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Agapov A, Baker KS, Bedekar P, Bhatia RP, Blower TR, Brockhurst MA, Brown C, Chong CE, Fothergill JL, Graham S, Hall JP, Maestri A, McQuarrie S, Olina A, Pagliara S, Recker M, Richmond A, Shaw SJ, Szczelkun MD, Taylor TB, van Houte S, Went SC, Westra ER, White MF, Wright R. Multi-layered genome defences in bacteria. Curr Opin Microbiol 2024; 78:102436. [PMID: 38368839 DOI: 10.1016/j.mib.2024.102436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 01/22/2024] [Accepted: 01/23/2024] [Indexed: 02/20/2024]
Abstract
Bacteria have evolved a variety of defence mechanisms to protect against mobile genetic elements, including restriction-modification systems and CRISPR-Cas. In recent years, dozens of previously unknown defence systems (DSs) have been discovered. Notably, diverse DSs often coexist within the same genome, and some co-occur at frequencies significantly higher than would be expected by chance, implying potential synergistic interactions. Recent studies have provided evidence of defence mechanisms that enhance or complement one another. Here, we review the interactions between DSs at the mechanistic, regulatory, ecological and evolutionary levels.
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Affiliation(s)
- Aleksei Agapov
- ESI, Centre for Ecology and Conservation, University of Exeter, UK
| | - Kate S Baker
- Department of Genetics, University of Cambridge, CB2 3EH, UK
| | - Paritosh Bedekar
- ESI, Centre for Ecology and Conservation, University of Exeter, UK
| | - Rama P Bhatia
- ESI, Centre for Ecology and Conservation, University of Exeter, UK
| | - Tim R Blower
- Department of Biosciences, Durham University, Stockton Road, Durham DH1 3LE, UK
| | - Michael A Brockhurst
- Division of Evolution, Infection and Genomics, School of Biological Sciences, University of Manchester, Dover Street, Manchester M13 9PT, UK
| | - Cooper Brown
- School of Biology, University of St Andrews, St Andrews KY16 9ST, UK
| | | | - Joanne L Fothergill
- Dept of Clinical Infection, Microbiology and Immunology, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, UK
| | - Shirley Graham
- School of Biology, University of St Andrews, St Andrews KY16 9ST, UK
| | - James Pj Hall
- Dept of Evolution, Ecology and Behaviour, Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, L69 7ZB, UK
| | - Alice Maestri
- ESI, Centre for Ecology and Conservation, University of Exeter, UK
| | - Stuart McQuarrie
- School of Biology, University of St Andrews, St Andrews KY16 9ST, UK
| | - Anna Olina
- ESI, Centre for Ecology and Conservation, University of Exeter, UK
| | | | - Mario Recker
- ESI, Centre for Ecology and Conservation, University of Exeter, UK
| | - Anna Richmond
- ESI, Centre for Ecology and Conservation, University of Exeter, UK
| | - Steven J Shaw
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS6 7YB, UK
| | - Mark D Szczelkun
- DNA-Protein Interactions Unit, School of Biochemistry, University of Bristol, Bristol BS6 7YB, UK
| | - Tiffany B Taylor
- Milner Centre for Evolution, Department of Life Sciences, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | | | - Sam C Went
- Department of Biosciences, Durham University, Stockton Road, Durham DH1 3LE, UK
| | - Edze R Westra
- ESI, Centre for Ecology and Conservation, University of Exeter, UK.
| | - Malcolm F White
- School of Biology, University of St Andrews, St Andrews KY16 9ST, UK
| | - Rosanna Wright
- Division of Evolution, Infection and Genomics, School of Biological Sciences, University of Manchester, Dover Street, Manchester M13 9PT, UK
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2
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Attrill EL, Łapińska U, Westra ER, Harding SV, Pagliara S. Slow growing bacteria survive bacteriophage in isolation. ISME Commun 2023; 3:95. [PMID: 37684358 PMCID: PMC10491631 DOI: 10.1038/s43705-023-00299-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 08/09/2023] [Accepted: 08/14/2023] [Indexed: 09/10/2023]
Abstract
The interactions between bacteria and bacteriophage have important roles in the global ecosystem; in turn changes in environmental parameters affect the interactions between bacteria and phage. However, there is a lack of knowledge on whether clonal bacterial populations harbour different phenotypes that respond to phage in distinct ways and whether the abundance of such phenotypes within bacterial populations is affected by variations in environmental parameters. Here we study the impact of variations in nutrient availability, bacterial growth rate and phage abundance on the interactions between the phage T4 and individual Escherichia coli cells confined in spatial refuges. Surprisingly, we found that fast growing bacteria survive together with all of their clonal kin cells, whereas slow growing bacteria survive in isolation. We also discovered that the number of bacteria that survive in isolation decreases at increasing phage doses possibly due to lysis inhibition in the presence of secondary adsorptions. We further show that these changes in the phenotypic composition of the E. coli population have important consequences on the bacterial and phage population dynamics and should therefore be considered when investigating bacteria-phage interactions in ecological, health or food production settings in structured environments.
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Affiliation(s)
- Erin L Attrill
- Living Systems Institute and Biosciences, University of Exeter, Exeter, UK
| | - Urszula Łapińska
- Living Systems Institute and Biosciences, University of Exeter, Exeter, UK
| | - Edze R Westra
- Environment and Sustainability Institute and Biosciences, University of Exeter, Penryn, UK
| | - Sarah V Harding
- Defence Science and Technology Laboratory, Porton Down, Salisbury, UK
- Department of Respiratory Sciences, University of Leicester, Leicester, UK
| | - Stefano Pagliara
- Living Systems Institute and Biosciences, University of Exeter, Exeter, UK.
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3
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Zhang B, Phetsang W, Stone MRL, Kc S, Butler MS, Cooper MA, Elliott AG, Łapińska U, Voliotis M, Tsaneva-Atanasova K, Pagliara S, Blaskovich MAT. Synthesis of vancomycin fluorescent probes that retain antimicrobial activity, identify Gram-positive bacteria, and detect Gram-negative outer membrane damage. Commun Biol 2023; 6:409. [PMID: 37055536 PMCID: PMC10102067 DOI: 10.1038/s42003-023-04745-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 03/22/2023] [Indexed: 04/15/2023] Open
Abstract
Antimicrobial resistance is an urgent threat to human health, and new antibacterial drugs are desperately needed, as are research tools to aid in their discovery and development. Vancomycin is a glycopeptide antibiotic that is widely used for the treatment of Gram-positive infections, such as life-threatening systemic diseases caused by methicillin-resistant Staphylococcus aureus (MRSA). Here we demonstrate that modification of vancomycin by introduction of an azide substituent provides a versatile intermediate that can undergo copper-catalysed azide-alkyne cycloaddition (CuAAC) reaction with various alkynes to readily prepare vancomycin fluorescent probes. We describe the facile synthesis of three probes that retain similar antibacterial profiles to the parent vancomycin antibiotic. We demonstrate the versatility of these probes for the detection and visualisation of Gram-positive bacteria by a range of methods, including plate reader quantification, flow cytometry analysis, high-resolution microscopy imaging, and single cell microfluidics analysis. In parallel, we demonstrate their utility in measuring outer-membrane permeabilisation of Gram-negative bacteria. The probes are useful tools that may facilitate detection of infections and development of new antibiotics.
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Affiliation(s)
- Bing Zhang
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Wanida Phetsang
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - M Rhia L Stone
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Sanjaya Kc
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Mark S Butler
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Matthew A Cooper
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Alysha G Elliott
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Urszula Łapińska
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4Q, UK
| | - Margaritis Voliotis
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Department of Mathematics, University of Exeter, Stocker Road, Exeter, UK
| | - Krasimira Tsaneva-Atanasova
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Department of Mathematics, University of Exeter, Stocker Road, Exeter, UK
- EPSRC Hub for Quantitative Modelling in Healthcare, University of Exeter, Exeter, EX4 4QJ, UK
- Department of Bioinformatics and Mathematical Modelling, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, 105 Acad. G. Bonchev Street, 1113, Sofia, Bulgaria
| | - Stefano Pagliara
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4Q, UK
| | - Mark A T Blaskovich
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, 4072, Australia.
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Łapińska U, Glover G, Kahveci Z, Irwin NAT, Milner DS, Tourte M, Albers SV, Santoro AE, Richards TA, Pagliara S. Systematic comparison of unilamellar vesicles reveals that archaeal core lipid membranes are more permeable than bacterial membranes. PLoS Biol 2023; 21:e3002048. [PMID: 37014915 PMCID: PMC10072491 DOI: 10.1371/journal.pbio.3002048] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 02/22/2023] [Indexed: 04/05/2023] Open
Abstract
One of the deepest branches in the tree of life separates the Archaea from the Bacteria. These prokaryotic groups have distinct cellular systems including fundamentally different phospholipid membrane bilayers. This dichotomy has been termed the lipid divide and possibly bestows different biophysical and biochemical characteristics on each cell type. Classic experiments suggest that bacterial membranes (formed from lipids extracted from Escherichia coli, for example) show permeability to key metabolites comparable to archaeal membranes (formed from lipids extracted from Halobacterium salinarum), yet systematic analyses based on direct measurements of membrane permeability are absent. Here, we develop a new approach for assessing the membrane permeability of approximately 10 μm unilamellar vesicles, consisting of an aqueous medium enclosed by a single lipid bilayer. Comparing the permeability of 18 metabolites demonstrates that diether glycerol-1-phosphate lipids with methyl branches, often the most abundant membrane lipids of sampled archaea, are permeable to a wide range of compounds useful for core metabolic networks, including amino acids, sugars, and nucleobases. Permeability is significantly lower in diester glycerol-3-phosphate lipids without methyl branches, the common building block of bacterial membranes. To identify the membrane characteristics that determine permeability, we use this experimental platform to test a variety of lipid forms bearing a diversity of intermediate characteristics. We found that increased membrane permeability is dependent on both the methyl branches on the lipid tails and the ether bond between the tails and the head group, both of which are present on the archaeal phospholipids. These permeability differences must have had profound effects on the cell physiology and proteome evolution of early prokaryotic forms. To explore this further, we compare the abundance and distribution of transmembrane transporter-encoding protein families present on genomes sampled from across the prokaryotic tree of life. These data demonstrate that archaea tend to have a reduced repertoire of transporter gene families, consistent with increased membrane permeation. These results demonstrate that the lipid divide demarcates a clear difference in permeability function with implications for understanding some of the earliest transitions in cell origins and evolution.
