Featured
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The colloidal nature of complex fluids enhances bacterial motility
Bacteria swimming in colloidal suspensions are shown to behave similarly to those in polymer solutions revealing a mechanism for motile behaviour in complex fluids.
- Shashank Kamdar
- , Seunghwan Shin
- & Xiang Cheng
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Cooperative epithelial phagocytosis enables error correction in the early embryo
Mechanical load-sharing enables the long-range cooperative uptake of apoptotic cells by multiple epithelial cells; and clearance of these apoptotic cells facilitates error correction, which is necessary for developmental robustness and survival of the embryo.
- Esteban Hoijman
- , Hanna-Maria Häkkinen
- & Verena Ruprecht
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Article |
Viscoelastic control of spatiotemporal order in bacterial active matter
Introducing viscoelasticity by addition of DNA into the fluid surrounding a suspension of Escherichia coli produces a giant oscillating vortex with a period controllable through the DNA concentration.
- Song Liu
- , Suraj Shankar
- & Yilin Wu
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Article |
Cryo-EM structure of the inhibited (10S) form of myosin II
High-resolution cryo-electron microscopy structure of smooth muscle myosin II in the inhibited state enables increased understanding of the functions of the head and tail regions in regulation of myosin activity and the pathological mechanisms of disease mutations.
- Shixin Yang
- , Prince Tiwari
- & Roger Craig
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Article |
Loopy Lévy flights enhance tracer diffusion in active suspensions
A theoretical framework describing the hydrodynamic interactions between a passive particle and an active medium in out-of-equilibrium systems predicts long-range Lévy flights for the diffusing particle driven by the density of the active component.
- Kiyoshi Kanazawa
- , Tomohiko G. Sano
- & Adrian Baule
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Article |
Bacterial coexistence driven by motility and spatial competition
In mixed bacterial populations that colonize nutrient patches, a growth–migration trade-off can lead to spatial exclusion that provides an advantage to populations that become rare, thereby stabilizing the community.
- Sebastian Gude
- , Erçağ Pinçe
- & Sander J. Tans
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Letter |
Collective intercellular communication through ultra-fast hydrodynamic trigger waves
Ultra-fast hydrodynamic communication between cells emerges in colonies of Spirostomum ambiguum through the generation of long-ranged vortex flows that are sensed by neighbouring cells, leading to propagating trigger waves that coordinate the release of toxins.
- Arnold J. T. M. Mathijssen
- , Joshua Culver
- & Manu Prakash
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Letter |
Nuclear positioning facilitates amoeboid migration along the path of least resistance
Geometrically defined microenvironments are used to show that leukocytes migrate along chemokine gradients using the nucleus as a mechanical gauge to sample potential paths and identify the path of least resistance.
- Jörg Renkawitz
- , Aglaja Kopf
- & Michael Sixt
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Article |
Reconstitution reveals motor activation for intraflagellar transport
Reconstitution of a functional intraflagellar transport complex in Caenorhabditis elegans provides insight into the recruitment and activation of the kinesin-2 motor protein.
- Mohamed A. A. Mohamed
- , Willi L. Stepp
- & Zeynep Ökten
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Letter |
Phytoplankton can actively diversify their migration strategy in response to turbulent cues
Here, marine phytoplankton are shown to diversify their migratory strategy in response to turbulent cues through a rapid change in shape, thus challenging a fundamental paradigm in oceanography that phytoplankton are passively at the mercy of ocean turbulence.
- Anupam Sengupta
- , Francesco Carrara
- & Roman Stocker
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Letter |
Force generation by skeletal muscle is controlled by mechanosensing in myosin filaments
It is widely accepted that contraction of skeletal muscle and the heart involves structural changes in actin-containing thin filaments to allow binding of myosin motors from neighbouring thick filaments, thus driving filament sliding; here, X-ray diffraction of single skeletal muscle cells reveals that this thin-filament mechanism can regulate muscle contraction against low load, but high-load contraction requires a second permissive step involving a structural change in the thick filament.
- Marco Linari
- , Elisabetta Brunello
- & Malcolm Irving
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Letter |
Vapour-mediated sensing and motility in two-component droplets
Droplets of mixed water and propylene glycol deposited on clean glass exhibit a contact angle but do not suffer from contact line pinning; their motion can be controlled by the vapour emitted from neighbouring droplets to create a variety of autonomous fluidic machines with integrated sensing and motility capabilities.
- N. J. Cira
- , A. Benusiglio
- & M. Prakash
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Letter |
Optogenetic control of organelle transport and positioning
An optogenetic strategy allowing light-mediated recruitment of distinct cytoskeletal motor proteins to specific organelles is established; this technique enabled rapid and reversible activation or inhibition of the transport of organelles such as peroxisomes, recycling endosomes and mitochondria with high spatiotemporal accuracy, and the approach was also applied to primary neurons to demonstrate optical control of axonal growth by recycling endosome repositioning.
