1
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Black ME, Fei C, Alert R, Wingreen NS, Shaevitz JW. Capillary interactions drive the self-organization of bacterial colonies. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.28.596252. [PMID: 38853967 PMCID: PMC11160631 DOI: 10.1101/2024.05.28.596252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
Many bacteria inhabit thin layers of water on solid surfaces both naturally in soils or on hosts or textiles and in the lab on agar hydrogels. In these environments, cells experience capillary forces, yet an understanding of how these forces shape bacterial collective behaviors remains elusive. Here, we show that the water menisci formed around bacteria lead to capillary attraction between cells while still allowing them to slide past one another. We develop an experimental apparatus that allows us to control bacterial collective behaviors by varying the strength and range of capillary forces. Combining 3D imaging and cell tracking with agent-based modeling, we demonstrate that capillary attraction organizes rod-shaped bacteria into densely packed, nematic groups, and profoundly influences their collective dynamics and morphologies. Our results suggest that capillary forces may be a ubiquitous physical ingredient in shaping microbial communities in partially hydrated environments.
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2
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Denisin AK, Kim H, Riedel-Kruse IH, Pruitt BL. Field Guide to Traction Force Microscopy. Cell Mol Bioeng 2024; 17:87-106. [PMID: 38737454 PMCID: PMC11082129 DOI: 10.1007/s12195-024-00801-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2024] [Accepted: 03/26/2024] [Indexed: 05/14/2024] Open
Abstract
Introduction Traction force microscopy (TFM) is a widely used technique to measure cell contractility on compliant substrates that mimic the stiffness of human tissues. For every step in a TFM workflow, users make choices which impact the quantitative results, yet many times the rationales and consequences for making these decisions are unclear. We have found few papers which show the complete experimental and mathematical steps of TFM, thus obfuscating the full effects of these decisions on the final output. Methods Therefore, we present this "Field Guide" with the goal to explain the mathematical basis of common TFM methods to practitioners in an accessible way. We specifically focus on how errors propagate in TFM workflows given specific experimental design and analytical choices. Results We cover important assumptions and considerations in TFM substrate manufacturing, substrate mechanical properties, imaging techniques, image processing methods, approaches and parameters used in calculating traction stress, and data-reporting strategies. Conclusions By presenting a conceptual review and analysis of TFM-focused research articles published over the last two decades, we provide researchers in the field with a better understanding of their options to make more informed choices when creating TFM workflows depending on the type of cell being studied. With this review, we aim to empower experimentalists to quantify cell contractility with confidence. Supplementary Information The online version contains supplementary material available at 10.1007/s12195-024-00801-6.
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Affiliation(s)
| | - Honesty Kim
- Department of Bioengineering, Stanford University, Stanford, CA 94305 USA
- Present Address: The Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158 USA
- Department of Molecular and Cellular Biology, and (by courtesy) Departments of Biomedical Engineering, Applied Mathematics, and Physics, University of Arizona, Tucson, AZ 85721 USA
| | - Ingmar H. Riedel-Kruse
- Department of Molecular and Cellular Biology, and (by courtesy) Departments of Biomedical Engineering, Applied Mathematics, and Physics, University of Arizona, Tucson, AZ 85721 USA
| | - Beth L. Pruitt
- Departments of Bioengineering and Mechanical Engineering, University of California Santa Barbara, Santa Barbara, CA 93106 USA
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3
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Pirouz A, Papakonstantinou I, Michalska M. Antimicrobial mechanisms of nanopatterned surfaces-a developing story. Front Chem 2024; 12:1354755. [PMID: 38348407 PMCID: PMC10859517 DOI: 10.3389/fchem.2024.1354755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 01/18/2024] [Indexed: 02/15/2024] Open
Abstract
Whilst it is now well recognized that some natural surfaces such as seemingly fragile insect wings possess extraordinary antimicrobial properties, a quest to engineer similar nanopatterned surfaces (NPSs) is ongoing. The stake is high as biofouling impacts critical infrastructure leading to massive social and economic burden with an antimicrobial resistance (AMR) issue at the forefront. AMR is one of the most imminent health challenges the world is facing today. Here, in the effort to find more sustainable solutions, the NPSs are proposed as highly promising technology as their antimicrobial activity arises from the topographical features, which could be realized on multiple material surfaces. To fully exploit these potentials however, it is crucial to mechanistically understand the underlying killing pathways. Thus far, several mechanisms have been proposed, yet they all have one thing in common. The antimicrobial process is initiated with bacteria contacting nanopatterns, which then imposes mechanical stress onto bacterial cell wall. Hence, the activity is called "mechano-bactericidal". From this point on, however, the suggested mechanisms start to diverge partly due to our limited understanding of force interactions at the interface. The aim of this mini review is to analyze the state-of-the-art in proposed killing mechanisms by categorizing them based on the characteristics of their driving force. We also highlight the current gaps and possible future directions in investigating the mechanisms, particularly by shifting towards quantification of forces at play and more elaborated biochemical assays, which can aid validating the current hypotheses.