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Affiliation(s)
- Urszula Łapińska
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
| | - Georgina Glover
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
| | - Zehra Kahveci
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
| | - Nicholas A T Irwin
- Merton College, University of Oxford, Oxford, United Kingdom
- Department of Biology, University of Oxford, Oxford, United Kingdom
| | - David S Milner
- Department of Biology, University of Oxford, Oxford, United Kingdom
| | - Maxime Tourte
- Molecular Biology of Archaea, Institute of Biology II, University of Freiburg, Freiburg, Germany
| | - Sonja-Verena Albers
- Molecular Biology of Archaea, Institute of Biology II, University of Freiburg, Freiburg, Germany
| | - Alyson E Santoro
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, California, United States of America
| | | | - Stefano Pagliara
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
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5
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Zhang Y, Kepiro I, Ryadnov MG, Pagliara S. Single Cell Killing Kinetics Differentiate Phenotypic Bacterial Responses to Different Antibacterial Classes. Microbiol Spectr 2023; 11:e0366722. [PMID: 36651776 PMCID: PMC9927147 DOI: 10.1128/spectrum.03667-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Accepted: 12/19/2022] [Indexed: 01/19/2023] Open
Abstract
With the spread of multidrug-resistant bacteria, there has been an increasing focus on molecular classes that have not yet yielded an antibiotic. A key capability for assessing and prescribing new antibacterial treatments is to compare the effects antibacterial agents have on bacterial growth at a phenotypic, single-cell level. Here, we combined time-lapse microscopy with microfluidics to investigate the concentration-dependent killing kinetics of stationary-phase Escherichia coli cells. We used antibacterial agents from three different molecular classes, β-lactams and fluoroquinolones, with the known antibiotics ampicillin and ciprofloxacin, respectively, and a new experimental class, protein Ψ-capsids. We found that bacterial cells elongated when treated with ampicillin and ciprofloxacin used at their minimum inhibitory concentration (MIC). This was in contrast to Ψ-capsids, which arrested bacterial elongation within the first two hours of treatment. At concentrations exceeding the MIC, all the antibacterial agents tested arrested bacterial growth within the first 2 h of treatment. Further, our single-cell experiments revealed differences in the modes of action of three different agents. At the MIC, ampicillin and ciprofloxacin caused the lysis of bacterial cells, whereas at higher concentrations, the mode of action shifted toward membrane disruption. The Ψ-capsids killed cells by disrupting their membranes at all concentrations tested. Finally, at increasing concentrations, ampicillin and Ψ-capsids reduced the fraction of the population that survived treatment in a viable but nonculturable state, whereas ciprofloxacin increased this fraction. This study introduces an effective capability to differentiate the killing kinetics of antibacterial agents from different molecular classes and offers a high content analysis of antibacterial mechanisms at the single-cell level. IMPORTANCE Antibiotics act against bacterial pathogens by inhibiting their growth or killing them directly. Different modes of action determine different antibacterial responses, whereas phenotypic differences in bacteria can challenge the efficacy of antibiotics. Therefore, it is important to be able to differentiate the concentration-dependent killing kinetics of antibacterial agents at a single-cell level, in particular for molecular classes which have not yielded an antibiotic before. Here, we measured single-cell responses using microfluidics-enabled imaging, revealing that a novel class of antibacterial agents, protein Ψ-capsids, arrests bacterial elongation at the onset of treatment, whereas elongation continues for cells treated with β-lactam and fluoroquinolone antibiotics. The study advances our current understanding of antibacterial function and offers an effective strategy for the comparative design of new antibacterial therapies, as well as clinical antibiotic susceptibility testing.
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Affiliation(s)
- Yuewen Zhang
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
- National Physical Laboratory, Teddington, United Kingdom
| | - Ibolya Kepiro
- National Physical Laboratory, Teddington, United Kingdom
| | - Maxim G. Ryadnov
- National Physical Laboratory, Teddington, United Kingdom
- Department of Physics, King’s College London, London, United Kingdom
| | - Stefano Pagliara
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
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6
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Binsley JL, Myers TO, Pagliara S, Ogrin FY. Herringbone micromixers for particle filtration. Biomicrofluidics 2023; 17:014106. [PMID: 36704613 PMCID: PMC9873379 DOI: 10.1063/5.0134431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 01/11/2023] [Indexed: 06/18/2023]
Abstract
Herringbone micromixers are a powerful tool for introducing advection into microfluidic systems. While these mixers are typically used for mixing fluids faster than the rate of diffusion, there has been recent interest in using the device to enhance interactions between suspended particles and channel walls. We show how the common approximations applied to herringbone micromixer theory can have a significant impact on results. We show that the inclusion of gravity can greatly alter the interaction probability between suspended particles and channel walls. We also investigate the proposed impedance matching condition and the inclusion of imperfect binding using numerical methods, and investigate transient behaviors using an experimental system. These results indicate that while traditional methods, such as simple streamline analysis, remain powerful tools, it should not be considered predictive in the general case.
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Affiliation(s)
- Jacob L. Binsley
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - Thomas O. Myers
- Platform Kinetics Limited, Pegholme, Wharfebank Mills, Otley LS21 3JP, United Kingdom
| | - Stefano Pagliara
- University of Exeter, Living Systems Institute and Biosciences, Exeter EX4 4QD, United Kingdom
| | - Feodor Y. Ogrin
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
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7
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Binsley JL, Pagliara S, Ogrin FY. Numerical investigation of flexible Purcell-like integrated microfluidic pumps. J Appl Phys 2022; 132:164701. [PMID: 36313737 PMCID: PMC9605776 DOI: 10.1063/5.0109263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 09/20/2022] [Indexed: 06/16/2023]
Abstract
Integrating miniature pumps within microfluidic devices is crucial for advancing point-of-care diagnostics. Understanding the emergence of flow from novel integrated pumping systems is the first step in their successful implementation. A Purcell-like elasto-magnetic integrated microfluidic pump has been simulated in COMSOL Multiphysics and its performance has been investigated and evaluated. An elastic, cilia-like element contains an embedded magnet, which allows for actuation via a weak, uniaxial, sinusoidally oscillating, external magnetic field. Pumping performance is correlated against a number of variables, such as the frequency of the driving field and the proximity of the pump to the channel walls, in order to understand the emergence of the pumping behavior. Crucially, these simulations capture many of the trends observed experimentally and shed light on the key interactions. The proximity of the channel walls in the in-plane direction strongly determines the direction of net fluid flow. This characterization has important implications for the design and optimization of this pump in practical applications.
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Affiliation(s)
- Jacob L. Binsley
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
| | - Stefano Pagliara
- Living Systems Institute and Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - Feodor Y. Ogrin
- Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom
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8
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Kellom M, Pagliara S, Richards TA, Santoro A. Correction to 'Exaggerated trans-membrane charge of ammonium transporters in nutrient-poor marine environments' (2022) by Kellom et al. Open Biol 2022; 12:220268. [PMID: 36167087 PMCID: PMC9514889 DOI: 10.1098/rsob.220268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Abstract
Transporter proteins are a vital interface between cells and their environment. In nutrient-limited environments, microbes with transporters that are effective at bringing substrates into their cells will gain a competitive advantage over variants with reduced transport function. Microbial ammonium transporters (Amt) bring ammonium into the cytoplasm from the surrounding periplasm space, but diagnosing Amt adaptations to low nutrient environments solely from sequence data has been elusive. Here, we report altered Amt sequence amino acid distribution from deep marine samples compared to variants sampled from shallow water in two important microbial lineages of the marine water column community-Marine Group I Archaea (Thermoproteota) and the uncultivated gammaproteobacterial lineage SAR86. This pattern indicates an evolutionary pressure towards an increasing dipole in Amt for these clades in deep ocean environments and is predicted to generate stronger electric fields facilitating ammonium acquisition. This pattern of increasing dipole charge with depth was not observed in lineages capable of accessing alternative nitrogen sources, including the abundant alphaproteobacterial clade SAR11. We speculate that competition for ammonium in the deep ocean drives transporter sequence evolution. The low concentration of ammonium in the deep ocean is therefore likely due to rapid uptake by Amts concurrent with decreasing nutrient flux.
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Affiliation(s)
- Matthew Kellom
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA
| | - Stefano Pagliara
- Living Systems Institute and Biosciences, University of Exeter, Exeter, Devon EX4 4QD, UK
| | - Thomas A. Richards
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK
| | - Alyson E. Santoro
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA
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10
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Łapińska U, Voliotis M, Lee KK, Campey A, Stone MRL, Tuck B, Phetsang W, Zhang B, Tsaneva-Atanasova K, Blaskovich MAT, Pagliara S. Fast bacterial growth reduces antibiotic accumulation and efficacy. eLife 2022; 11:74062. [PMID: 35670099 PMCID: PMC9173744 DOI: 10.7554/elife.74062] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 05/08/2022] [Indexed: 12/11/2022] Open
Abstract
Phenotypic variations between individual microbial cells play a key role in the resistance of microbial pathogens to pharmacotherapies. Nevertheless, little is known about cell individuality in antibiotic accumulation. Here, we hypothesise that phenotypic diversification can be driven by fundamental cell-to-cell differences in drug transport rates. To test this hypothesis, we employed microfluidics-based single-cell microscopy, libraries of fluorescent antibiotic probes and mathematical modelling. This approach allowed us to rapidly identify phenotypic variants that avoid antibiotic accumulation within populations of Escherichia coli, Pseudomonas aeruginosa, Burkholderia cenocepacia, and Staphylococcus aureus. Crucially, we found that fast growing phenotypic variants avoid macrolide accumulation and survive treatment without genetic mutations. These findings are in contrast with the current consensus that cellular dormancy and slow metabolism underlie bacterial survival to antibiotics. Our results also show that fast growing variants display significantly higher expression of ribosomal promoters before drug treatment compared to slow growing variants. Drug-free active ribosomes facilitate essential cellular processes in these fast-growing variants, including efflux that can reduce macrolide accumulation. We used this new knowledge to eradicate variants that displayed low antibiotic accumulation through the chemical manipulation of their outer membrane inspiring new avenues to overcome current antibiotic treatment failures.
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Affiliation(s)
- Urszula Łapińska
- Living Systems Institute, University of ExeterExeterUnited Kingdom
- Biosciences, University of ExeterExeterUnited Kingdom
| | - Margaritis Voliotis
- Living Systems Institute, University of ExeterExeterUnited Kingdom
- Department of Mathematics, University of ExeterExeterUnited Kingdom
| | - Ka Kiu Lee
- Living Systems Institute, University of ExeterExeterUnited Kingdom
- Biosciences, University of ExeterExeterUnited Kingdom
| | - Adrian Campey
- Living Systems Institute, University of ExeterExeterUnited Kingdom
- Biosciences, University of ExeterExeterUnited Kingdom
| | - M Rhia L Stone
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of QueenslandBrisbaneAustralia
- Department of Chemistry and Chemical Biology, Rutgers, the State University of New JerseyPiscatawayUnited States
| | - Brandon Tuck
- Living Systems Institute, University of ExeterExeterUnited Kingdom
- Biosciences, University of ExeterExeterUnited Kingdom
| | - Wanida Phetsang
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of QueenslandBrisbaneAustralia
| | - Bing Zhang
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of QueenslandBrisbaneAustralia
| | - Krasimira Tsaneva-Atanasova
- Living Systems Institute, University of ExeterExeterUnited Kingdom
- Department of Mathematics, University of ExeterExeterUnited Kingdom
- EPSRC Hub for Quantitative Modelling in Healthcare, University of ExeterExeterUnited Kingdom
- Department of Bioinformatics and Mathematical Modelling, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of SciencesSofiaBulgaria
| | - Mark AT Blaskovich
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of QueenslandBrisbaneAustralia
| | - Stefano Pagliara
- Living Systems Institute, University of ExeterExeterUnited Kingdom
- Biosciences, University of ExeterExeterUnited Kingdom
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11
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Glover G, Voliotis M, Łapińska U, Invergo BM, Soanes D, O'Neill P, Moore K, Nikolic N, Petrov PG, Milner DS, Roy S, Heesom K, Richards TA, Tsaneva-Atanasova K, Pagliara S. Nutrient and salt depletion synergistically boosts glucose metabolism in individual Escherichia coli cells. Commun Biol 2022; 5:385. [PMID: 35444215 PMCID: PMC9021252 DOI: 10.1038/s42003-022-03336-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 03/30/2022] [Indexed: 12/16/2022] Open
Abstract
The interaction between a cell and its environment shapes fundamental intracellular processes such as cellular metabolism. In most cases growth rate is treated as a proximal metric for understanding the cellular metabolic status. However, changes in growth rate might not reflect metabolic variations in individuals responding to environmental fluctuations. Here we use single-cell microfluidics-microscopy combined with transcriptomics, proteomics and mathematical modelling to quantify the accumulation of glucose within Escherichia coli cells. In contrast to the current consensus, we reveal that environmental conditions which are comparatively unfavourable for growth, where both nutrients and salinity are depleted, increase glucose accumulation rates in individual bacteria and population subsets. We find that these changes in metabolic function are underpinned by variations at the translational and posttranslational level but not at the transcriptional level and are not dictated by changes in cell size. The metabolic response-characteristics identified greatly advance our fundamental understanding of the interactions between bacteria and their environment and have important ramifications when investigating cellular processes where salinity plays an important role.
