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Guar gum propionate-kojic acid films for Escherichia coli biofilm disruption and simultaneous inhibition of planktonic growth. Int J Biol Macromol 2022; 211:57-73. [DOI: 10.1016/j.ijbiomac.2022.05.052] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 05/05/2022] [Accepted: 05/06/2022] [Indexed: 11/21/2022]
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2
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Chang YW, Shaffer CL, Rettberg LA, Ghosal D, Jensen GJ. In Vivo Structures of the Helicobacter pylori cag Type IV Secretion System. Cell Rep 2019; 23:673-681. [PMID: 29669273 PMCID: PMC5931392 DOI: 10.1016/j.celrep.2018.03.085] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 01/16/2018] [Accepted: 03/19/2018] [Indexed: 02/06/2023] Open
Abstract
The type IV secretion system (T4SS) is a versatile nanomachine that translocates diverse effector molecules between microbes and into eukaryotic cells. Here, using electron cryotomography, we reveal the molecular architecture of the Helicobacter pylori cag T4SS. Although most components are unique to H. pylori, the cag T4SS exhibits remarkable architectural similarity to other T4SSs. Our images revealed that, when H. pylori encounters host cells, the bacterium elaborates membranous tubes perforated by lateral ports. Sub-tomogram averaging of the cag T4SS machinery revealed periplasmic densities associated with the outer membrane, a central stalk, and peripheral wing-like densities. Additionally, we resolved pilus-like rod structures extending from the cag T4SS into the inner membrane, as well as densities within the cytoplasmic apparatus corresponding to a short central barrel surrounded by four longer barrels. Collectively, these studies reveal the structure of a dynamic molecular machine that evolved to function in the human gastric niche.
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Affiliation(s)
- Yi-Wei Chang
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Carrie L Shaffer
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Lee A Rettberg
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Howard Hughes Medical Institute, Pasadena, CA 91125, USA
| | - Debnath Ghosal
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Grant J Jensen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Howard Hughes Medical Institute, Pasadena, CA 91125, USA.
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3
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Abstract
Type IV secretion systems (T4SSs) are large multisubunit translocons, found in both gram-negative and gram-positive bacteria and in some archaea. These systems transport a diverse array of substrates from DNA and protein-DNA complexes to proteins, and play fundamental roles in both bacterial pathogenesis and bacterial adaptation to the cellular milieu in which bacteria live. This review describes the various biochemical and structural advances made toward understanding the biogenesis, architecture, and function of T4SSs.
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Affiliation(s)
- Vidya Chandran Darbari
- Section of Structural Biology, Department of Medicine, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
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4
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Van Der Hofstadt M, Hüttener M, Juárez A, Gomila G. Nanoscale imaging of the growth and division of bacterial cells on planar substrates with the atomic force microscope. Ultramicroscopy 2015; 154:29-36. [PMID: 25791909 DOI: 10.1016/j.ultramic.2015.02.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 02/27/2015] [Accepted: 02/28/2015] [Indexed: 02/05/2023]
Abstract
With the use of the atomic force microscope (AFM), the Nanomicrobiology field has advanced drastically. Due to the complexity of imaging living bacterial processes in their natural growing environments, improvements have come to a standstill. Here we show the in situ nanoscale imaging of the growth and division of single bacterial cells on planar substrates with the atomic force microscope. To achieve this, we minimized the lateral shear forces responsible for the detachment of weakly adsorbed bacteria on planar substrates with the use of the so called dynamic jumping mode with very soft cantilever probes. With this approach, gentle imaging conditions can be maintained for long periods of time, enabling the continuous imaging of the bacterial cell growth and division, even on planar substrates. Present results offer the possibility to observe living processes of untrapped bacteria weakly attached to planar substrates.
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Affiliation(s)
- M Van Der Hofstadt
- Institut de Bioenginyeria de Catalunya (IBEC), C/ Baldiri i Reixac 11-15, 08028 Barcelona, Spain
| | - M Hüttener
- Institut de Bioenginyeria de Catalunya (IBEC), C/ Baldiri i Reixac 11-15, 08028 Barcelona, Spain; Departament de Microbiologia, Universitat de Barcelona, Avinguda Diagonal 645, 08028 Barcelona, Spain
| | - A Juárez
- Institut de Bioenginyeria de Catalunya (IBEC), C/ Baldiri i Reixac 11-15, 08028 Barcelona, Spain; Departament de Microbiologia, Universitat de Barcelona, Avinguda Diagonal 645, 08028 Barcelona, Spain
| | - G Gomila
- Institut de Bioenginyeria de Catalunya (IBEC), C/ Baldiri i Reixac 11-15, 08028 Barcelona, Spain; Departament d'Electronica, Universitat de Barcelona, C/ Marti i Franqués 1, 08028 Barcelona, Spain.
