101
|
Nikolov SV, Shum H, Balazs AC, Alexeev A. Computational design of microscopic swimmers and capsules: From directed motion to collective behavior. Curr Opin Colloid Interface Sci 2016. [DOI: 10.1016/j.cocis.2015.10.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|
102
|
|
103
|
Küchler N, Löwen H, Menzel AM. Getting drowned in a swirl: Deformable bead-spring model microswimmers in external flow fields. Phys Rev E 2016; 93:022610. [PMID: 26986380 DOI: 10.1103/physreve.93.022610] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Indexed: 06/05/2023]
Abstract
Deformability is a central feature of many types of microswimmers, e.g., for artificially generated self-propelled droplets. Here, we analyze deformable bead-spring microswimmers in an externally imposed solvent flow field as simple theoretical model systems. We focus on their behavior in a circular swirl flow in two spatial dimensions. Linear (straight) two-bead swimmers are found to circle around the swirl with a slight drift to the outside with increasing activity. In contrast to that, we observe for triangular three-bead or squarelike four-bead swimmers a tendency of being drawn into the swirl and finally getting drowned, although a radial inward component is absent in the flow field. During one cycle around the swirl, the self-propulsion direction of an active triangular or squarelike swimmer remains almost constant, while their orbits become deformed exhibiting an "egglike" shape. Over time, the swirl flow induces slight net rotations of these swimmer types, which leads to net rotations of the egg-shaped orbits. Interestingly, in certain cases, the orbital rotation changes sense when the swimmer approaches the flow singularity. Our predictions can be verified in real-space experiments on artificial microswimmers.
Collapse
Affiliation(s)
- Niklas Küchler
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
| | - Andreas M Menzel
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany
| |
Collapse
|
104
|
Yang J, Kupka I, Schuss Z, Holcman D. Search for a small egg by spermatozoa in restricted geometries. J Math Biol 2015; 73:423-46. [PMID: 26707857 PMCID: PMC4940446 DOI: 10.1007/s00285-015-0955-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 09/19/2015] [Indexed: 10/26/2022]
Abstract
The search by swimmers for a small target in a bounded domain is ubiquitous in cellular biology, where a prominent case is that of the search by spermatozoa for an egg in the uterus. This is one of the severest selection processes in animal reproduction. We present here a mathematical model of the search, its analysis, and numerical simulations. In the proposed model the swimmers' trajectories are rectilinear and the speed is constant. When a trajectory hits an obstacle or the boundary, it is reflected at a random angle and continues the search with the same speed. Because hitting a small target by a trajectory is a rare event, asymptotic approximations and stochastic simulations are needed to estimate the mean search time in various geometries. We consider searches in a disk, in convex planar domains, and in domains with cusps. The exploration of the parameter space for spermatozoa motion in different uterus geometries leads to scaling laws for the search process.
Collapse
Affiliation(s)
- J Yang
- Applied Mathematics and Computational Biology, Ecole Normale Supérieure, IBENS, 46 rue d'Ulm, 75005, Paris, France.,School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin, 541004, Guangxi, China
| | - I Kupka
- Applied Mathematics and Computational Biology, Ecole Normale Supérieure, IBENS, 46 rue d'Ulm, 75005, Paris, France
| | - Z Schuss
- Department of Mathematics, Tel-Aviv University, 69978, Tel-Aviv, Israel
| | - D Holcman
- Applied Mathematics and Computational Biology, Ecole Normale Supérieure, IBENS, 46 rue d'Ulm, 75005, Paris, France. .,Mathematical Institute, University of Oxford, Andrew Wiles Building, Woodstock Rd, Oxford, OX2 6GG, UK.
| |
Collapse
|
105
|
Bimodal rheotactic behavior reflects flagellar beat asymmetry in human sperm cells. Proc Natl Acad Sci U S A 2015; 112:15904-9. [PMID: 26655343 DOI: 10.1073/pnas.1515159112] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Rheotaxis, the directed response to fluid velocity gradients, has been shown to facilitate stable upstream swimming of mammalian sperm cells along solid surfaces, suggesting a robust physical mechanism for long-distance navigation during fertilization. However, the dynamics by which a human sperm orients itself relative to an ambient flow is poorly understood. Here, we combine microfluidic experiments with mathematical modeling and 3D flagellar beat reconstruction to quantify the response of individual sperm cells in time-varying flow fields. Single-cell tracking reveals two kinematically distinct swimming states that entail opposite turning behaviors under flow reversal. We constrain an effective 2D model for the turning dynamics through systematic large-scale parameter scans, and find good quantitative agreement with experiments at different shear rates and viscosities. Using a 3D reconstruction algorithm to identify the flagellar beat patterns causing left or right turning, we present comprehensive 3D data demonstrating the rolling dynamics of freely swimming sperm cells around their longitudinal axis. Contrary to current beliefs, this 3D analysis uncovers ambidextrous flagellar waveforms and shows that the cell's turning direction is not defined by the rolling direction. Instead, the different rheotactic turning behaviors are linked to a broken mirror symmetry in the midpiece section, likely arising from a buckling instability. These results challenge current theoretical models of sperm locomotion.
