Swimming bacteria power microscopic gears

Sokolov, Andrey; Apodaca, Mario M.; Grzybowski, Bartosz A.; Aranson, Igor S.

doi:10.1073/pnas.0913015107

Cited by 522 publications

(422 citation statements)

References 33 publications

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“…However, nature has its own solutions since billions of years ago: flagellated swimming bacteria can efficiently convert chemical energy into mechanical actuation with their nanoscale biomotors. Over the past decade, numerous studies have been conducted on harnessing the flagellated bacteria, such as E. coli and S. marcescens , as propellers for biohybrid microswimmers,1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 aiming to develop a new type of targeted drug delivery system for tumor therapy 14, 16, 18, 19. Recently, efforts have also been made to guide the motion of such bacteria‐driven microswimmers through taxis‐based14, 17, 20, 21, 22, 23, 24, 25 and magnetic steering16, 26 approaches.…”

Section: Introductionmentioning

confidence: 99%

Propulsion and Chemotaxis in Bacteria‐Driven Microswimmers

2017

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Despite the large body of experimental work recently on biohybrid microsystems, few studies have focused on theoretical modeling of such systems, which is essential to understand their underlying functioning mechanisms and hence design them optimally for a given application task. Therefore, this study focuses on developing a mathematical model to describe the 3D motion and chemotaxis of a type of widely studied biohybrid microswimmer, where spherical microbeads are driven by multiple attached bacteria. The model is developed based on the biophysical observations of the experimental system and is validated by comparing the model simulation with experimental 3D swimming trajectories and other motility characteristics, including mean squared displacement, speed, diffusivity, and turn angle. The chemotaxis modeling results of the microswimmers also agree well with the experiments, where a collective chemotactic behavior among multiple bacteria is observed. The simulation result implies that such collective chemotaxis behavior is due to a synchronized signaling pathway across the bacteria attached to the same microswimmer. Furthermore, the dependencies of the motility and chemotaxis of the microswimmers on certain system parameters, such as the chemoattractant concentration gradient, swimmer body size, and number of attached bacteria, toward an optimized design of such biohybrid system are studied. The optimized microswimmers would be used in targeted cargo, e.g., drug, imaging agent, gene, and RNA, transport and delivery inside the stagnant or low‐velocity fluids of the human body as one of their potential biomedical applications.

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Section: Introductionmentioning

confidence: 99%

Propulsion and Chemotaxis in Bacteria‐Driven Microswimmers

2017

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“…This effect has been used to direct bacterial motion [50] and harness bacterial power to propel microscopic gears [51][52][53]. However, optimizing such devices for technological applications requires understanding the interaction of an active fluid with boundaries of arbitrary shape.…”

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confidence: 99%

Dynamics of self-propelled particles under strong confinement

2014

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We develop a statistical theory for the dynamics of non-aligning, non-interacting self-propelled particles confined in a convex box in two dimensions. We find that when the size of the box is small compared to the persistence length of a particle's trajectory (strong confinement), the steady-state density is zero in the bulk and proportional to the local curvature on the boundary. Conversely, the theory may be used to construct the box shape that yields any desired density distribution on the boundary. When the curvature variations are small, we also predict the distribution of orientations at the boundary and the exponential decay of pressure as a function of box size recently observed in 3D simulations in a spherical box.Active fluids consisting of self-propelled units are found in biology on scales ranging from the dynamically reconfigurable cell cytoskeleton [1] to swarming bacterial colonies [2,3], healing tissues [4,5], and flocking animals [6]. Experiments have begun to achieve the extraordinary capabilities and emergent properties of these biological systems in nonliving active fluids of self-propelled particles, consisting of chemically [7][8][9][10][11][12] or electrically [13] propelled colloids, or monolayers of vibrated granular particles [14][15][16].In contrast to thermal motion, active motion is correlated over experimentally accessible time and length scales. When the persistence length of active motion becomes comparable to the mean free path, uniquely active effects arise that transcend the thermodynamically allowed behaviors of equilibrium systems, including giant number fluctuations and spontaneous flow [3,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Importantly, a sufficient active persistence length is the only requirement for macroscopic manifestations of activity, as revealed by athermal phase separation of nonaligning, repulsive self-propelled particles [31][32][33][34][35][36][37][38][39][40][41].When boundaries and obstacles are patterned on the scale of the active correlation length, they dramatically alter the dynamics of the system, and striking macroscopic properties emerge [42][43][44][45][46][47][48][49]; for example, ratchets and funnels drive spontaneous flow in active fluids [42][43][44][45][46]. This effect has been used to direct bacterial motion [50] and harness bacterial power to propel microscopic gears [51][52][53]. However, optimizing such devices for technological applications requires understanding the interaction of an active fluid with boundaries of arbitrary shape. More generally, any real-world device necessarily includes boundaries, and thus the effects of boundary size and shape are essential design parameters. Although recent studies have explored confinement in simple geometries [43,47,[54][55][56], there is no general theory for the effect of boundary shape.In this Letter, we study the dynamics of non-aligning and non-interacting self-propelled particles confined to two-dimensional convex containers, such as ellipses and polygons. We find...

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“…At the outset of modern studies of collective decision-making, circular milling behaviour was seen as a key characteristic of ultracohesive group movement [10]. It has been reported, for example, in Bacillus bacteria [12,13], Daphnia [14], processionary caterpillars [15], army ants [16], fish [17,18] and tadpoles [19].…”

Section: Introductionmentioning

confidence: 99%

Social behaviour and collective motion in plant-animal worms

et al. 2016

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Social behaviour may enable organisms to occupy ecological niches that would otherwise be unavailable to them. Here, we test this major evolutionary principle by demonstrating self-organizing social behaviour in the plant-animal, Symsagittifera roscoffensis. These marine aceol flat worms rely for all of their nutrition on the algae within their bodies: hence their common name. We show that individual worms interact with one another to coordinate their movements so that even at low densities they begin to swim in small polarized groups and at increasing densities such flotillas turn into circular mills. We use computer simulations to: (i) determine if real worms interact socially by comparing them with virtual worms that do not interact and (ii) show that the social phase transitions of the real worms can occur based only on local interactions between and among them. We hypothesize that such social behaviour helps the worms to form the dense biofilms or mats observed on certain sunexposed sandy beaches in the upper intertidal of the East Atlantic and to become in effect a super-organismic seaweed in a habitat where macro-algal seaweeds cannot anchor themselves. Symsagittifera roscoffensis, a model organism in many other areas in biology (including stem cell regeneration), also seems to be an ideal model for understanding how individual behaviours can lead, through collective movement, to social assemblages.

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Swimming bacteria power microscopic gears

Cited by 522 publications

References 33 publications

Propulsion and Chemotaxis in Bacteria‐Driven Microswimmers

Propulsion and Chemotaxis in Bacteria‐Driven Microswimmers

Dynamics of self-propelled particles under strong confinement

Social behaviour and collective motion in plant-animal worms

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