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Sawabe T, Ojima Y, Nakagawa M, Sawada T, Tahara YO, Miyata M, Azuma M. Construction and characterization of a hypervesiculation strain of Escherichia coli Nissle 1917. PLoS One 2024; 19:e0301613. [PMID: 38564580 PMCID: PMC10986995 DOI: 10.1371/journal.pone.0301613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 03/19/2024] [Indexed: 04/04/2024] Open
Abstract
Outer membrane vesicles (OMVs) are produced by Gram-negative bacteria and deliver microbial molecules to distant target cells in a host. OMVs secreted by probiotic probiotic strain Escherichia coli Nissle 1917 (EcN) have been reported to induce an immune response. In this study, we aimed to increase the OMV production of EcN. The double gene knockout of mlaE and nlpI was conducted in EcN because the ΔmlaEΔnlpI of experimental strain E. coli K12 showed the highest OMV production in our previous report. The ΔmlaEΔnlpI of EcN showed approximately 8 times higher OMV production compared with the parental (wild-type) strain. Quick-freeze, deep-etch replica electron microscopy revealed that plasmolysis occurred in the elongated ΔmlaEΔnlpI cells and the peptidoglycan (PG) had numerous holes. While these phenomena are similar to the findings for the ΔmlaEΔnlpI of K12, there were more PG holes in the ΔmlaEΔnlpI of EcN than the K12 strain, which were observed not only at the tip of the long axis but also in the whole PG structure. Further analysis clarified that the viability of ΔmlaEΔnlpI of EcN decreased compared with that of the wild-type. Although the amount of PG in ΔmlaEΔnlpI cells was about half of that in wild-type, the components of amino acids in PG did not change in ΔmlaEΔnlpI. Although the viability decreased compared to the wild-type, the ΔmlaEΔnlpI grew in normal culture conditions. The hypervesiculation strain constructed here is expected to be used as an enhanced probiotic strain.
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Affiliation(s)
- Tomomi Sawabe
- Department of Chemistry and Bioengineering, Graduate School of Engineering, Osaka Metropolitan University, Osaka, Japan
| | - Yoshihiro Ojima
- Department of Chemistry and Bioengineering, Graduate School of Engineering, Osaka Metropolitan University, Osaka, Japan
| | - Mao Nakagawa
- Department of Chemistry and Bioengineering, Graduate School of Engineering, Osaka Metropolitan University, Osaka, Japan
| | - Toru Sawada
- Department of Chemistry and Bioengineering, Graduate School of Engineering, Osaka Metropolitan University, Osaka, Japan
| | - Yuhei O. Tahara
- Graduate School of Science, Osaka Metropolitan University, Osaka, Japan
| | - Makoto Miyata
- Graduate School of Science, Osaka Metropolitan University, Osaka, Japan
| | - Masayuki Azuma
- Department of Chemistry and Bioengineering, Graduate School of Engineering, Osaka Metropolitan University, Osaka, Japan
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2
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Ojima Y, Sawabe T, Nakagawa M, Tahara YO, Miyata M, Azuma M. Aberrant Membrane Structures in Hypervesiculating Escherichia coli Strain ΔmlaE ΔnlpI Visualized by Electron Microscopy. Front Microbiol 2021; 12:706525. [PMID: 34456889 PMCID: PMC8386018 DOI: 10.3389/fmicb.2021.706525] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/21/2021] [Indexed: 11/13/2022] Open
Abstract
Escherichia coli produces extracellular vesicles called outer membrane vesicles (OMVs) by releasing a part of its outer membrane. We previously reported that the combined deletion of nlpI and mlaE, related to envelope structure and phospholipid accumulation in the outer leaflet of the outer membrane, respectively, resulted in the synergistic increase of OMV production. In this study, the analysis of ΔmlaEΔnlpI cells using quick-freeze, deep-etch electron microscopy (QFDE-EM) revealed that plasmolysis occurred at the tip of the long axis in cells and that OMVs formed from this tip. Plasmolysis was also observed in the single-gene knockout mutants ΔnlpI and ΔmlaE. This study has demonstrated that plasmolysis was induced in the hypervesiculating mutant E. coli cells. Furthermore, intracellular vesicles and multilamellar OMV were observed in the ΔmlaEΔnlpI cells. Meanwhile, the secretion of recombinant green fluorescent protein (GFP) expressed in the cytosol of the ΔmlaEΔnlpI cells was more than 100 times higher than that of WT and ΔnlpI, and about 50 times higher than that of ΔmlaE in the OMV fraction, suggesting that cytosolic components were incorporated into outer-inner membrane vesicles (OIMVs) and released into the extracellular space. Additionally, QFDE-EM analysis revealed that ΔmlaEΔnlpI sacculi contained many holes noticeably larger than the mean radius of the peptidoglycan (PG) pores in wild-type (WT) E. coli. These results suggest that in ΔmlaEΔnlpI cells, cytoplasmic membrane materials protrude into the periplasmic space through the peptidoglycan holes and are released as OIMVs.