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Affiliation(s)
- Arash Pirouz
- Manufacturing Futures Lab, Department of Mechanical Engineering, University College London, London, United Kingdom
| | - Ioannis Papakonstantinou
- Photonic Innovations Lab, Department of Electronic and Electrical Engineering, University College London, London, United Kingdom
| | - Martyna Michalska
- Manufacturing Futures Lab, Department of Mechanical Engineering, University College London, London, United Kingdom
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4
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Zheng P, Kumadaki K, Quek C, Lim ZH, Ashenafi Y, Yip ZT, Newby J, Alverson AJ, Jie Y, Jedd G. Cooperative motility, force generation and mechanosensing in a foraging non-photosynthetic diatom. Open Biol 2023; 13:230148. [PMID: 37788707 PMCID: PMC10547550 DOI: 10.1098/rsob.230148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Accepted: 09/01/2023] [Indexed: 10/05/2023] Open
Abstract
Diatoms are ancestrally photosynthetic microalgae. However, some underwent a major evolutionary transition, losing photosynthesis to become obligate heterotrophs. The molecular and physiological basis for this transition is unclear. Here, we isolate and characterize new strains of non-photosynthetic diatoms from the coastal waters of Singapore. These diatoms occupy diverse ecological niches and display glucose-mediated catabolite repression, a classical feature of bacterial and fungal heterotrophs. Live-cell imaging reveals deposition of secreted extracellular polymeric substance (EPS). Diatoms moving on pre-existing EPS trails (runners) move faster than those laying new trails (blazers). This leads to cell-to-cell coupling where runners can push blazers to make them move faster. Calibrated micropipettes measure substantial single-cell pushing forces, which are consistent with high-order myosin motor cooperativity. Collisions that impede forward motion induce reversal, revealing navigation-related force sensing. Together, these data identify aspects of metabolism and motility that are likely to promote and underpin diatom heterotrophy.
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Affiliation(s)
- Peng Zheng
- Temasek Life Sciences Laboratory, 117604 Singapore
| | - Kayo Kumadaki
- Department of Physics, National University of Singapore, 117542 Singapore
- Mechanobiology Institute, National University of Singapore, 117411 Singapore
| | | | - Zeng Hao Lim
- Temasek Life Sciences Laboratory, 117604 Singapore
- Department of Biological Sciences, National University of Singapore, 117543 Singapore, Singapore
| | - Yonatan Ashenafi
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1
| | - Zhi Ting Yip
- Department of Biological Sciences, National University of Singapore, 117543 Singapore, Singapore
| | - Jay Newby
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2G1
| | - Andrew J. Alverson
- Department of Biological Sciences, University of Arkansas, SCEN 601, Fayetteville, AR 72701, USA
| | - Yan Jie
- Department of Physics, National University of Singapore, 117542 Singapore
- Mechanobiology Institute, National University of Singapore, 117411 Singapore
| | - Gregory Jedd
- Temasek Life Sciences Laboratory, 117604 Singapore
- Department of Biological Sciences, National University of Singapore, 117543 Singapore, Singapore
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5
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Han E, Fei C, Alert R, Copenhagen K, Koch MD, Wingreen NS, Shaevitz JW. Local polar order controls mechanical stress and triggers layer formation in developing Myxococcus xanthus colonies. ARXIV 2023:arXiv:2308.00368v1. [PMID: 37576128 PMCID: PMC10418523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Colonies of the social bacterium Myxococcus xanthus go through a morphological transition from a thin colony of cells to three-dimensional droplet-like fruiting bodies as a strategy to survive starvation. The biological pathways that control the decision to form a fruiting body have been studied extensively. However, the mechanical events that trigger the creation of multiple cell layers and give rise to droplet formation remain poorly understood. By measuring cell orientation, velocity, polarity, and force with cell-scale resolution, we reveal a stochastic local polar order in addition to the more obvious nematic order. Average cell velocity and active force at topological defects agree with predictions from active nematic theory, but their fluctuations are anomalously large due to polar active forces generated by the self-propelled rod-shaped cells. We find that M. xanthus cells adjust their reversal frequency to tune the magnitude of this local polar order, which in turn controls the mechanical stresses and triggers layer formation in the colonies.