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5
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Freese PD, Korolev KS, Jiménez JI, Chen IA. Genetic drift suppresses bacterial conjugation in spatially structured populations. Biophys J 2014; 106:944-54. [PMID: 24559997 DOI: 10.1016/j.bpj.2014.01.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Revised: 01/02/2014] [Accepted: 01/10/2014] [Indexed: 11/24/2022] Open
Abstract
Conjugation is the primary mechanism of horizontal gene transfer that spreads antibiotic resistance among bacteria. Although conjugation normally occurs in surface-associated growth (e.g., biofilms), it has been traditionally studied in well-mixed liquid cultures lacking spatial structure, which is known to affect many evolutionary and ecological processes. Here we visualize spatial patterns of gene transfer mediated by F plasmid conjugation in a colony of Escherichia coli growing on solid agar, and we develop a quantitative understanding by spatial extension of traditional mass-action models. We found that spatial structure suppresses conjugation in surface-associated growth because strong genetic drift leads to spatial isolation of donor and recipient cells, restricting conjugation to rare boundaries between donor and recipient strains. These results suggest that ecological strategies, such as enforcement of spatial structure and enhancement of genetic drift, could complement molecular strategies in slowing the spread of antibiotic resistance genes.
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Affiliation(s)
- Peter D Freese
- FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts
| | - Kirill S Korolev
- FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts; Department of Physics, Harvard University, Cambridge, Massachusetts; Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts; Department of Physics and Program in Bioinformatics, Boston University, Boston, Massachusetts
| | - José I Jiménez
- FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts; Faculty of Health and Medical Sciences, University of Surrey, United Kingdom
| | - Irene A Chen
- FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts; Department of Chemistry and Biochemistry, Program in Biomolecular Sciences and Engineering, University of California at Santa Barbara, Santa Barbara, California.
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6
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Expression and functional characterization of the Agrobacterium VirB2 amino acid substitution variants in T-pilus biogenesis, virulence, and transient transformation efficiency. PLoS One 2014; 9:e101142. [PMID: 24971727 PMCID: PMC4074166 DOI: 10.1371/journal.pone.0101142] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 06/02/2014] [Indexed: 11/19/2022] Open
Abstract
Agrobacterium tumefaciens is a phytopathogenic bacterium that causes crown gall disease by transferring transferred DNA (T-DNA) into the plant genome. The translocation process is mediated by the type IV secretion system (T4SS) consisting of the VirD4 coupling protein and 11 VirB proteins (VirB1 to VirB11). All VirB proteins are required for the production of T-pilus, which consists of processed VirB2 (T-pilin) and VirB5 as major and minor subunits, respectively. VirB2 is an essential component of T4SS, but the roles of VirB2 and the assembled T-pilus in Agrobacterium virulence and the T-DNA transfer process remain unknown. Here, we generated 34 VirB2 amino acid substitution variants to study the functions of VirB2 involved in VirB2 stability, extracellular VirB2/T-pilus production and virulence of A. tumefaciens. From the capacity for extracellular VirB2 production (ExB2+ or ExB2−) and tumorigenesis on tomato stems (Vir+ or Vir−), the mutants could be classified into three groups: ExB2−/Vir−, ExB2−/Vir+, and ExB2+/Vir+. We also confirmed by electron microscopy that five ExB2−/Vir+ mutants exhibited a wild-type level of virulence with their deficiency in T-pilus formation. Interestingly, although the five T-pilus−/Vir+ uncoupling mutants retained a wild-type level of tumorigenesis efficiency on tomato stems and/or potato tuber discs, their transient transformation efficiency in Arabidopsis seedlings was highly attenuated. In conclusion, we have provided evidence for a role of T-pilus in Agrobacterium transformation process and have identified the domains and amino acid residues critical for VirB2 stability, T-pilus biogenesis, tumorigenesis, and transient transformation efficiency.
