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Oda H, Shimizu N, Morimoto Y, Takeuchi S. Harnessing the Propulsive Force of Microalgae with Microtrap to Drive Micromachines. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024:e2402923. [PMID: 38973080 DOI: 10.1002/smll.202402923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Revised: 06/02/2024] [Indexed: 07/09/2024]
Abstract
Microorganisms possess remarkable locomotion abilities, making them potential candidates for micromachine propulsion. Here, the use of Chlamydomonas Reinhardtii (CR) is explored, a motile green alga, as a micromotor by harnessing its propulsive force with microtraps. The objectives include developing the microtrap structure, evaluating trapping efficiency, and investigating the movement dynamics of biohybrid micromachines driven by CR. Experimental analysis demonstrates that trap design significantly influences trapping efficiency, with a specific trap configuration (multi-ring structure with diameters of 7 µm - 10 µm - 13 µm) showing the highest effectiveness. The micromachine empowered with two CRs facing the same direction exhibits complex, random-like motion with yaw, pitch, and roll movements, while the micromachine with four CRs in a circular position each facing the tangential direction of the circle demonstrates controlled rotational motion. These findings highlight the degree of freedom and movement potential of biohybrid micromachines.
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Affiliation(s)
- Haruka Oda
- Graduate School of Information Science and Technology, Department of Mechano-Infomatics, the University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo, 113-8656, Japan
| | - Naoto Shimizu
- Graduate School of Information Science and Technology, Department of Mechano-Infomatics, the University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo, 113-8656, Japan
| | - Yuya Morimoto
- Graduate School of Information Science and Technology, Department of Mechano-Infomatics, the University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo, 113-8656, Japan
| | - Shoji Takeuchi
- Graduate School of Information Science and Technology, Department of Mechano-Infomatics, the University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo, 113-8656, Japan
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2
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Kurjahn M, Deka A, Girot A, Abbaspour L, Klumpp S, Lorenz M, Bäumchen O, Karpitschka S. Quantifying gliding forces of filamentous cyanobacteria by self-buckling. eLife 2024; 12:RP87450. [PMID: 38864737 PMCID: PMC11178357 DOI: 10.7554/elife.87450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2024] Open
Abstract
Filamentous cyanobacteria are one of the oldest and today still most abundant lifeforms on earth, with manifold implications in ecology and economics. Their flexible filaments, often several hundred cells long, exhibit gliding motility in contact with solid surfaces. The underlying force generating mechanism is not yet understood. Here, we demonstrate that propulsion forces and friction coefficients are strongly coupled in the gliding motility of filamentous cyanobacteria. We directly measure their bending moduli using micropipette force sensors, and quantify propulsion and friction forces by analyzing their self-buckling behavior, complemented with analytical theory and simulations. The results indicate that slime extrusion unlikely generates the gliding forces, but support adhesion-based hypotheses, similar to the better-studied single-celled myxobacteria. The critical self-buckling lengths align well with the peaks of natural length distributions, indicating the importance of self-buckling for the organization of their collective in natural and artificial settings.