Collapse
|
106
|
Hu J, Yang M, Gompper G, Winkler RG. Modelling the mechanics and hydrodynamics of swimming E. coli. SOFT MATTER 2015; 11:7867-7876. [PMID: 26256240 DOI: 10.1039/c5sm01678a] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The swimming properties of an E. coli-type model bacterium are investigated by mesoscale hydrodynamic simulations, combining molecular dynamics simulations of the bacterium with the multiparticle particle collision dynamics method for the embedding fluid. The bacterium is composed of a spherocylindrical body with attached helical flagella, built up from discrete particles for an efficient coupling with the fluid. We measure the hydrodynamic friction coefficients of the bacterium and find quantitative agreement with experimental results of swimming E. coli. The flow field of the bacterium shows a force-dipole-like pattern in the swimming plane and two vortices perpendicular to its swimming direction arising from counterrotation of the cell body and the flagella. By comparison with the flow field of a force dipole and rotlet dipole, we extract the force-dipole and rotlet-dipole strengths for the bacterium and find that counterrotation of the cell body and the flagella is essential for describing the near-field hydrodynamics of the bacterium.
Collapse
Affiliation(s)
- Jinglei Hu
- Theoretical Soft Matter and Biophysics, Institute for Advanced Simulation and Institute of Complex Systems, Forschungszentrum Jülich, D-52425 Jülich, Germany.
| | | | | | | |
Collapse
|
107
|
Uspal WE, Popescu MN, Dietrich S, Tasinkevych M. Rheotaxis of spherical active particles near a planar wall. SOFT MATTER 2015. [PMID: 26200672 DOI: 10.1039/c5sm01088h] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
For active particles the interplay between the self-generated hydrodynamic flow and an external shear flow, especially near bounding surfaces, can result in a rich behavior of the particles not easily foreseen from the consideration of the active and external driving mechanisms in isolation. For instance, under certain conditions, the particles exhibit "rheotaxis", i.e., they align their direction of motion with the plane of shear spanned by the direction of the flow and the normal of the bounding surface and move with or against the flow. To date, studies of rheotaxis have focused on elongated particles (e.g., spermatozoa), for which rheotaxis can be understood intuitively in terms of a "weather vane" mechanism. Here we investigate the possibility that spherical active particles, for which the "weather vane" mechanism is excluded due to the symmetry of the shape, may nevertheless exhibit rheotaxis. Combining analytical and numerical calculations, we show that, for a broad class of spherical active particles, rheotactic behavior may emerge via a mechanism which involves "self-trapping" near a hard wall owing to the active propulsion of the particles, combined with their rotation, alignment, and "locking" of the direction of motion into the shear plane. In this state, the particles move solely up- or downstream at a steady height and orientation.
Collapse
Affiliation(s)
- W E Uspal
- Max-Planck-Institut für Intelligente Systeme, Heisenbergstr. 3, D-70569 Stuttgart, Germany.
| | | | | | | |
Collapse
|
108
|
Figueroa-Morales N, Leonardo Miño G, Rivera A, Caballero R, Clément E, Altshuler E, Lindner A. Living on the edge: transfer and traffic of E. coli in a confined flow. SOFT MATTER 2015; 11:6284-6293. [PMID: 26161542 DOI: 10.1039/c5sm00939a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We quantitatively study the transport of E. coli near the walls of confined microfluidic channels, and in more detail along the edges formed by the interception of two perpendicular walls. Our experiments establish the connection between bacterial motion at the flat surface and at the edges and demonstrate the robustness of the upstream motion at the edges. Upstream migration of E. coli at the edges is possible at much larger flow rates compared to motion at the flat surfaces. Interestingly, the speed of bacteria at the edges mainly results from collisions between bacteria moving along this single line. We show that upstream motion not only takes place at the edge but also in an "edge boundary layer" whose size varies with the applied flow rate. We quantify the bacterial fluxes along the bottom walls and the edges and show that they result from both the transport velocity of bacteria and the decrease of surface concentration with increasing flow rate due to erosion processes. We rationalize our findings as a function of local variations in the shear rate in the rectangular channels and hydrodynamic attractive forces between bacteria and walls.
Collapse
Affiliation(s)
- Nuris Figueroa-Morales
- PMMH, UMR 7636 CNRS-ESPCI-Universités Pierre et Marie Curie and Denis Diderot, 10, rue Vauquelin, 75231 Paris Cedex 5, France.
| | | | | | | | | | | | | |
Collapse
|
109
|
Quantitative analysis of Caenorhabditis elegans chemotaxis using a microfluidic device. Anal Chim Acta 2015; 887:155-162. [PMID: 26320797 DOI: 10.1016/j.aca.2015.07.036] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 04/24/2015] [Accepted: 07/17/2015] [Indexed: 11/24/2022]
Abstract
Caenorhabditis elegans, one of the widely studied model organisms, sense external chemical cues and perform relative chemotaxis behaviors through its simple chemosensory neuronal system. To study the mechanism underlying chemosensory behavior, a rapid and reliable method for quantitatively analyzing the worms' behaviors is essential. In this work, we demonstrated a microfluidic approach for investigating chemotaxis responses of worms to chemical gradients. The flow-based microfluidic chip was consisted of circular tree-like microchannels, which was able to generate eight flow streams containing stepwise chemical concentrations without the difference in flow velocity. Worms' upstream swimming into microchannels with various concentrations was monitored for quantitative analysis of the chemotaxis behavior. By using this microfluidic chip, the attractive and repellent responses of C. elegans to NaCl were successfully quantified within several minutes. The results demonstrated the wild type-like repellent responses and severely impaired attractive responses in grk-2 mutant animals with defects in calcium influx. In addition, the chemotaxis analysis of the third stage larvae revealed that its gustatory response was different from that in the adult stage. Thus, our microfluidic method provided a useful platform for studying the chemosensory behaviors of C. elegans and screening of chemosensation-related chemical drugs.