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Affiliation(s)
- Yoshihiro Ojima
- Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, Osaka, Japan
| | - Tomomi Sawabe
- Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, Osaka, Japan
| | - Mao Nakagawa
- Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, Osaka, Japan
| | - Yuhei O Tahara
- Graduate School of Science, Osaka City University, Osaka, Japan.,The OCU Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka City University, Osaka, Japan
| | - Makoto Miyata
- Graduate School of Science, Osaka City University, Osaka, Japan.,The OCU Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka City University, Osaka, Japan
| | - Masayuki Azuma
- Department of Applied Chemistry and Bioengineering, Graduate School of Engineering, Osaka City University, Osaka, Japan
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3
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Michael E, Nitzan Y, Langzam Y, Luboshits G, Cahan R. Effect of toluene on Pseudomonas stutzeri ST-9 morphology - plasmolysis, cell size, and formation of outer membrane vesicles. Can J Microbiol 2016; 62:682-91. [PMID: 27256870 DOI: 10.1139/cjm-2016-0099] [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] [Indexed: 11/22/2022]
Abstract
Isolated toluene-degrading Pseudomonas stutzeri ST-9 bacteria were grown in a minimal medium containing toluene (100 mg·L(-1)) (MMT) or glucose (MMG) as the sole carbon source, with specific growth rates of 0.019 h(-1) and 0.042 h(-1), respectively. Scanning (SEM) as well as transmission (TEM) electron microscope analyses showed that the bacterial cells grown to mid-log phase in the presence of toluene possess a plasmolysis space. TEM analysis revealed that bacterial cells that were grown in MMT were surrounded by an additional "material" with small vesicles in between. Membrane integrity was analyzed by leakage of 260 nm absorbing material and demonstrated only 7% and 8% leakage from cultures grown in MMT compared with MMG. X-ray microanalysis showed a 4.3-fold increase in Mg and a 3-fold increase in P in cells grown in MMT compared with cells grown in MMG. Fluorescence-activated cell sorting (FACS) analysis indicated that the permeability of the membrane to propidium iodide was 12.6% and 19.6% when the cultures were grown in MMG and MMT, respectively. The bacterial cell length increased by 8.5% ± 0.1% and 17% ± 2%, as measured using SEM images and FACS analysis, respectively. The results obtained in this research show that the presence of toluene led to morphology changes, such as plasmolysis, cell size, and formation of outer membrane vesicles. However, it does not cause significant damage to membrane integrity.
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Affiliation(s)
- Esti Michael
- a Department of Chemical Engineering, Ariel University, Ariel 40700, Israel.,b The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Yeshayahu Nitzan
- b The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Yakov Langzam
- b The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Galia Luboshits
- a Department of Chemical Engineering, Ariel University, Ariel 40700, Israel
| | - Rivka Cahan
- a Department of Chemical Engineering, Ariel University, Ariel 40700, Israel
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4
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Zaritsky A, Woldringh CL. Chromosome replication, cell growth, division and shape: a personal perspective. Front Microbiol 2015; 6:756. [PMID: 26284044 PMCID: PMC4522554 DOI: 10.3389/fmicb.2015.00756] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 07/10/2015] [Indexed: 11/13/2022] Open
Abstract
The origins of Molecular Biology and Bacterial Physiology are reviewed, from our personal standpoints, emphasizing the coupling between bacterial growth, chromosome replication and cell division, dimensions and shape. Current knowledge is discussed with historical perspective, summarizing past and present achievements and enlightening ideas for future studies. An interactive simulation program of the bacterial cell division cycle (BCD), described as "The Central Dogma in Bacteriology," is briefly represented. The coupled process of transcription/translation of genes encoding membrane proteins and insertion into the membrane (so-called transertion) is invoked as the functional relationship between the only two unique macromolecules in the cell, DNA and peptidoglycan embodying the nucleoid and the sacculus respectively. We envision that the total amount of DNA associated with the replication terminus, so called "nucleoid complexity," is directly related to cell size and shape through the transertion process. Accordingly, the primary signal for cell division transmitted by DNA dynamics (replication, transcription and segregation) to the peptidoglycan biosynthetic machinery is of a physico-chemical nature, e.g., stress in the plasma membrane, relieving nucleoid occlusion in the cell's center hence enabling the divisome to assemble and function between segregated daughter nucleoids.
