Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session W14: Biological Active Matter IIFocus
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Sponsoring Units: DBIO Chair: Endao Han, Princeton University Room: Room 206 |
Thursday, March 9, 2023 3:00PM - 3:12PM |
W14.00001: Autonomous waves and global motion modes in living active solids Haoran Xu, Yulu HUANG, Rui Zhang, Yilin Wu Elastic active matter or active solid consists of self-propelled units embedded in an elastic matrix. Active solid resists deformation; the shape-preserving property and the intrinsic non-equilibrium nature make active solids a superior component for self-driven devices. Nonetheless, the mechanical properties and emergent behavior of active solids are poorly understood. Using a biofilm-based bacterial active solid, here we discovered self-sustained elastic waves with unique wave properties not seen in passive solids, such as power-law scaling of wave speed with activity. Under isotropic confinement, the active solid develops two topologically distinct global motion modes that can be selectively excited, with a surprising step-like frequency jump at mode transition. Our findings reveal novel spatiotemporal order in elastic active matter and may guide the development of solid-state adaptive or living materials. |
Thursday, March 9, 2023 3:12PM - 3:24PM Author not Attending |
W14.00002: Two dimensional bacterial turbulence at a liquid-air interface Yuanfeng Yin Active turbulence is a ubiquitous signature of active matter systems, as observed in dense suspensions of E. coli bacteria and cytoskeleton-motor systems. In experiment, 2D bacterial turbulence is normally formed in a thin layer of liquid near a substrate, or between two liquids phases. Here, we use Serratia marcescens bacteria that swim at a water-air interface to study 2D bacterial turbulence. By cell culture, Serratia bacterial with body length from 1 to 10um can be obtained. By using a microbubble assay, the thickness of the liquid layer can be adjusted from 0 to several mm. In low-viscosity aqueous solutions, the energy spectrum E(k) of 2D turbulence shows a universal power-law scaling that is independent of cell length and liquid thickness. At the meantime, we observe transition from nematic-order to turbulence in 2D bacterial suspension. |
Thursday, March 9, 2023 3:24PM - 3:36PM |
W14.00003: Size-distribution dynamics in growing bacterial colonies with mechano-sensing René Wittmann, Fabian Jan Schwarzendahl, Hartmut Löwen Inspired by our recent work on smectic liquid crystals in extreme confinement [1-2], we develop a microscopic theory for growing bacteria colonies based on classical dynamical density functional theory (DDFT). Our first-principles approach pays special attention to the particle length as a key ingredient and explicitly accounts for growth and cell division [3]. The length-dependent interactions between the particles, which naturally arise in the framework of DDFT, ensure that the bacteria colony does not grow indefinitely due to spatial constraints. Our model thus accounts for an environmental feedback on the effective growth rate of individual agents, which we interpret as a form of mechano-sensing. |
Thursday, March 9, 2023 3:36PM - 3:48PM |
W14.00004: Energy profiles and statistics of spontaneous T1 transitions in confluent tissues Harish Pruthviraj Jain, Luiza Angheluta, Axel Voigt Cellular rearrangements play a vital role in several morphogenetic processes. T1 transitions are an important type of such cellular rearragements that are observed in biological foam structures like morphogenesis of developing embryos and in unjammed epithelial cells. We use a multi phase field model to study spontaneously generated T1 transitions under different regimes of cell deformability and cell-cell interaction. We have found an universal profile of energy evolution at the site of T1 transitions that indicates a slow buildup of energy followed by a fast decay. This profile is remisniscent of avalanches in granular matter and energy release in earthquakes. We have also studied how cell shape deformability and intercellular interactions affect properties of T1 transitions including rate of T1 transitions, their durations and the amount of energy build up during them. We also show that in confleunt tissues, large deformations only happen when there are T1 transitions provided there is no apoptosis or cell division. |
Thursday, March 9, 2023 3:48PM - 4:00PM |
