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Abstract
Optical tweezers have great potential in microbiology for holding and manipulating single cells under a microscope. However, the methodology to use optical tweezers for live cell studies is still at its infancy. In this work, we determined suitable parameters for stable trapping of single Escherichia coli bacteria, and identified the upper limits of IR-exposure that can be applied without affecting viability. We found that the maximum tolerable IR-exposure is 2.5-fold higher when employing oscillating instead of stationary optical trapping (20 J and 8 J, respectively). We found that good stability of cells in an oscillating trap is achieved when the effective trap length is 20% larger than the cell length, the oscillation frequency higher than 100 Hz and the trap oriented perpendicular to the medium flow direction. Further, we show, using an IR power just sufficient for stable holding, that bacteria remain viable during at least 30 min of holding in an oscillating trap. In this work, we established a method for long-term stable handling of single E. coli cells using optical tweezers. This work will pave the way for future use of optical tweezers in microbiology.
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Extending calibration-free force measurements to optically-trapped rod-shaped samples. Sci Rep 2017; 7:42960. [PMID: 28220855 PMCID: PMC5318951 DOI: 10.1038/srep42960] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/17/2017] [Indexed: 12/14/2022] Open
Abstract
Optical trapping has become an optimal choice for biological research at the microscale due to its non-invasive performance and accessibility for quantitative studies, especially on the forces involved in biological processes. However, reliable force measurements depend on the calibration of the optical traps, which is different for each experiment and hence requires high control of the local variables, especially of the trapped object geometry. Many biological samples have an elongated, rod-like shape, such as chromosomes, intracellular organelles (e.g., peroxisomes), membrane tubules, certain microalgae, and a wide variety of bacteria and parasites. This type of samples often requires several optical traps to stabilize and orient them in the correct spatial direction, making it more difficult to determine the total force applied. Here, we manipulate glass microcylinders with holographic optical tweezers and show the accurate measurement of drag forces by calibration-free direct detection of beam momentum. The agreement between our results and slender-body hydrodynamic theoretical calculations indicates potential for this force-sensing method in studying protracted, rod-shaped specimens.
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Abstract
Thirty years after their invention by Arthur Ashkin and colleagues at Bell Labs in 1986 [1], optical tweezers (or traps) have become a versatile tool to address numerous biological problems. Put simply, an optical trap is a highly focused laser beam that is capable of holding and applying forces to micron-sized dielectric objects. However, their development over the last few decades has converted these tools from boutique instruments into highly versatile instruments of molecular biophysics. This introductory chapter intends to give a brief overview of the field, highlight some important scientific achievements, and demonstrate why optical traps have become a powerful tool in the biological sciences. We introduce a typical optical setup, describe the basic theoretical concepts of how trapping forces arise, and present the quantitative position and force measurement techniques that are most widely used today.
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Martínez IA, Roldán É, Dinis L, Rica RA. Colloidal heat engines: a review. SOFT MATTER 2016; 13:22-36. [PMID: 27477856 DOI: 10.1039/c6sm00923a] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Stochastic heat engines can be built using colloidal particles trapped using optical tweezers. Here we review recent experimental realizations of microscopic heat engines. We first revisit the theoretical framework of stochastic thermodynamics that allows to describe the fluctuating behavior of the energy fluxes that occur at mesoscopic scales, and then discuss recent implementations of the colloidal equivalents to the macroscopic Stirling, Carnot and steam engines. These small-scale motors exhibit unique features in terms of power and efficiency fluctuations that have no equivalent in the macroscopic world. We also consider a second pathway for work extraction from colloidal engines operating between active bacterial reservoirs at different temperatures, which could significantly boost the performance of passive heat engines at the mesoscale. Finally, we provide some guidance on how the work extracted from colloidal heat engines can be used to generate net particle or energy currents, proposing a new generation of experiments with colloidal systems.