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7
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King A, Chakrabarty S, Zhang W, Zeng X, Ohman DE, Wood LF, Abraham S, Rao R, Wynne KJ. High antimicrobial effectiveness with low hemolytic and cytotoxic activity for PEG/quaternary copolyoxetanes. Biomacromolecules 2014; 15:456-67. [PMID: 24422429 PMCID: PMC3998775 DOI: 10.1021/bm401794p] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
![]()
The
alkyl chain length of quaternary ammonium/PEG copolyoxetanes
has been varied to discern effects on solution antimicrobial efficacy,
hemolytic activity and cytotoxicity. Monomers 3-((4-bromobutoxy)methyl)-3-methyloxetane
(BBOx) and 3-((2-(2-methoxyethoxy)ethoxy)methyl)-3-methyloxetane (ME2Ox)
were used to prepare precursor P[(BBOx)(ME2Ox)-50:50–4 kDa]
copolyoxetane via cationic ring opening polymerization. The 1:1 copolymer
composition and Mn (4 kDa) were confirmed
by 1H NMR spectroscopy. After C–Br substitution
by a series of tertiary amines, ionic liquid Cx-50
copolyoxetanes were obtained, where 50 is the mole percent of quaternary
repeat units and “x” is quaternary
alkyl chain length (2, 6, 8, 10, 12, 14, or 16 carbons). Modulated
differential scanning calorimetry (MDSC) studies showed Tgs between −40 and −60 °C and melting
endotherms for C14–50 and C16–50. Minimum inhibitory
concentrations (MIC) were determined for Escherichia
coli, Staphylococcus aureus, and Pseudomonas aeruginosa. A systematic
dependence of MIC on alkyl chain length was found. The most effective
antimicrobials were in the C6–50 to C12–50 range. C8–50
had better overall performance with MICs of 4 μg/mL, E. coli; 2 μg/mL, S. aureus; and 24 μg/mL, P. aeruginosa. At 5 × MIC, C8–50 effected >99% kill in 1 h against S. aureus, E. coli, and P. aeruginosa challenges of
108 cfu/mL; log reductions (1 h) were 7, 3, and 5, respectively.
To provide additional insight into polycation interactions with bacterial
membranes, a geometric model based on the dimensions of E. coli is described that provides an estimate of
the maximum number of polycations that can chemisorb. Chain dimensions
were estimated for polycation C8–50 with a molecular weight
of 5 kDa. Considering the approximations for polycation chemisorption
(PCC), it is surprising that a calculation based on geometric considerations
gives a C8–50 concentration within a factor of 2 of the MIC,
4.0 (±1.2) μg/mL for E. coli. Cx-50 copolyoxetane cytotoxicity was low for human
red blood cells, human dermal fibroblasts (HDF), and human foreskin
fibroblasts (HFF). Selectivities for bacterial kill over cell lysis
were among the highest ever reported for polycations indicating good
prospects for biocompatibility.
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Affiliation(s)
- Allison King
- Department of Chemical and Life Science Engineering, ‡Department of Microbiology and Immunology, and ∥Integrated Life Sciences Program, Virginia Commonwealth University Richmond, Virginia 23284, United States
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8
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Cheng MS, Ho JS, Lau SH, Chow VTK, Toh CS. Impedimetric microbial sensor for real-time monitoring of phage infection of Escherichia coli. Biosens Bioelectron 2013; 47:340-4. [PMID: 23603131 DOI: 10.1016/j.bios.2013.03.050] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Revised: 03/20/2013] [Accepted: 03/21/2013] [Indexed: 01/02/2023]
Abstract
We describe an impedimetric microbial sensor for real-time monitoring of the non-lytic M13 bacteriophage infection of Escherichia coli cells using a gold electrode covalently grafted with a monolayer of lipopolysaccharide specific antibody. After infection, damage to the lipopolysaccharide layer on the outer membrane of E. coli causes changes to its surface charge and morphology, resulting in the aggregation of redox probe, Fe(CN)6(3-/4-) at the electrode surface and thereby increases its electron-transfer rate. This consequent decrease of electron-transfer resistance in the presence of bacteriophage can be easily monitored using Faradaic impedance spectroscopy. Non-lytic bacterium-phage interaction which is hardly observable using conventional microscopic methods is detected within 3h using this impedimetric microbial sensor which demonstrates its excellent performance in terms of analysis time, ease and reduced reliance on labeling steps during in-situ monitoring of the phage infection process.
