - David L. Steer
- Monash Biomedical Proteomics Facility, Monash UniversityMelbourne, VIC, Australia
| | - Seth L. Masters
- Inflammation Division, The Walter and Eliza Hall InstituteMelbourne, VIC, Australia
| | - Ben A. Croker
- Inflammation Division, The Walter and Eliza Hall InstituteMelbourne, VIC, Australia
| | - Maria Kaparakis-Liaskos
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical ResearchMelbourne, VIC, Australia
| | - Richard L. Ferrero
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical ResearchMelbourne, VIC, Australia
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash UniversityMelbourne, VIC, Australia
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109
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Nickels JD, Chatterjee S, Stanley CB, Qian S, Cheng X, Myles DAA, Standaert RF, Elkins JG, Katsaras J. The in vivo structure of biological membranes and evidence for lipid domains. PLoS Biol 2017; 15:e2002214. [PMID: 28542493 PMCID: PMC5441578 DOI: 10.1371/journal.pbio.2002214] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 04/11/2017] [Indexed: 12/19/2022] Open
Abstract
Examining the fundamental structure and processes of living cells at the nanoscale poses a unique analytical challenge, as cells are dynamic, chemically diverse, and fragile. A case in point is the cell membrane, which is too small to be seen directly with optical microscopy and provides little observational contrast for other methods. As a consequence, nanoscale characterization of the membrane has been performed ex vivo or in the presence of exogenous labels used to enhance contrast and impart specificity. Here, we introduce an isotopic labeling strategy in the gram-positive bacterium Bacillus subtilis to investigate the nanoscale structure and organization of its plasma membrane in vivo. Through genetic and chemical manipulation of the organism, we labeled the cell and its membrane independently with specific amounts of hydrogen (H) and deuterium (D). These isotopes have different neutron scattering properties without altering the chemical composition of the cells. From neutron scattering spectra, we confirmed that the B. subtilis cell membrane is lamellar and determined that its average hydrophobic thickness is 24.3 ± 0.9 Ångstroms (Å). Furthermore, by creating neutron contrast within the plane of the membrane using a mixture of H- and D-fatty acids, we detected lateral features smaller than 40 nm that are consistent with the notion of lipid rafts. These experiments-performed under biologically relevant conditions-answer long-standing questions in membrane biology and illustrate a fundamentally new approach for systematic in vivo investigations of cell membrane structure.
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Affiliation(s)
- Jonathan D. Nickels
- Shull Wollan Center—A Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Sneha Chatterjee
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Christopher B. Stanley
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Shuo Qian
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Xiaolin Cheng
- Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Dean A. A. Myles
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
| | - Robert F. Standaert
- Shull Wollan Center—A Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America
- * E-mail: (RFS); (JGE); (JK)
| | - James G. Elkins
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America
- * E-mail: (RFS); (JGE); (JK)
| | - John Katsaras
- Shull Wollan Center—A Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee, United States of America
- * E-mail: (RFS); (JGE); (JK)
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110
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Pader V, Edwards AM. Daptomycin: new insights into an antibiotic of last resort. Future Microbiol 2017; 12:461-464. [DOI: 10.2217/fmb-2017-0034] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Affiliation(s)
- Vera Pader
- MRC Centre for Molecular Bacteriology & Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK
| | - Andrew M Edwards
- MRC Centre for Molecular Bacteriology & Infection, Imperial College London, Armstrong Road, London, SW7 2AZ, UK
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111
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Rashid R, Cazenave-Gassiot A, Gao IH, Nair ZJ, Kumar JK, Gao L, Kline KA, Wenk MR. Comprehensive analysis of phospholipids and glycolipids in the opportunistic pathogen Enterococcus faecalis. PLoS One 2017; 12:e0175886. [PMID: 28423018 PMCID: PMC5397010 DOI: 10.1371/journal.pone.0175886] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Accepted: 04/02/2017] [Indexed: 02/07/2023] Open
Abstract
Enterococcus faecalis is a Gram-positive, opportunistic, pathogenic bacterium that causes a significant number of antibiotic-resistant infections in hospitalized patients. The development of antibiotic resistance in hospital-associated pathogens is a formidable public health threat. In E. faecalis and other Gram-positive pathogens, correlations exist between lipid composition and antibiotic resistance. Resistance to the last-resort antibiotic daptomycin is accompanied by a decrease in phosphatidylglycerol (PG) levels, whereas multiple peptide resistance factor (MprF) converts anionic PG into cationic lysyl-PG via a trans-esterification reaction, providing resistance to cationic antimicrobial peptides. Unlike previous studies that relied on thin layer chromatography and spectrophotometry, we have performed liquid chromatography-tandem mass spectrometry (LC-MS/MS) directly on lipids extracted from E. faecalis, and quantified the phospholipids through multiple reaction monitoring (MRM). In the daptomycin-sensitive E. faecalis strain OG1RF, we have identified 17 PGs, 8 lysyl-PGs (LPGs), 23 cardiolipins (CL), 3 glycerophospho-diglucosyl-diacylglycerols (GPDGDAG), 5 diglucosyl-diacylglycerols (DGDAG), 3 diacylglycerols (DAGs), and 4 triacylglycerols (TAGs). We have quantified PG and shown that PG levels vary during growth of E. faecalis in vitro. We also show that two daptomycin-resistant (DapR) strains of E. faecalis have substantially lower levels of PG and LPG levels. Since LPG levels in these strains are lower, daptomycin resistance is likely due to the reduction in PG. This lipidome map is the first comprehensive analysis of membrane phospholipids and glycolipids in the important human pathogen E. faecalis, for which antimicrobial resistance and altered lipid homeostasis have been intimately linked.