W14.00005: Characteristics of growing, tangled branches Thomas C Day, Peter Yunker, William C Ratcliff, G. Ozan Bozdag, Seyed Alireza Zamani Dahaj Multicellular organisms often exhibit morphologies featuring branching chains of cells. Examples include root systems, mycelial networks, cyanobacterial mats, and dense brush and bushes. Notably, filamentous, branching objects can wind around each other, thus forming tangles that are difficult to disassemble. This phenomenon, called "entanglement'', is well-known to occur in non-growing materials. However, entanglement is typically studied in non-living, and thus non-growing materials, such as polymers. Further, with few exceptions, currently studied systems are filamentous rather than branching, and generally flexible rather than rigid. Much less studied is the emergence of entanglement in the regime of growing, branching, and relatively rigid systems, despite their prevalence across the domains of life. Consequently, many open questions regarding entanglement remain unclear: how readily does entanglement emerge in growing systems? Do predictions for static components remain relevant for these non-equilibrium cases? Here, we use a combination of experiments and simulations to show that entanglement through growth is easy to achieve, can result in configurations that are impossible to access through mechanical agitation alone, and can be tuned through branch geometric changes. |
Thursday, March 9, 2023 4:00PM - 4:12PM |
W14.00006: The secret life of sarcomeres: stochastic heterogeneity of sarcomeres in beating stem-cell derived cardiomyocytes Christoph F Schmidt, Daniel Haertter, Wolfram-Hubertus Zimmermann, Lara Hauke, Til Driehorst, Branimir Berecic, Lukas Cyganec, Malte Tiburcy Sarcomeres are the basic contractile units of cardiac muscle cells. We cultured individual hiPSC-derived cardiomyocytes on biomimetic patterned substrates. We automatically tracked single sarcomere dynamics from high-speed confocal recordings with a custom machine-learning tool. While emergent cell-level contractions were smooth, we found highly stochastic and heterogeneous motions of single sarcomeres. Rigid mechanical constraints force sarcomeres into a tug-of-war like competition driving dynamic heterogeneity. Analysis of a large data set (>1200 cells) indicates that sarcomere heterogeneity is not caused by static non-uniformity among sarcomeres (e.g., strong/weak units), but can be primarily attributed to the stochastic and non-linear nature of sarcomere dynamics. We show that a simple dynamic model reproduces crucial experimental findings by assuming non-monotonic force-velocity relations for single sarcomeres, as previously predicted for ensembles of motor proteins. This led us to a novel, active matter perspective on sarcomere motion, with sarcomeres as interacting non-linear, stochastic agents. |
Thursday, March 9, 2023 4:12PM - 4:24PM |
W14.00007: Spatial patterning of mitochondrial metabolism in mouse oocytes Yash Rana, Xingbo Yang, Daniel J Needleman Metabolism provides a continuous flux of energy that keeps living systems out of equilibrium and gives rise to biological form and function. Energy production is patterned across space and time within cells via the organization of mitochondria and spatial distributions in mitochondrial activity. In mouse oocytes, there exists a gradient in metabolic activity with distance from the meiotic spindle. The physical mechanism that gives rise to this emergent pattern is unknown. I am using quantitative microscopy, molecular perturbations, and biophysical modeling to decipher the mechanism behind the formation of subcellular spatial patterns of mitochondrial metabolism in mouse oocytes. Understanding these mechanisms will not only teach us quantitative cell biological principles that underlie the patterning of energy metabolism but will also reveal the physics of how energy fluxes influence the collective behavior of living active matter. |
Thursday, March 9, 2023 4:24PM - 4:36PM |