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Affiliation(s)
- Endao Han
- Joseph Henry Laboratories of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Chenyi Fei
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Ricard Alert
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzerstraße 38, 01187 Dresden, Germany
- Center for Systems Biology Dresden, Pfotenhauerstraße 108, 01307 Dresden, Germany
- Cluster of Excellence Physics of Life, TU Dresden, 01062, Dresden, Germany
| | - Katherine Copenhagen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Matthias D. Koch
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Ned S. Wingreen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Joshua W. Shaevitz
- Joseph Henry Laboratories of Physics, Princeton University, Princeton, NJ 08544, USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
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6
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Asp ME, Thanh MTH, Dutta S, Comstock JA, Welch RD, Patteson AE. Mechanobiology as a tool for addressing the genotype-to-phenotype problem in microbiology. BIOPHYSICS REVIEWS 2023; 4:021304. [PMID: 38504926 PMCID: PMC10903382 DOI: 10.1063/5.0142121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 04/03/2023] [Indexed: 03/21/2024]
Abstract
The central hypothesis of the genotype-phenotype relationship is that the phenotype of a developing organism (i.e., its set of observable attributes) depends on its genome and the environment. However, as we learn more about the genetics and biochemistry of living systems, our understanding does not fully extend to the complex multiscale nature of how cells move, interact, and organize; this gap in understanding is referred to as the genotype-to-phenotype problem. The physics of soft matter sets the background on which living organisms evolved, and the cell environment is a strong determinant of cell phenotype. This inevitably leads to challenges as the full function of many genes, and the diversity of cellular behaviors cannot be assessed without wide screens of environmental conditions. Cellular mechanobiology is an emerging field that provides methodologies to understand how cells integrate chemical and physical environmental stress and signals, and how they are transduced to control cell function. Biofilm forming bacteria represent an attractive model because they are fast growing, genetically malleable and can display sophisticated self-organizing developmental behaviors similar to those found in higher organisms. Here, we propose mechanobiology as a new area of study in prokaryotic systems and describe its potential for unveiling new links between an organism's genome and phenome.
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7
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Simsek AN, Koch MD, Sanfilippo JE, Gitai Z, Gompper G, Sabass B. Type-IV pili tune an adhesion-migration trade-off during surface colonization of Pseudomonas aeruginosa. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.09.538458. [PMID: 37215001 PMCID: PMC10197611 DOI: 10.1101/2023.05.09.538458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Bacterial pathogenicity relies on both firm surface adhesion and cell dissemination. How twitching bacteria resolve the fundamental contradiction between adhesion and migration is unknown. To address this question, we employ live-cell imaging of type-IV pili (T4P) and therewith construct a comprehensive mathematical model of Pseudomonas aeruginosa migration. The data show that only 10% to 50% of T4P bind to substrates and contribute to migration through random extension and retraction. Individual T4P do not display a measurable sensory response to surfaces, but their number increases on cellular surface contact. Attachment to surfaces is mediated, besides T4P, by passive adhesive forces acting on the cell body. Passive adhesions slow down cell migration and result in local random motion on short time scales, which is followed by directionally persistent, superdiffusive motion on longer time scales. Moreover, passive adhesions strongly enhance surface attachment under shear flow. Δ pilA mutants, which produce no T4P, robustly stick to surfaces under shear flow. In contrast, rapidly migrating Δ pilH cells, which produce an excessive number of T4P, are easily detached by shear. Wild-type cells sacrifice migration speed for robust surface attachment by maintaining a low number of active pili. The different cell strains pertain to disjunct regimes in a generic adhesion-migration trait space. Depending on the nature of the adhesion structures, adhesion and migration are either compatible or a trade-off is required for efficient bacterial surface colonization under different conditions.