Collapse
|
110
|
Tournus M, Kirshtein A, Berlyand LV, Aranson IS. Flexibility of bacterial flagella in external shear results in complex swimming trajectories. J R Soc Interface 2015; 12:20140904. [PMID: 25376876 DOI: 10.1098/rsif.2014.0904] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Many bacteria use rotating helical flagella in swimming motility. In the search for food or migration towards a new habitat, bacteria occasionally unbundle their flagellar filaments and tumble, leading to an abrupt change in direction. Flexible flagella can also be easily deformed by external shear flow, leading to complex bacterial trajectories. Here, we examine the effects of flagella flexibility on the navigation of bacteria in two fundamental shear flows: planar shear and Poiseuille flow realized in long channels. On the basis of slender body elastodynamics and numerical analysis, we discovered a variety of non-trivial effects stemming from the interplay of self-propulsion, elasticity and shear-induced flagellar bending. We show that in planar shear flow the bacteria execute periodic motion, whereas in Poiseuille flow, they migrate towards the centre of the channel or converge towards a limit cycle. We also find that even a small amount of random reorientation can induce a strong response of bacteria, leading to overall non-periodic trajectories. Our findings exemplify the sensitive role of flagellar flexibility and shed new light on the navigation of bacteria in complex shear flows.
Collapse
Affiliation(s)
- M Tournus
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
| | - A Kirshtein
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
| | - L V Berlyand
- Department of Mathematics, Pennsylvania State University, University Park, PA 16802, USA
| | - I S Aranson
- Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439, USA Engineering Sciences and Applied Mathematics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60202, USA
| |
Collapse
|
111
|
Siryaporn A, Kim MK, Shen Y, Stone HA, Gitai Z. Colonization, competition, and dispersal of pathogens in fluid flow networks. Curr Biol 2015; 25:1201-7. [PMID: 25843031 PMCID: PMC4422760 DOI: 10.1016/j.cub.2015.02.074] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 01/02/2015] [Accepted: 02/26/2015] [Indexed: 11/29/2022]
Abstract
The colonization of bacteria in complex fluid flow networks, such as those found in host vasculature, remains poorly understood. Recently, it was reported that many bacteria, including Bacillus subtilis [1], Escherichia coli [2], and Pseudomonas aeruginosa [3, 4], can move in the opposite direction of fluid flow. Upstream movement results from the interplay between fluid shear stress and bacterial motility structures, and such rheotactic-like behavior is predicted to occur for a wide range of conditions [1]. Given the potential ubiquity of upstream movement, its impact on population-level behaviors within hosts could be significant. Here, we find that P. aeruginosa communities use a diverse set of motility strategies, including a novel surface-motility mechanism characterized by counter-advection and transverse diffusion, to rapidly disperse throughout vasculature-like flow networks. These motility modalities give P. aeruginosa a selective growth advantage, enabling it to self-segregate from other human pathogens such as Proteus mirabilis and Staphylococcus aureus that outcompete P. aeruginosa in well-mixed non-flow environments. We develop a quantitative model of bacterial colonization in flow networks, confirm our model in vivo in plant vasculature, and validate a key prediction that colonization and dispersal can be inhibited by modifying surface chemistry. Our results show that the interaction between flow mechanics and motility structures shapes the formation of mixed-species communities and suggest a general mechanism by which bacteria could colonize hosts. Furthermore, our results suggest novel strategies for tuning the composition of multi-species bacterial communities in hosts, preventing inappropriate colonization in medical devices, and combatting bacterial infections.
Collapse
Affiliation(s)
- Albert Siryaporn
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Minyoung Kevin Kim
- Frick Laboratory, Department of Chemistry, Princeton University, Washington Road, Princeton, NJ 08544, USA
| | - Yi Shen
- Engineering Quad, Department of Mechanical and Aerospace Engineering, Princeton University, Olden Street, Princeton, NJ 08544, USA
| | - Howard A Stone
- Engineering Quad, Department of Mechanical and Aerospace Engineering, Princeton University, Olden Street, Princeton, NJ 08544, USA
| | - Zemer Gitai
- Lewis Thomas Laboratory, Department of Molecular Biology, Princeton University, Washington Road, Princeton, NJ 08544, USA.
| |
Collapse
|
112
|
Palacci J, Sacanna S, Abramian A, Barral J, Hanson K, Grosberg AY, Pine DJ, Chaikin PM. Artificial rheotaxis. SCIENCE ADVANCES 2015; 1:e1400214. [PMID: 26601175 PMCID: PMC4640647 DOI: 10.1126/sciadv.1400214] [Citation(s) in RCA: 94] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Accepted: 03/30/2015] [Indexed: 05/18/2023]
Abstract
Motility is a basic feature of living microorganisms, and how it works is often determined by environmental cues. Recent efforts have focused on developing artificial systems that can mimic microorganisms, in particular their self-propulsion. We report on the design and characterization of synthetic self-propelled particles that migrate upstream, known as positive rheotaxis. This phenomenon results from a purely physical mechanism involving the interplay between the polarity of the particles and their alignment by a viscous torque. We show quantitative agreement between experimental data and a simple model of an overdamped Brownian pendulum. The model notably predicts the existence of a stagnation point in a diverging flow. We take advantage of this property to demonstrate that our active particles can sense and predictably organize in an imposed flow. Our colloidal system represents an important step toward the realization of biomimetic microsystems with the ability to sense and respond to environmental changes.