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Affiliation(s)
- Maximilian Kurjahn
- Max Planck Institute for Dynamics and Self-Organization (MPI-DS)GöttingenGermany
| | - Antaran Deka
- Max Planck Institute for Dynamics and Self-Organization (MPI-DS)GöttingenGermany
| | - Antoine Girot
- Max Planck Institute for Dynamics and Self-Organization (MPI-DS)GöttingenGermany
- Experimental Physics V, University of BayreuthBayreuthGermany
| | - Leila Abbaspour
- Max Planck School Matter to Life, University of GöttingenGöttingenGermany
- Institute for Dynamics of Complex Systems, University of GöttingenGöttingenGermany
| | - Stefan Klumpp
- Max Planck School Matter to Life, University of GöttingenGöttingenGermany
- Institute for Dynamics of Complex Systems, University of GöttingenGöttingenGermany
| | - Maike Lorenz
- Department of Experimental Phycology and SAG Culture Collection of Algae Albrecht-von-Haller Institute for Plant Science, University of GöttingenGöttingenGermany
| | - Oliver Bäumchen
- Max Planck Institute for Dynamics and Self-Organization (MPI-DS)GöttingenGermany
- Experimental Physics V, University of BayreuthBayreuthGermany
| | - Stefan Karpitschka
- Max Planck Institute for Dynamics and Self-Organization (MPI-DS)GöttingenGermany
- Fachbereich Physik, University of KonstanzKonstanzGermany
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Bondoc-Naumovitz KG, Laeverenz-Schlogelhofer H, Poon RN, Boggon AK, Bentley SA, Cortese D, Wan KY. Methods and Measures for Investigating Microscale Motility. Integr Comp Biol 2023; 63:1485-1508. [PMID: 37336589 PMCID: PMC10755196 DOI: 10.1093/icb/icad075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/31/2023] [Accepted: 06/06/2023] [Indexed: 06/21/2023] Open
Abstract
Motility is an essential factor for an organism's survival and diversification. With the advent of novel single-cell technologies, analytical frameworks, and theoretical methods, we can begin to probe the complex lives of microscopic motile organisms and answer the intertwining biological and physical questions of how these diverse lifeforms navigate their surroundings. Herein, we summarize the main mechanisms of microscale motility and give an overview of different experimental, analytical, and mathematical methods used to study them across different scales encompassing the molecular-, individual-, to population-level. We identify transferable techniques, pressing challenges, and future directions in the field. This review can serve as a starting point for researchers who are interested in exploring and quantifying the movements of organisms in the microscale world.
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Affiliation(s)
| | | | - Rebecca N Poon
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
| | - Alexander K Boggon
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
| | - Samuel A Bentley
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
| | - Dario Cortese
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
| | - Kirsty Y Wan
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, Exeter, UK
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Catalan RE, Fragkopoulos AA, von Trott N, Kelterborn S, Baidukova O, Hegemann P, Bäumchen O. Light-regulated adsorption and desorption of Chlamydomonas cells at surfaces. SOFT MATTER 2023; 19:306-314. [PMID: 36520090 DOI: 10.1039/d2sm01039a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Microbial colonization of surfaces represents the first step towards biofilm formation, which is a recurring phenomenon in nature with beneficial and detrimental implications in technological and medical settings. Consequently, there is interest in elucidating the fundamental aspects of the initial stages of biofilm formation of microorganisms on solid surfaces. While most of the research is oriented to understand bacterial surface colonization, the fundamental principles of surface colonization of motile, photosynthetic microbes remain largely unexplored so far. Recent single-cell studies showed that the flagellar adhesion of Chlamydomonas reinhardtii is switched on in blue light and switched off under red light [Kreis et al., Nat. Phys., 2018, 14, 45-49]. Here, we study this light-switchable surface association on the population level and measure the kinetics of adsorption and desorption of suspensions of motile C. reinhardtii cells on glass surfaces using bright-field optical microscopy. We observe that both processes exhibit a response lag relative to the time at which the blue- and red-light conditions are set and model this feature using time-delayed Langmuir-type kinetics. We find that cell adsorption occurs significantly faster than desorption, which we attribute to the protein-mediated molecular adhesion mechanism of the cells. Adsorption experiments using phototactically blind C. reinhardtii mutants demonstrate that phototaxis does not affect the cell adsorption kinetics. Hence, this framework can be used as an assay for characterizing the dynamics of the surface colonization of microbial species exhibiting light-regulated surface adhesion under precisely controlled environmental conditions.
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Affiliation(s)
- Rodrigo E Catalan
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
- Experimental Physics V, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
| | - Alexandros A Fragkopoulos
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
- Experimental Physics V, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
| | - Nicolas von Trott
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
| | - Simon Kelterborn
- Institute of Biology, Experimental Biophysics, Humboldt-Universität, Invalidenstraße 42, 10115 Berlin, Germany
- Institute of Translational Physiology, Charité - Universitätsmedizin Berlin, Corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, 10117 Berlin, Germany
| | - Olga Baidukova
- Institute of Biology, Experimental Biophysics, Humboldt-Universität, Invalidenstraße 42, 10115 Berlin, Germany
| | - Peter Hegemann
- Institute of Biology, Experimental Biophysics, Humboldt-Universität, Invalidenstraße 42, 10115 Berlin, Germany
| | - Oliver Bäumchen
- Max Planck Institute for Dynamics and Self-Organization (MPIDS), Am Faßberg 17, 37077 Göttingen, Germany
- Experimental Physics V, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany.