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Affiliation(s)
- Rafi Rashid
- Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Amaury Cazenave-Gassiot
- Singapore Lipidomics Incubator, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Iris H. Gao
- Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Zeus J. Nair
- Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Jaspal K. Kumar
- Singapore Lipidomics Incubator, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Liang Gao
- Singapore Lipidomics Incubator, National University of Singapore, Singapore, Singapore
- Life Sciences Institute, National University of Singapore, Singapore, Singapore
| | - Kimberly A. Kline
- Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore, Singapore
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- * E-mail: (KAK); (MRW)
| | - Markus R. Wenk
- Singapore Lipidomics Incubator, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Department of Biological Sciences, Faculty of Science, National University of Singapore, Singapore, Singapore
- * E-mail: (KAK); (MRW)
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112
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Lopez D, Koch G. Exploring functional membrane microdomains in bacteria: an overview. Curr Opin Microbiol 2017; 36:76-84. [PMID: 28237903 DOI: 10.1016/j.mib.2017.02.001] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Accepted: 02/01/2017] [Indexed: 01/08/2023]
Abstract
Recent studies show that internal organization of bacterial cells is more complex than previously appreciated. A clear example of this is the assembly of the nanoscale membrane platforms termed functional membrane microdomains. The lipid composition of these regions differs from that of the surrounding membrane; these domains confine a set of proteins involved in specific cellular processes such as protease secretion and signal transduction. It is currently thought that functional membrane microdomains act as oligomerization platforms and promote efficient oligomerization of interacting protein partners in bacterial membranes. In this review, we highlight the most noteworthy achievements, challenges and controversies of this emerging research field over the past five years.
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Affiliation(s)
- Daniel Lopez
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany; Spanish National Centre for Biotechnology (CNB), Madrid 28049, Spain.
| | - Gudrun Koch
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany; Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
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113
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Vega-Cabrera LA, Pardo-López L. Membrane remodeling and organization: Elements common to prokaryotes and eukaryotes. IUBMB Life 2017; 69:55-62. [DOI: 10.1002/iub.1604] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 12/15/2016] [Indexed: 01/14/2023]
Affiliation(s)
- Luz A. Vega-Cabrera
- Instituto de Biotecnología, Universidad Nacional Autónoma de México; Apdo. Postal 510-3 Cuernavaca Morelos México
| | - Liliana Pardo-López
- Instituto de Biotecnología, Universidad Nacional Autónoma de México; Apdo. Postal 510-3 Cuernavaca Morelos México
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114
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Bach JN, Giacomelli G, Bramkamp M. Sample Preparation and Choice of Fluorophores for Single and Dual Color Photo-Activated Localization Microscopy (PALM) with Bacterial Cells. Methods Mol Biol 2017; 1563:129-141. [PMID: 28324606 DOI: 10.1007/978-1-4939-6810-7_9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Photo-activated localization microscopy (PALM) is one of the light microscopy techniques providing highest resolution. Single photo-activatable or photo-switchable fluorescent molecules are stochastically excited. The point spread function of this event is recorded and the exact fluorophore position is calculated. This chapter describes how bacterial samples can be prepared for PALM to achieve routinely a resolution of ≤30 nm using fluorophores such as mNeonGreen, Dendra2, and PAmCherry. It is also explained how to perform multicolor PALM and combine it with total internal reflection (TIRF) microscopy to increase resolution.
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Affiliation(s)
- Juri N Bach
- Faculty of Biology, Ludwig-Maximilians-University Munich, Großhaderner Str. 2-4, Planegg-Martinsried, Munich, 82152, Germany
| | - Giacomo Giacomelli
- Faculty of Biology, Ludwig-Maximilians-University Munich, Großhaderner Str. 2-4, Planegg-Martinsried, Munich, 82152, Germany
| | - Marc Bramkamp
- Faculty of Biology, Ludwig-Maximilians-University Munich, Großhaderner Str. 2-4, Planegg-Martinsried, Munich, 82152, Germany.
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115
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Abstract
As discovered over the past 25 years, the cytoskeletons of bacteria and archaea are complex systems of proteins whose central components are dynamic cytomotive filaments. They perform roles in cell division, DNA partitioning, cell shape determination and the organisation of intracellular components. The protofilament structures and polymerisation activities of various actin-like, tubulin-like and ESCRT-like proteins of prokaryotes closely resemble their eukaryotic counterparts but show greater diversity. Their activities are modulated by a wide range of accessory proteins but these do not include homologues of the motor proteins that supplement filament dynamics to aid eukaryotic cell motility. Numerous other filamentous proteins, some related to eukaryotic IF-proteins/lamins and dynamins etc, seem to perform structural roles similar to those in eukaryotes.
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Affiliation(s)
- Linda A Amos
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
| | - Jan Löwe
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, CB2 0QH, UK.