Collapse
Affiliation(s)
- Jérémie Palacci
- Department of Physics, New York University, New York, NY 10003, USA
- Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA
- Corresponding author. E-mail:
| | - Stefano Sacanna
- Department of Chemistry, New York University, New York, NY 10003, USA
| | - Anaïs Abramian
- Département de Physique, Ecole Normale Supérieure de Lyon, 69007 Lyon, France
| | - Jérémie Barral
- Center for Neural Science, New York University, New York, NY 10003, USA
| | - Kasey Hanson
- School of Materials Science and Engineering, College of Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | | | - David J. Pine
- Department of Physics, New York University, New York, NY 10003, USA
| | - Paul M. Chaikin
- Department of Physics, New York University, New York, NY 10003, USA
| |
Collapse
|
113
|
Elgeti J, Winkler RG, Gompper G. Physics of microswimmers--single particle motion and collective behavior: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2015; 78:056601. [PMID: 25919479 DOI: 10.1088/0034-4885/78/5/056601] [Citation(s) in RCA: 701] [Impact Index Per Article: 70.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Locomotion and transport of microorganisms in fluids is an essential aspect of life. Search for food, orientation toward light, spreading of off-spring, and the formation of colonies are only possible due to locomotion. Swimming at the microscale occurs at low Reynolds numbers, where fluid friction and viscosity dominates over inertia. Here, evolution achieved propulsion mechanisms, which overcome and even exploit drag. Prominent propulsion mechanisms are rotating helical flagella, exploited by many bacteria, and snake-like or whip-like motion of eukaryotic flagella, utilized by sperm and algae. For artificial microswimmers, alternative concepts to convert chemical energy or heat into directed motion can be employed, which are potentially more efficient. The dynamics of microswimmers comprises many facets, which are all required to achieve locomotion. In this article, we review the physics of locomotion of biological and synthetic microswimmers, and the collective behavior of their assemblies. Starting from individual microswimmers, we describe the various propulsion mechanism of biological and synthetic systems and address the hydrodynamic aspects of swimming. This comprises synchronization and the concerted beating of flagella and cilia. In addition, the swimming behavior next to surfaces is examined. Finally, collective and cooperate phenomena of various types of isotropic and anisotropic swimmers with and without hydrodynamic interactions are discussed.
Collapse
Affiliation(s)
- J Elgeti
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich, Germany
| | | | | |
Collapse
|
114
|
Microbes in flow. Curr Opin Microbiol 2015; 25:1-8. [PMID: 25812434 DOI: 10.1016/j.mib.2015.03.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 02/28/2015] [Accepted: 03/05/2015] [Indexed: 11/22/2022]
Abstract
Microbes often live in moving fluids. Despite the multitude of implications that flow has on microbial ecology and environmental microbiology, only recently have experimental tools and conceptual frameworks from fluid physics been applied systematically to further our knowledge of the behavior of microbes in flow. This nascent research field, which truly straddles biology and physics, has already produced important contributions to our understanding of the physical interaction between microbes and flow, both in bulk fluid and close to surfaces, at the same time revealing the richness and complexity of the resulting dynamics.
Collapse
|
115
|
Tran NP. Effect of dielectrophoretic force on swimming bacteria. Electrophoresis 2015; 36:1485-92. [PMID: 25785901 DOI: 10.1002/elps.201400503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 01/19/2015] [Accepted: 02/15/2015] [Indexed: 11/07/2022]
Abstract
Dielectrophoresis (DEP) has been applied widely in bacterial manipulation such as separating, concentrating, and focusing. Previous studies primarily focused on the collective effects of DEP force on the bacterial population. However, the influence of DEP force on the swimming of a single bacterium had not been investigated. In this study, we present a model to analyze the effect of DEP force on a swimming helically flagellated bacterium, particularly on its swimming direction and velocity. We consider a simple DEP force that acts along the X-direction, and its strength as well as direction varies with the X- and Y-positions. Resistive force theory is employed to compute the hydrodynamic force on the bacterium's flagellar bundle, and the effects of both DEP force and rotational diffusion on the swimming of the bacterium are simultaneously taken into consideration using the Fokker-Planck equation. We show the mechanism of how DEP force alters the orientation and velocity of the bacterium. In most cases, the DEP force dominantly influences the orientation of the swimming bacterium; however, when the DEP force strongly varies along the Y-direction, the rotational diffusion is also responsible for determining the bacterium's reorientation. More interestingly, the variance of DEP force along the Y-direction causes the bacterium to experience a translational velocity perpendicular to its primary axis, and this phenomenon could be utilized to focus the bacteria. Finally, we show the feasibility of applying our findings to achieve bacterial focusing.