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Leptos KC, Chioccioli M, Furlan S, Pesci AI, Goldstein RE. Phototaxis of Chlamydomonas arises from a tuned adaptive photoresponse shared with multicellular Volvocine green algae. Phys Rev E 2023; 107:014404. [PMID: 36797913 PMCID: PMC7616094 DOI: 10.1103/physreve.107.014404] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 12/16/2022] [Indexed: 06/18/2023]
Abstract
A fundamental issue in biology is the nature of evolutionary transitions from unicellular to multicellular organisms. Volvocine algae are models for this transition, as they span from the unicellular biflagellate Chlamydomonas to multicellular species of Volvox with up to 50,000 Chlamydomonas-like cells on the surface of a spherical extracellular matrix. The mechanism of phototaxis in these species is of particular interest since they lack a nervous system and intercellular connections; steering is a consequence of the response of individual cells to light. Studies of Volvox and Gonium, a 16-cell organism with a plate-like structure, have shown that the flagellar response to changing illumination of the cellular photosensor is adaptive, with a recovery time tuned to the rotation period of the colony around its primary axis. Here, combining high-resolution studies of the flagellar photoresponse of micropipette-held Chlamydomonas with 3D tracking of freely swimming cells, we show that such tuning also underlies its phototaxis. A mathematical model is developed based on the rotations around an axis perpendicular to the flagellar beat plane that occur through the adaptive response to oscillating light levels as the organism spins. Exploiting a separation of timescales between the flagellar photoresponse and phototurning, we develop an equation of motion that accurately describes the observed photoalignment. In showing that the adaptive timescales in Volvocine algae are tuned to the organisms' rotational periods across three orders of magnitude in cell number, our results suggest a unified picture of phototaxis in green algae in which the asymmetry in torques that produce phototurns arise from the individual flagella of Chlamydomonas, the flagellated edges of Gonium, and the flagellated hemispheres of Volvox.
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Affiliation(s)
- Kyriacos C. Leptos
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
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Shimizu I, Yamashita K, Tokunaga E. Development of a Simple Fabrication Method for Magnetic Micro Stir Bars and Induction of Rotational Motion in Chlamydomonas reinhardtii. MICROMACHINES 2022; 13:1842. [PMID: 36363863 PMCID: PMC9695637 DOI: 10.3390/mi13111842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/16/2022] [Accepted: 10/25/2022] [Indexed: 06/16/2023]
Abstract
A magnetic micro stirrer bar (MMSB) is used in the mixing operation of microfluidic devices. We have established a low-cost and easy method to make MMSBs using magnetic (neodymium magnets, magnet sheets) or non-magnetic powders (SUS304) as materials. We demonstrated three kinds of MMSB have respective advantages. To confirm the practical use of this MMSB, a cell suspension of the motile unicellular green alga Chlamydomonas reinhardtii was stirred in microwells. As a result, the number of rotating cells increased with only one of the two flagella mechanically removed by the shear force of the rotating bar, which facilitates the kinetic analysis of the flagellar motion of the cell. The rotational motion of the monoflagellate cell was modeled as translational (orbital) + spinning motion of a sphere in a viscous fluid and the driving force per flagellum was confirmed to be consistent with previous literature. Since the present method does not use genetic manipulations or chemicals to remove a flagellum, it is possible to obtain cells in a more naturally viable state quickly and easily than before. However, since the components eluted from the powder material harm the health of cells, it was suggested that MMSB coated with resin for long-term use would be suitable for more diverse applications.