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Affiliation(s)
- Ignacio A Martínez
- Laboratoire de Physique, École Normale Supérieure, CNRS UMR5672, 46 Allée d'Italie, 69364 Lyon, France
| | - Édgar Roldán
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer strasse 38, 01187 Dresden, Germany and GISC - Grupo Interdisciplinar de Sistemas Complejos, Madrid, Spain
| | - Luis Dinis
- GISC - Grupo Interdisciplinar de Sistemas Complejos, Madrid, Spain and Departamento de Fisica Atómica, Molecular y Nuclear, Universidad Complutense Madrid, 28040 Madrid, Spain
| | - Raúl A Rica
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels (Barcelona), Spain.
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Mishra A, Maltais TR, Walter TM, Wei A, Williams SJ, Wereley ST. Trapping and viability of swimming bacteria in an optoelectric trap. LAB ON A CHIP 2016; 16:1039-1046. [PMID: 26891971 PMCID: PMC5562368 DOI: 10.1039/c5lc01559f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Non-contact manipulation methods capable of trapping and transporting swimming bacteria can significantly aid in chemotaxis studies. However, high swimming speed makes the trapping of these organisms an inherently challenging task. We demonstrate that an optoelectric technique, rapid electrokinetic patterning (REP), can effectively trap and manipulate Enterobacter aerogenes bacteria swimming at velocities greater than 20 μm s(-1). REP uses electro-orientation, laser-induced AC electrothermal flow, and particle-electrode interactions for capturing these cells. In contrast to trapping non-swimming bacteria and inert microspheres, we observe that electro-orientation is critical to the trapping of the swimming cells, since unaligned bacteria can swim faster than the radially inward electrothermal flow and escape the trap. By assessing the cell membrane integrity, we study the effect of REP trapping conditions, including optical radiation, laser-induced heating, and the electric field on cell viability. When applied individually, the optical radiation and laser-induced heating have negligible effect on cells. At the standard REP trapping conditions fewer than 2% of cells have a compromised membrane after four minutes. To our knowledge this is the first study detailing the effect of REP trapping on cell viability. The presented results provide a clear guideline on selecting suitable REP parameters for trapping living bacteria.
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Affiliation(s)
- A Mishra
- Department of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, 47907, USA.
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SOS System Induction Inhibits the Assembly of Chemoreceptor Signaling Clusters in Salmonella enterica. PLoS One 2016; 11:e0146685. [PMID: 26784887 PMCID: PMC4718596 DOI: 10.1371/journal.pone.0146685] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 12/21/2015] [Indexed: 01/08/2023] Open
Abstract
Swarming, a flagellar-driven multicellular form of motility, is associated with bacterial virulence and increased antibiotic resistance. In this work we demonstrate that activation of the SOS response reversibly inhibits swarming motility by preventing the assembly of chemoreceptor-signaling polar arrays. We also show that an increase in the concentration of the RecA protein, generated by SOS system activation, rather than another function of this genetic network impairs chemoreceptor polar cluster formation. Our data provide evidence that the molecular balance between RecA and CheW proteins is crucial to allow polar cluster formation in Salmonella enterica cells. Thus, activation of the SOS response by the presence of a DNA-injuring compound increases the RecA concentration, thereby disturbing the equilibrium between RecA and CheW and resulting in the cessation of swarming. Nevertheless, when the DNA-damage decreases and the SOS response is no longer activated, basal RecA levels and thus polar cluster assembly are reestablished. These results clearly show that bacterial populations moving over surfaces make use of specific mechanisms to avoid contact with DNA-damaging compounds.
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S Bezryadina A, C Preece D, Chen JC, Chen Z. Optical disassembly of cellular clusters by tunable 'tug-of-war' tweezers. LIGHT, SCIENCE & APPLICATIONS 2016; 5. [PMID: 27818838 PMCID: PMC5091843 DOI: 10.1038/lsa.2016.158] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Bacterial biofilms underlie many persistent infections, posing major hurdles in antibiotic treatment. Here we design and demonstrate 'tug-of-war' optical tweezers that can facilitate the assessment of cell-cell adhesion-a key contributing factor to biofilm development, thanks to the combined actions of optical scattering and gradient forces. With a customized optical landscape distinct from that of conventional tweezers, not only can such 'tug-of-war' tweezers stably trap and stretch a rod-shaped bacterium in the observing plane, but, more importantly, they can also impose a tunable lateral force that pulls apart cellular clusters without any tethering or mechanical movement. As a proof of principle, we examined a Sinorhizobium meliloti strain that forms robust biofilms and found that the strength of intercellular adhesion depends on the growth medium. This technique may herald new photonic tools for optical manipulation and biofilm study, as well as other biological applications.