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116
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Oswald F, Varadarajan A, Lill H, Peterman EJG, Bollen YJM. MreB-Dependent Organization of the E. coli Cytoplasmic Membrane Controls Membrane Protein Diffusion. Biophys J 2016; 110:1139-49. [PMID: 26958890 PMCID: PMC4788719 DOI: 10.1016/j.bpj.2016.01.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/05/2016] [Accepted: 01/11/2016] [Indexed: 01/13/2023] Open
Abstract
The functional organization of prokaryotic cell membranes, which is essential for many cellular processes, has been challenging to analyze due to the small size and nonflat geometry of bacterial cells. Here, we use single-molecule fluorescence microscopy and three-dimensional quantitative analyses in live Escherichia coli to demonstrate that its cytoplasmic membrane contains microdomains with distinct physical properties. We show that the stability of these microdomains depends on the integrity of the MreB cytoskeletal network underneath the membrane. We explore how the interplay between cytoskeleton and membrane affects trans-membrane protein (TMP) diffusion and reveal that the mobility of the TMPs tested is subdiffusive, most likely caused by confinement of TMP mobility by the submembranous MreB network. Our findings demonstrate that the dynamic architecture of prokaryotic cell membranes is controlled by the MreB cytoskeleton and regulates the mobility of TMPs.
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Affiliation(s)
- Felix Oswald
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, the Netherlands; Department of Molecular Cell Biology, Vrije Universiteit Amsterdam, the Netherlands; LaserLaB Amsterdam, the Netherlands
| | - Aravindan Varadarajan
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, the Netherlands; LaserLaB Amsterdam, the Netherlands
| | - Holger Lill
- Department of Molecular Cell Biology, Vrije Universiteit Amsterdam, the Netherlands; LaserLaB Amsterdam, the Netherlands
| | - Erwin J G Peterman
- Department of Physics and Astronomy, Vrije Universiteit Amsterdam, the Netherlands; LaserLaB Amsterdam, the Netherlands
| | - Yves J M Bollen
- Department of Molecular Cell Biology, Vrije Universiteit Amsterdam, the Netherlands; LaserLaB Amsterdam, the Netherlands.
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117
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Sen S, Sirobhushanam S, Johnson SR, Song Y, Tefft R, Gatto C, Wilkinson BJ. Growth-Environment Dependent Modulation of Staphylococcus aureus Branched-Chain to Straight-Chain Fatty Acid Ratio and Incorporation of Unsaturated Fatty Acids. PLoS One 2016; 11:e0165300. [PMID: 27788193 PMCID: PMC5082858 DOI: 10.1371/journal.pone.0165300] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 10/07/2016] [Indexed: 12/14/2022] Open
Abstract
The fatty acid composition of membrane glycerolipids is a major determinant of Staphylococcus aureus membrane biophysical properties that impacts key factors in cell physiology including susceptibility to membrane active antimicrobials, pathogenesis, and response to environmental stress. The fatty acids of S. aureus are considered to be a mixture of branched-chain fatty acids (BCFAs), which increase membrane fluidity, and straight-chain fatty acids (SCFAs) that decrease it. The balance of BCFAs and SCFAs in USA300 strain JE2 and strain SH1000 was affected considerably by differences in the conventional laboratory medium in which the strains were grown with media such as Mueller-Hinton broth and Luria broth resulting in high BCFAs and low SCFAs, whereas growth in Tryptic Soy Broth and Brain-Heart Infusion broth led to reduction in BCFAs and an increase in SCFAs. Straight-chain unsaturated fatty acids (SCUFAs) were not detected. However, when S. aureus was grown ex vivo in serum, the fatty acid composition was radically different with SCUFAs, which increase membrane fluidity, making up a substantial proportion of the total (<25%) with SCFAs (>37%) and BCFAs (>36%) making up the rest. Staphyloxanthin, an additional major membrane lipid component unique to S. aureus, tended to be greater in content in cells with high BCFAs or SCUFAs. Cells with high staphyloxanthin content had a lower membrane fluidity that was attributed to increased production of staphyloxanthin. S. aureus saves energy and carbon by utilizing host fatty acids for part of its total fatty acids when growing in serum, which may impact biophysical properties and pathogenesis given the role of SCUFAs in virulence. The nutritional environment in which S. aureus is grown in vitro or in vivo in an infection is likely to be a major determinant of membrane fatty acid composition.