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7
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Zhang F, Li Z, Duan Y, Abbas A, Mundaca-Uribe R, Yin L, Luan H, Gao W, Fang RH, Zhang L, Wang J. Gastrointestinal tract drug delivery using algae motors embedded in a degradable capsule. Sci Robot 2022; 7:eabo4160. [PMID: 36170380 PMCID: PMC9884493 DOI: 10.1126/scirobotics.abo4160] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The use of micromotors for active drug delivery via oral administration has recently gained considerable interest. However, efficient motor-assisted delivery into the gastrointestinal (GI) tract remains challenging, owing to the short propulsion lifetime of currently used micromotor platforms. Here, we report on an efficient algae-based motor platform, which takes advantage of the fast and long-lasting swimming behavior of natural microalgae in intestinal fluid to prolong local retention within the GI tract. Fluorescent dye or cell membrane-coated nanoparticle functionalized algae motors were further embedded inside a pH-sensitive capsule to enhance delivery to the small intestines. In vitro, the algae motors displayed a constant motion behavior in simulated intestinal fluid after 12 hours of continuous operation. When orally administered in vivo into mice, the algae motors substantially improved GI distribution of the dye payload compared with traditional magnesium-based micromotors, which are limited by short propulsion lifetimes, and they also enhanced retention of a model chemotherapeutic payload in the GI tract compared with a passive nanoparticle formulation. Overall, combining the efficient motion and extended lifetime of natural algae-based motors with the protective capabilities of oral capsules results in a promising micromotor platform capable of achieving greatly improved cargo delivery in GI tissue for practical biomedical applications.
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Affiliation(s)
| | | | | | - Amal Abbas
- Department of NanoEngineering and Chemical Engineering Program, University of California San Diego, La Jolla, CA 92093, United States
| | - Rodolfo Mundaca-Uribe
- Department of NanoEngineering and Chemical Engineering Program, University of California San Diego, La Jolla, CA 92093, United States
| | - Lu Yin
- Department of NanoEngineering and Chemical Engineering Program, University of California San Diego, La Jolla, CA 92093, United States
| | - Hao Luan
- Department of NanoEngineering and Chemical Engineering Program, University of California San Diego, La Jolla, CA 92093, United States
| | - Weiwei Gao
- Department of NanoEngineering and Chemical Engineering Program, University of California San Diego, La Jolla, CA 92093, United States
| | - Ronnie H. Fang
- Department of NanoEngineering and Chemical Engineering Program, University of California San Diego, La Jolla, CA 92093, United States
| | - Liangfang Zhang
- Department of NanoEngineering and Chemical Engineering Program, University of California San Diego, La Jolla, CA 92093, United States
| | - Joseph Wang
- Department of NanoEngineering and Chemical Engineering Program, University of California San Diego, La Jolla, CA 92093, United States
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8
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Abstract
When the motion of a motile cell is observed closely, it appears erratic, and yet the combination of nonequilibrium forces and surfaces can produce striking examples of organization in microbial systems. While most of our current understanding is based on bulk systems or idealized geometries, it remains elusive how and at which length scale self-organization emerges in complex geometries. Here, using experiments and analytical and numerical calculations, we study the motion of motile cells under controlled microfluidic conditions and demonstrate that probability flux loops organize active motion, even at the level of a single cell exploring an isolated compartment of nontrivial geometry. By accounting for the interplay of activity and interfacial forces, we find that the boundary's curvature determines the nonequilibrium probability fluxes of the motion. We theoretically predict a universal relation between fluxes and global geometric properties that is directly confirmed by experiments. Our findings open the possibility to decipher the most probable trajectories of motile cells and may enable the design of geometries guiding their time-averaged motion.
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Bittermann MR, Bonn D, Woutersen S, Deblais A. Light-switchable deposits from evaporating drops containing motile microalgae. SOFT MATTER 2021; 17:6536-6541. [PMID: 34259707 DOI: 10.1039/d1sm00792k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Deposits from evaporating drops have been shown to take a variety of shapes, depending on the physicochemical properties of both solute and solvent. Classically, the evaporation of drops of colloidal suspensions leads to the so-called coffee ring effect, caused by radially outward flows. Here we investigate deposits from evaporating drops containing living motile microalgae (Chlamydomonas reinhardtii), which are capable of resisting these flows. We show that utilizing their light-sensitivity allows control of the final pattern: adjusting the wavelength and incident angle of the light source enables forcing the formation, completely suppressing and even directing the spatial structure of algal coffee rings.