Collapse
Affiliation(s)
- Ngoc Phu Tran
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore
| |
Collapse
|
116
|
Propensity of undulatory swimmers, such as worms, to go against the flow. Proc Natl Acad Sci U S A 2015; 112:3606-11. [PMID: 25775552 DOI: 10.1073/pnas.1424962112] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ability to orient oneself in response to environmental cues is crucial to the survival and function of diverse organisms. One such orientation behavior is the alignment of aquatic organisms with (negative rheotaxis) or against (positive rheotaxis) fluid current. The questions of whether low-Reynolds-number, undulatory swimmers, such as worms, rheotax and whether rheotaxis is a deliberate or an involuntary response to mechanical forces have been the subject of conflicting reports. To address these questions, we use Caenorhabditis elegans as a model undulatory swimmer and examine, in experiment and theory, the orientation of C. elegans in the presence of flow. We find that when close to a stationary surface the animal aligns itself against the direction of the flow. We elucidate for the first time to our knowledge the mechanisms of rheotaxis in worms and show that rheotaxis can be explained solely by mechanical forces and does not require sensory input or deliberate action. The interaction between the flow field induced by the swimmer and a nearby surface causes the swimmer to tilt toward the surface and the velocity gradient associated with the flow rotates the animal to face upstream. Fluid mechanical computer simulations faithfully mimic the behavior observed in experiments, supporting the notion that rheotaxis behavior can be fully explained by hydrodynamics. Our study highlights the important role of hydrodynamics in the behavior of small undulating swimmers and may assist in developing control strategies to affect the animals' life cycles.
Collapse
|
117
|
Molaei M, Sheng J. Imaging bacterial 3D motion using digital in-line holographic microscopy and correlation-based de-noising algorithm. OPTICS EXPRESS 2014; 22:32119-37. [PMID: 25607177 PMCID: PMC4317141 DOI: 10.1364/oe.22.032119] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 11/30/2014] [Accepted: 11/30/2014] [Indexed: 05/24/2023]
Abstract
Better understanding of bacteria environment interactions in the context of biofilm formation requires accurate 3-dimentional measurements of bacteria motility. Digital Holographic Microscopy (DHM) has demonstrated its capability in resolving 3D distribution and mobility of particulates in a dense suspension. Due to their low scattering efficiency, bacteria are substantially difficult to be imaged by DHM. In this paper, we introduce a novel correlation-based de-noising algorithm to remove the background noise and enhance the quality of the hologram. Implemented in conjunction with DHM, we demonstrate that the method allows DHM to resolve 3-D E. coli bacteria locations of a dense suspension (>107 cells/ml) with submicron resolutions (<0.5 µm) over substantial depth and to obtain thousands of 3D cell trajectories.
Collapse
Affiliation(s)
- Mehdi Molaei
- Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79409,
USA
| | - Jian Sheng
- Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79409,
USA
| |
Collapse
|
118
|
Abstract
Motile bacteria often have to pass through small tortuous pores in soil or tissue of higher organisms. However, their motion in this prevalent type of niche is not fully understood. Here, we modeled it with narrow glass capillaries and identified a critical radius (Rc) for bacterial motion. Near the surface of capillaries narrower than that, the swimming trajectories are helices. In larger capillaries, they swim in distorted circles. Under non-slip condition, the peritrichous Escherichia coli swam in left-handed helices with an Rc of ~10 μm near glass surface. However, slipping could occur in the fast monotrichous Pseudomonas fluorescens, when a speed threshold was exceeded, and thus both left-handed and right-handed helices were executed in glass capillaries. In the natural non-cylindrical pores, the near-surface trajectories would be spirals and twisted loops. Engaging in such motions reduces the bacterial migration rate. With a given pore size, the run length and the tumbling angle of the bacterium determine the probability and duration of their near-surface motion. Shear flow and chemotaxis potentially enhance it. Based on this observation, the puzzling previous observations on bacterial migration in porous environments can be interpreted.
Collapse
Affiliation(s)
- Liyan Ping
- Max Planck Institute for Chemical Ecology, Hans-Knoell-Str. 8, D-07745 Jena, Germany Current address: Rowland Institute at Harvard University, 100 Edwin H. Land Blvd, Cambridge, MA 02142, USA
| | - Vaibhav Wasnik
- Physics Department, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Eldon Emberly
- Physics Department, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| |
Collapse
|
119
|
A multiple-relaxation-time lattice-boltzmann model for bacterial chemotaxis: effects of initial concentration, diffusion, and hydrodynamic dispersion on traveling bacterial bands. Bull Math Biol 2014; 76:2449-75. [PMID: 25223537 DOI: 10.1007/s11538-014-0020-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 09/04/2014] [Indexed: 10/24/2022]
Abstract
Bacterial chemotaxis can enhance the bioremediation of contaminants in aqueous and subsurface environments if the contaminant is a chemoattractant that the bacteria degrade. The process can be promoted by traveling bands of chemotactic bacteria that form due to metabolism-generated gradients in chemoattractant concentration. We developed a multiple-relaxation-time (MRT) lattice-Boltzmann method (LBM) to model chemotaxis, because LBMs are well suited to model reactive transport in the complex geometries that are typical for subsurface porous media. This MRT-LBM can attain a better numerical stability than its corresponding single-relaxation-time LBM. We performed simulations to investigate the effects of substrate diffusion, initial bacterial concentration, and hydrodynamic dispersion on the formation, shape, and propagation of bacterial bands. Band formation requires a sufficiently high initial number of bacteria and a small substrate diffusion coefficient. Uniform flow does not affect the bands while shear flow does. Bacterial bands can move both upstream and downstream when the flow velocity is small. However, the bands disappear once the velocity becomes too large due to hydrodynamic dispersion. Generally bands can only be observed if the dimensionless ratio between the chemotactic sensitivity coefficient and the effective diffusion coefficient of the bacteria exceeds a critical value, that is, when the biased movement due to chemotaxis overcomes the diffusion-like movement due to the random motility and hydrodynamic dispersion.