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Affiliation(s)
- Georgina Glover
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK
| | - Margaritis Voliotis
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Department of Mathematics, University of Exeter, Stocker Road, Exeter, UK
| | - Urszula Łapińska
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4Q, UK
| | - Brandon M Invergo
- Translational Research Exchange at Exeter, University of Exeter, Exeter, UK
| | - Darren Soanes
- Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4Q, UK
| | - Paul O'Neill
- Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4Q, UK
| | - Karen Moore
- Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4Q, UK
| | - Nela Nikolic
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Institute of Science and Technology Austria, 3400, Klosterneuburg, Austria
| | - Peter G Petrov
- Department of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK
| | - David S Milner
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK
| | - Sumita Roy
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4Q, UK
| | - Kate Heesom
- University of Bristol Proteomics Facility, University Walk, Bristol, BS8 1TD, UK
| | - Thomas A Richards
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford, OX1 3SZ, UK
| | - Krasimira Tsaneva-Atanasova
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
- Department of Mathematics, University of Exeter, Stocker Road, Exeter, UK
- Department of Bioinformatics and Mathematical Modelling, Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, 105 Acad. G. Bonchev Str., 1113, Sofia, Bulgaria
| | - Stefano Pagliara
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK.
- Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4Q, UK.
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12
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Conners R, McLaren M, Łapińska U, Sanders K, Stone MRL, Blaskovich MAT, Pagliara S, Daum B, Rakonjac J, Gold VAM. CryoEM structure of the outer membrane secretin channel pIV from the f1 filamentous bacteriophage. Nat Commun 2021; 12:6316. [PMID: 34728631 PMCID: PMC8563730 DOI: 10.1038/s41467-021-26610-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 10/13/2021] [Indexed: 11/09/2022] Open
Abstract
The Ff family of filamentous bacteriophages infect gram-negative bacteria, but do not cause lysis of their host cell. Instead, new virions are extruded via the phage-encoded pIV protein, which has homology with bacterial secretins. Here, we determine the structure of pIV from the f1 filamentous bacteriophage at 2.7 Å resolution by cryo-electron microscopy, the first near-atomic structure of a phage secretin. Fifteen f1 pIV subunits assemble to form a gated channel in the bacterial outer membrane, with associated soluble domains projecting into the periplasm. We model channel opening and propose a mechanism for phage egress. By single-cell microfluidics experiments, we demonstrate the potential for secretins such as pIV to be used as adjuvants to increase the uptake and efficacy of antibiotics in bacteria. Finally, we compare the f1 pIV structure to its homologues to reveal similarities and differences between phage and bacterial secretins.
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Affiliation(s)
- Rebecca Conners
- Living Systems Institute, University of Exeter, Exeter, UK
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, UK
| | - Mathew McLaren
- Living Systems Institute, University of Exeter, Exeter, UK
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, UK
| | - Urszula Łapińska
- Living Systems Institute, University of Exeter, Exeter, UK
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, UK
| | - Kelly Sanders
- Living Systems Institute, University of Exeter, Exeter, UK
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, UK
| | - M Rhia L Stone
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Mark A T Blaskovich
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | - Stefano Pagliara
- Living Systems Institute, University of Exeter, Exeter, UK
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, UK
| | - Bertram Daum
- Living Systems Institute, University of Exeter, Exeter, UK
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, UK
| | - Jasna Rakonjac
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Vicki A M Gold
- Living Systems Institute, University of Exeter, Exeter, UK.
- College of Life and Environmental Sciences, Geoffrey Pope, University of Exeter, Exeter, UK.
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13
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Attrill EL, Claydon R, Łapińska U, Recker M, Meaden S, Brown AT, Westra ER, Harding SV, Pagliara S. Individual bacteria in structured environments rely on phenotypic resistance to phage. PLoS Biol 2021; 19:e3001406. [PMID: 34637438 PMCID: PMC8509860 DOI: 10.1371/journal.pbio.3001406] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 09/02/2021] [Indexed: 12/12/2022] Open
Abstract
Bacteriophages represent an avenue to overcome the current antibiotic resistance crisis, but evolution of genetic resistance to phages remains a concern. In vitro, bacteria evolve genetic resistance, preventing phage adsorption or degrading phage DNA. In natural environments, evolved resistance is lower possibly because the spatial heterogeneity within biofilms, microcolonies, or wall populations favours phenotypic survival to lytic phages. However, it is also possible that the persistence of genetically sensitive bacteria is due to less efficient phage amplification in natural environments, the existence of refuges where bacteria can hide, and a reduced spread of resistant genotypes. Here, we monitor the interactions between individual planktonic bacteria in isolation in ephemeral refuges and bacteriophage by tracking the survival of individual cells. We find that in these transient spatial refuges, phenotypic resistance due to reduced expression of the phage receptor is a key determinant of bacterial survival. This survival strategy is in contrast with the emergence of genetic resistance in the absence of ephemeral refuges in well-mixed environments. Predictions generated via a mathematical modelling framework to track bacterial response to phages reveal that the presence of spatial refuges leads to fundamentally different population dynamics that should be considered in order to predict and manipulate the evolutionary and ecological dynamics of bacteria–phage interactions in naturally structured environments. Bacteriophages represent a promising avenue to overcome the current antibiotic resistance crisis, but evolution of phage resistance remains a concern. This study shows that in the presence of spatial refuges, genetic resistance to phage is less of a problem than commonly assumed, but the persistence of genetically susceptible bacteria suggests that eradicating bacterial pathogens from structured environments may require combined phage-antibiotic therapies.
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Affiliation(s)
- Erin L. Attrill
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
| | - Rory Claydon
- SUPA, School of Physics and Astronomy, The University of Edinburgh, United Kingdom
| | - Urszula Łapińska
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
| | - Mario Recker
- Centre for Ecology and Conservation, University of Exeter, Penryn, United Kingdom
| | - Sean Meaden
- Environment and Sustainability Institute and Biosciences, University of Exeter, Penryn, United Kingdom
- Department of Microbiology and Immunology, University of Otago, Dunedin, New Zealand
| | - Aidan T. Brown
- SUPA, School of Physics and Astronomy, The University of Edinburgh, United Kingdom
| | - Edze R. Westra
- Environment and Sustainability Institute and Biosciences, University of Exeter, Penryn, United Kingdom
| | - Sarah V. Harding
- Defence Science and Technology Laboratory, Porton Down, Salisbury, United Kingdom
| | - Stefano Pagliara
- Living Systems Institute and Biosciences, University of Exeter, Exeter, United Kingdom
- * E-mail:
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14
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Binsley JL, Martin EL, Myers TO, Pagliara S, Ogrin FY. Correction: Microfluidic devices powered by integrated elasto-magnetic pumps. Lab Chip 2021; 21:3019-3020. [PMID: 34165486 PMCID: PMC8729331 DOI: 10.1039/d1lc90063c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 05/31/2021] [Indexed: 06/13/2023]
Abstract
Correction for 'Microfluidic devices powered by integrated elasto-magnetic pumps' by Jacob L. Binsley et al., Lab Chip, 2020, 20, 4285-4295, DOI: .
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Affiliation(s)
- Jacob L Binsley
- Department of Physics and Astronomy, University of Exeter, Physics Building, Stocker Road, Exeter, EX4 4QL, UK.
| | - Elizabeth L Martin
- Department of Physics and Astronomy, University of Exeter, Physics Building, Stocker Road, Exeter, EX4 4QL, UK.
| | - Thomas O Myers
- Platform Kinetics Limited, Pegholme, Wharfebank Mills, Otley, LS21 3JP, UK
| | - Stefano Pagliara
- Department of Biosciences, University of Exeter, Living Systems Institute, Stocker Road, Exeter, EX4 4QD, UK
| | - Feodor Y Ogrin
- Department of Physics and Astronomy, University of Exeter, Physics Building, Stocker Road, Exeter, EX4 4QL, UK.
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15
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Palombo F, Pagliara S, Singh A, Chahwan R. Editorial: Probing the Chromatin Architecture. Front Cell Dev Biol 2021; 9:727803. [PMID: 34395452 PMCID: PMC8358443 DOI: 10.3389/fcell.2021.727803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Accepted: 07/07/2021] [Indexed: 11/21/2022] Open
Affiliation(s)
- Francesca Palombo
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Stefano Pagliara
- Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Ankur Singh
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States.,Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University School of Medicine, Atlanta, GA, United States
| | - Richard Chahwan
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
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16
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Hammond K, Cipcigan F, Al Nahas K, Losasso V, Lewis H, Cama J, Martelli F, Simcock PW, Fletcher M, Ravi J, Stansfeld PJ, Pagliara S, Hoogenboom BW, Keyser UF, Sansom MSP, Crain J, Ryadnov MG. Switching Cytolytic Nanopores into Antimicrobial Fractal Ruptures by a Single Side Chain Mutation. ACS Nano 2021; 15:9679-9689. [PMID: 33885289 PMCID: PMC8219408 DOI: 10.1021/acsnano.1c00218] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Disruption of cell membranes is a fundamental host defense response found in virtually all forms of life. The molecular mechanisms vary but generally lead to energetically favored circular nanopores. Here, we report an elaborate fractal rupture pattern induced by a single side-chain mutation in ultrashort (8-11-mers) helical peptides, which otherwise form transmembrane pores. In contrast to known mechanisms, this mode of membrane disruption is restricted to the upper leaflet of the bilayer where it exhibits propagating fronts of peptide-lipid interfaces that are strikingly similar to viscous instabilities in fluid flow. The two distinct disruption modes, pores and fractal patterns, are both strongly antimicrobial, but only the fractal rupture is nonhemolytic. The results offer wide implications for elucidating differential membrane targeting phenomena defined at the nanoscale.
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Affiliation(s)
- Katharine Hammond
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
- London Centre for Nanotechnology, University College London, London WC1H 0AH, UK
- Department of Physics & Astronomy, University College London, London WC1E 6BT, UK
| | | | - Kareem Al Nahas
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | | | - Helen Lewis
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
| | - Jehangir Cama
- Living Systems Institute, University of Exeter, Exeter EX4 4QD, UK
- College of Engineering, Mathematics and Phys Sciences, University of Exeter, Exeter EX4 4QF, UK
| | | | - Patrick W Simcock
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Marcus Fletcher
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Jascindra Ravi
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
| | | | - Stefano Pagliara
- Living Systems Institute, University of Exeter, Exeter EX4 4QD, UK
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Bart W Hoogenboom
- London Centre for Nanotechnology, University College London, London WC1H 0AH, UK
- Department of Physics & Astronomy, University College London, London WC1E 6BT, UK
| | - Ulrich F Keyser
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Jason Crain
- IBM Research Europe, Hartree Centre, Daresbury WA4 4AD, UK
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Maxim G Ryadnov
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
- Department of Physics, King’s College London, London, WC2R 2LS, UK
- Corresponding author: Prof Maxim G Ryadnov; National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK, Tel: (+44) 20 89436078;
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17
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Goode O, Smith A, Łapińska U, Bamford R, Kahveci Z, Glover G, Attrill E, Carr A, Metz J, Pagliara S. Heterologous Protein Expression Favors the Formation of Protein Aggregates in Persister and Viable but Nonculturable Bacteria. ACS Infect Dis 2021; 7:1848-1858. [PMID: 34000805 DOI: 10.1021/acsinfecdis.1c00154] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Environmental and intracellular stresses can perturb protein homeostasis and trigger the formation and accumulation of protein aggregates. It has been recently suggested that the level of protein aggregates accumulated in bacteria correlates with the frequency of persister and viable but nonculturable cells that transiently survive treatment with multiple antibiotics. However, these findings have often been obtained employing fluorescent reporter strains. This enforced heterologous protein expression facilitates the visualization of protein aggregates but could also trigger the formation and accumulation of protein aggregates. Using microfluidics-based single-cell microscopy and a library of green fluorescent protein reporter strains, we show that heterologous protein expression favors the formation of protein aggregates. We found that persister and viable but nonculturable bacteria surviving treatment with antibiotics are more likely to contain protein aggregates and downregulate the expression of heterologous proteins. Our data also suggest that such aggregates are more basic with respect to the rest of the cell. These findings provide evidence for a strong link between heterologous protein expression, protein aggregation, intracellular pH, and phenotypic survival to antibiotics, suggesting that antibiotic treatments against persister and viable but nonculturable cells could be developed by modulating protein aggregation and pH regulation.