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Affiliation(s)
- Marius R Bittermann
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
| | - Daniel Bonn
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
| | - Sander Woutersen
- Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands
| | - Antoine Deblais
- Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
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Théry A, Wang Y, Dvoriashyna M, Eloy C, Elias F, Lauga E. Rebound and scattering of motile Chlamydomonas algae in confined chambers. SOFT MATTER 2021; 17:4857-4873. [PMID: 33890590 PMCID: PMC8115209 DOI: 10.1039/d0sm02207a] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Motivated by recent experiments demonstrating that motile algae get trapped in draining foams, we study the trajectories of microorganisms confined in model foam channels (section of a Plateau border). We track single Chlamydomonas reinhardtii cells confined in a thin three-circle microfluidic chamber and show that their spatial distribution exhibits strong corner accumulation. Using empirical scattering laws observed in previous experiments (scattering with a constant scattering angle), we next develop a two-dimension geometrical model and compute the phase space of trapped and periodic trajectories of swimmers inside a three-circles billiard. We find that the majority of cell trajectories end up in a corner, providing a geometrical mechanism for corner accumulation. Incorporating the distribution of scattering angles observed in our experiments and including hydrodynamic interactions between the cells and the surfaces into the geometrical model enables us to reproduce the experimental probability density function of micro-swimmers in microfluidic chambers. Both our experiments and models demonstrate therefore that motility leads generically to trapping in complex geometries.
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Affiliation(s)
- Albane Théry
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK.
| | - Yuxuan Wang
- Université de Paris, CNRS UMR 7057, Laboratoire Matière et Systèmes Complexes MSC, F-75006 Paris, France
| | - Mariia Dvoriashyna
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK.
| | - Christophe Eloy
- Aix Marseille Univ., CNRS, Centrale Marseille, IRPHE, 13013 Marseille, France
| | - Florence Elias
- Université de Paris, CNRS UMR 7057, Laboratoire Matière et Systèmes Complexes MSC, F-75006 Paris, France
| | - Eric Lauga
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK.
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Cortese D, Wan KY. Control of Helical Navigation by Three-Dimensional Flagellar Beating. PHYSICAL REVIEW LETTERS 2021; 126:088003. [PMID: 33709750 DOI: 10.1103/physrevlett.126.088003] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Revised: 12/10/2020] [Accepted: 01/13/2021] [Indexed: 06/12/2023]
Abstract
Helical swimming is a ubiquitous strategy for motile cells to generate self-gradients for environmental sensing. The model biflagellate Chlamydomonas reinhardtii rotates at a constant 1-2 Hz as it swims, but the mechanism is unclear. Here, we show unequivocally that the rolling motion derives from a persistent, nonplanar flagellar beat pattern. This is revealed by high-speed imaging and micromanipulation of live cells. We construct a fully 3D model to relate flagellar beating directly to the free-swimming trajectories. For realistic geometries, the model reproduces both the sense and magnitude of the axial rotation of live cells. We show that helical swimming requires further symmetry breaking between the two flagella. These functional differences underlie all tactic responses, particularly phototaxis. We propose a control strategy by which cells steer toward or away from light by modulating the sign of biflagellar dominance.
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Affiliation(s)
- Dario Cortese
- Living Systems Institute and College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - Kirsty Y Wan
- Living Systems Institute and College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter EX4 4QD, United Kingdom
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Tainio O, Sohrabi F, Janarek N, Koivisto J, Puisto A, Viitanen L, Timonen JVI, Alava M. Chlamydomonas reinhardtii swimming in the Plateau borders of 2D foams. SOFT MATTER 2021; 17:145-152. [PMID: 33155584 DOI: 10.1039/d0sm01206h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Unicellular Chlamydomonas reinhardtii micro-algae cells were inserted into a quasi-2D Hele-Shaw chamber filled with saponin foam. The movement of the algae along the bubble borders was then manipulated and tracked. These self-propelled particles generate flow and stresses in their surrounding matter. In addition, the algae possess the capability of exerting forces that alter bubble boundaries while maintaining an imminent phototactic movement. We find that by controlling the gas fraction of the foam we can change the interaction of the algae and bubbles. Specifically, our data expose three distinct swimming regimes for the algae with respect to the level of confinement due to the Plateau border cross-section: unlimited bulk, transition, and overdamped regimes. At the transition regime we find the speed of the algae to be modeled by a simple force balance equation emerging from the shear inside the Plateau border. Thus, we have shown that it is possible to create an algae-friendly foam while controlling the algae motion. This opens doors to multiple applications where the flow of nutrients, oxygen and recirculation of living organisms is essential.
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Affiliation(s)
- Oskar Tainio
- Department of Applied Physics, Aalto University, 00076 Aalto, Finland.
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