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8
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Gorobets S, Gorobets O, Sharai I, Polyakova T, Zablotskii V. Gradient Magnetic Field Accelerates Division of E. coli Nissle 1917. Cells 2023; 12:315. [PMID: 36672251 PMCID: PMC9857180 DOI: 10.3390/cells12020315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 01/07/2023] [Accepted: 01/11/2023] [Indexed: 01/19/2023] Open
Abstract
Cell-cycle progression is regulated by numerous intricate endogenous mechanisms, among which intracellular forces and protein motors are central players. Although it seems unlikely that it is possible to speed up this molecular machinery by applying tiny external forces to the cell, we show that magnetic forcing of magnetosensitive bacteria reduces the duration of the mitotic phase. In such bacteria, the coupling of the cell cycle to the splitting of chains of biogenic magnetic nanoparticles (BMNs) provides a biological realization of such forcing. Using a static gradient magnetic field of a special spatial configuration, in probiotic bacteria E. coli Nissle 1917, we shortened the duration of the mitotic phase and thereby accelerated cell division. Thus, focused magnetic gradient forces exerted on the BMN chains allowed us to intervene in the processes of division and growth of bacteria. The proposed magnetic-based cell division regulation strategy can improve the efficiency of microbial cell factories and medical applications of magnetosensitive bacteria.
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Affiliation(s)
- Svitlana Gorobets
- Faculty of Biotechnology and Biotechnics, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 03056 Kyiv, Ukraine
| | - Oksana Gorobets
- Faculty of Physics and Mathematics, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 03056 Kyiv, Ukraine
- Institute of Magnetism of the National Academy of Sciences of Ukraine and Ministry of Education and Science of Ukraine, 03142 Kyiv, Ukraine
| | - Iryna Sharai
- Faculty of Physics and Mathematics, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 03056 Kyiv, Ukraine
- Institute of Magnetism of the National Academy of Sciences of Ukraine and Ministry of Education and Science of Ukraine, 03142 Kyiv, Ukraine
| | - Tatyana Polyakova
- Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 182 00 Prague, Czech Republic
| | - Vitalii Zablotskii
- Institute of Physics of the Czech Academy of Sciences, Na Slovance 1999/2, 182 00 Prague, Czech Republic
- International Magnetobiology Frontier Research Center (iMFRC), Science Island, Hefei 230000, China
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9
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Charlton SGV, Kurz DL, Geisel S, Jimenez-Martinez J, Secchi E. The role of biofilm matrix composition in controlling colony expansion and morphology. Interface Focus 2022; 12:20220035. [PMID: 36330326 PMCID: PMC9560791 DOI: 10.1098/rsfs.2022.0035] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 09/09/2022] [Indexed: 08/01/2023] Open
Abstract
Biofilms are biological viscoelastic gels composed of bacterial cells embedded in a self-secreted polymeric extracellular matrix (ECM). In environmental settings, such as in the rhizosphere and phyllosphere, biofilm colonization occurs at the solid-air interface. The biofilms' ability to colonize and expand over these surfaces depends on the formation of osmotic gradients and ECM viscoelastic properties. In this work, we study the influence of biofilm ECM components on its viscoelasticity and expansion, using the model organism Bacillus subtilis and deletion mutants of its three major ECM components, TasA, EPS and BslA. Using a multi-scale approach, we quantified macro-scale viscoelasticity and expansion dynamics. Furthermore, we used a microsphere assay to visualize the micro-scale expansion patterns. We find that the viscoelastic phase angle Φ is likely the best viscoelastic parameter correlating to biofilm expansion dynamics. Moreover, we quantify the sensitivity of the biofilm to changes in substrate water potential as a function of ECM composition. Finally, we find that the deletion of ECM components significantly increases the coherence of micro-scale colony expansion patterns. These results demonstrate the influence of ECM viscoelasticity and substrate water potential on the expansion of biofilm colonies on wet surfaces at the air-solid interface, commonly found in natural environments.