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Affiliation(s)
- Anna S Bezryadina
- Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132, USA
| | - Daryl C Preece
- School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia
- Department of NanoEngineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Joseph C Chen
- Department of Biology, San Francisco State University, San Francisco, CA 94132, USA
| | - Zhigang Chen
- Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132, USA
- The MOE Key Laboratory of Weak-Light Nonlinear Photonics, TEDA Applied Physical Institute and School of Physics, Nankai University, Tianjin 300457, China
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Samadi A, Zhang C, Chen J, Reihani SNS, Chen Z. Evaluating the toxic effect of an antimicrobial agent on single bacterial cells with optical tweezers. BIOMEDICAL OPTICS EXPRESS 2015; 6:112-7. [PMID: 25657879 PMCID: PMC4317123 DOI: 10.1364/boe.6.000112] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 12/04/2014] [Accepted: 12/04/2014] [Indexed: 05/12/2023]
Abstract
We implement an optical tweezers technique to assess the effects of chemical agents on single bacterial cells. As a proof of principle, the viability of a trapped Escherichia coli bacterium is determined by monitoring its flagellar motility in the presence of varying concentrations of ethyl alcohol. We show that the "killing time" of the bacterium can be effectively identified from the correlation statistics of the positional time series recorded from the trap, while direct quantification from the time series or associated power spectra is intractable. Our results, which minimize the lethal effects of bacterial photodamage, are consistent with previous reports of ethanol toxicity that used conventional culture-based methods. This approach can be adapted to study other pairwise combinations of drugs and motile bacteria, especially to measure the response times of single cells with better precision.
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Affiliation(s)
- Akbar Samadi
- Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132,
USA
| | - Chensong Zhang
- Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132,
USA
| | - Joseph Chen
- Department of Biology, San Francisco State University, San Francisco, CA 94132,
USA
| | - S. N. S. Reihani
- Department of Physics, Sharif University of Technology, Tehran 11365-9161,
Iran
| | - Zhigang Chen
- Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132,
USA
- TEDA Applied Physics Institute and School of Physics, Nankai University, Tianjin 300457,
China
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9
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Stellamanns E, Uppaluri S, Hochstetter A, Heddergott N, Engstler M, Pfohl T. Optical trapping reveals propulsion forces, power generation and motility efficiency of the unicellular parasites Trypanosoma brucei brucei. Sci Rep 2014; 4:6515. [PMID: 25269514 PMCID: PMC4180810 DOI: 10.1038/srep06515] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 09/12/2014] [Indexed: 12/01/2022] Open
Abstract
Unicellular parasites have developed sophisticated swimming mechanisms to survive in a wide range of environments. Cell motility of African trypanosomes, parasites responsible for fatal illness in humans and animals, is crucial both in the insect vector and the mammalian host. Using millisecond-scale imaging in a microfluidics platform along with a custom made optical trap, we are able to confine single cells to study trypanosome motility. From the trapping characteristics of the cells, we determine the propulsion force generated by cells with a single flagellum as well as of dividing trypanosomes with two fully developed flagella. Estimates of the dissipative energy and the power generation of single cells obtained from the motility patterns of the trypanosomes within the optical trap indicate that specific motility characteristics, in addition to locomotion, may be required for antibody clearance. Introducing a steerable second optical trap we could further measure the force, which is generated at the flagellar tip. Differences in the cellular structure of the trypanosomes are correlated with the trapping and motility characteristics and in consequence with their propulsion force, dissipative energy and power generation.