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Affiliation(s)
- Arieh Zaritsky
- Faculty of Natural Sciences, Ben-Gurion University of the Negev, Be’er-Sheva, Israel
| | - Conrad L. Woldringh
- Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, Netherlands
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5
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Lan G, Wolgemuth CW, Sun SX. Z-ring force and cell shape during division in rod-like bacteria. Proc Natl Acad Sci U S A 2007; 104:16110-5. [PMID: 17913889 PMCID: PMC2042170 DOI: 10.1073/pnas.0702925104] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Indexed: 11/18/2022] Open
Abstract
The life cycle of bacterial cells consists of repeated elongation, septum formation, and division. Before septum formation, a division ring called the Z-ring, which is made of a filamentous tubulin analog, FtsZ, is seen at the mid cell. Together with several other proteins, FtsZ is essential for cell division. Visualization of strains with GFP-labeled FtsZ shows that the Z-ring contracts before septum formation and pinches the cell into two equal halves. Thus, the Z-ring has been postulated to act as a force generator, although the magnitude of the contraction force is unknown. In this article, we develop a mathematical model to describe the process of growth and Z-ring contraction in rod-like bacteria. The elasticity and growth of the cell wall is incorporated in the model to predict the contraction speed, the cell shape, and the contraction force. With reasonable parameters, the model shows that a small force from the Z-ring (8 pN in Escherichia coli) is sufficient to accomplish division.
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Affiliation(s)
- Ganhui Lan
- *Department of Mechanical Engineering and
| | - Charles W. Wolgemuth
- Department of Cell Biology and Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030-3505
| | - Sean X. Sun
- *Department of Mechanical Engineering and
- Whitaker Institute of Biomedical Engineering, The Johns Hopkins University, Baltimore, MD 21218; and
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6
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Pradel N, Santini CL, Bernadac A, Shih YL, Goldberg MB, Wu LF. Polar positional information in Escherichia coli spherical cells. Biochem Biophys Res Commun 2007; 353:493-500. [PMID: 17188233 DOI: 10.1016/j.bbrc.2006.12.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Accepted: 12/06/2006] [Indexed: 11/23/2022]
Abstract
Shigella surface protein IcsA and its cytoplasmic derivatives are localized to the old pole of rod-shaped cells when expressed in Escherichia coli. In spherical mreB cells, IcsA is targeted to ectopic sites and close to one extremity of actin-like MamK filament. To gain insight into the properties of the sites containing polar material, we studied the IcsA localization in spherical cells. GFP was exported into the periplasm via the Tat pathway and used as a periplasmic space marker. GFP displayed zonal fluorescence in both mreB and rodA-pbpA spherical E. coli cells, indicating an uneven periplasmic space. Deconvolution images revealed that the cytoplasmic IcsA fused to mCherry was localized outside or at the edge of the GFP zones. These observations strongly suggest that polar material is restricted to the positions where the periplasm possesses particular structural or biochemical properties.