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Affiliation(s)
- Olivia Goode
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Ashley Smith
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Urszula Łapińska
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Rosemary Bamford
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Zehra Kahveci
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Georgina Glover
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Erin Attrill
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Alice Carr
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Jeremy Metz
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
| | - Stefano Pagliara
- Living Systems Institute and Biosciences, University of Exeter, Stocker Road, EX4 4QD, Exeter, United Kingdom
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18
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Morrish R, Yim KHW, Pagliara S, Palombo F, Chahwan R, Stone N. Single Cell Label-Free Probing of Chromatin Dynamics During B Lymphocyte Maturation. Front Cell Dev Biol 2021; 9:646616. [PMID: 33842468 PMCID: PMC8033168 DOI: 10.3389/fcell.2021.646616] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Accepted: 03/08/2021] [Indexed: 01/11/2023] Open
Abstract
Large-scale intracellular signaling during developmental growth or in response to environmental alterations are largely orchestrated by chromatin within the cell nuclei. Chemical and conformational modifications of the chromatin architecture are critical steps in the regulation of differential gene expression and ultimately cell fate determination. Therefore, establishing chemical properties of the nucleus could provide key markers for phenotypic characterization of cellular processes on a scale of individual cells. Raman microscopy is a sensitive technique that is capable of probing single cell chemical composition—and sub-cellular regions—in a label-free optical manner. As such, it has great potential in both clinical and basic research. However, perceived limitations of Raman spectroscopy such as low signal intensity and the difficulty in linking alterations in vibrational signals directly with ensuing biological effects have hampered advances in the field. Here we use immune B lymphocyte development as a model to assess chromatin and transcriptional changes using confocal Raman microscopy in combination with microfluidic devices and correlative transcriptomics, thereby linking changes in chemical and structural properties to biological outcomes. Live B lymphocytes were assessed before and after maturation. Multivariate analysis was applied to distinguish cellular components within each cell. The spectral differences between non-activated and activated B lymphocytes were then identified, and their correlation with known intracellular biological changes were assessed in comparison to conventional RNA-seq analysis. Our data shows that spectral analysis provides a powerful tool to study gene activation that can complement conventional molecular biology techniques and opens the way for mapping the dynamics in the biochemical makeup of individual cells.
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Affiliation(s)
- Rikke Morrish
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom.,Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Kevin Ho Wai Yim
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
| | - Stefano Pagliara
- Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Francesca Palombo
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Richard Chahwan
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
| | - Nicholas Stone
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
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19
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Abstract
Antibiotic resistance is a major challenge for modern medicine, and there is a dire need to refresh the antibiotic development pipeline to treat infections that are resistant to currently available drugs. Peptide-based antimicrobials represent a promising source of novel anti-infectives, but their development is severely impeded due to the lack of suitable techniques to accurately quantify their antimicrobial efficacy. A major problem involves the heterogeneity of cellular phenotypes in response to these peptides, even within a clonal population of bacteria. There is thus a need to develop single-cell resolution assays to quantify drug efficacy for these novel therapeutics. We present here a detailed microfluidics-microscopy protocol for testing the efficacy of peptide-based antimicrobials on hundreds to thousands of individual bacteria in well-defined microenvironments. This enables the study of cell-to-cell differences in drug response within a clonal population. It is a highly versatile tool, which can be used to quantify drug efficacy, including the number of individual survivors at defined drug doses; it even enables the potential exploration of the molecular mechanisms of action of the drug, which are often unknown in the early stages of drug development. We present here protocols for working with Escherichia coli, but organisms of different geometric shapes and sizes may also be tested with suitable modifications of the microfluidic device.
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Affiliation(s)
- Jehangir Cama
- Living Systems Institute, University of Exeter, Exeter, UK.
- College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, UK.
| | - Stefano Pagliara
- Living Systems Institute, University of Exeter, Exeter, UK.
- College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
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20
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Stone MRL, Łapińska U, Pagliara S, Masi M, Blanchfield JT, Cooper MA, Blaskovich MAT. Fluorescent macrolide probes - synthesis and use in evaluation of bacterial resistance. RSC Chem Biol 2020; 1:395-404. [PMID: 34458770 PMCID: PMC8341779 DOI: 10.1039/d0cb00118j] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 10/28/2020] [Indexed: 12/19/2022] Open
Abstract
The emerging crisis of antibiotic resistance requires a multi-pronged approach in order to avert the onset of a post-antibiotic age. Studies of antibiotic uptake and localisation in live cells may inform the design of improved drugs and help develop a better understanding of bacterial resistance and persistence. To facilitate this research, we have synthesised fluorescent derivatives of the macrolide antibiotic erythromycin. These analogues exhibit a similar spectrum of antibiotic activity to the parent drug and are capable of labelling both Gram-positive and -negative bacteria for microscopy. The probes localise intracellularly, with uptake in Gram-negative bacteria dependent on the level of efflux pump activity. A plate-based assay established to quantify bacterial labelling and localisation demonstrated that the probes were taken up by both susceptible and resistant bacteria. Significant intra-strain and -species differences were observed in these preliminary studies. In order to examine uptake in real-time, the probe was used in single-cell microfluidic microscopy, revealing previously unseen heterogeneity of uptake in populations of susceptible bacteria. These studies illustrate the potential of fluorescent macrolide probes to characterise and explore drug uptake and efflux in bacteria. Macrolide fluorescent probes illuminate the interactions between antibiotics and bacteria, providing new insight into mechanisms of resistance.![]()
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Affiliation(s)
- M Rhia L Stone
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland 306 Carmody Road St Lucia 4072 Brisbane Australia
| | - Urszula Łapińska
- Living Systems Institute, University of Exeter Exeter EX4 4QD UK
| | - Stefano Pagliara
- Living Systems Institute, University of Exeter Exeter EX4 4QD UK
| | - Muriel Masi
- Université Paris-Saclay, CEA, CNRS Institute for Integrative Biology of the Cell (I2BC) 911198 Gif-sur-Yvette France
| | - Joanne T Blanchfield
- School of Chemistry and Molecular Biosciences, The University of Queensland 68 Cooper Road St Lucia 4072 Brisbane Australia
| | - Matthew A Cooper
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland 306 Carmody Road St Lucia 4072 Brisbane Australia
| | - Mark A T Blaskovich
- Centre for Superbug Solutions, Institute for Molecular Bioscience, The University of Queensland 306 Carmody Road St Lucia 4072 Brisbane Australia
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21
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Binsley JL, Martin EL, Myers TO, Pagliara S, Ogrin FY. Microfluidic devices powered by integrated elasto-magnetic pumps. Lab Chip 2020; 20:4285-4295. [PMID: 33094306 PMCID: PMC7654506 DOI: 10.1039/d0lc00935k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 10/18/2020] [Indexed: 06/11/2023]
Abstract
We show how an asymmetric elasto-magnetic system provides a novel integrated pumping solution for lab-on-a-chip and point of care devices. This monolithic pumping solution, inspired by Purcell's 3-link swimmer, is integrated within a simple microfluidic device, bypassing the requirement of external connections. We experimentally prove that this system can provide tuneable fluid flow with a flow rate of up to 600 μL h-1. This fluid flow is achieved by actuating the pump using a weak, uniform, uniaxial, oscillating magnetic field, with field amplitudes in the range of 3-6 mT. Crucially, the fluid flow can be reversed by adjusting the driving frequency. We experimentally prove that this device can successfully operate on fluids with a range of viscosities, where pumping at higher viscosity correlates with a decreasing optimal driving frequency. The fluid flow produced by this device is understood here by examining the non-reciprocal motion of the elasto-magnetic component. This device has the capability to replace external pumping systems with a simple, integrated, lab-on-a-chip component.
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Affiliation(s)
- Jacob L Binsley
- Department of Physics and Astronomy, University of Exeter, Physics Building, Stocker Road, Exeter, EX4 4QL, UK.
| | - Elizabeth L Martin
- Department of Physics and Astronomy, University of Exeter, Physics Building, Stocker Road, Exeter, EX4 4QL, UK.
| | - Thomas O Myers
- Platform Kinetics Limited, Pegholme, Wharfebank Mills, Otley, LS21 3JP, UK
| | - Stefano Pagliara
- Department of Biosciences, University of Exeter, Living Systems Institute, Stocker Road, Exeter, EX4 4QD, UK
| | - Feodor Y Ogrin
- Department of Physics and Astronomy, University of Exeter, Physics Building, Stocker Road, Exeter, EX4 4QL, UK.
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22
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Cama J, Voliotis M, Metz J, Smith A, Iannucci J, Keyser UF, Tsaneva-Atanasova K, Pagliara S. Single-cell microfluidics facilitates the rapid quantification of antibiotic accumulation in Gram-negative bacteria. Lab Chip 2020; 20:2765-2775. [PMID: 32613221 PMCID: PMC7953842 DOI: 10.1039/d0lc00242a] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/15/2020] [Indexed: 06/01/2023]
Abstract
The double-membrane cell envelope of Gram-negative bacteria is a formidable barrier to intracellular antibiotic accumulation. A quantitative understanding of antibiotic transport in these cells is crucial for drug development, but this has proved elusive due to a dearth of suitable investigative techniques. Here we combine microfluidics and time-lapse auto-fluorescence microscopy to rapidly quantify antibiotic accumulation in hundreds of individual Escherichia coli cells. By serially manipulating the microfluidic environment, we demonstrated that stationary phase Escherichia coli, traditionally more refractory to antibiotics than growing cells, display reduced accumulation of the antibiotic ofloxacin compared to actively growing cells. Our novel microfluidic method facilitates the quantitative comparison of the role of the microenvironment versus that of the absence of key membrane transport pathways in cellular drug accumulation. Unlike traditional techniques, our assay is rapid, studying accumulation as the cells are dosed with the drug. This platform provides a powerful new tool for studying antibiotic accumulation in bacteria, which will be critical for the rational development of the next generation of antibiotics.
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Affiliation(s)
- Jehangir Cama
- Living Systems Institute
, University of Exeter
,
Exeter EX4 4QD
, UK
.
- College of Engineering
, Mathematics and Physical Sciences
, University of Exeter
,
Exeter EX4 4QF
, UK
- Cavendish Laboratory
, Department of Physics
, University of Cambridge
,
JJ Thomson Avenue
, Cambridge CB3 0HE
, UK
| | - Margaritis Voliotis
- Living Systems Institute
, University of Exeter
,
Exeter EX4 4QD
, UK
.
- College of Engineering
, Mathematics and Physical Sciences
, University of Exeter
,
Exeter EX4 4QF
, UK
| | - Jeremy Metz
- Living Systems Institute
, University of Exeter
,
Exeter EX4 4QD
, UK
.
- School of Biosciences
, College of Life and Environmental Sciences
, University of Exeter
,
Exeter EX4 4QD
, UK
.
| | - Ashley Smith
- Living Systems Institute
, University of Exeter
,
Exeter EX4 4QD
, UK
.
- School of Biosciences
, College of Life and Environmental Sciences
, University of Exeter
,
Exeter EX4 4QD
, UK
.
| | - Jari Iannucci
- Living Systems Institute
, University of Exeter
,
Exeter EX4 4QD
, UK
.
- School of Biosciences
, College of Life and Environmental Sciences
, University of Exeter
,
Exeter EX4 4QD
, UK
.
| | - Ulrich F. Keyser
- Cavendish Laboratory
, Department of Physics
, University of Cambridge
,
JJ Thomson Avenue
, Cambridge CB3 0HE
, UK
| | - Krasimira Tsaneva-Atanasova
- Living Systems Institute
, University of Exeter
,
Exeter EX4 4QD
, UK
.