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Affiliation(s)
- Ming Soon Cheng
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore
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9
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Abstract
Bacteria have evolved several secretion machineries to bring about transport of various virulence factors, nutrients, nucleic acids and cell-surface appendages that are essential for their pathogenesis. T4S (Type IV secretion) systems are versatile secretion systems found in various Gram-negative and Gram-positive bacteria and in few archaea. They are large multisubunit translocons secreting a diverse array of substrates varying in size and nature from monomeric proteins to nucleoprotein complexes. T4S systems have evolved from conjugation machineries and are implicated in antibiotic resistance gene transfer and transport of virulence factors in Legionella pneumophila causing Legionnaires’ disease, Brucella suis causing brucellosis and Helicobacter pylori causing gastroduodenal diseases. The best-studied are the Agrobacterium tumefaciens VirB/D4 and the Escherichia coli plasmid pKM101 T4S systems. Recent structural advances revealing the cryo-EM (electron microscopy) structure of the core translocation assembly and high-resolution structure of the outer-membrane pore of T4S systems have made paradigm shifts in the understanding of T4S systems. The present paper reviews the advances made in biochemical and structural studies and summarizes our current understanding of the molecular architecture of this mega-assembly.
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10
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Abstract
Unraveling the structure of microbial cells is a major challenge in current microbiology and offers exciting prospects in biomedicine. Atomic force microscopy (AFM) appears as a powerful method to image the surface ultrastructure of live cells under physiological conditions and allows real-time imaging to follow dynamic processes such as cell growth, and division and effects of drugs and chemicals. The following chapter introduces different methods of sample preparation to gain insights into the microbial cell organization. Successful strategies to immobilize microorganisms, including physical entrapment and chemical attachment, are described. This step is a key step and a prerequisite of any analysis and persists as an important limitation to the application of AFM to microbiology due to the wide diversity of microorganisms. Finally, some applications are depicted which underlie the ability of AFM to explore living microbes with unprecedented resolution.
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11
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Harel M, Weiss G, Daniel E, Wilenz A, Hadas O, Sukenik A, Sedmak B, Dittmann E, Braun S, Kaplan A. Casting a net: fibres produced by Microcystis sp. in field and laboratory populations. ENVIRONMENTAL MICROBIOLOGY REPORTS 2012; 4:342-349. [PMID: 23760798 DOI: 10.1111/j.1758-2229.2012.00339.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The reasons for the apparent dominance of the toxic cyanobacterium Microcystis sp., reflected by its massive blooms in many fresh water bodies, are poorly understood. We show that in addition to a large array of secondary metabolites, some of which are toxic to eukaryotes, Microcystis sp. secretes large amounts of fibrous exopolysaccharides that form extremely long fibres several millimetres in length. This phenomenon was detected in field and laboratory cultures of various Microcystis strains. In addition, we have identified and characterized three of the proteins associated with the fibres and the genes encoding them in Microcystis sp. PCC 7806 but were unable to completely delete them from its genome. Phylogenetic analysis of the most abundant one, designated IPF-469, showed its presence only in cyanobacteria. Its closest relatives were detected in Synechocystis sp. PCC 6803 and in Cyanothece sp. strains; in the latter the genomic organization of the IPF-469 was highly conserved. IPF-469 and the other two proteins identified here, a haloperoxidase and a haemolysin-type calcium-binding protein, may be part of the fibres secretion pathway. The biological role of the fibres in Microcystis sp. is discussed.
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Affiliation(s)
- Moshe Harel
- The Alexander Silberman Institute of Life Sciences, Edmond J. Safra Campus, Givat Ram, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel The Yigal Allon Kinneret Limnological Laboratory, Israel Oceanographic and Limnological Research, PO Box 447, Migdal 14950, Israel Department of Genetic Toxicology and Cancer Biology, National Institute of Biology, Ljubljana, Slovenia Institute of Biochemistry and Biology, University of Potsdam, 14476 Golm, Germany
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12
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Merkey BV, Lardon LA, Seoane JM, Kreft JU, Smets BF. Growth dependence of conjugation explains limited plasmid invasion in biofilms: an individual-based modelling study. Environ Microbiol 2011; 13:2435-52. [DOI: 10.1111/j.1462-2920.2011.02535.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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13
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Allison DP, Mortensen NP, Sullivan CJ, Doktycz MJ. Atomic force microscopy of biological samples. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2011; 2:618-34. [PMID: 20672388 DOI: 10.1002/wnan.104] [Citation(s) in RCA: 108] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The ability to evaluate structural-functional relationships in real time has allowed scanning probe microscopy (SPM) to assume a prominent role in post genomic biological research. In this mini-review, we highlight the development of imaging and ancillary techniques that have allowed SPM to permeate many key areas of contemporary research. We begin by examining the invention of the scanning tunneling microscope (STM) by Binnig and Rohrer in 1982 and discuss how it served to team biologists with physicists to integrate high-resolution microscopy into biological science. We point to the problems of imaging nonconductive biological samples with the STM and relate how this led to the evolution of the atomic force microscope (AFM) developed by Binnig, Quate, and Gerber, in 1986. Commercialization in the late 1980s established SPM as a powerful research tool in the biological research community. Contact mode AFM imaging was soon complemented by the development of non-contact imaging modes. These non-contact modes eventually became the primary focus for further new applications including the development of fast scanning methods. The extreme sensitivity of the AFM cantilever was recognized and has been developed into applications for measuring forces required for indenting biological surfaces and breaking bonds between biomolecules. Further functional augmentation to the cantilever tip allowed development of new and emerging techniques including scanning ion-conductance microscopy (SICM), scanning electrochemical microscope (SECM), Kelvin force microscopy (KFM) and scanning near field ultrasonic holography (SNFUH).