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Affiliation(s)
- Nathalie Pradel
- Laboratoire de Chimie Bactérienne, UPR9043, Institut de Biologie Structurale et Microbiologie, CNRS, 31 chemin Joseph Aiguier, F-13402 Marseille cedex 20, France
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7
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Konopka MC, Shkel IA, Cayley S, Record MT, Weisshaar JC. Crowding and confinement effects on protein diffusion in vivo. J Bacteriol 2006; 188:6115-23. [PMID: 16923878 PMCID: PMC1595386 DOI: 10.1128/jb.01982-05] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The first in vivo measurements of a protein diffusion coefficient versus cytoplasmic biopolymer volume fraction are presented. Fluorescence recovery after photobleaching yields the effective diffusion coefficient on a 1-mum-length scale of green fluorescent protein within the cytoplasm of Escherichia coli grown in rich medium. Resuspension into hyperosmotic buffer lacking K+ and nutrients extracts cytoplasmic water, systematically increasing mean biopolymer volume fraction, <phi>, and thus the severity of possible crowding, binding, and confinement effects. For resuspension in isosmotic buffer (osmotic upshift, or Delta, of 0), the mean diffusion coefficient, <D>, in cytoplasm (6.1 +/- 2.4 microm2 s(-1)) is only 0.07 of the in vitro value (87 microm2 s(-1)); the relative dispersion among cells, sigmaD/<D> (standard deviation, sigma(D), relative to the mean), is 0.39. Both <D> and sigmaD/<D> remain remarkably constant over the range of Delta values of 0 to 0.28 osmolal. For a Delta value of > or =0.28 osmolal, formation of visible plasmolysis spaces (VPSs) coincides with the onset of a rapid decrease in <D> by a factor of 380 over the range of Delta values of 0.28 to 0.70 osmolal and a substantial increase in sigmaD/<D>. Individual values of D vary by a factor of 9 x 10(4) but correlate well with f(VPS), the fractional change in cytoplasmic volume on VPS formation. The analysis reveals two levels of dispersion in D among cells: moderate dispersion at low Delta values for cells lacking a VPS, perhaps related to variation in phi or biopolymer organization during the cell cycle, and stronger dispersion at high Delta values related to variation in f(VPS). Crowding effects alone cannot explain the data, nor do these data alone distinguish crowding from possible binding or confinement effects within a cytoplasmic meshwork.
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Affiliation(s)
- Michael C Konopka
- Department of Chemistry, University of Wisconsin-Madison, Madison, 1101 University Avenue, WI 53706, USA
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8
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Zaritsky A, Woldringh CL, Einav M, Alexeeva S. Use of thymine limitation and thymine starvation to study bacterial physiology and cytology. J Bacteriol 2006; 188:1667-79. [PMID: 16484178 PMCID: PMC1426543 DOI: 10.1128/jb.188.5.1667-1679.2006] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Arieh Zaritsky
- Department of Life Sciences, Ben-Gurion University of the Negev, POB 653, Be'er-Sheva 84105, Israel.
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9
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Poolman B, Blount P, Folgering JHA, Friesen RHE, Moe PC, van der Heide T. How do membrane proteins sense water stress? Mol Microbiol 2002; 44:889-902. [PMID: 12010487 DOI: 10.1046/j.1365-2958.2002.02894.x] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Maintenance of cell turgor is a prerequisite for almost any form of life as it provides a mechanical force for the expansion of the cell envelope. As changes in extracellular osmolality will have similar physicochemical effects on cells from all biological kingdoms, the responses to osmotic stress may be alike in all organisms. The primary response of bacteria to osmotic upshifts involves the activation of transporters, to effect the rapid accumulation of osmoprotectants, and sensor kinases, to increase the transport and/or biosynthetic capacity for these solutes. Upon osmotic downshift, the excess of cytoplasmic solutes is released via mechanosensitive channel proteins. A number of breakthroughs in the last one or two years have led to tremendous advances in our understanding of the molecular mechanisms of osmosensing in bacteria. The possible mechanisms of osmosensing, and the actual evidence for a particular mechanism, are presented for well studied, osmoregulated transport systems, sensor kinases and mechanosensitive channel proteins. The emerging picture is that intracellular ionic solutes (or ionic strength) serve as a signal for the activation of the upshift-activated transporters and sensor kinases. For at least one system, there is strong evidence that the signal is transduced to the protein complex via alterations in the protein-lipid interactions rather than direct sensing of ion concentration or ionic strength by the proteins. The osmotic downshift-activated mechanosensitive channels, on the other hand, sense tension in the membrane but other factors such as hydration state of the protein may affect the equilibrium between open and closed states of the proteins.