Collapse
|
120
|
El-Sherry TM, Elsayed M, Abdelhafez HK, Abdelgawad M. Characterization of rheotaxis of bull sperm using microfluidics. Integr Biol (Camb) 2014; 6:1111-21. [DOI: 10.1039/c4ib00196f] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
121
|
Abstract
Microfluidics has significantly contributed to the expansion of the frontiers of microbial ecology over the past decade by allowing researchers to observe the behaviors of microbes in highly controlled microenvironments, across scales from a single cell to mixed communities. Spatially and temporally varying distributions of organisms and chemical cues that mimic natural microbial habitats can now be established by exploiting physics at the micrometer scale and by incorporating structures with specific geometries and materials. In this article, we review applications of microfluidics that have resulted in insightful discoveries on fundamental aspects of microbial life, ranging from growth and sensing to cell-cell interactions and population dynamics. We anticipate that this flexible multidisciplinary technology will continue to facilitate discoveries regarding the ecology of microorganisms and help uncover strategies to control microbial processes such as biofilm formation and antibiotic resistance.
Collapse
Affiliation(s)
- Roberto Rusconi
- Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; , ,
| | | | | |
Collapse
|
122
|
Molaei M, Barry M, Stocker R, Sheng J. Failed escape: solid surfaces prevent tumbling of Escherichia coli. PHYSICAL REVIEW LETTERS 2014; 113:068103. [PMID: 25148353 DOI: 10.1103/physrevlett.113.068103] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2013] [Indexed: 05/11/2023]
Abstract
Understanding how bacteria move close to surfaces is crucial for a broad range of microbial processes including biofilm formation, bacterial dispersion, and pathogenic infections. We used digital holographic microscopy to capture a large number (>10(3)) of three-dimensional Escherichia coli trajectories near and far from a surface. We found that within 20 μm from a surface tumbles are suppressed by 50% and reorientations are largely confined to surface-parallel directions, preventing escape of bacteria from the near-surface region. A hydrodynamic model indicates that the tumble suppression is likely due to a surface-induced reduction in the hydrodynamic force responsible for the flagellar unbundling that causes tumbling. These findings imply that tumbling does not provide an effective means to escape trapping near surfaces.
Collapse
Affiliation(s)
- Mehdi Molaei
- Mechanical Engineering Department, Texas Tech University, 2703 7th Street, Lubbock, Texas 79409, USA
| | - Michael Barry
- Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 15 Vassar Street, Cambridge, Massachusetts 02139, USA
| | - Roman Stocker
- Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 15 Vassar Street, Cambridge, Massachusetts 02139, USA
| | - Jian Sheng
- Mechanical Engineering Department, Texas Tech University, 2703 7th Street, Lubbock, Texas 79409, USA
| |
Collapse
|
123
|
Kantsler V, Dunkel J, Blayney M, Goldstein RE. Rheotaxis facilitates upstream navigation of mammalian sperm cells. eLife 2014; 3:e02403. [PMID: 24867640 PMCID: PMC4031982 DOI: 10.7554/elife.02403] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 04/29/2014] [Indexed: 12/11/2022] Open
Abstract
A major puzzle in biology is how mammalian sperm maintain the correct swimming direction during various phases of the sexual reproduction process. Whilst chemotaxis may dominate near the ovum, it is unclear which cues guide spermatozoa on their long journey towards the egg. Hypothesized mechanisms range from peristaltic pumping to temperature sensing and response to fluid flow variations (rheotaxis), but little is known quantitatively about them. We report the first quantitative study of mammalian sperm rheotaxis, using microfluidic devices to investigate systematically swimming of human and bull sperm over a range of physiologically relevant shear rates and viscosities. Our measurements show that the interplay of fluid shear, steric surface-interactions, and chirality of the flagellar beat leads to stable upstream spiralling motion of sperm cells, thus providing a generic and robust rectification mechanism to support mammalian fertilisation. A minimal mathematical model is presented that accounts quantitatively for the experimental observations.DOI: http://dx.doi.org/10.7554/eLife.02403.001.
Collapse
Affiliation(s)
- Vasily Kantsler
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Jörn Dunkel
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | | | - Raymond E Goldstein
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| |
Collapse
|
124
|
Tung CK, Ardon F, Fiore A, Suarez SS, Wu M. Cooperative roles of biological flow and surface topography in guiding sperm migration revealed by a microfluidic model. LAB ON A CHIP 2014; 14:1348-56. [PMID: 24535032 PMCID: PMC4497544 DOI: 10.1039/c3lc51297e] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Successful reproduction in mammals requires sperm to swim against a fluid flow and through the long and complex female reproductive tract before reaching the egg in the oviduct. Millions of them do not make it. Despite their clinical importance, the roles played in sperm migration by the diverse biophysical and biochemical microenvironments within the reproductive tract are largely unknown. In this article, we present the development of a double layer microfluidic device that recreates two important biophysical environments within the female reproductive tract: fluid flow and surface topography. The unique feature of the device is that it enables one to study the cooperative roles of fluid flow and surface topography in guiding sperm migration. Using bull sperm as a model system, we found that microfluidic grooves embedded on a channel surface facilitate sperm migration against fluid flow. These findings suggest ways to design in vitro fertilization devices to treat infertility and to develop non-invasive contraceptives that use a microarchitectural design to entrap sperm.