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Affiliation(s)
- David P Allison
- Biosciences Division, Oak Ridge National Laboratory, TN 37831-6445, USA
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14
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Seoane J, Yankelevich T, Dechesne A, Merkey B, Sternberg C, Smets BF. An individual-based approach to explain plasmid invasion in bacterial populations. FEMS Microbiol Ecol 2010; 75:17-27. [PMID: 21091520 DOI: 10.1111/j.1574-6941.2010.00994.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
We present an individual-based experimental framework to identify and estimate the main parameters governing bacterial conjugation at the individual cell scale. From this analysis, we have established that transient periods of unregulated plasmid transfer within newly formed transconjugant cells, together with contact mechanics arising from cellular growth and division, are the two main processes determining the emergent inability of the pWW0 TOL plasmid to fully invade spatially structured Pseudomonas putida populations. We have also shown that pWW0 conjugation occurs mainly at advanced stages of the growth cycle and that nongrowing cells, even when exposed to high nutrient concentrations, do not display conjugal activity. These results do not support previous hypotheses relating conjugation decay in the deeper cell layers of bacterial biofilms to nutrient depletion and low physiological activity. We observe, however, that transient periods of elevated plasmid transfer in newly formed transconjugant cells are offset by unfavorable cell-to-cell contact mechanics, which ultimately precludes the pWWO TOL plasmid from fully invading tightly packed multicellular P. putida populations such as microcolonies and biofilms.
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Affiliation(s)
- Jose Seoane
- Department of Environmental Engineering, Technical University of Denmark, Lyngby, Denmark
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15
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Abstract
Type IV secretion systems (T4SSs) are large protein complexes which traverse the cell envelope of many bacteria. They contain a channel through which proteins or protein–DNA complexes can be translocated. This translocation is driven by a number of cytoplasmic ATPases which might energize large conformational changes in the translocation complex. The family of T4SSs is very versatile, shown by the great variety of functions among family members. Some T4SSs are used by pathogenic Gram-negative bacteria to translocate a wide variety of virulence factors into the host cell. Other T4SSs are utilized to mediate horizontal gene transfer, an event that greatly facilitates the adaptation to environmental changes and is the basis for the spread of antibiotic resistance among bacteria. Here we review the recent advances in the characterization of the architecture and mechanism of substrate transfer in a few representative T4SSs with a particular focus on their diversity of structure and function.
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Affiliation(s)
- Karin Wallden
- Institute of Structural and Molecular Biology, UCL and Birkbeck, London WC1E 7HX, UK
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16
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Waksman G, Fronzes R. Molecular architecture of bacterial type IV secretion systems. Trends Biochem Sci 2010; 35:691-8. [PMID: 20621482 DOI: 10.1016/j.tibs.2010.06.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Revised: 06/10/2010] [Accepted: 06/10/2010] [Indexed: 11/18/2022]
Abstract
In Gram-negative bacteria, type IV secretion (T4S) systems form ATP-powered complexes that span the entire cellular envelope and secrete a wide variety of substrates from single proteins to protein-protein and protein-DNA complexes. Recent structural data, namely the electron microscopy structure of the T4S core complex and the atomic-resolution structure of its outer-membrane pore, have profoundly altered our understanding of T4S architecture and mechanisms.
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Affiliation(s)
- Gabriel Waksman
- Institute of Structural and Molecular Biology, University College London and Birkbeck College, Malet Street, London WC1E 7HX, UK.