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Affiliation(s)
- Bert Poolman
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh, Groningen, The Netherlands.
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10
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Burr SE, Diep DB, Buckley JT. Type II secretion by Aeromonas salmonicida: evidence for two periplasmic pools of proaerolysin. J Bacteriol 2001; 183:5956-63. [PMID: 11566995 PMCID: PMC99674 DOI: 10.1128/jb.183.20.5956-5963.2001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Aeromonas salmonicida containing the cloned gene for proaerolysin secretes the protein via the type II secretory pathway. Here we show that altering a region near the beginning of aerA led to a dramatic increase in the amount of proaerolysin that was produced and that a large amount of the protein was cell associated. All of the cell-associated protein had crossed the cytoplasmic membrane, because the signal sequence had been removed, and all of it was accessible to processing by trypsin during osmotic shock. Enlargement of the periplasm was observed by electron microscopy in overproducing cells, likely caused by the osmotic effect of the very large concentrations of accumulated proaerolysin. Immunogold electron microscopy localized nearly all of the proaerolysin in the enlarged periplasm; however, only half of the protoxin was released from the cells by osmotic shocking. Cross-linking studies showed that this fraction contained normal dimeric proaerolysin but that proaerolysin in the fraction that was not shockable had not dimerized, although it appeared to be correctly folded. Both periplasmic fractions were secreted by the cells; however, the nonshockable fraction was secreted much more slowly than the shockable fraction. We estimated a rate for maximal secretion of proaerolysin from the bacteria that was much lower than the rates that have been estimated for inner membrane transit, which suggests that transit across the outer membrane is rate limiting and may account for the periplasmic accumulation of the protein. Finally, we show that overproduction of proaerolysin inhibited the release of the protease that is secreted by A. salmonicida.
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Affiliation(s)
- S E Burr
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada V8W 3P6
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11
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Abstract
Development of a sensitive assay that measures the rate of cellular internalization of an infecting bacteriophage T7 genome has led to surprising observations on the initiation of infection. Proteins ejected from the phage virion probably function as an extensible tail to form a channel across the cell envelope. This channel is subsequently used for translocating the phage genome into the cell. One of these ejected proteins also controls the amount of DNA that enters the cell, rendering subsequent internalization of the remainder of the genome dependent on transcription. Mutations affecting this protein allow the entire phage genome to enter a cell by the transcription-independent process. This process exhibits pseudo-zero-order reaction kinetics and a temperature dependence of translocation rate that are not expected if DNA ejection from a phage capsid were caused by a physical process. The temperature dependence of transcription-independent T7 DNA translocation rate is similar to those of enzyme-catalysed reactions. Current data suggest a highly speculative model, in which two of the proteins ejected from the phage head establish a molecular motor that ratchets the phage genome into the cell.
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Affiliation(s)
- I J Molineux
- Molecular Genetics and Microbiology, University of Texas, Austin, TX 78712-1095, USA.
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12
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Santini CL, Bernadac A, Zhang M, Chanal A, Ize B, Blanco C, Wu LF. Translocation of jellyfish green fluorescent protein via the Tat system of Escherichia coli and change of its periplasmic localization in response to osmotic up-shock. J Biol Chem 2001; 276:8159-64. [PMID: 11099493 DOI: 10.1074/jbc.c000833200] [Citation(s) in RCA: 156] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bacterial twin arginine translocation (Tat) pathway is capable of exporting cofactor-containing enzymes into the periplasm. To assess the capacity of the Tat pathway to export heterologous proteins and to gain information about the property of the periplasm, we fused the twin arginine signal peptide of the trimethylamine N-oxide reductase to the jellyfish green fluorescent protein (GFP). Unlike the Sec pathway, the Tat system successfully exported correctly folded GFP into the periplasm of Escherichia coli. Interestingly, GFP appeared as a halo in most cells and occasionally showed a polar localization in wild type strains. When subjected to a mild osmotic up-shock, GFP relocalized very quickly at the two poles of the cells. The conversion from the halo structure to a periplasmic gathering at particular locations was also observed with spherical cells of the DeltarodA-pbpA mutant or of the wild type strain treated with lysozyme. Therefore, the periplasm is not a uniform compartment and the polarization of GFP is unlikely to be caused by simple invagination of the cytoplasmic membrane at the poles. Moreover, the polar gathering of GFP is reversible; the reversion was accelerated by glucose and inhibited by azide and carbonyl cyanide m-chlorophenylhydrazone, indicating an active adaptation of the bacteria to the osmolarity in the medium. These results strongly suggest a relocalization of periplasmic substances in response to environmental changes. The polar area might be the preferential zone where bacteria sense the change in the environment.