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Affiliation(s)
- Samuel G. V. Charlton
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zürich, Zürich, Switzerland
| | - Dorothee L. Kurz
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zürich, Zürich, Switzerland
- Department Water Resources and Drinking Water, Swiss Federal Institute of Aquatic Science and Technology, Eawag, Dübendorf, Switzerland
| | - Steffen Geisel
- Department of Materials, Soft Materials, ETH Zürich, Zürich, Switzerland
| | - Joaquin Jimenez-Martinez
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zürich, Zürich, Switzerland
- Department Water Resources and Drinking Water, Swiss Federal Institute of Aquatic Science and Technology, Eawag, Dübendorf, Switzerland
| | - Eleonora Secchi
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zürich, Zürich, Switzerland
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10
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Pseudomonas aeruginosa distinguishes surfaces by stiffness using retraction of type IV pili. Proc Natl Acad Sci U S A 2022; 119:e2119434119. [PMID: 35561220 PMCID: PMC9171759 DOI: 10.1073/pnas.2119434119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
While many bacteria can sense the presence of a surface, the mechanical properties of different surfaces vary tremendously and can be as rigid as bone or as soft as mucus. We show that the pathogen Pseudomonas aeruginosa distinguishes surfaces by stiffness and transcriptionally tunes its virulence to surface rigidity. This connection between pathogenicity and mechanical properties of the infection site presents an interesting potential for clinical applications. The mechanism behind stiffness sensing relies on the retraction of external appendages called type IV pili that deform the surface. While this mechanism has interesting parallels to stiffness sensing in mammalian cells, our results suggest that stiffness sensing in much smaller bacterial cells relies on temporal sensing instead of spatial sensing strategies. The ability of eukaryotic cells to differentiate surface stiffness is fundamental for many processes like stem cell development. Bacteria were previously known to sense the presence of surfaces, but the extent to which they could differentiate stiffnesses remained unclear. Here we establish that the human pathogen Pseudomonas aeruginosa actively measures surface stiffness using type IV pili (TFP). Stiffness sensing is nonlinear, as induction of the virulence factor regulator is peaked with stiffness in a physiologically important range between 0.1 kPa (similar to mucus) and 1,000 kPa (similar to cartilage). Experiments on surfaces with distinct material properties establish that stiffness is the specific biophysical parameter important for this sensing. Traction force measurements reveal that the retraction of TFP is capable of deforming even stiff substrates. We show how slow diffusion of the pilin PilA in the inner membrane yields local concentration changes at the base of TFP during extension and retraction that change with substrate stiffness. We develop a quantitative biomechanical model that explains the transcriptional response to stiffness. A competition between PilA diffusion in the inner membrane and a loss/gain of monomers during TFP extension/retraction produces substrate stiffness-dependent dynamics of the local PilA concentration. We validated this model by manipulating the ATPase activity of the TFP motors to change TFP extension and retraction velocities and PilA concentration dynamics, altering the stiffness response in a predictable manner. Our results highlight stiffness sensing as a shared behavior across biological kingdoms, revealing generalizable principles of environmental sensing across small and large cells.
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11
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Nakane D, Enomoto G, Bähre H, Hirose Y, Wilde A, Nishizaka T. Thermosynechococcus switches the direction of phototaxis by a c-di-GMP-dependent process with high spatial resolution. eLife 2022; 11:73405. [PMID: 35535498 PMCID: PMC9090330 DOI: 10.7554/elife.73405] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 03/21/2022] [Indexed: 11/13/2022] Open
Abstract
Many cyanobacteria, which use light as an energy source via photosynthesis, show directional movement towards or away from a light source. However, the molecular and cell biological mechanisms for switching the direction of movement remain unclear. Here, we visualized type IV pilus-dependent cell movement in the rod-shaped thermophilic cyanobacterium Thermosynechococcus vulcanus using optical microscopy at physiological temperature and light conditions. Positive and negative phototaxis were controlled on a short time scale of 1 min. The cells smoothly moved over solid surfaces towards green light, but the direction was switched to backward movement when we applied additional blue light illumination. The switching was mediated by three photoreceptors, SesA, SesB, and SesC, which have cyanobacteriochrome photosensory domains and synthesis/degradation activity of the bacterial second messenger cyclic dimeric GMP (c-di-GMP). Our results suggest that the decision-making process for directional switching in phototaxis involves light-dependent changes in the cellular concentration of c-di-GMP. Direct visualization of type IV pilus filaments revealed that rod-shaped cells can move perpendicular to the light vector, indicating that the polarity can be controlled not only by pole-to-pole regulation but also within-a-pole regulation. This study provides insights into previously undescribed rapid bacterial polarity regulation via second messenger signalling with high spatial resolution.