- College of Engineering
, Mathematics and Physical Sciences
, University of Exeter
,
Exeter EX4 4QF
, UK
| | - Stefano Pagliara
- Living Systems Institute
, University of Exeter
,
Exeter EX4 4QD
, UK
.
- School of Biosciences
, College of Life and Environmental Sciences
, University of Exeter
,
Exeter EX4 4QD
, UK
.
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23
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Gironi B, Kahveci Z, McGill B, Lechner BD, Pagliara S, Metz J, Morresi A, Palombo F, Sassi P, Petrov PG. Effect of DMSO on the Mechanical and Structural Properties of Model and Biological Membranes. Biophys J 2020; 119:274-286. [PMID: 32610089 PMCID: PMC7376087 DOI: 10.1016/j.bpj.2020.05.037] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 04/08/2020] [Accepted: 05/22/2020] [Indexed: 12/23/2022] Open
Abstract
Dimethyl sulfoxide (DMSO) is widely used in a number of biological and biotechnological applications, mainly because of its effects on the cell plasma membrane, but the molecular origins of this action are yet to be fully clarified. In this work, we used two- and three-component synthetic membranes (liposomes) and the plasma membrane of human erythrocytes to investigate the effect of DMSO when added to the membrane-solvating environment. Fourier transform infrared spectroscopy and thermal fluctuation spectroscopy revealed significant differences in the response of the two types of liposome systems to DMSO in terms of the bilayer thermotropic behavior, available free volume of the bilayer, its excess surface area, and bending elasticity. DMSO also alters the mechanical properties of the erythrocyte membrane in a concentration-dependent manner and is capable of increasing membrane permeability to ATP at even relatively low concentrations (3% v/v and above). Taken in its entirety, these results show that DMSO is likely to have a differential effect on heterogeneous biological membranes, depending on their local composition and structure, and could affect membrane-hosted biological functions.
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Affiliation(s)
- Beatrice Gironi
- Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, Perugia, Italy
| | - Zehra Kahveci
- Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Beth McGill
- Department of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Bob-Dan Lechner
- Department of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Stefano Pagliara
- Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Jeremy Metz
- Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Assunta Morresi
- Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, Perugia, Italy
| | - Francesca Palombo
- Department of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Paola Sassi
- Dipartimento di Chimica Biologia e Biotecnologie, Università di Perugia, Perugia, Italy.
| | - Peter G Petrov
- Department of Physics and Astronomy, University of Exeter, Exeter, United Kingdom.
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24
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Ambrosio G, Brown A, Daukiya L, Drera G, Di Santo G, Petaccia L, De Feyter S, Sangaletti L, Pagliara S. Impact of covalent functionalization by diazonium chemistry on the electronic properties of graphene on SiC. Nanoscale 2020; 12:9032-9037. [PMID: 32270844 DOI: 10.1039/d0nr01186j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Plenty of strategies focused on covalent interaction have been developed to functionalize graphene's surface in order to employ it in a wide range of applications. Among them, the use of radical species including nitrene, carbene and aryl diazonium salts is regarded as a promising strategy to establish the covalent functionalization of graphene. In this work, we highlight the effect of diazonium chemistry on the electronic properties of graphene on SiC. On the basis of X-ray and synchrotron-based photoemission experiments, we were able to prove that 3,4,5-trimethoxybenzenediazonium (TMeOD) units, reduced and chemisorbed onto graphene using electrochemistry, preserve the electronic structure of the Dirac cone, through inducing a slightly additional n-type doping of graphene, as revealed by a downshift of the Dirac cone probed by angle-resolved photoemission experiments.
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Affiliation(s)
- G Ambrosio
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Via dei Musei 41, 25121 Brescia, Italy.
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25
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Kepiro IE, Marzuoli I, Hammond K, Ba X, Lewis H, Shaw M, Gunnoo SB, De Santis E, Łapińska U, Pagliara S, Holmes MA, Lorenz CD, Hoogenboom BW, Fraternali F, Ryadnov MG. Engineering Chirally Blind Protein Pseudocapsids into Antibacterial Persisters. ACS Nano 2020; 14:1609-1622. [PMID: 31794180 DOI: 10.1021/acsnano.9b06814] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Antimicrobial resistance stimulates the search for antimicrobial forms that may be less subject to acquired resistance. Here we report a conceptual design of protein pseudocapsids exhibiting a broad spectrum of antimicrobial activities. Unlike conventional antibiotics, these agents are effective against phenotypic bacterial variants, while clearing "superbugs" in vivo without toxicity. The design adopts an icosahedral architecture that is polymorphic in size, but not in shape, and that is available in both l and d epimeric forms. Using a combination of nanoscale and single-cell imaging we demonstrate that such pseudocapsids inflict rapid and irreparable damage to bacterial cells. In phospholipid membranes they rapidly convert into nanopores, which remain confined to the binding positions of individual pseudocapsids. This mechanism ensures precisely delivered influxes of high antimicrobial doses, rendering the design a versatile platform for engineering structurally diverse and functionally persistent antimicrobial agents.
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Affiliation(s)
- Ibolya E Kepiro
- National Physical Laboratory , Hampton Road , Teddington , TW11 0LW , U.K
| | - Irene Marzuoli
- National Physical Laboratory , Hampton Road , Teddington , TW11 0LW , U.K
- Randall Centre for Cell and Molecular Biophysics , King's College London , London , SE1 1UL , U.K
| | - Katharine Hammond
- National Physical Laboratory , Hampton Road , Teddington , TW11 0LW , U.K
- Department of Physics and Astronomy , University College London , London , WC1E 6BT , U.K
- London Centre for Nanotechnology , University College London , London , WC1H 0AH , U.K
| | - Xiaoliang Ba
- Department of Veterinary Medicine , University of Cambridge , Cambridge , CB3 0ES , U.K
| | - Helen Lewis
- National Physical Laboratory , Hampton Road , Teddington , TW11 0LW , U.K
| | - Michael Shaw
- National Physical Laboratory , Hampton Road , Teddington , TW11 0LW , U.K
- Department of Computer Science , University College London , London , WC1 6BT , U.K
| | - Smita B Gunnoo
- National Physical Laboratory , Hampton Road , Teddington , TW11 0LW , U.K
| | - Emiliana De Santis
- National Physical Laboratory , Hampton Road , Teddington , TW11 0LW , U.K
| | - Urszula Łapińska
- Living Systems Institute , University of Exeter , Exeter , EX4 4QD , U.K
| | - Stefano Pagliara
- Living Systems Institute , University of Exeter , Exeter , EX4 4QD , U.K
| | - Mark A Holmes
- Department of Veterinary Medicine , University of Cambridge , Cambridge , CB3 0ES , U.K
| | - Christian D Lorenz
- Department of Physics , King's College London , Strand Lane , London , WC2R 2LS , U.K
| | - Bart W Hoogenboom
- Department of Physics and Astronomy , University College London , London , WC1E 6BT , U.K
- London Centre for Nanotechnology , University College London , London , WC1H 0AH , U.K
| | - Franca Fraternali
- Randall Centre for Cell and Molecular Biophysics , King's College London , London , SE1 1UL , U.K
| | - Maxim G Ryadnov
- National Physical Laboratory , Hampton Road , Teddington , TW11 0LW , U.K
- Department of Physics , King's College London , Strand Lane , London , WC2R 2LS , U.K
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26
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Łapińska U, Glover G, Capilla-Lasheras P, Young AJ, Pagliara S. Bacterial ageing in the absence of external stressors. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180442. [PMID: 31587633 PMCID: PMC6792439 DOI: 10.1098/rstb.2018.0442] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2019] [Indexed: 12/03/2022] Open
Abstract
Evidence of ageing in the bacterium Escherichia coli was a landmark finding in senescence research, as it suggested that even organisms with morphologically symmetrical fission may have evolved strategies to permit damage accumulation. However, recent work has suggested that ageing is only detectable in this organism in the presence of extrinsic stressors, such as the fluorescent proteins and strong light sources typically used to excite them. Here we combine microfluidics with brightfield microscopy to provide evidence of ageing in E. coli in the absence of these stressors. We report (i) that the doubling time of the lineage of cells that consistently inherits the 'maternal old pole' progressively increases with successive rounds of cell division until it reaches an apparent asymptote, and (ii) that the parental cell divides asymmetrically, with the old pole daughter showing a longer doubling time and slower glucose accumulation than the new pole daughter. Notably, these patterns arise without the progressive accumulation or asymmetric partitioning of observable misfolded-protein aggregates, phenomena previously hypothesized to cause the ageing phenotype. Our findings suggest that ageing is part of the naturally occurring ecologically-relevant phenotype of this bacterium and highlight the importance of alternative mechanisms of damage accumulation in this context. This article is part of a discussion meeting issue 'Single cell ecology'.
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Affiliation(s)
- Urszula Łapińska
- Biosciences, University of Exeter, Exeter, Devon EX4 4QD, UK
- Living Systems Institute, University of Exeter, Exeter, Devon EX4 4QD, UK
| | - Georgina Glover
- Biosciences, University of Exeter, Exeter, Devon EX4 4QD, UK
- Living Systems Institute, University of Exeter, Exeter, Devon EX4 4QD, UK
| | - Pablo Capilla-Lasheras
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE, UK
| | - Andrew J. Young
- Centre for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, Penryn, Cornwall TR10 9FE, UK
| | - Stefano Pagliara
- Biosciences, University of Exeter, Exeter, Devon EX4 4QD, UK
- Living Systems Institute, University of Exeter, Exeter, Devon EX4 4QD, UK
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27
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Abstract
Cells are the building blocks of life, from single-celled microbes through to multi-cellular organisms. To understand a multitude of biological processes we need to understand how cells behave, how they interact with each other and how they respond to their environment. The use of new methodologies is changing the way we study cells allowing us to study them on minute scales and in unprecedented detail. These same methods are allowing researchers to begin to sample the vast diversity of microbes that dominate natural environments. The aim of this special issue is to bring together research and perspectives on the application of new approaches to understand the biological properties of cells, including how they interact with other biological entities. This article is part of a discussion meeting issue 'Single cell ecology'.
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Affiliation(s)
- Thomas A Richards
- Biosciences and Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | - Ramon Massana
- Department of Marine Biology and Oceanography, Institut de Ciències del Mar (CSIC), 08003 Barcelona, Spain
| | - Stefano Pagliara
- Biosciences and Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | - Neil Hall
- Earlham Institute, Norwich Research Park, Norwich, NR4 7UZ, UK.,School of Biological Sciences, University of East Anglia, Norwich, NR4 7TU, UK
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28
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Morrish RB, Hermes M, Metz J, Stone N, Pagliara S, Chahwan R, Palombo F. Single Cell Imaging of Nuclear Architecture Changes. Front Cell Dev Biol 2019; 7:141. [PMID: 31396512 PMCID: PMC6668442 DOI: 10.3389/fcell.2019.00141] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 07/10/2019] [Indexed: 12/31/2022] Open
Abstract
The dynamic architecture of chromatin, the macromolecular complex comprised primarily of DNA and histones, is vital for eukaryotic cell growth. Chemical and conformational changes to chromatin are important markers of functional and developmental processes in cells. However, chromatin architecture regulation has not yet been fully elucidated. Therefore, novel approaches to assessing chromatin changes at the single-cell level are required. Here we report the use of FTIR imaging and microfluidic cell-stretcher chips to assess changes to chromatin architecture and its effect on the mechanical properties of the nucleus in immune cells. FTIR imaging enables label-free chemical imaging with subcellular resolution. By optimizing the FTIR methodology and coupling it with cell segmentation analysis approach, we have identified key spectral changes corresponding to changes in DNA levels and chromatin conformation at the single cell level. By further manipulating live single cells using pressure-driven microfluidics, we found that chromatin decondensation – either during general transcriptional activation or during specific immune cell maturation – can ultimately lead to nuclear auxeticity which is a new biological phenomenon recently identified. Taken together our findings demonstrate the tight and, potentially bilateral, link between extra-cellular mechanotransduction and intra-cellular nuclear architecture.