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Affiliation(s)
- Suranjana Sen
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Sirisha Sirobhushanam
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Seth R. Johnson
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Yang Song
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Ryan Tefft
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Craig Gatto
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
| | - Brian J. Wilkinson
- School of Biological Sciences, Illinois State University, Normal, Illinois, United States of America
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118
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Daptomycin inhibits cell envelope synthesis by interfering with fluid membrane microdomains. Proc Natl Acad Sci U S A 2016; 113:E7077-E7086. [PMID: 27791134 DOI: 10.1073/pnas.1611173113] [Citation(s) in RCA: 265] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Daptomycin is a highly efficient last-resort antibiotic that targets the bacterial cell membrane. Despite its clinical importance, the exact mechanism by which daptomycin kills bacteria is not fully understood. Different experiments have led to different models, including (i) blockage of cell wall synthesis, (ii) membrane pore formation, and (iii) the generation of altered membrane curvature leading to aberrant recruitment of proteins. To determine which model is correct, we carried out a comprehensive mode-of-action study using the model organism Bacillus subtilis and different assays, including proteomics, ionomics, and fluorescence light microscopy. We found that daptomycin causes a gradual decrease in membrane potential but does not form discrete membrane pores. Although we found no evidence for altered membrane curvature, we confirmed that daptomycin inhibits cell wall synthesis. Interestingly, using different fluorescent lipid probes, we showed that binding of daptomycin led to a drastic rearrangement of fluid lipid domains, affecting overall membrane fluidity. Importantly, these changes resulted in the rapid detachment of the membrane-associated lipid II synthase MurG and the phospholipid synthase PlsX. Both proteins preferentially colocalize with fluid membrane microdomains. Delocalization of these proteins presumably is a key reason why daptomycin blocks cell wall synthesis. Finally, clustering of fluid lipids by daptomycin likely causes hydrophobic mismatches between fluid and more rigid membrane areas. This mismatch can facilitate proton leakage and may explain the gradual membrane depolarization observed with daptomycin. Targeting of fluid lipid domains has not been described before for antibiotics and adds another dimension to our understanding of membrane-active antibiotics.
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119
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Cebrián G, Condón S, Mañas P. Influence of growth and treatment temperature on Staphylococcus aureus resistance to pulsed electric fields: Relationship with membrane fluidity. INNOV FOOD SCI EMERG 2016. [DOI: 10.1016/j.ifset.2016.08.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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120
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Functional Membrane Microdomains Organize Signaling Networks in Bacteria. J Membr Biol 2016; 250:367-378. [PMID: 27566471 DOI: 10.1007/s00232-016-9923-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Accepted: 08/16/2016] [Indexed: 11/27/2022]
Abstract
Membrane organization is usually associated with the correct function of a number of cellular processes in eukaryotic cells as diverse as signal transduction, protein sorting, membrane trafficking, or pathogen invasion. It has been recently discovered that bacterial membranes are able to compartmentalize their signal transduction pathways in functional membrane microdomains (FMMs). In this review article, we discuss the biological significance of the existence of FMMs in bacteria and comment on possible beneficial roles that FMMs play on the harbored signal transduction cascades. Moreover, four different membrane-associated signal transduction cascades whose functions are linked to the integrity of FMMs are introduced, and the specific role that FMMs play in stabilizing and promoting interactions of their signaling components is discussed. Altogether, FMMs seem to play a relevant role in promoting more efficient activation of signal transduction cascades in bacterial cells and show that bacteria are more sophisticated organisms than previously appreciated.
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121
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Danchin A, Fang G. Unknown unknowns: essential genes in quest for function. Microb Biotechnol 2016; 9:530-40. [PMID: 27435445 PMCID: PMC4993169 DOI: 10.1111/1751-7915.12384] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 06/24/2016] [Indexed: 01/18/2023] Open
Abstract
The experimental design of a minimal synthetic genome revealed the presence of a large number of genes without ascribed function, in part because the abstract laws of life must be implemented within ad hoc material contraptions. Creating a function needs recruitment of some pre‐existing structure and this reveals kludges in their set‐up and history. Here, we show that looking for functions as an engineer would help in discovery of a significant number of those, proposed together with conceptual handles allowing investigators to pursue this endeavour in other contexts.
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Affiliation(s)
- Antoine Danchin
- Institute of Cardiometabolism and Nutrition, CHU Pitié-Salpêtrière, 47 boulevard de l'Hôpital, 75013, Paris, France
| | - Gang Fang
- Department of Biology, New York University Shanghai Campus, 1555 Century Avenue, Pudong New Area, Shanghai, 200122, China
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122
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Rashid R, Veleba M, Kline KA. Focal Targeting of the Bacterial Envelope by Antimicrobial Peptides. Front Cell Dev Biol 2016; 4:55. [PMID: 27376064 PMCID: PMC4894902 DOI: 10.3389/fcell.2016.00055] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 05/23/2016] [Indexed: 01/15/2023] Open
Abstract
Antimicrobial peptides (AMPs) are utilized by both eukaryotic and prokaryotic organisms. AMPs such as the human beta defensins, human neutrophil peptides, human cathelicidin, and many bacterial bacteriocins are cationic and capable of binding to anionic regions of the bacterial surface. Cationic AMPs (CAMPs) target anionic lipids [e.g., phosphatidylglycerol (PG) and cardiolipins (CL)] in the cell membrane and anionic components [e.g., lipopolysaccharide (LPS) and lipoteichoic acid (LTA)] of the cell envelope. Bacteria have evolved mechanisms to modify these same targets in order to resist CAMP killing, e.g., lysinylation of PG to yield cationic lysyl-PG and alanylation of LTA. Since CAMPs offer a promising therapeutic alternative to conventional antibiotics, which are becoming less effective due to rapidly emerging antibiotic resistance, there is a strong need to improve our understanding about the AMP mechanism of action. Recent literature suggests that AMPs often interact with the bacterial cell envelope at discrete foci. Here we review recent AMP literature, with an emphasis on focal interactions with bacteria, including (1) CAMP disruption mechanisms, (2) delocalization of membrane proteins and lipids by CAMPs, and (3) CAMP sensing systems and resistance mechanisms. We conclude with new approaches for studying the bacterial membrane, e.g., lipidomics, high resolution imaging, and non-detergent-based membrane domain extraction.