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Affiliation(s)
- Daisuke Nakane
- Department of Engineering Science, Graduate School of Informatics and Engineering, The University of Electro-Communications, Tokyo, Japan
| | - Gen Enomoto
- Institute of Biology III, University of Freiburg, Freiburg, Germany
| | - Heike Bähre
- Research Core Unit Metabolomics, Hannover Medical School, Hannover, Germany
| | - Yuu Hirose
- Department of Applied Chemistry and Life Science, Toyohashi University of Technology, Toyohashi, Japan
| | - Annegret Wilde
- Institute of Biology III, University of Freiburg, Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, Freiburg, Germany
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12
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Chen J, Nan B. Flagellar Motor Transformed: Biophysical Perspectives of the Myxococcus xanthus Gliding Mechanism. Front Microbiol 2022; 13:891694. [PMID: 35602090 PMCID: PMC9120999 DOI: 10.3389/fmicb.2022.891694] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 04/13/2022] [Indexed: 11/13/2022] Open
Abstract
Many bacteria move on solid surfaces using gliding motility, without involvement of flagella or pili. Gliding of Myxococcus xanthus is powered by a proton channel homologous to the stators in the bacterial flagellar motor. Instead of being fixed in place and driving the rotation of a circular protein track like the flagellar basal body, the gliding machinery of M. xanthus travels the length of the cell along helical trajectories, while mechanically engaging with the substrate. Such movement entails a different molecular mechanism to generate propulsion on the cell. In this perspective, we will discuss the similarities and differences between the M. xanthus gliding machinery and bacterial flagellar motor, and use biophysical principles to generate hypotheses about the operating mechanism, efficiency, sensitivity to control, and mechanosensing of M. xanthus gliding.
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Affiliation(s)
- Jing Chen
- Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
- *Correspondence: Jing Chen,
| | - Beiyan Nan
- Department of Biology, Texas A&M University, College Station, TX, United States
- Beiyan Nan,
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13
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Asp ME, Ho Thanh MT, Germann DA, Carroll RJ, Franceski A, Welch RD, Gopinath A, Patteson AE. Spreading rates of bacterial colonies depend on substrate stiffness and permeability. PNAS NEXUS 2022; 1:pgac025. [PMID: 36712798 PMCID: PMC9802340 DOI: 10.1093/pnasnexus/pgac025] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 01/25/2022] [Accepted: 03/09/2022] [Indexed: 02/01/2023]
Abstract
The ability of bacteria to colonize and grow on different surfaces is an essential process for biofilm development. Here, we report the use of synthetic hydrogels with tunable stiffness and porosity to assess physical effects of the substrate on biofilm development. Using time-lapse microscopy to track the growth of expanding Serratia marcescens colonies, we find that biofilm colony growth can increase with increasing substrate stiffness, unlike what is found on traditional agar substrates. Using traction force microscopy-based techniques, we find that biofilms exert transient stresses correlated over length scales much larger than a single bacterium, and that the magnitude of these forces also increases with increasing substrate stiffness. Our results are consistent with a model of biofilm development in which the interplay between osmotic pressure arising from the biofilm and the poroelastic response of the underlying substrate controls biofilm growth and morphology.