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Affiliation(s)
- Rikke Brandstrup Morrish
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom.,Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Michael Hermes
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Jeremy Metz
- Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Nicholas Stone
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Stefano Pagliara
- Living Systems Institute and School of Biosciences, University of Exeter, Exeter, United Kingdom
| | - Richard Chahwan
- Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland
| | - Francesca Palombo
- School of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
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29
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Smith A, Metz J, Pagliara S. MMHelper: An automated framework for the analysis of microscopy images acquired with the mother machine. Sci Rep 2019; 9:10123. [PMID: 31300741 PMCID: PMC6626022 DOI: 10.1038/s41598-019-46567-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 06/26/2019] [Indexed: 11/23/2022] Open
Abstract
Live-cell imaging in microfluidic devices now allows the investigation of cellular heterogeneity within microbial populations. In particular, the mother machine technology developed by Wang et al. has been widely employed to investigate single-cell physiological parameters including gene expression, growth rate, mutagenesis, and response to antibiotics. One of the advantages of the mother machine technology is the ability to generate vast amounts of images; however, the time consuming analysis of these images constitutes a severe bottleneck. Here we overcome this limitation by introducing MMHelper ( https://doi.org/10.5281/zenodo.3254394 ), a publicly available custom software implemented in Python which allows the automated analysis of brightfield or phase contrast, and any associated fluorescence, images of bacteria confined in the mother machine. We show that cell data extracted via MMHelper from tens of thousands of individual cells imaged in brightfield are consistent with results obtained via semi-automated image analysis based on ImageJ. Furthermore, we benchmark our software capability in processing phase contrast images from other laboratories against other publicly available software. We demonstrate that MMHelper has over 90% detection efficiency for brightfield and phase contrast images and provides a new open-source platform for the extraction of single-bacterium data, including cell length, area, and fluorescence intensity.
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Affiliation(s)
- Ashley Smith
- Living Systems Institute, University of Exeter, Exeter, United Kingdom
- Biosciences, University of Exeter, Exeter, United Kingdom
| | - Jeremy Metz
- Living Systems Institute, University of Exeter, Exeter, United Kingdom.
- Biosciences, University of Exeter, Exeter, United Kingdom.
| | - Stefano Pagliara
- Living Systems Institute, University of Exeter, Exeter, United Kingdom.
- Biosciences, University of Exeter, Exeter, United Kingdom.
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30
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Smith A, Kaczmar A, Bamford RA, Smith C, Frustaci S, Kovacs-Simon A, O'Neill P, Moore K, Paszkiewicz K, Titball RW, Pagliara S. The Culture Environment Influences Both Gene Regulation and Phenotypic Heterogeneity in Escherichia coli. Front Microbiol 2018; 9:1739. [PMID: 30158905 PMCID: PMC6104134 DOI: 10.3389/fmicb.2018.01739] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Accepted: 07/11/2018] [Indexed: 11/13/2022] Open
Abstract
Microorganisms shape the composition of the medium they are growing in, which in turn has profound consequences on the reprogramming of the population gene-expression profile. In this paper, we investigate the progressive changes in pH and sugar availability in the medium of a growing Escherichia coli (E. coli) culture. We show how these changes have an effect on both the cellular heterogeneity within the microbial community and the gene-expression profile of the microbial population. We measure the changes in gene-expression as E. coli moves from lag, to exponential, and finally into stationary phase. We found that pathways linked to the changes in the medium composition such as ribosomal, tricarboxylic acid cycle (TCA), transport, and metabolism pathways are strongly regulated during the different growth phases. In order to quantify the corresponding temporal changes in the population heterogeneity, we measure the fraction of E. coli persisters surviving different antibiotic treatments during the various phases of growth. We show that the composition of the medium in which β-lactams or quinolones, but not aminoglycosides, are dissolved strongly affects the measured phenotypic heterogeneity within the culture. Our findings contribute to a better understanding on how the composition of the culture medium influences both the reprogramming in the population gene-expression and the emergence of phenotypic variants.
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Affiliation(s)
- Ashley Smith
- Living Systems Institute, University of Exeter, Exeter, United Kingdom.,Biosciences, University of Exeter, Exeter, United Kingdom
| | - Agnieszka Kaczmar
- Living Systems Institute, University of Exeter, Exeter, United Kingdom.,Biosciences, University of Exeter, Exeter, United Kingdom
| | - Rosemary A Bamford
- Living Systems Institute, University of Exeter, Exeter, United Kingdom.,Biosciences, University of Exeter, Exeter, United Kingdom
| | | | - Simona Frustaci
- Living Systems Institute, University of Exeter, Exeter, United Kingdom
| | | | - Paul O'Neill
- Biosciences, University of Exeter, Exeter, United Kingdom
| | - Karen Moore
- Biosciences, University of Exeter, Exeter, United Kingdom
| | | | | | - Stefano Pagliara
- Living Systems Institute, University of Exeter, Exeter, United Kingdom.,Biosciences, University of Exeter, Exeter, United Kingdom
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31
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Lutz T, Clowsley AH, Lin R, Pagliara S, di Michele L, Soeller C. Versatile Multiplexed Super-Resolution Imaging of Nanostructures by Quencher-Exchange-Paint. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.1946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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32
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Bamford RA, Smith A, Metz J, Glover G, Titball RW, Pagliara S. Investigating the physiology of viable but non-culturable bacteria by microfluidics and time-lapse microscopy. BMC Biol 2017; 15:121. [PMID: 29262826 PMCID: PMC5738893 DOI: 10.1186/s12915-017-0465-4] [Citation(s) in RCA: 95] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 11/30/2017] [Indexed: 11/29/2022] Open
Abstract
Background Clonal microbial populations often harbor rare phenotypic variants that are typically hidden within the majority of the remaining cells, but are crucial for the population’s resilience to external perturbations. Persister and viable but non-culturable (VBNC) cells are two important clonal bacterial subpopulations that can survive antibiotic treatment. Both persister and VBNC cells pose a serious threat to human health. However, unlike persister cells, which quickly resume growth following drug removal, VBNC cells can remain non-growing for prolonged periods of time, thus eluding detection via traditional microbiological assays. Therefore, understanding the molecular mechanisms underlying the formation of VBNC cells requires the characterization of the clonal population with single-cell resolution. A combination of microfluidics, time-lapse microscopy, and fluorescent reporter strains offers the perfect platform for investigating individual cells while manipulating their environment. Methods Here, we report a novel single-cell approach to investigate VBNC cells. We perform drug treatment, bacterial culturing, and live/dead staining in series by using transcriptional reporter strains and novel adaptations to the mother machine technology. Since we track each cell throughout the experiment, we are able to quantify the size, morphology and fluorescence that each VBNC cell displayed before, during and after drug treatment. Results We show that VBNC cells are not dead or dying cells but share similar phenotypic features with persister cells, suggesting a link between these two subpopulations, at least in the Escherichia coli strain under investigation. We strengthen this link by demonstrating that, before drug treatment, both persister and VBNC cells can be distinguished from the remainder of the population by their lower fluorescence when using a reporter strain for tnaC, encoding the leader peptide of the tnaCAB operon responsible for tryptophan metabolism. Conclusion Our data demonstrates the suitability of our approach for studying the physiology of non-growing cells in response to external perturbations. Our approach will allow the identification of novel biomarkers for the isolation of VBNC and persister cells and will open new opportunities to map the detailed biochemical makeup of these clonal subpopulations. Electronic supplementary material The online version of this article (doi:10.1186/s12915-017-0465-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Rosemary A Bamford
- Biosciences, University of Exeter, Exeter, Devon, EX4 4QD, UK.,Living Systems Institute, University of Exeter, Exeter, Devon, EX4 4QD, UK
| | - Ashley Smith
- Biosciences, University of Exeter, Exeter, Devon, EX4 4QD, UK.,Living Systems Institute, University of Exeter, Exeter, Devon, EX4 4QD, UK
| | - Jeremy Metz
- Biosciences, University of Exeter, Exeter, Devon, EX4 4QD, UK.,Living Systems Institute, University of Exeter, Exeter, Devon, EX4 4QD, UK
| | - Georgina Glover
- Biosciences, University of Exeter, Exeter, Devon, EX4 4QD, UK.,Living Systems Institute, University of Exeter, Exeter, Devon, EX4 4QD, UK
| | | | - Stefano Pagliara
- Biosciences, University of Exeter, Exeter, Devon, EX4 4QD, UK. .,Living Systems Institute, University of Exeter, Exeter, Devon, EX4 4QD, UK.
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33
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Abstract
Membrane protein transporters alternate their substrate-binding sites between the extracellular and cytosolic side of the membrane according to the alternating access mechanism. Inspired by this intriguing mechanism devised by nature, we study particle transport through a channel coupled with an energy well that oscillates its position between the two entrances of the channel. We optimize particle transport across the channel by adjusting the oscillation frequency. At the optimal oscillation frequency, the translocation rate through the channel is a hundred times higher with respect to free diffusion across the channel. Our findings reveal the effect of time-dependent potentials on particle transport across a channel and will be relevant for membrane transport and microfluidics application.
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Affiliation(s)
- Yizhou Tan
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Jannes Gladrow
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Ulrich F Keyser
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Leonardo Dagdug
- Departamento de Fisica, Universidad Autonoma Metropolitana-Iztapalapa, 09340 Mexico City, Mexico
| | - Stefano Pagliara
- Living Systems Institute, University of Exeter, Exeter EX4 4QD, United Kingdom and Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom
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34
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Rigoni F, Freddi S, Pagliara S, Drera G, Sangaletti L, Suisse JM, Bouvet M, Malovichko AM, Emelianov AV, Bobrinetskiy II. Humidity-enhanced sub-ppm sensitivity to ammonia of covalently functionalized single-wall carbon nanotube bundle layers. Nanotechnology 2017; 28:255502. [PMID: 28561009 DOI: 10.1088/1361-6528/aa6da7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A low-cost method for carbon nanotubes (CNTs) network production from solutions on flexible polyethylene naphthalate substrates has been adopted to prepare high quality and well characterized SWCNT bundle layers to be used as the active layer in chemiresistor gas sensors. Two types of SWCNTs have been tested: pristine SWCNTs, deposited from a surfactant solution, and covalently functionalized SWCNTs, deposited from a dimethyl-acetamide solution. The humidity effects on the sensitivity of the SWCNTs network to NH3 have been investigated. The results show that relative humidity favors the response to NH3, confirming recent theoretical predictions. The COOH-functionalized sample displays the largest response owing to both its hydrophilic nature, favoring the interaction with H2O molecules, and its largest surface area. Compared to data available in the literature, the present sensors display a remarkable sensitivity well below the ppm range, which makes them quite promising for environmental and medical applications, where NH3 concentrations (mostly of the order of tens of ppb) have to be detected.
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Affiliation(s)
- F Rigoni
- Surface Science and Spectroscopy Lab @I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Brescia, Italy
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35
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Rigoni F, Pintossi C, Drera G, Pagliara S, Lanti G, Castrucci P, De Crescenzi M, Sangaletti L. A cross-functional nanostructured platform based on carbon nanotube-Si hybrid junctions: where photon harvesting meets gas sensing. Sci Rep 2017; 7:44413. [PMID: 28294128 PMCID: PMC5353639 DOI: 10.1038/srep44413] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 02/10/2017] [Indexed: 11/09/2022] Open
Abstract
A combination of the functionalities of carbon nanotube (CNT)-Si hybrid heterojunctions is presented as a novel method to steer the efficiency of the photovoltaic (PV) cell based on these junctions, and to increase the selectivity and sensitivity of the chemiresistor gas sensor operated with the p-doped CNT layer. The electrical characteristics of the junctions have been tracked by exposing the devices to oxidizing (NO2) and reducing (NH3) molecules. It is shown that when used as PV cells, the cell efficiency can be reversibly steered by gas adsorption, providing a tool to selectively dope the p-type layer through molecular adsorption. Tracking of the current-voltage curve upon gas exposure also allowed to use these cells as gas sensors with an enhanced sensitivity as compared to that provided by a readout of the electrical signal from the CNT layer alone. In turn, the chemiresistive response was improved, both in terms of selectivity and sensitivity, by operating the system under illumination, as the photo-induced charges at the junction increase the p-doping of CNTs making them more sensitive to NH3 and less to NO2.