Collapse
Affiliation(s)
- Chih-kuan Tung
- Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY, USA
| | - Florencia Ardon
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
| | - Alyssa Fiore
- Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY, USA
| | - Susan S. Suarez
- Department of Biomedical Sciences, Cornell University, Ithaca, NY, USA
| | - Mingming Wu
- Department of Biological and Environmental Engineering, Cornell University, Ithaca, NY, USA
| |
Collapse
|
125
|
Jaimes-Lizcano YA, Hunn DD, Papadopoulos KD. Filamentous Escherichia coli cells swimming in tapered microcapillaries. Res Microbiol 2014; 165:166-74. [PMID: 24566556 DOI: 10.1016/j.resmic.2014.01.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 01/30/2014] [Indexed: 10/25/2022]
Abstract
This study analyzed the swimming characteristics of filamentous Escherichia coli cells inside tapered capillaries with a diameter decreasing from 700 μm to 4 μm and a mean body length of 27.8 μm ± 11.9 μm. Cells that were pre-oriented towards the narrower diameter section of the tapered capillary swam with high directional persistence, following conical-helix trajectories along the capillary wall. The confinement of the tapered capillary significantly diminished the mean swimming speed of filamentous cells when compared to their unrestricted mean swimming speed. The cell body rotation of individual filamentous bacteria decreased along the tapered direction, likely due to increased steric interactions with the capillary wall. Filamentous cells that swam under imposed flow rates ranging from 0.2 μl/min to 0.8 μl/min showed positive rheotaxis inside the 150 μm-350 μm diameter region of the tapered capillary. Depending on the imposed flow rate, none of the bacteria could advance beyond a critical diameter in the tapered capillary. This critical diameter is likely to be the position of the maximum shear rate they can tolerate without being flushed away. This work showed experimental evidence of how a simple flow constriction such as a tapered tube forms a hydrodynamic barrier that can deter the advance of bacterial rheotaxis.
Collapse
Affiliation(s)
- Yuly A Jaimes-Lizcano
- Department of Chemical & Biomolecular Engineering, Tulane University, New Orleans, LA 70118, USA.
| | - Dayton D Hunn
- Department of Chemical & Biomolecular Engineering, Tulane University, New Orleans, LA 70118, USA.
| | - Kyriakos D Papadopoulos
- Department of Chemical & Biomolecular Engineering, Tulane University, New Orleans, LA 70118, USA.
| |
Collapse
|
126
|
Xue C. Macroscopic equations for bacterial chemotaxis: integration of detailed biochemistry of cell signaling. J Math Biol 2013; 70:1-44. [PMID: 24366373 DOI: 10.1007/s00285-013-0748-5] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 11/15/2013] [Indexed: 01/16/2023]
Abstract
Chemotaxis of single cells has been extensively studied and a great deal on intracellular signaling and cell movement is known. However, systematic methods to embed such information into continuum PDE models for cell population dynamics are still in their infancy. In this paper, we consider chemotaxis of run-and-tumble bacteria and derive continuum models that take into account of the detailed biochemistry of intracellular signaling. We analytically show that the macroscopic bacterial density can be approximated by the Patlak-Keller-Segel equation in response to signals that change slowly in space and time. We derive, for the first time, general formulas that represent the chemotactic sensitivity in terms of detailed descriptions of single-cell signaling dynamics in arbitrary space dimensions. These general formulas are useful in explaining relations of single cell behavior and population dynamics. As an example, we apply the theory to chemotaxis of bacterium Escherichia coli and show how the structure and kinetics of the intracellular signaling network determine the sensing properties of E. coli populations. Numerical comparison of the derived PDEs and the underlying cell-based models show quantitative agreements for signals that change slowly, and qualitative agreements for signals that change extremely fast. The general theory we develop here is readily applicable to chemotaxis of other run-and-tumble bacteria, or collective behavior of other individuals that move using a similar strategy.
Collapse
Affiliation(s)
- Chuan Xue
- Department of Mathematics, Ohio State University, Columbus, OH, 43210, USA,
| |
Collapse
|
127
|
Jeong HH, Lee SH, Lee CS. Pump-less static microfluidic device for analysis of chemotaxis of Pseudomonas aeruginosa using wetting and capillary action. Biosens Bioelectron 2013; 47:278-84. [DOI: 10.1016/j.bios.2013.03.031] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Revised: 03/07/2013] [Accepted: 03/14/2013] [Indexed: 12/22/2022]
|
128
|
Halder P, Nasabi M, Lopez FJT, Jayasuriya N, Bhattacharya S, Deighton M, Mitchell A, Bhuiyan MA. A novel approach to determine the efficacy of patterned surfaces for biofouling control in relation to its microfluidic environment. BIOFOULING 2013; 29:697-713. [PMID: 23789960 DOI: 10.1080/08927014.2013.800192] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Biofouling, the unwanted growth of sessile microorganisms on submerged surfaces, presents a serious problem for underwater structures. While biofouling can be controlled to various degrees with different microstructure-based patterned surfaces, understanding of the underlying mechanism is still imprecise. Researchers have long speculated that microtopographies might influence near-surface microfluidic conditions, thus microhydrodynamically preventing the settlement of microorganisms. It is therefore very important to identify the microfluidic environment developed on patterned surfaces and its relation with the antifouling behaviour of those surfaces. This study considered the wall shear stress distribution pattern as a significant aspect of this microfluidic environment. In this study, patterned surfaces with microwell arrays were assessed experimentally with a real-time biofilm development monitoring system using a novel microchannel-based flow cell reactor. Finally, computational fluid dynamics simulations were carried out to show how the microfluidic conditions were affecting the initial settlement of microorganisms.