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Affiliation(s)
- Merrill E Asp
- Physics Department, Syracuse University, Syracuse, NY 13244, USA,BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Minh-Tri Ho Thanh
- Physics Department, Syracuse University, Syracuse, NY 13244, USA,BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Danielle A Germann
- Physics Department, Syracuse University, Syracuse, NY 13244, USA,BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Robert J Carroll
- Physics Department, Syracuse University, Syracuse, NY 13244, USA,BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| | - Alana Franceski
- BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA,Biology Department, Syracuse University, Syracuse, NY 13244, USA
| | - Roy D Welch
- BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA,Biology Department, Syracuse University, Syracuse, NY 13244, USA
| | - Arvind Gopinath
- Department of Bioengineering, University of California, Merced, Merced, CA 95343, USA,Health Sciences Research Institute, University of California, Merced, Merced, CA 95343, USA
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14
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Patteson AE, Asp ME, Janmey PA. Materials science and mechanosensitivity of living matter. APPLIED PHYSICS REVIEWS 2022; 9:011320. [PMID: 35392267 PMCID: PMC8969880 DOI: 10.1063/5.0071648] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 02/08/2022] [Indexed: 06/14/2023]
Abstract
Living systems are composed of molecules that are synthesized by cells that use energy sources within their surroundings to create fascinating materials that have mechanical properties optimized for their biological function. Their functionality is a ubiquitous aspect of our lives. We use wood to construct furniture, bacterial colonies to modify the texture of dairy products and other foods, intestines as violin strings, bladders in bagpipes, and so on. The mechanical properties of these biological materials differ from those of other simpler synthetic elastomers, glasses, and crystals. Reproducing their mechanical properties synthetically or from first principles is still often unattainable. The challenge is that biomaterials often exist far from equilibrium, either in a kinetically arrested state or in an energy consuming active state that is not yet possible to reproduce de novo. Also, the design principles that form biological materials often result in nonlinear responses of stress to strain, or force to displacement, and theoretical models to explain these nonlinear effects are in relatively early stages of development compared to the predictive models for rubberlike elastomers or metals. In this Review, we summarize some of the most common and striking mechanical features of biological materials and make comparisons among animal, plant, fungal, and bacterial systems. We also summarize some of the mechanisms by which living systems develop forces that shape biological matter and examine newly discovered mechanisms by which cells sense and respond to the forces they generate themselves, which are resisted by their environment, or that are exerted upon them by their environment. Within this framework, we discuss examples of how physical methods are being applied to cell biology and bioengineering.
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Affiliation(s)
- Alison E. Patteson
- Physics Department and BioInspired Institute, Syracuse University, Syracuse NY, 13244, USA
| | - Merrill E. Asp
- Physics Department and BioInspired Institute, Syracuse University, Syracuse NY, 13244, USA
| | - Paul A. Janmey
- Institute for Medicine and Engineering and Departments of Physiology and Physics & Astronomy, University of Pennsylvania, Philadelphia PA, 19104, USA
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15
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An In Vitro Model System to Test Mechano-Microbiological Interactions Between Bacteria and Host Cells. Methods Mol Biol 2021. [PMID: 34542856 DOI: 10.1007/978-1-0716-1661-1_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The aim of this chapter is to present an innovative technique to visualize changes of the F-actin cytoskeleton in response to locally applied force. We developed an in vitro system that combines micromanipulation of force by magnetic tweezers with simultaneous live cell fluorescence microscopy. We applied pulling forces to magnetic beads coated with the Neisseria gonorrhoeae Type IV pili in the same order of magnitude than the forces generated by live bacteria. We saw quick and robust F-actin accumulation in individual cells at the sites where pulling forces were applied. Using the magnetic tweezers, we were able to mimic the local response of the F-actin cytoskeleton to bacteria-generated forces. In this chapter, we describe our magnetic tweezers system and show how to control it in order to study cellular responses to force.
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16
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Lam T, Ellison CK, Eddington DT, Brun YV, Dalia AB, Morrison DA. Competence pili in Streptococcus pneumoniae are highly dynamic structures that retract to promote DNA uptake. Mol Microbiol 2021; 116:381-396. [PMID: 33754381 DOI: 10.1111/mmi.14718] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 03/11/2021] [Accepted: 03/17/2021] [Indexed: 01/11/2023]
Abstract
The competence pili of transformable Gram-positive species are phylogenetically related to the diverse and widespread class of extracellular filamentous organelles known as type IV pili. In Gram-negative bacteria, type IV pili act through dynamic cycles of extension and retraction to carry out diverse activities including attachment, motility, protein secretion, and DNA uptake. It remains unclear whether competence pili in Gram-positive species exhibit similar dynamic activity, and their mechanism of action for DNA uptake remains unclear. They are hypothesized to either (1) leave transient cavities in the cell wall that facilitate DNA passage, (2) form static adhesins to enrich DNA near the cell surface for subsequent uptake by membrane-embedded transporters, or (3) play an active role in translocating bound DNA via dynamic activity. Here, we use a recently described pilus labeling approach to demonstrate that competence pili in Streptococcus pneumoniae are highly dynamic structures that rapidly extend and retract from the cell surface. By labeling the principal pilus monomer, ComGC, with bulky adducts, we further demonstrate that pilus retraction is essential for natural transformation. Together, our results suggest that Gram-positive competence pili in other species may also be dynamic and retractile structures that play an active role in DNA uptake.