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Affiliation(s)
- F. Rigoni
- Surface Science and Spectroscopy Lab @ I-Lamp and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Brescia, Italy
- CNR-INO and Sensor Lab, Dept. of Information Engineering, University of Brescia, Italy
| | - C. Pintossi
- Surface Science and Spectroscopy Lab @ I-Lamp and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Brescia, Italy
| | - G. Drera
- Surface Science and Spectroscopy Lab @ I-Lamp and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Brescia, Italy
| | - S. Pagliara
- Surface Science and Spectroscopy Lab @ I-Lamp and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Brescia, Italy
| | - G. Lanti
- Surface Science and Spectroscopy Lab @ I-Lamp and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Brescia, Italy
| | - P. Castrucci
- Dipartimento di Fisica, Università di Roma, Tor Vergata, Italy
| | - M. De Crescenzi
- Dipartimento di Fisica, Università di Roma, Tor Vergata, Italy
| | - L. Sangaletti
- Surface Science and Spectroscopy Lab @ I-Lamp and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, Brescia, Italy
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36
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Hodgson AC, Verstreken CM, Fisher CL, Keyser UF, Pagliara S, Chalut KJ. A microfluidic device for characterizing nuclear deformations. Lab Chip 2017; 17:805-813. [PMID: 28116393 DOI: 10.1039/c6lc01308b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Cell nuclei experience and respond to a wide range of forces, both in vivo and in vitro. In order to characterize the nuclear response to physical stress, we developed a microfluidic chip and used it to apply mechanical stress to live cells and measure their nuclear deformability. The device design is optimized for the detection of both nucleus and cytoplasm, which can then be conveniently quantified using a custom-written Matlab program. We measured nuclear sizes and strains of embryonic stem cells, for which we observed negative Poisson ratios in the nuclei. In addition, we were able to detect changes in the nuclear response after treatment with actin depolymerizing and chromatin decondensing agents. Finally, we showed that the device can be used for biologically relevant high-resolution confocal imaging of cells under compression. Thus, the device presented here allows for accurate physical phenotyping at high throughput and has the potential to be applied to a range of cell types.
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Affiliation(s)
- Andrew C Hodgson
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK.
| | - Christophe M Verstreken
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK. and Wellcome Trust/Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of Cambridge, Cambridge CB3 0ES, UK
| | - Cynthia L Fisher
- Wellcome Trust/Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of Cambridge, Cambridge CB3 0ES, UK
| | - Ulrich F Keyser
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK.
| | - Stefano Pagliara
- Department of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, Devon EX4, UK.
| | - Kevin J Chalut
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK. and Wellcome Trust/Medical Research Council Cambridge Stem Cell Institute and Department of Clinical Neurosciences, University of Cambridge, Cambridge CB3 0ES, UK
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37
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Rigoni F, Drera G, Pagliara S, Perghem E, Pintossi C, Goldoni A, Sangaletti L. Gas sensing at the nanoscale: engineering SWCNT-ITO nano-heterojunctions for the selective detection of NH 3 and NO 2 target molecules. Nanotechnology 2017; 28:035502. [PMID: 27966471 DOI: 10.1088/1361-6528/28/3/035502] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The gas response of single-wall carbon nanotubes (SWCNT) functionalized with indium tin oxide (ITO) nanoparticles (NP) has been studied at room temperature and an enhanced sensitivity to ammonia and nitrogen dioxide is demonstrated. The higher sensitivity in the functionalized sample is related to the creation of nano-heterojunctions at the interface between SWCNT bundles and ITO NP. Furthermore, the different response of the two devices upon NO2 exposure provides a way to enhance also the selectivity. This behavior is rationalized by considering a gas sensing mechanism based on the build-up of space-charge layers at the junctions. Finally, full recovery of the signal after exposure to NO2 is achieved by UV irradiation for the functionalized sample, where the ITO NP can play a role to hinder the poisoning effects on SWCNT due to NO2 chemisorption.
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Affiliation(s)
- F Rigoni
- Interdisciplinary Laboratory for Advanced Materials Physics and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, via dei Musei 41 I-25121 Brescia, Italy. Sensor Lab, Department of Information Engineering, University of Brescia & CNR-INO, Brescia-Italy
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38
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Tognolini S, Achilli S, Longetti L, Fava E, Mariani C, Trioni MI, Pagliara S. Tognolini et al. Reply. Phys Rev Lett 2016; 117:239702. [PMID: 27982607 DOI: 10.1103/physrevlett.117.239702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Indexed: 06/06/2023]
Affiliation(s)
- S Tognolini
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica, 25121 Brescia, Italy
| | - S Achilli
- Dipartimento di Chimica, Università degli Studi di Milano and CNR-ISTM, via Golgi 19, 20133 Milano, Italy
| | - L Longetti
- Dipartimento di Fisica, CNISM, Università di Roma "La Sapienza", 00185 Roma, Italy
| | - E Fava
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica, 25121 Brescia, Italy
| | - C Mariani
- Dipartimento di Fisica, CNISM, Università di Roma "La Sapienza", 00185 Roma, Italy
| | - M I Trioni
- Dipartimento di Chimica, Università degli Studi di Milano and CNR-ISTM, via Golgi 19, 20133 Milano, Italy
| | - S Pagliara
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica, 25121 Brescia, Italy
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39
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Locatelli E, Pierno M, Baldovin F, Orlandini E, Tan Y, Pagliara S. Single-File Escape of Colloidal Particles from Microfluidic Channels. Phys Rev Lett 2016; 117:038001. [PMID: 27472142 DOI: 10.1103/physrevlett.117.038001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Indexed: 06/06/2023]
Abstract
Single-file diffusion is a ubiquitous physical process exploited by living and synthetic systems to exchange molecules with their environment. It is paramount to quantify the escape time needed for single files of particles to exit from constraining synthetic channels and biological pores. This quantity depends on complex cooperative effects, whose predominance can only be established through a strict comparison between theory and experiments. By using colloidal particles, optical manipulation, microfluidics, digital microscopy, and theoretical analysis we uncover the self-similar character of the escape process and provide closed-formula evaluations of the escape time. We find that the escape time scales inversely with the diffusion coefficient of the last particle to leave the channel. Importantly, we find that at the investigated microscale, bias forces as tiny as 10^{-15} N determine the magnitude of the escape time by drastically reducing interparticle collisions. Our findings provide crucial guidelines to optimize the design of micro- and nanodevices for a variety of applications including drug delivery, particle filtering, and transport in geometrical constrictions.
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Affiliation(s)
- Emanuele Locatelli
- Dipartimento di Fisica e Astronomia "G. Galilei" (DFA) and Sezione CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy
| | - Matteo Pierno
- Dipartimento di Fisica e Astronomia "G. Galilei" (DFA) and Sezione CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy
| | - Fulvio Baldovin
- Dipartimento di Fisica e Astronomia "G. Galilei" (DFA), Sezione INFN and Sezione CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy
| | - Enzo Orlandini
- Dipartimento di Fisica e Astronomia "G. Galilei" (DFA), Sezione INFN and Sezione CNISM, Università di Padova, Via Marzolo 8, 35131 Padova, Italy
| | - Yizhou Tan
- Cavendish Laboratory, Cambridge CB30HE, United Kingdom
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40
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Manzoni G, Ponzoni S, Galimberti G, Scarselli M, Pulci O, Camilli L, Matthes L, Castrucci P, Pagliara S. Ultrafast dynamics in unaligned MWCNTs decorated with metal nanoparticles. Nanotechnology 2016; 27:235704. [PMID: 27146216 DOI: 10.1088/0957-4484/27/23/235704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The relaxation dynamics of unaligned multi-walled carbon nanotubes decorated with metallic nanoparticles have been studied by using transient optical measurements. The fast dynamics due to the short-lived free-charge carriers excited by the pump are not affected by the presence of nanoparticles. Conversely, a second long dynamics, absent in bare carbon nanotubes, appears only in the decorated samples. A combination of experiment and theory allows us to ascribe this long dynamics to relaxation channels involving electronic states localized at the tube-nanoparticle interface.
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Affiliation(s)
- G Manzoni
- -LAMP and Dipartimento di Matematica e Fisica, Università Cattolica, 25121 Brescia, Italy
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41
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Cama J, Bajaj H, Pagliara S, Maier T, Braun Y, Winterhalter M, Keyser UF. Quantification of Fluoroquinolone Uptake through the Outer Membrane Channel OmpF of Escherichia coli. J Am Chem Soc 2015; 137:13836-43. [DOI: 10.1021/jacs.5b08960] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jehangir Cama
- Biological
and Soft Systems, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Harsha Bajaj
- Jacobs University Bremen, Campus
Ring 1, D-28759, Bremen, Germany
| | - Stefano Pagliara
- Biological
and Soft Systems, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
- Department
of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, Devon EX4, United Kingdom
| | - Theresa Maier
- Biological
and Soft Systems, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Yvonne Braun
- Jacobs University Bremen, Campus
Ring 1, D-28759, Bremen, Germany
| | | | - Ulrich F. Keyser
- Biological
and Soft Systems, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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42
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Tognolini S, Achilli S, Longetti L, Fava E, Mariani C, Trioni MI, Pagliara S. Rashba Spin-Orbit Coupling in Image Potential States. Phys Rev Lett 2015; 115:046801. [PMID: 26252703 DOI: 10.1103/physrevlett.115.046801] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Indexed: 06/04/2023]
Abstract
The search in two-dimensional condensed matter systems of Rashba-type spin-polarized electronic states is aimed by the possibility to control and manipulate the spin orientation. In this Letter, for the first time, we report on the experimental evidence of a Rashba-type spin splitting in the n=1 image potential state. The image potential state Rashba splitting here measured at the graphene/Ir(111) interface, as confirmed by theoretical considerations, can be detectable to any metal surface with a significant spin-orbit coupling.
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Affiliation(s)
- S Tognolini
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica, 25121 Brescia, Italy
| | - S Achilli
- Dipartimento di Chimica, Università degli Studi di Milano and CNR-ISTM, via Golgi 19, 20133 Milano, Italy
| | - L Longetti
- Dipartimento di Fisica, CNISM, Università di Roma "La Sapienza", 00185 Roma, Italy
| | - E Fava
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica, 25121 Brescia, Italy
| | - C Mariani
- Dipartimento di Fisica, CNISM, Università di Roma "La Sapienza", 00185 Roma, Italy
| | - M I Trioni
- Dipartimento di Chimica, Università degli Studi di Milano and CNR-ISTM, via Golgi 19, 20133 Milano, Italy
| | - S Pagliara
- I-LAMP and Dipartimento di Matematica e Fisica, Università Cattolica, 25121 Brescia, Italy
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43
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Misiunas K, Pagliara S, Lauga E, Lister JR, Keyser UF. Nondecaying Hydrodynamic Interactions along Narrow Channels. Phys Rev Lett 2015; 115:038301. [PMID: 26230830 DOI: 10.1103/physrevlett.115.038301] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Indexed: 06/04/2023]
Abstract
Particle-particle interactions are of paramount importance in every multibody system as they determine the collective behavior and coupling strength. Many well-known interactions such as electrostatic, van der Waals, or screened Coulomb interactions, decay exponentially or with negative powers of the particle spacing r. Similarly, hydrodynamic interactions between particles undergoing Brownian motion decay as 1/r in bulk, and are assumed to decay in small channels. Such interactions are ubiquitous in biological and technological systems. Here we confine two particles undergoing Brownian motion in narrow, microfluidic channels and study their coupling through hydrodynamic interactions. Our experiments show that the hydrodynamic particle-particle interactions are distance independent in these channels. This finding is of fundamental importance for the interpretation of experiments where dense mixtures of particles or molecules diffuse through finite length, water-filled channels or pore networks.