- Petra van Bergeijk
- , Max Adrian
- & Lukas C. Kapitein
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Letter |
A chain mechanism for flagellum growth
Growth of a flagellum outside the bacterial cell proceeds by successive subunit acquisition from the cell export machinery to form a chain that is pulled to the flagellum tip, where subunit crystallization provides the entropic force to drive the process.
- Lewis D. B. Evans
- , Simon Poulter
- & Gillian M. Fraser
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Letter |
Emergence of macroscopic directed motion in populations of motile colloids
Populations of millions of colloidal rolling particles are shown to self-organize to achieve coherent motion; comparison between experiment and theory based on the microscopic interactions between these ‘rollers’ suggests that hydrodynamic interactions promote the emergence of the collective motion.
- Antoine Bricard
- , Jean-Baptiste Caussin
- & Denis Bartolo
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Letter |
Compartmentalized calcium dynamics in a C. elegans interneuron encode head movement
Subcellular compartmentalization established by mobilization of intracellular calcium stores in RIA interneurons provides a means of self-motion monitoring and a cellular basis for integrating sensory and motor signals in nematodes’ brains.
- Michael Hendricks
- , Heonick Ha
- & Yun Zhang
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News & Views |
A staggering giant
The protein dynein 'walks' along filaments to transport various cargoes within the cell. Two studies reveal that, unlike other motor proteins, dynein's steps are not strictly coordinated.
- Wilhelm J. Walter
- & Stefan Diez
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News & Views |
Push it, pull it
During migration, cells interact with their environment by exerting mechanical forces on it. A combination of two techniques shows that they do so in all three dimensions by a push–pull mechanism.
- Pascal Hersen
- & Benoît Ladoux
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Letter |
Interdependence of behavioural variability and response to small stimuli in bacteria
In his study of Brownian motion, Einstein realized that the same random molecular movements characterizing a substance at rest should affect, for example, the drag it opposes to a particle pushed through it. This was later generalized as the fluctuation–response theorem (FRT), but whether and how it may apply to biological systems, which operate far from equilibrium, has remained an open question. Based on the unmatched fine-scale measurements possible in the study of bacterial chemotaxis, it is now revealed that the FRT does apply in this case, and ways to dissect which features in the biochemical network couple its internal states with its responses to external stimuli are suggested.
- Heungwon Park
- , William Pontius
- & Philippe Cluzel
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Article |
Video imaging of walking myosin V by high-speed atomic force microscopy
High-speed atomic force microscopy can be used to record the structure and dynamics of biomolecules simultaneously. These authors use this method to directly observe the dynamics of the motor protein myosin V moving along actin filaments, with unprecedented time resolution. The high-resolution movies provide evidence supporting the 'swinging lever-arm' model of myosin motility, and provide important insights into the mechanism of motor movement.
- Noriyuki Kodera
- , Daisuke Yamamoto
- & Toshio Ando
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Letter |
Polar patterns of driven filaments
Collective motion is a ubiquitous self-organization phenomenon that can be observed in systems ranging from flocks of animals to the cytoskeleton. Similarities between these systems suggest that there are universal underlying principles. This idea can be tested with 'active' or 'driven' fluids, but so far such systems have offered limited parameter control. Here, an active fluid is studied that contains only a few components — actin filaments and molecular motors — allowing the control of all relevant system parameters.
- Volker Schaller
- , Christoph Weber
- & Andreas R. Bausch
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Letter |
Structure of the torque ring of the flagellar motor and the molecular basis for rotational switching
The bacterial flagellar motor drives the rotation of flagellar filaments, propelling bacteria through viscous media. The rotation can switch from an anticlockwise to a clockwise direction, determining a smooth or tumbling motion. A protein called FliG forms a ring in the motor's rotor, and has been proposed to adopt distinct conformations that induce switching. Here, the full-length structure of FliG is presented, and conformational changes are identified that are involved in switching between clockwise and anticlockwise rotations.
- Lawrence K. Lee
- , Michael A. Ginsburg
- & Daniela Stock
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Letter |
A random cell motility gradient downstream of FGF controls elongation of an amniote embryo
Most animal embryos grow through cell accumulation in a posterior growth zone, but the underlying forces are unknown. It is now proposed that posterior elongation in chicken embryos is an emergent property that arises from graded cell motility in random directions (as opposed to directed movement). This occurs in response to signalling through the fibroblast growth factor.
- Bertrand Bénazéraf
- , Paul Francois
- & Olivier Pourquié
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Letter |
Myosin II contributes to cell-scale actin network treadmilling through network disassembly
Eukaryotic cells crawl through a process in which the front of the cell is propelled forwards by the force provided by polymerization of actin filaments. These must be disassembled at the rear of the cell to allow sustained motility. It is now shown that non-muscle myosin II protein is needed for the disassembly of actin networks at the rear of crawling cells.
- Cyrus A. Wilson
- , Mark A. Tsuchida
- & Julie A. Theriot
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News & Views |
How cilia beat
Physics provides new approaches to difficult biological problems: a plausible mathematical model of how cilia and flagella beat has been formulated, but it needs to be subjected to rigorous experimental tests.
- T. J. Mitchison
- & H. M. Mitchison