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Affiliation(s)
- C L Santini
- Laboratoire de Chimie Bactérienne, UPR9043, Institut de Biologie Structurale et Microbiologie, CNRS, 31 chemin Joseph Aiguier, F-13402 Marseille cedex 20, France
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13
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Cayley DS, Guttman HJ, Record MT. Biophysical characterization of changes in amounts and activity of Escherichia coli cell and compartment water and turgor pressure in response to osmotic stress. Biophys J 2000; 78:1748-64. [PMID: 10733957 PMCID: PMC1300771 DOI: 10.1016/s0006-3495(00)76726-9] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
To obtain turgor pressure, intracellular osmolalities, and cytoplasmic water activity of Escherichia coli as a function of osmolality of growth, we have quantified and analyzed amounts of cell, cytoplasmic, and periplasmic water as functions of osmolality of growth and osmolality of plasmolysis of nongrowing cells with NaCl. The effects are large; NaCl (plasmolysis) titrations of cells grown in minimal medium at 0.03 Osm reduce cytoplasmic and cell water to approximately 20% and approximately 50% of their original values, and increase periplasmic water by approximately 300%. Independent analysis of amounts of cytoplasmic and cell water demonstrate that turgor pressure decreases with increasing osmolality of growth, from approximately 3.1 atm at 0.03 Osm to approximately 1.5 at 0.1 Osm and to less than 0.5 atm above 0.5 Osm. Analysis of periplasmic membrane-derived oligosaccharide (MDO) concentrations as a function of osmolality, calculated from literature analytical data and measured periplasmic volumes, provides independent evidence that turgor pressure decreases with increasing osmolality, and verifies that cytoplasmic and periplasmic osmolalities are equal. We propose that MDO play a key role in periplasmic volume regulation at low-to-moderate osmolality. At high growth osmolalities, where only a small amount of cytoplasmic water is observed, the small turgor pressure of E. coli demonstrates that cytoplasmic water activity is only slightly less than extracellular water activity. From these findings, we deduce that the activity of cytoplasmic water exceeds its mole fraction at high osmolality, and, therefore, conclude that the activity coefficient of cytoplasmic water increases with increasing growth osmolality and exceeds unity at high osmolality, presumably as a consequence of macromolecular crowding. These novel findings are significant for thermodynamic analyses of effects of changes in growth osmolality on biopolymer processes in general and osmoregulatory processes in particular in the E. coli cytoplasm.
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Affiliation(s)
- D S Cayley
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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14
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Abstract
Formation of the bacterial division septum is catalyzed by a number of essential proteins that assemble into a ring structure at the future division site. Assembly of proteins into the cytokinetic ring appears to occur in a hierarchial order that is initiated by the FtsZ protein, a structural and functional analog of eukaryotic tubulins. Placement of the division site at its correct location in Escherichia coli requires a division inhibitor (MinC), that is responsible for preventing septation at unwanted sites near the cell poles, and a topological specificity protein (MinE), that forms a ring at midcell and protects the midcell site from the division inhibitor. However, the mechanism responsible for identifying the position of the midcell site or the polar sites used for spore septum formation is still unclear. Regulation of the division process and its coordination with other cell cycle events, such as chromosome replication, are poorly understood. However, a protein has been identified in Caulobacter (CtrA) that regulates both the initiation of chromosome regulation and the transcription of ftsZ, and that may play an important role in the coordination process.
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Affiliation(s)
- L Rothfield
- Department of Microbiology, University of Connecticut Health Center, Farmington 06032, USA.