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Affiliation(s)
- Rafi Rashid
- Singapore Centre for Environmental Life Sciences Engineering, School of Biological Sciences, Nanyang Technological University Singapore, Singapore
| | - Mark Veleba
- Singapore Centre for Environmental Life Sciences Engineering, School of Biological Sciences, Nanyang Technological University Singapore, Singapore
| | - Kimberly A Kline
- Singapore Centre for Environmental Life Sciences Engineering, School of Biological Sciences, Nanyang Technological University Singapore, Singapore
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123
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Mitra SD, Afonina I, Kline KA. Right Place, Right Time: Focalization of Membrane Proteins in Gram-Positive Bacteria. Trends Microbiol 2016; 24:611-621. [PMID: 27117048 DOI: 10.1016/j.tim.2016.03.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 03/03/2016] [Accepted: 03/24/2016] [Indexed: 11/25/2022]
Abstract
Membrane proteins represent a significant proportion of total bacterial proteins and perform vital cellular functions ranging from exchanging metabolites and genetic material, secretion and sorting, sensing signal molecules, and cell division. Many of these functions are carried out at distinct foci on the bacterial membrane, and this subcellular localization can be coordinated by a number of factors, including lipid microdomains, protein-protein interactions, and membrane curvature. Elucidating the mechanisms behind focal protein localization in bacteria informs not only protein structure-function correlation, but also how to disrupt the protein function to limit virulence. Here we review recent advances describing a functional role for subcellular localization of membrane proteins involved in genetic transfer, secretion and sorting, cell division and growth, and signaling.
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Affiliation(s)
- Sumitra D Mitra
- Singapore Centre for Environmental Life Sciences Engineering, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Irina Afonina
- Singapore Centre for Environmental Life Sciences Engineering, School of Biological Sciences, Nanyang Technological University, Singapore
| | - Kimberly A Kline
- Singapore Centre for Environmental Life Sciences Engineering, School of Biological Sciences, Nanyang Technological University, Singapore.
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124
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Somani VK, Aggarwal S, Singh D, Prasad T, Bhatnagar R. Identification of Novel Raft Marker Protein, FlotP in Bacillus anthracis. Front Microbiol 2016; 7:169. [PMID: 26925042 PMCID: PMC4756111 DOI: 10.3389/fmicb.2016.00169] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 02/01/2016] [Indexed: 01/14/2023] Open
Abstract
Lipid rafts are dynamic, nanoscale assemblies of specific proteins and lipids, distributed heterogeneously on eukaryotic membrane. Flotillin-1, a conserved eukaryotic raft marker protein (RMP) harbor SPFH (Stomatin, Prohibitin, Flotillin, and HflK/C) and oligomerization domains to regulate various cellular processes through its interactions with other signaling or transport proteins. Rafts were thought to be absent in prokaryotes hitherto, but recent report of its presence and significance in physiology of Bacillus subtilis prompted us to investigate the same in pathogenic bacteria (PB) also. In prokaryotes, proteins of SPFH2a subfamily show highest identity to SPFH domain of Flotillin-1. Moreover, bacterial genome organization revealed that Flotillin homolog harboring SPFH2a domain exists in an operon with an upstream gene containing NFeD domain. Here, presence of RMP in PB was initially investigated in silico by analyzing the presence of SPFH2a, oligomerization domains in the concerned gene and NfeD domain in the adjacent upstream gene. After investigating 300 PB, four were found to harbor RMP. Among them, domains of Bas0525 (FlotP) of Bacillus anthracis (BA) showed highest identity with characteristic domains of RMP. Considering the global threat of BA as the bioterror agent, it was selected as a model for further in vitro characterization of rafts in PB. In silico and in vitro analysis showed significant similarity of FlotP with numerous attributes of Flotillin-1. Its punctate distribution on membrane with exclusive localization in detergent resistant membrane fraction; strongly favors presence of raft with RMP FlotP in BA. Furthermore, significant effect of Zaragozic acid (ZA), a raft associated lipid biosynthesis inhibitor, on several patho-physiological attributes of BA such as growth, morphology, membrane rigidity etc., were also observed. Specifically, a considerable decrease in membrane rigidity, strongly recommended presence of an unknown raft associated lipid molecule on membrane of BA. In addition, treatment with ZA decreased secretion of anthrax toxins and FlotP expression, suggesting potential role of raft in pathogenesis and physiology of BA. Thus, the present study not only suggest the existence and role of raft like entity in pathophysiology of BA but also its possible use for the development of novel drugs or vaccines against anthrax.