Collapse
Affiliation(s)
- Partha Halder
- School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne, Australia.
| | | | | | | | | | | | | | | |
Collapse
|
129
|
Chengala A, Hondzo M, Sheng J. Microalga propels along vorticity direction in a shear flow. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2013; 87:052704. [PMID: 23767563 DOI: 10.1103/physreve.87.052704] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 08/21/2012] [Indexed: 06/02/2023]
Abstract
Using high-speed digital holographic microscopy and microfluidics, we discover that, when encountering fluid flow shear above a threshold, unicellular green alga Dunaliella primolecta migrates unambiguously in the cross-stream direction that is normal to the plane of shear and coincides with the local fluid flow vorticity. The flow shear drives motile microalgae to collectively migrate in a thin two-dimensional horizontal plane and consequently alters the spatial distribution of microalgal cells within a given suspension. This shear-induced algal migration differs substantially from periodic rotational motion of passive ellipsoids, known as Jeffery orbits, as well as gyrotaxis by bottom-heavy swimming microalgae in a shear flow due to the subtle interplay between torques generated by gravity and viscous shear. Our findings could facilitate mechanistic solutions for modeling planktonic thin layers and sustainable cultivation of microalgae for human nutrition and bioenergy feedstock.
Collapse
Affiliation(s)
- Anwar Chengala
- St. Anthony Falls Laboratory, Department of Civil Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | | | | |
Collapse
|
130
|
Zöttl A, Stark H. Periodic and quasiperiodic motion of an elongated microswimmer in Poiseuille flow. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2013; 36:4. [PMID: 23321716 DOI: 10.1140/epje/i2013-13004-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Revised: 10/22/2012] [Accepted: 12/12/2012] [Indexed: 06/01/2023]
Abstract
We study the dynamics of a prolate spheroidal microswimmer in Poiseuille flow for different flow geometries. When moving between two parallel plates or in a cylindrical microchannel, the swimmer performs either periodic swinging or periodic tumbling motion. Although the trajectories of spherical and elongated swimmers are qualitatively similar, the swinging and tumbling frequency strongly depends on the aspect ratio of the swimmer. In channels with reduced symmetry the swimmers perform quasiperiodic motion which we demonstrate explicitly for swimming in a channel with elliptical cross-section.
Collapse
Affiliation(s)
- Andreas Zöttl
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623, Berlin, Germany.
| | | |
Collapse
|
131
|
Shen Y, Siryaporn A, Lecuyer S, Gitai Z, Stone HA. Flow directs surface-attached bacteria to twitch upstream. Biophys J 2012; 103:146-51. [PMID: 22828341 DOI: 10.1016/j.bpj.2012.05.045] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 04/11/2012] [Accepted: 05/15/2012] [Indexed: 10/28/2022] Open
Abstract
Bacteria inhabit a wide variety of environments in which fluid flow is present, including healthcare and food processing settings and the vasculature of animals and plants. The motility of bacteria on surfaces in the presence of flow has not been well characterized. Here we focus on Pseudomonas aeruginosa, an opportunistic human pathogen that thrives in flow conditions such as in catheters and respiratory tracts. We investigate the effects of flow on P. aeruginosa cells and describe a mechanism in which surface shear stress orients surface-attached P. aeruginosa cells along the flow direction, causing cells to migrate against the flow direction while pivoting in a zig-zag motion. This upstream movement is due to the retraction of type IV pili by the ATPase motors PilT and PilU and results from the effects of flow on the polar localization of type IV pili. This directed upstream motility could be beneficial in environments where flow is present, allowing bacteria to colonize environments that cannot be reached by other surface-attached bacteria.
Collapse
Affiliation(s)
- Yi Shen
- Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, USA
| | | | | | | | | |
Collapse
|
132
|
Abstract
Marine bacteria influence Earth's environmental dynamics in fundamental ways by controlling the biogeochemistry and productivity of the oceans. These large-scale consequences result from the combined effect of countless interactions occurring at the level of the individual cells. At these small scales, the ocean is surprisingly heterogeneous, and microbes experience an environment of pervasive and dynamic chemical and physical gradients. Many species actively exploit this heterogeneity, while others rely on gradient-independent adaptations. This is an exciting time to explore this frontier of oceanography, but understanding microbial behavior and competition in the context of the water column's microarchitecture calls for new ecological frameworks, such as a microbial optimal foraging theory, to determine the relevant trade-offs and global consequences of microbial life in a sea of gradients.
Collapse
Affiliation(s)
- Roman Stocker
- Ralph M. Parsons Laboratory, Department of Civil and Environmental Engineering, 49-213, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
| |
Collapse
|
133
|
Conrad JC. Physics of bacterial near-surface motility using flagella and type IV pili: implications for biofilm formation. Res Microbiol 2012; 163:619-29. [PMID: 23103335 DOI: 10.1016/j.resmic.2012.10.016] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 10/23/2012] [Indexed: 11/28/2022]
Abstract
We review physically-motivated studies of bacterial near-surface motility driven by flagella and type IV pili (TfP) in the context of biofilm formation. We describe the motility mechanisms that individual bacteria deploying flagella and TfP use to move on and near surfaces, and discuss how the interactions of motility appendages with fluid and surfaces promote motility, attachment and dispersal of bacteria on surfaces prior to biofilm formation.
Collapse
Affiliation(s)
- Jacinta C Conrad
- Department of Chemical and Biomolecular Engineering and Petroleum Engineering Program, University of Houston, S222 Engineering Building 1, Houston, TX, USA.
| |
Collapse
|