W14.00008: Effects of obesity on the dynamics of cancer cell invasion into adipose tissue Yitong Zheng, Dong Wang, Garrett Beeghly, Claudia Fischbach, Mark D Shattuck, Corey S O'Hern Tumor cell invasion into white adipose tissue (WAT) is an important step in the progression of breast cancer. While numerous studies have focused on the genetic influences on breast cancer, much less is known about the role of the mechanical properties of adipose tissue in tumor cell invasion. We have developed discrete element method (DEM) simulations of tumor cell invasion into WAT. We model the adipocytes as deformable particles that can explicitly change their shape in response to external forces and the cancer cells as active, sticky soft spheres. Prior experimental studies of breast cancer in mouse models have shown that the stiffness and size of the adipocytes increase when the mice have high-fat diets. Using DEM simulations, we show that the invasion depth of cancer cells into WAT decreases with increasing stiffness and size of the adipocytes. Experimental studies that induce breast cancer in mouse models show that tumor cells cause lipolysis in WAT and that rates of lipid loss are larger in mice with high-fat diets. In the DEM simulations, we show that rapid lipolysis can accelerate tumor cell invasion even in systems with stiff and densely packed adipocytes. |
Thursday, March 9, 2023 4:36PM - 4:48PM |
W14.00009: Modeling collective cell behavior in the presence of external stimuli Kurmanbek Kaiyrbekov, Kirsten D Endresen, Francesca Serra, Brian A Camley Controlling collective movement, arrangement and affecting proliferation of cell monolayers via external stimuli could be useful in organoid development, wound healing, and drug discovery research. A plethora of experiments have focused on these topics, here we present a computational model that simultaneously captures cell motility, division, and nematic order within the cell monolayer. We model different cells as self-propelled deformable ellipses that interact via a Gay-Berne potential. We perform 2D Monte-Carlo simulation in the presence of topographic patterns that induce topological defects and argue that a shape dependent mitosis mechanism is sufficient to explain monolayer density variations near defects of charge +1 and -1 observed in experiments by Serra group [1]. We then extend our model to address other types of guiding cues, such as electrical fields. |
Thursday, March 9, 2023 4:48PM - 5:00PM |
W14.00010: Topology protects the emergence of coherent oscillations in the circadian rhythm Chongbin Zheng, Evelyn Tang Stable collective dynamics are often observed in complex biochemical networks, such as in emergent oscillations. How these robust dynamics arise remains unclear, given the large reaction space and stochasticity demonstrated by underlying components. We propose a topological model that demonstrates emergent oscillations at the network boundary, effectively reducing the system dynamics to a lower-dimensional space. Inspired by topological band theory, we introduce a predictor of oscillation coherence from the analysis of spectral gaps. Using this to model KaiC, which regulates the circadian rhythm in cyanobacteria, we compare the coherence of oscillations produced to that in other KaiC models. We find that localization of currents on the system edge in the topological model supports a regime with simultaneously decreased cost and increased precision. We conclude with a discussion of the model’s relevance to experimental data and propose testable predictions. Our work highlights a new paradigm for robust dynamics in complex biological networks and the robustness of biological function despite pervasive stochasticity. |
Thursday, March 9, 2023 5:00PM - 5:12PM |
W14.00011: Effect of boundary elastic interactions on motile cells Subhaya Bose, Haiqin Wang, Xinpeng Xu, Arvind Gopinath, Kinjal Dasbiswas Elastic substrate-adhered cells actively deform and exert mechanical forces on the underlying substrate to sense their environment and crawl. Cells have been observed to perform durotaxis or preferential migration towards a stiffer substrate region. We explain this with a physical model where cells are described as motile agents that exert contractile, traction forces on the underlying substrate, which lead to elastic forces and torques on the cells at boundaries. Specifically, we model a sharp stiffness gradient as a clamped or free boundary, which corresponds to an interface with a stiffer or softer medium. The persistent motion of the particle and the elastic interactions with the boundary determine its probability of localization at or away from the boundary, a measure of its ability to cross the substrate interface. We characterize the dependence of the mean escape time from the attractive clamped boundary on elastic interactions and motility. Varying reorientation time yields qualitatively different escape behavior, whereas higher motility does not ensure lower escape time. |
Thursday, March 9, 2023 5:12PM - 5:48PM |
W14.00012: TBD Invited Speaker: Thomas Lecuit TBD |
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