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Affiliation(s)
- Vikas K Somani
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University New Delhi, India
| | - Somya Aggarwal
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University New Delhi, India
| | - Damini Singh
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University New Delhi, India
| | | | - Rakesh Bhatnagar
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University New Delhi, India
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125
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Carquin M, D'Auria L, Pollet H, Bongarzone ER, Tyteca D. Recent progress on lipid lateral heterogeneity in plasma membranes: From rafts to submicrometric domains. Prog Lipid Res 2015; 62:1-24. [PMID: 26738447 DOI: 10.1016/j.plipres.2015.12.004] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 12/22/2015] [Accepted: 12/22/2015] [Indexed: 12/29/2022]
Abstract
The concept of transient nanometric domains known as lipid rafts has brought interest to reassess the validity of the Singer-Nicolson model of a fluid bilayer for cell membranes. However, this new view is still insufficient to explain the cellular control of surface lipid diversity or membrane deformability. During the past decades, the hypothesis that some lipids form large (submicrometric/mesoscale vs nanometric rafts) and stable (>min vs s) membrane domains has emerged, largely based on indirect methods. Morphological evidence for stable submicrometric lipid domains, well-accepted for artificial and highly specialized biological membranes, was further reported for a variety of living cells from prokaryot es to yeast and mammalian cells. However, results remained questioned based on limitations of available fluorescent tools, use of poor lipid fixatives, and imaging artifacts due to non-resolved membrane projections. In this review, we will discuss recent evidence generated using powerful and innovative approaches such as lipid-specific toxin fragments that support the existence of submicrometric domains. We will integrate documented mechanisms involved in the formation and maintenance of these domains, and provide a perspective on their relevance on membrane deformability and regulation of membrane protein distribution.
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Affiliation(s)
- Mélanie Carquin
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium
| | - Ludovic D'Auria
- The Myelin Regeneration Group at the Dept. Anatomy & Cell Biology, College of Medicine, University of Illinois, 808 S. Wood St. MC512, Chicago, IL. 60612. USA
| | - Hélène Pollet
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium
| | - Ernesto R Bongarzone
- The Myelin Regeneration Group at the Dept. Anatomy & Cell Biology, College of Medicine, University of Illinois, 808 S. Wood St. MC512, Chicago, IL. 60612. USA
| | - Donatienne Tyteca
- CELL Unit, de Duve Institute & Université Catholique de Louvain, UCL B1.75.05, Avenue Hippocrate, 75, B-1200 Brussels, Belgium.
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126
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Toyofuku M, Tashiro Y, Hasegawa Y, Kurosawa M, Nomura N. Bacterial membrane vesicles, an overlooked environmental colloid: Biology, environmental perspectives and applications. Adv Colloid Interface Sci 2015; 226:65-77. [PMID: 26422802 DOI: 10.1016/j.cis.2015.08.013] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 08/27/2015] [Accepted: 08/27/2015] [Indexed: 12/31/2022]
Abstract
Phospholipid vesicles play important roles in biological systems. Bacteria are one of the most abundant organisms on Earth, and bacterial membrane vesicles (MVs) were first observed 50 years ago. Many bacteria release MVs to the environment that mainly consist of the cell membrane and typically range from 20 to 400 nm in size. Bacterial MVs are involved in several biological functions, such as delivery of cargo, virulence and gene transfer. MVs can be isolated from laboratory culture and directly from the environment, indicating their high abundance in and impact on ecosystems. Many colloidal particles in the environment ranging in size from 1 nm to 1 μm have been reported but not characterized at the molecular level, and MVs remain to be explored. Hence, MVs can be considered terra incognita in environmental colloid research. Although MV biogenesis and biological roles are yet to be fully understood, the accumulation of knowledge has opened new avenues for their applications. Via genetic engineering, the MV yield can be greatly increased, and the components of MVs can be tailored. Recent studies have demonstrated that MVs have promising potential for applications such as drug delivery systems and nanobiocatalysts. For instance, MV vaccines have been extensively studied and have already been approved in Europe. Recent MV studies have evoked great interest in the fields of biology and biotechnology, but fundamental questions, such as their transport in the environment or physicochemical features of MVs, remain to be addressed. In this review, we present the current understanding of bacterial MVs and environmental perspectives and further introduce their applications.
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Affiliation(s)
- Masanori Toyofuku
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
| | - Yosuke Tashiro
- Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University, Hamamatsu, Shizuoka 432-8561, Japan
| | - Yusuke Hasegawa
- Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University, Hamamatsu, Shizuoka 432-8561, Japan
| | - Masaharu Kurosawa
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan
| | - Nobuhiko Nomura
- Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan.
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127
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Magalon A, Alberge F. Distribution and dynamics of OXPHOS complexes in the bacterial cytoplasmic membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1857:198-213. [PMID: 26545610 DOI: 10.1016/j.bbabio.2015.10.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 10/28/2015] [Accepted: 10/29/2015] [Indexed: 12/23/2022]
Abstract
Oxidative phosphorylation (OXPHOS) is an essential process for most living organisms mostly sustained by protein complexes embedded in the cell membrane. In order to thrive, cells need to quickly respond to changes in the metabolic demand or in their environment. An overview of the strategies that can be employed by bacterial cells to adjust the OXPHOS outcome is provided. Regulation at the level of gene expression can only provide a means to adjust the OXPHOS outcome to long-term trends in the environment. In addition, the actual view is that bioenergetic membranes are highly compartmentalized structures. This review discusses what is known about the spatial organization of OXPHOS complexes and the timescales at which they occur. As exemplified with the commensal gut bacterium Escherichia coli, three levels of spatial organization are at play: supercomplexes, membrane microdomains and polar assemblies. This review provides a particular focus on whether dynamic spatial organization can fine-tune the OXPHOS through the definition of specialized functional membrane microdomains. Putative mechanisms responsible for spatio-temporal regulation of the OXPHOS complexes are discussed. This article is part of a Special Issue entitled Organization and dynamics of bioenergetic systems in bacteria, edited by Conrad Mullineaux.