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15
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Abstract
Bacteria can survive dramatic osmotic shifts. Osmoregulatory responses mitigate the passive adjustments in cell structure and the growth inhibition that may ensue. The levels of certain cytoplasmic solutes rise and fall in response to increases and decreases, respectively, in extracellular osmolality. Certain organic compounds are favored over ions as osmoregulatory solutes, although K+ fluxes are intrinsic to the osmoregulatory response for at least some organisms. Osmosensors must undergo transitions between "off" and "on" conformations in response to changes in extracellular water activity (direct osmosensing) or resulting changes in cell structure (indirect osmosensing). Those located in the cytoplasmic membranes and nucleoids of bacteria are positioned for indirect osmosensing. Cytoplasmic membrane-based osmosensors may detect changes in the periplasmic and/or cytoplasmic solvent by experiencing changes in preferential interactions with particular solvent constituents, cosolvent-induced hydration changes, and/or macromolecular crowding. Alternatively, the membrane may act as an antenna and osmosensors may detect changes in membrane structure. Cosolvents may modulate intrinsic biomembrane strain and/or topologically closed membrane systems may experience changes in mechanical strain in response to imposed osmotic shifts. The osmosensory mechanisms controlling membrane-based K+ transporters, transcriptional regulators, osmoprotectant transporters, and mechanosensitive channels intrinsic to the cytoplasmic membrane of Escherichia coli are under intensive investigation. The osmoprotectant transporter ProP and channel MscL act as osmosensors after purification and reconstitution in proteoliposomes. Evidence that sensor kinase KdpD receives multiple sensory inputs is consistent with the effects of K+ fluxes on nucleoid structure, cellular energetics, cytoplasmic ionic strength, and ion composition as well as on cytoplasmic osmolality. Thus, osmoregulatory responses accommodate and exploit the effects of individual cosolvents on cell structure and function as well as the collective contribution of cosolvents to intracellular osmolality.
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Affiliation(s)
- J M Wood
- Department of Microbiology and Guelph-Waterloo Centre for Graduate Work in Chemistry, University of Guelph, Guelph, Ontario, Canada N1G
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Comas-Riu J, Vives-Rego J. Use of calcein and SYTO-13 to assess cell cycle phases and osmotic shock effects on E. coli and Staphylococcus aureus by flow cytometry. J Microbiol Methods 1999. [DOI: 10.1016/s0167-7012(98)00091-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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17
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Abstract
When subject to an osmotic 'up-shock', water flows outward from bacterial cytoplasm of the bacterium. Lipid bilayers can shrink very little in area and therefore must wrinkle to accommodate the smaller volume. The usual consequence is that all the layers of the cell envelope must become wrinkled together because they adhere to each other and must now cover a smaller surface. Plasmolysis spaces are formed if the cytoplasmic membrane (CM) separates from the other components of the wall. However, because the CM bilayer is essentially an incompressible two-dimensional liquid, this constraint restricts the location and shape of plasmolysis spaces. With mild up-shocks they form at the pole and around constricting regions in the cell. Elsewhere their creation requires the formation of endocytotic or exocytotic vesicles. The formation of endocytotic vesicles occurs in animal and plant cells as well as in bacterial cells. With stronger up-shocks tubular structures (Bayer adhesion sites), or other special geometric shapes (e.g., Scheie structures) allow the bilayer to surround an irregular shaped cytoplast. Periosmotic agents, that is, those that extract water from the periplasm as well as the cytoplasm, are molecules such as poly-vinyl-pyrrolidone and alpha-cyclodextrin that are too large to pass through the porins in the outer membrane. They were found to significantly inhibit the formation of plasmolysis spaces. Presumably, they inhibit the plasmolysis process, which requires that extracellular fluid enter between the CM and the outer membrane (OM). In the extreme case, with the dehydrating action of both osmotic agents and periosmotic agents, periplasmic space formation tends to be prevented and a new kind of space develops within the cytoplasm. We have designated these as 'cytoplasmic voids'. These novel structures are not bounded by lipid bilayers, in contrast to the endocytotic vesicles. These new spaces appear to result from the negative turgor pressure generated by the application of the combination of osmotic and periosmotic agents causing bubble formation. Several ideas in the literature about the wall biology (periseptal annuli, leading edge, osmotic pressure in the periplasm) are presented and critiqued. The basic criticism of these is that much of the phenomena can be explained because of the physics of the phospholipid bilayers and osmotic forces and thus does not imply the existence of a special control mechanism to regulate growth and division.