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17
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Abstract
DNA pumps play important roles in bacteria during cell division and during the transfer of genetic material by conjugation and transformation. The FtsK/SpoIIIE proteins carry out the translocation of double-stranded DNA to ensure complete chromosome segregation during cell division. In contrast, the complex molecular machines that mediate conjugation and genetic transformation drive the transport of single stranded DNA. The transformation machine also processes this internalized DNA and mediates its recombination with the resident chromosome during and after uptake, whereas the conjugation apparatus processes DNA before transfer. This article reviews these three types of DNA pumps, with attention to what is understood of their molecular mechanisms, their energetics and their cellular localizations.
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Affiliation(s)
- Briana Burton
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA
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18
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Ray R, Lizewski S, Fitzgerald LA, Little B, Ringeisen BR. Methods for imaging Shewanella oneidensis MR-1 nanofilaments. J Microbiol Methods 2010; 82:187-91. [PMID: 20561956 DOI: 10.1016/j.mimet.2010.05.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Accepted: 05/22/2010] [Indexed: 11/27/2022]
Abstract
Nanofilament production by Shewanella oneidensis MR-1 was evaluated as a function of lifestyle (planktonic vs. sessile) under aerobic and anaerobic conditions using different sample preparation techniques prior to imaging with scanning electron microscopy. Nanofilaments could be imaged on MR-1 cells grown in biofilms or planktonically under both aerobic and anaerobic batch culture conditions after fixation, critical point drying and coating with a conductive metal. Critical point drying was a requirement for imaging nanofilaments attached to planktonically grown MR-1 cells, but not for cells grown in a biofilm. Techniques described in this paper cannot be used to differentiate nanowires from pili or flagella.
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Affiliation(s)
- R Ray
- US Naval Research Laboratory, John C. Stennis Space Center, MS 39529, USA
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19
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TURNER R, THOMSON N, KIRKHAM J, DEVINE D. Improvement of the pore trapping method to immobilize vital coccoid bacteria for high-resolution AFM: a study ofStaphylococcus aureus. J Microsc 2010; 238:102-10. [DOI: 10.1111/j.1365-2818.2009.03333.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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20
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Fronzes R, Christie PJ, Waksman G. The structural biology of type IV secretion systems. Nat Rev Microbiol 2009; 7:703-14. [PMID: 19756009 DOI: 10.1038/nrmicro2218] [Citation(s) in RCA: 281] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Type IV secretion systems (T4SSs) are versatile secretion systems that are found in both Gram-negative and Gram-positive bacteria and secrete a wide range of substrates, from single proteins to protein-protein and protein-DNA complexes. They usually consist of 12 components that are organized into ATP-powered, double-membrane-spanning complexes. The structures of single soluble components or domains have been solved, but an understanding of how these structures come together has only recently begun to emerge. This Review focuses on the structural advances that have been made over the past 10 years and how the corresponding structural insights have helped to elucidate many of the details of the mechanism of type IV secretion.
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Affiliation(s)
- Rémi Fronzes
- Institute of Structural and Molecular Biology, Malet Street, London WC1E 7HX, UK
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21
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Chen YY, Wu CC, Hsu JL, Peng HL, Chang HY, Yew TR. Surface rigidity change of Escherichia coli after filamentous bacteriophage infection. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:4607-4614. [PMID: 19366225 DOI: 10.1021/la8036346] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In this study, the feasibility using atomic force microscopy (AFM) to study the interaction between bacteriophages (phages) and bacteria in situ was demonstrated here. Filamentous phage M13 specifically infects the male Escherichia coli, which expresses F-pili. After infection, E. coli become fragile and grows at a slower rate. AFM provides a powerful tool for investigating these changes in a near-physiological environment. Using high-resolution AFM in phosphate-buffered saline, the damage to the lipopolysaccharide (LPS) layer on the outer membrane of the M13 phage-infected E. coli was observed. The membrane became smoother and more featureless compared to those that were not infected. Besides, the force-distance (f-d) curves were measured to reveal the surface rigidity change in E. coli after M13 phage infection. The effective spring constant and Young's modulus of E. coli decreased after M13 phage infection. Furthermore, the AFM tip was pressed against E. coli to study the response of E. coli under load before and after M13 phage infection. The results showed that after infection E. coli became less rigid and the membrane was also damaged. However, the stiffness changes, including the spring constant and Young's modulus of E. coli, are negligible after M13 phage infection compared with those in previous reports, which may be one of the reasons that E. coli still can maintain its viability after filamentous phage infection.
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Affiliation(s)
- Yi-Yang Chen
- Department of Materials Science and Engineering, National Tsing-Hua University, Hsinchu, Taiwan
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