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Affiliation(s)
- Axel Magalon
- CNRS, Laboratoire de Chimie Bactérienne (UMR 7283), Institut de Microbiologie de la Méditerranée, 13009 Marseille, France; Aix-Marseille University, UMR 7283, 13009 Marseille, France.
| | - François Alberge
- CNRS, Laboratoire de Chimie Bactérienne (UMR 7283), Institut de Microbiologie de la Méditerranée, 13009 Marseille, France; Aix-Marseille University, UMR 7283, 13009 Marseille, France
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128
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Abstract
The functionality of cellular membranes relies on the molecular order imparted by lipids. In eukaryotes, sterols such as cholesterol modulate membrane order, yet they are not typically found in prokaryotes. The structurally similar bacterial hopanoids exhibit similar ordering properties as sterols in vitro, but their exact physiological role in living bacteria is relatively uncharted. We present evidence that hopanoids interact with glycolipids in bacterial outer membranes to form a highly ordered bilayer in a manner analogous to the interaction of sterols with sphingolipids in eukaryotic plasma membranes. Furthermore, multidrug transport is impaired in a hopanoid-deficient mutant of the gram-negative Methylobacterium extorquens, which introduces a link between membrane order and an energy-dependent, membrane-associated function in prokaryotes. Thus, we reveal a convergence in the architecture of bacterial and eukaryotic membranes and implicate the biosynthetic pathways of hopanoids and other order-modulating lipids as potential targets to fight pathogenic multidrug resistance.
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129
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Lopez D. Molecular composition of functional microdomains in bacterial membranes. Chem Phys Lipids 2015; 192:3-11. [PMID: 26320704 DOI: 10.1016/j.chemphyslip.2015.08.015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 08/10/2015] [Accepted: 08/24/2015] [Indexed: 12/14/2022]
Abstract
Membranes of eukaryotic cells organize a number of proteins related to signal transduction and membrane trafficking into microdomains, which are enriched in particular lipids, like cholesterol and sphingolipids and are commonly referred as to lipid rafts or membrane rafts. The existence of this type of signaling platforms was traditionally associated with eukaryotic membranes because prokaryotic cells were considered too simple organisms to require a sophisticated organization of their signaling networks. However, the research that have been performed during last years have shown that bacteria organize many signaling transduction processes in Functional Membrane Microdomains (FMMs), which are similar to the lipid rafts that are found in eukaryotic cells. The current knowledge of the existence of FMMs in bacteria is described in this review and the specific structural and biological properties of these membrane microdomains are introduced. The organization of FMMs in bacterial membranes reveals an unexpected level of sophistication in signaling transduction and membrane organization that is unprecedented in bacteria, suggesting that bacteria as more complex organisms than previously considered.
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Affiliation(s)
- Daniel Lopez
- Research Center for Infectious Diseases (ZINF), Institute for Molecular Infection Biology (IMIB), University of Würzburg, Josef-Schneider Strasse (2), 97080 Würzburg, Germany; Spanish National Center for Biotechnology (CNB), Campus de Cantoblanco, Darwin 3, 28049 Madrid, Spain.
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130
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Heberle FA, Myles DAA, Katsaras J. Biomembranes research using thermal and cold neutrons. Chem Phys Lipids 2015; 192:41-50. [PMID: 26241882 DOI: 10.1016/j.chemphyslip.2015.07.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Revised: 07/25/2015] [Accepted: 07/27/2015] [Indexed: 01/26/2023]
Abstract
In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: "whatever the radiation from Be may be, it has most remarkable properties." Where it concerns hydrogen-rich biological materials, the "most remarkable" property is the neutron's differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, imparting sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. This article describes recent biomembranes research using a variety of neutron scattering techniques.
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Affiliation(s)
- F A Heberle
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge, TN, 37831, United States; Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, United States
| | - D A A Myles
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge, TN, 37831, United States
| | - J Katsaras
- Biology and Soft Matter Division, Neutron Sciences Directorate, Oak Ridge, TN, 37831, United States; Joint Institute for Neutron Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, United States; Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, United States.
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131
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Schneider J, Mielich-Süss B, Böhme R, Lopez D. In vivo characterization of the scaffold activity of flotillin on the membrane kinase KinC of Bacillus subtilis. MICROBIOLOGY-SGM 2015; 161:1871-1887. [PMID: 26297017 DOI: 10.1099/mic.0.000137] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Scaffold proteins are ubiquitous chaperones that bind to proteins and facilitate the physical interaction of the components of signal transduction pathways or multi-enzymic complexes. In this study, we used a biochemical approach to dissect the molecular mechanism of a membrane-associated scaffold protein, FloT, a flotillin-homologue protein that is localized in functional membrane microdomains of the bacterium Bacillus subtilis. This study provides unambiguous evidence that FloT physically binds to and interacts with the membrane-bound sensor kinase KinC. This sensor kinase activates biofilm formation in B. subtilis in response to the presence of the self-produced signal surfactin. Furthermore, we have characterized the mechanism by which the interaction of FloT with KinC benefits the activity of KinC. Two separate and synergistic effects constitute this mechanism: first, the scaffold activity of FloT promotes more efficient self-interaction of KinC and facilitates dimerization into its active form. Second, the selective binding of FloT to KinC prevents the occurrence of unspecific aggregation between KinC and other proteins that may generate dead-end intermediates that could titrate the activity of KinC. Flotillin proteins appear to play an important role in prokaryotes in promoting effective binding of signalling proteins with their correct protein partners.