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Affiliation(s)
- A L Koch
- Biology Department, Indiana University, Bloomington 47405-6801, USA
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18
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Abstract
The shape of Escherichia coli is strikingly simple compared to those of higher eukaryotes. In fact, the end result of E. coli morphogenesis is a cylindrical tube with hemispherical caps. It is argued that physical principles affect biological forms. In this view, genes code for products that contribute to the production of suitable structures for physical factors to act upon. After introduction of a physical model, the discussion is focused on the shape-maintaining (peptidoglycan) layer of E. coli. This is followed by a detailed analysis of the structural relationship of the cellular interior to the cytoplasmic membrane. A basic theme of this review is that the transcriptionally active nucleoid and the cytoplasmic translation machinery form a structural continuity with the growing cellular envelope. An attempt has been made to show how this dynamic relationship during the cell cycle affects cell polarity and how it leads to cell division.
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Affiliation(s)
- N Nanninga
- Institute for Molecular Cell Biology, BioCentrum Amsterdam, University of Amsterdam, The Netherlands.
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19
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Murphy LD, Zimmerman SB. Isolation and characterization of spermidine nucleoids from Escherichia coli. J Struct Biol 1997; 119:321-35. [PMID: 9245770 DOI: 10.1006/jsbi.1997.3883] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Nucleoids isolated from Escherichia coli at low salt concentrations in the presence of spermidine (Kornberg et al., Proc. Natl. Acad. Sci. USA, 71, 3189-3193 (1974)) retain large amounts of protein and RNA and are, thus, potentially useful in structural and other studies. However, these preparations have neither been visualized nor extensively characterized with regard to their protein and other components. We have investigated this type of nucleoid preparation and here supply both light and electron microscope appearances and a description of the DNA-associated proteins. Light microscopy is used to follow the stages of nucleoid release and to demonstrate characteristically rounded nucleoids after chloramphenicol treatment of the cells from which the nucleoids were isolated. The nucleoids are "envelope-associated" particles. Electron microscopy shows an irregular central core that is partially covered with small, membranous vesicles. A significant fraction of the nucleoids have a characteristic doublet/dumbbell-shaped appearance by light microscopy. The nucleoids contain large amounts of protein and RNA in addition to DNA. The DNA and RNA are rendered acid-soluble by very low levels of nucleases, indicating an open structure. A small group of proteins, including H-NS, FIS, HU, and RNA polymerase, is released from the particles upon enzymatic digestion of the DNA.
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Affiliation(s)
- L D Murphy
- Laboratory of Molecular Biology, National Institutes of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0560, USA
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20
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Affiliation(s)
- A J Dijkstra
- Pharma Research Department, F. Hoffmann-La Roche Ltd., Basel, Switzerland
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21
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Kellenberger E, Kellenberger-Van der Kamp C. Unstained and in vivo fluorescently stained bacterial nucleoids and plasmolysis observed by a new specimen preparation method for high-power light microscopy of metabolically active cells. J Microsc 1994; 176:132-42. [PMID: 7853387 DOI: 10.1111/j.1365-2818.1994.tb03507.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Microscope slides were coated with a layer of gelatin, the thickness of the gelatin increasing linearly along the long axis. The bacterial suspension is applied to the dried gelatin and covered by a coverslip. The medium is absorbed by the gelatin and thus the cells applied against the coverslip. By this method, cultures of concentrations below 10(8) cells/ml provide statistically relevant numbers for observation without prior concentration steps. It is easier to apply than the existing methods for the observation of bacterial nucleoids by phase contrast imaging. Because the cells are maintained in growing conditions the method is useful for the vital fluorescence DAPI-staining of various bacterial species and for observations of plasmolysis and its reversal at different physiological conditions and extracellular osmolalities. The previously generally assumed view that the plasmolytic changes of the cell morphology are immediate upon the hyperosmotic shock and are rapidly repaired when the cell is able to metabolize actively was confirmed; this is in contrast to some recent claims.
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Affiliation(s)
- E Kellenberger
- Institut de Génétique et de Biologie Microbiennes, Université de Lausanne, Switzerland
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