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Affiliation(s)
- Karolis Misiunas
- Cavendish Laboratory, University of Cambridge, United Kingdom and Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Stefano Pagliara
- Cavendish Laboratory, University of Cambridge, United Kingdom and Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Eric Lauga
- Cavendish Laboratory, University of Cambridge, United Kingdom and Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - John R Lister
- Cavendish Laboratory, University of Cambridge, United Kingdom and Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
| | - Ulrich F Keyser
- Cavendish Laboratory, University of Cambridge, United Kingdom and Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom
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44
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Pintossi C, Pagliara S, Drera G, De Nicola F, Castrucci P, De Crescenzi M, Crivellari M, Boscardin M, Sangaletti L. Steering the efficiency of carbon nanotube-silicon photovoltaic cells by acid vapor exposure: a real-time spectroscopic tracking. ACS Appl Mater Interfaces 2015; 7:9436-9444. [PMID: 25902284 DOI: 10.1021/am508973b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Hybrid carbon nanotube-silicon (CNT-Si) junctions have been investigated by angle resolved photoemission spectroscopy (AR-XPS) with the aim to clarify the effects of a nonstoichiometric silicon oxide buried interface on the overall cell efficiency. A complex silicon oxide interface has been clearly identified and its origin and role in the heterojunction have been probed by exposing the cells to hydrofluoric (HF) and nitric (HNO3) acid. Real-time monitoring of the cell efficiencies during the steps following acid exposure (up to 1 week after etching) revealed a correlation between the thickness and chemical state of the oxide layer and the cell efficiencies. By matching the AR-XPS and Raman spectroscopy with the electrical response data it has been possible to discriminate the effects on the cell efficiency of the buried SiO(x) interface from those related to CNT acid doping. The overall cell behavior recorded for different thicknesses of the SiO(x) interface indicates that the buried oxide layer is likely acting as a passivating/inversion layer in a metal-insulator-semiconductor junction.
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Affiliation(s)
- C Pintossi
- †Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy
| | - S Pagliara
- †Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy
| | - G Drera
- †Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy
| | - F De Nicola
- ‡Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, I-00133 Rome, Italy
- §Istituto Nazionale di Fisica Nucleare, Università di Roma Tor Vergata (INFN-Roma Tor Vergata), I-00133, Rome, Italy
| | - P Castrucci
- ‡Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, I-00133 Rome, Italy
- §Istituto Nazionale di Fisica Nucleare, Università di Roma Tor Vergata (INFN-Roma Tor Vergata), I-00133, Rome, Italy
| | - M De Crescenzi
- ‡Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, I-00133 Rome, Italy
- §Istituto Nazionale di Fisica Nucleare, Università di Roma Tor Vergata (INFN-Roma Tor Vergata), I-00133, Rome, Italy
| | - M Crivellari
- ∥Fondazione Bruno Kessler, I-38100 Trento, Italy
| | - M Boscardin
- ∥Fondazione Bruno Kessler, I-38100 Trento, Italy
| | - L Sangaletti
- †Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy
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45
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Otto O, Rosendahl P, Mietke A, Golfier S, Herold C, Klaue D, Girardo S, Pagliara S, Ekpenyong A, Jacobi A, Wobus M, Töpfner N, Keyser UF, Mansfeld J, Fischer-Friedrich E, Guck J. Real-time deformability cytometry: on-the-fly cell mechanical phenotyping. Nat Methods 2015; 12:199-202, 4 p following 202. [DOI: 10.1038/nmeth.3281] [Citation(s) in RCA: 442] [Impact Index Per Article: 49.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 12/23/2014] [Indexed: 12/22/2022]
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46
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Pagliara S, Dettmer SL, Keyser UF. Channel-facilitated diffusion boosted by particle binding at the channel entrance. Phys Rev Lett 2014; 113:048102. [PMID: 25105657 DOI: 10.1103/physrevlett.113.048102] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Indexed: 06/03/2023]
Abstract
We investigate single-file diffusion of Brownian particles in arrays of closely confining microchannels permeated by a variety of attractive optical potentials and connecting two baths with equal particle concentration. We simultaneously test free diffusion in the channel, diffusion in optical traps coupled in the center of the channel, and diffusion in traps extending into the baths. We found that both classes of attractive optical potentials enhance the translocation rate through the channel with respect to free diffusion. Surprisingly, for the latter class of potentials we measure a 40-fold enhancement in the translocation rate with respect to free diffusion and find a sublinear power law dependence of the translocation rate on the average number of particles in the channel. Our results reveal the function of particle binding at the channel entrances for diffusive transport and open the way to a better understanding of membrane transport and design of synthetic membranes with enhanced diffusion rate.
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47
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Cama J, Chimerel C, Pagliara S, Javer A, Keyser UF. A label-free microfluidic assay to quantitatively study antibiotic diffusion through lipid membranes. Lab Chip 2014; 14:2303-2308. [PMID: 24825393 DOI: 10.1039/c4lc00217b] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
With the rise in antibiotic resistance amongst pathogenic bacteria, the study of antibiotic activity and transport across cell membranes is gaining widespread importance. We present a novel, label-free microfluidic assay that quantifies the permeability coefficient of a broad spectrum fluoroquinolone antibiotic, norfloxacin, across lipid membranes using the UV autofluorescence of the drug. We use giant lipid vesicles as highly controlled model systems to study the diffusion through lipid membranes. Our technique directly determines the permeability coefficient without requiring the measurement of the partition coefficient of the antibiotic.
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Affiliation(s)
- J Cama
- Biological and Soft Systems, Dept. of Physics, Univ. of Cambridge, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK.
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48
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Schleicher KD, Dettmer SL, Kapinos LE, Pagliara S, Keyser UF, Jeney S, Lim RYH. Selective transport control on molecular velcro made from intrinsically disordered proteins. Nat Nanotechnol 2014; 9:525-530. [PMID: 24929341 DOI: 10.1038/nnano.2014.103] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 04/30/2014] [Indexed: 06/03/2023]
Abstract
The selectivity and speed of many biological transport processes transpire from a 'reduction of dimensionality' that confines diffusion to one or two dimensions instead of three. This behaviour remains highly sought after on polymeric surfaces as a means to expedite diffusional search processes in molecular engineered systems. Here, we have reconstituted the two-dimensional diffusion of colloidal particles on a molecular brush surface. The surface is composed of phenylalanine-glycine nucleoporins (FG Nups)--intrinsically disordered proteins that facilitate selective transport through nuclear pore complexes in eukaryotic cells. Local and ensemble-level experiments involving optical trapping using a photonic force microscope and particle tracking by video microscopy, respectively, reveal that 1-µm-sized colloidal particles bearing nuclear transport receptors called karyopherins can exhibit behaviour that varies from highly localized to unhindered two-dimensional diffusion. Particle diffusivity is controlled by varying the amount of free karyopherins in solution, which modulates the multivalency of Kap-binding sites within the molecular brush. We conclude that the FG Nups resemble stimuli-responsive molecular 'velcro', which can impart 'reduction of dimensionality' as a means of biomimetic transport control in artificial environments.
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Affiliation(s)
- Kai D Schleicher
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 50/70 CH - 4056, Basel, Switzerland
| | - Simon L Dettmer
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Larisa E Kapinos
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 50/70 CH - 4056, Basel, Switzerland
| | - Stefano Pagliara
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Ulrich F Keyser
- Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
| | - Sylvia Jeney
- Biozentrum, University of Basel and the Laboratory of Physics of Complex Matter, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Roderick Y H Lim
- Biozentrum and the Swiss Nanoscience Institute, University of Basel, Klingelbergstrasse 50/70 CH - 4056, Basel, Switzerland
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49
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Dettmer SL, Pagliara S, Misiunas K, Keyser UF. Anisotropic diffusion of spherical particles in closely confining microchannels. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 89:062305. [PMID: 25019774 DOI: 10.1103/physreve.89.062305] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Indexed: 06/03/2023]
Abstract
We present here the measurement of the diffusivity of spherical particles closely confined by narrow microchannels. Our experiments yield a two-dimensional map of the position-dependent diffusion coefficients parallel and perpendicular to the channel axis with a resolution down to 129 nm. The diffusivity was measured simultaneously in the channel interior, the bulk reservoirs, as well as the channel entrance region. In the channel interior we found strongly anisotropic diffusion. While the perpendicular diffusion coefficient close to the confining walls decreased down to approximately 25% of the value on the channel axis, the parallel diffusion coefficient remained constant throughout the entire channel width. In addition to the experiment, we performed finite element simulations for the diffusivity in the channel interior and found good agreement with the measurements. Our results reveal the distinctive influence of strong confinement on Brownian motion, which is of significance to microfluidics as well as quantitative models of facilitated membrane transport.
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Affiliation(s)
- Simon L Dettmer
- Cavendish Laboratory, University of Cambridge, 19 J J Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Stefano Pagliara
- Cavendish Laboratory, University of Cambridge, 19 J J Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Karolis Misiunas
- Cavendish Laboratory, University of Cambridge, 19 J J Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Ulrich F Keyser
- Cavendish Laboratory, University of Cambridge, 19 J J Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
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50
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Pagliara S, Franze K, McClain CR, Wylde G, Fisher CL, Franklin RJ, Kabla AJ, Keyser UF, Chalut KJ. Auxetic nuclei in embryonic stem cells exiting pluripotency. Nat Mater 2014; 13:638-644. [PMID: 24747782 PMCID: PMC4283157 DOI: 10.1038/nmat3943] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 03/11/2014] [Indexed: 05/18/2023]
Abstract
Embryonic stem cells (ESCs) self-renew in a state of naïve pluripotency in which they are competent to generate all somatic cells. It has been hypothesized that, before irreversibly committing, ESCs pass through at least one metastable transition state. This transition would represent a gateway for differentiation and reprogramming of somatic cells. Here, we show that during the transition, the nuclei of ESCs are auxetic: they exhibit a cross-sectional expansion when stretched and a cross-sectional contraction when compressed, and their stiffness increases under compression. We also show that the auxetic phenotype of transition ESC nuclei is driven at least in part by global chromatin decondensation. Through the regulation of molecular turnover in the differentiating nucleus by external forces, auxeticity could be a key element in mechanotransduction. Our findings highlight the importance of nuclear structure in the regulation of differentiation and reprogramming.
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Affiliation(s)
- Stefano Pagliara
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, Downing Street, University of Cambridge, Cambridge, CB2 3DY, UK
| | - Crystal R. McClain
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
- Wellcome Trust/Medical Research Council Cambridge Stem Cell Research Institute and Madingley Road, University of Cambridge, Cambridge, CB3 0ES, UK
| | - George Wylde
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Cynthia L. Fisher
- Wellcome Trust/Medical Research Council Cambridge Stem Cell Research Institute, Tennis Court Road, University of Cambridge, Cambridge, CB2 1QR, UK
| | - Robin J.M. Franklin
- Wellcome Trust/Medical Research Council Cambridge Stem Cell Research Institute and Madingley Road, University of Cambridge, Cambridge, CB3 0ES, UK
| | - Alexandre J. Kabla
- Department of Engineering, University of Cambridge, Cambridge, CB2 1PZ, UK
| | - Ulrich F. Keyser
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Kevin J. Chalut
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
- Wellcome Trust/Medical Research Council Cambridge Stem Cell Research Institute, Tennis Court Road, University of Cambridge, Cambridge, CB2 1QR, UK
- Correspondence and requests for materials should be addressed to K.J.C.
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