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Affiliation(s)
- Eric Stellamanns
- 1] Department of Complex Fluids, Max Planck Institute for Dynamics and Self-Organization, 37073 Göttingen, Germany [2]
| | - Sravanti Uppaluri
- 1] Department of Complex Fluids, Max Planck Institute for Dynamics and Self-Organization, 37073 Göttingen, Germany [2]
| | - Axel Hochstetter
- Department of Chemistry, University of Basel, 4056 Basel, Switzerland
| | - Niko Heddergott
- Department of Cell and Developmental Biology, Biocentre, University of Würzburg, 97074 Würzburg, Germany
| | - Markus Engstler
- Department of Cell and Developmental Biology, Biocentre, University of Würzburg, 97074 Würzburg, Germany
| | - Thomas Pfohl
- 1] Department of Complex Fluids, Max Planck Institute for Dynamics and Self-Organization, 37073 Göttingen, Germany [2] Department of Chemistry, University of Basel, 4056 Basel, Switzerland
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Mayola A, Irazoki O, Martínez IA, Petrov D, Menolascina F, Stocker R, Reyes-Darias JA, Krell T, Barbé J, Campoy S. RecA protein plays a role in the chemotactic response and chemoreceptor clustering of Salmonella enterica. PLoS One 2014; 9:e105578. [PMID: 25147953 PMCID: PMC4141790 DOI: 10.1371/journal.pone.0105578] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 07/21/2014] [Indexed: 01/17/2023] Open
Abstract
The RecA protein is the main bacterial recombinase and the activator of the SOS system. In Escherichia coli and Salmonella enterica sv. Typhimurium, RecA is also essential for swarming, a flagellar-driven surface translocation mechanism widespread among bacteria. In this work, the direct interaction between RecA and the CheW coupling protein was confirmed, and the motility and chemotactic phenotype of a S. Typhimurium ΔrecA mutant was characterized through microfluidics, optical trapping, and quantitative capillary assays. The results demonstrate the tight association of RecA with the chemotaxis pathway and also its involvement in polar chemoreceptor cluster formation. RecA is therefore necessary for standard flagellar rotation switching, implying its essential role not only in swarming motility but also in the normal chemotactic response of S. Typhimurium.
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Affiliation(s)
- Albert Mayola
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain
| | - Oihane Irazoki
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain
| | | | - Dmitri Petrov
- ICFO-Institut de Ciències Fotòniques, Castelldefels, Spain
| | - Filippo Menolascina
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Roman Stocker
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - José A. Reyes-Darias
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Tino Krell
- Department of Environmental Protection, Estación Experimental del Zaidín-Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Jordi Barbé
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain
| | - Susana Campoy
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Spain
- * E-mail:
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Roxworthy BJ, Johnston MT, Lee-Montiel FT, Ewoldt RH, Imoukhuede PI, Toussaint KC. Plasmonic optical trapping in biologically relevant media. PLoS One 2014; 9:e93929. [PMID: 24710326 PMCID: PMC3977964 DOI: 10.1371/journal.pone.0093929] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 03/11/2014] [Indexed: 12/14/2022] Open
Abstract
We present plasmonic optical trapping of micron-sized particles in biologically relevant buffer media with varying ionic strength. The media consist of 3 cell-growth solutions and 2 buffers and are specifically chosen due to their widespread use and applicability to breast-cancer and angiogenesis studies. High-precision rheological measurements on the buffer media reveal that, in all cases excluding the 8.0 pH Stain medium, the fluids exhibit Newtonian behavior, thereby enabling straightforward measurements of optical trap stiffness from power-spectral particle displacement data. Using stiffness as a trapping performance metric, we find that for all media under consideration the plasmonic nanotweezers generate optical forces 3–4x a conventional optical trap. Further, plasmonic trap stiffness values are comparable to those of an identical water-only system, indicating that the performance of a plasmonic nanotweezer is not degraded by the biological media. These results pave the way for future biological applications utilizing plasmonic optical traps.
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Affiliation(s)
- Brian J. Roxworthy
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Michael T. Johnston
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Felipe T. Lee-Montiel
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Randy H. Ewoldt
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Princess I. Imoukhuede
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Kimani C. Toussaint
- Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail:
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