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Affiliation(s)
- Johannes Schneider
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany
- Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
| | - Benjamin Mielich-Süss
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany
- Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
| | - Richard Böhme
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany
- Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
| | - Daniel Lopez
- Institute for Molecular Infection Biology (IMIB), University of Würzburg, Würzburg 97080, Germany
- National Center for Biotechnology (CNB), Spanish Research Council (CSIC), Madrid 28050, Spain
- Research Centre for Infectious Diseases (ZINF), University of Würzburg, Würzburg 97080, Germany
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Matsumoto K, Hara H, Fishov I, Mileykovskaya E, Norris V. The membrane: transertion as an organizing principle in membrane heterogeneity. Front Microbiol 2015; 6:572. [PMID: 26124753 PMCID: PMC4464175 DOI: 10.3389/fmicb.2015.00572] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/25/2015] [Indexed: 01/05/2023] Open
Abstract
The bacterial membrane exhibits a significantly heterogeneous distribution of lipids and proteins. This heterogeneity results mainly from lipid-lipid, protein-protein, and lipid-protein associations which are orchestrated by the coupled transcription, translation and insertion of nascent proteins into and through membrane (transertion). Transertion is central not only to the individual assembly and disassembly of large physically linked groups of macromolecules (alias hyperstructures) but also to the interactions between these hyperstructures. We review here these interactions in the context of the processes in Bacillus subtilis and Escherichia coli of nutrient sensing, membrane synthesis, cytoskeletal dynamics, DNA replication, chromosome segregation, and cell division.
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Affiliation(s)
- Kouji Matsumoto
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, SaitamaJapan
| | - Hiroshi Hara
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, SaitamaJapan
| | - Itzhak Fishov
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer-ShevaIsrael
| | - Eugenia Mileykovskaya
- Department of Biochemistry and Molecular Biology, University of Texas Medical School at HoustonHouston, TX, USA
| | - Vic Norris
- Laboratory of Microbiology Signals and Microenvironment EA 4312, Department of Science, University of Rouen, Mont-Saint-AignanFrance
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133
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Preiss L, Hicks DB, Suzuki S, Meier T, Krulwich TA. Alkaliphilic Bacteria with Impact on Industrial Applications, Concepts of Early Life Forms, and Bioenergetics of ATP Synthesis. Front Bioeng Biotechnol 2015; 3:75. [PMID: 26090360 PMCID: PMC4453477 DOI: 10.3389/fbioe.2015.00075] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 05/10/2015] [Indexed: 12/28/2022] Open
Abstract
Alkaliphilic bacteria typically grow well at pH 9, with the most extremophilic strains growing up to pH values as high as pH 12–13. Interest in extreme alkaliphiles arises because they are sources of useful, stable enzymes, and the cells themselves can be used for biotechnological and other applications at high pH. In addition, alkaline hydrothermal vents represent an early evolutionary niche for alkaliphiles and novel extreme alkaliphiles have also recently been found in alkaline serpentinizing sites. A third focus of interest in alkaliphiles is the challenge raised by the use of proton-coupled ATP synthases for oxidative phosphorylation by non-fermentative alkaliphiles. This creates a problem with respect to tenets of the chemiosmotic model that remains the core model for the bioenergetics of oxidative phosphorylation. Each of these facets of alkaliphilic bacteria will be discussed with a focus on extremely alkaliphilic Bacillus strains. These alkaliphilic bacteria have provided a cogent experimental system to probe adaptations that enable their growth and oxidative phosphorylation at high pH. Adaptations are clearly needed to enable secreted or partially exposed enzymes or protein complexes to function at the high external pH. Also, alkaliphiles must maintain a cytoplasmic pH that is significantly lower than the pH of the outside medium. This protects cytoplasmic components from an external pH that is alkaline enough to impair their stability or function. However, the pH gradient across the cytoplasmic membrane, with its orientation of more acidic inside than outside, is in the reverse of the productive orientation for bioenergetic work. The reversed gradient reduces the trans-membrane proton-motive force available to energize ATP synthesis. Multiple strategies are hypothesized to be involved in enabling alkaliphiles to circumvent the challenge of a low bulk proton-motive force energizing proton-coupled ATP synthesis at high pH.
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Affiliation(s)
- Laura Preiss
- Department of Structural Biology, Max Planck Institute of Biophysics , Frankfurt , Germany
| | - David B Hicks
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai , New York, NY , USA
| | - Shino Suzuki
- Geomicrobiology Group, Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology , Nankoku , Japan ; Microbial and Environmental Genomics, J. Craig Venter Institutes , La Jolla, CA , USA
| | - Thomas Meier
- Department of Structural Biology, Max Planck Institute of Biophysics , Frankfurt , Germany
| | - Terry Ann Krulwich
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai , New York, NY , USA
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