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Affiliation(s)
- Trinh Lam
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Courtney K Ellison
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ, USA.,Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - David T Eddington
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA
| | - Yves V Brun
- Department of Biology, Indiana University, Bloomington, IN, USA.,Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, QC, Canada
| | - Ankur B Dalia
- Department of Biology, Indiana University, Bloomington, IN, USA
| | - Donald A Morrison
- Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL, USA
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17
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Koch MD, Fei C, Wingreen NS, Shaevitz JW, Gitai Z. Competitive binding of independent extension and retraction motors explains the quantitative dynamics of type IV pili. Proc Natl Acad Sci U S A 2021; 118:e2014926118. [PMID: 33593905 PMCID: PMC7923367 DOI: 10.1073/pnas.2014926118] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Type IV pili (TFP) function through cycles of extension and retraction. The coordination of these cycles remains mysterious due to a lack of quantitative measurements of multiple features of TFP dynamics. Here, we fluorescently label TFP in the pathogen Pseudomonas aeruginosa and track full extension and retraction cycles of individual filaments. Polymerization and depolymerization dynamics are stochastic; TFP are made at random times and extend, pause, and retract for random lengths of time. TFP can also pause for extended periods between two extension or two retraction events in both wild-type cells and a slowly retracting PilT mutant. We developed a biophysical model based on the stochastic binding of two dedicated extension and retraction motors to the same pilus machine that predicts the observed features of the data with no free parameters. We show that only a model in which both motors stochastically bind and unbind to the pilus machine independent of the piliation state of the machine quantitatively explains the experimentally observed pilus production rate. In experimental support of this model, we show that the abundance of the retraction motor dictates the pilus production rate and that PilT is bound to pilus machines even in their unpiliated state. Together, the strong quantitative agreement of our model with a variety of experiments suggests that the entire repetitive cycle of pilus extension and retraction is coordinated by the competition of stochastic motor binding to the pilus machine, and that the retraction motor is the major throttle for pilus production.
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Affiliation(s)
- Matthias D Koch
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08540
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540
| | - Chenyi Fei
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08540
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540
| | - Ned S Wingreen
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08540
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540
| | - Joshua W Shaevitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08540;
- Joseph Henry Laboratories of Physics, Princeton University, Princeton, NJ 08540
| | - Zemer Gitai
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540;
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18
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Craig L, Forest KT, Maier B. Type IV pili: dynamics, biophysics and functional consequences. Nat Rev Microbiol 2020; 17:429-440. [PMID: 30988511 DOI: 10.1038/s41579-019-0195-4] [Citation(s) in RCA: 222] [Impact Index Per Article: 55.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The surfaces of many bacteria are decorated with long, exquisitely thin appendages called type IV pili (T4P), dynamic filaments that are rapidly polymerized and depolymerized from a pool of pilin subunits. Cycles of pilus extension, binding and retraction enable T4P to perform a phenomenally diverse array of functions, including twitching motility, DNA uptake and microcolony formation. On the basis of recent developments, a comprehensive understanding is emerging of the molecular architecture of the T4P machinery and the filament it builds, providing mechanistic insights into the assembly and retraction processes. Combined microbiological and biophysical approaches have revealed how T4P dynamics influence self-organization of bacteria, how bacteria respond to external stimuli to regulate T4P activity for directed movement, and the role of T4P retraction in surface sensing. In this Review, we discuss the T4P machine architecture and filament structure and present current molecular models for T4P dynamics, with a particular focus on recent insights into T4P retraction. We also discuss the functional consequences of T4P dynamics, which have important implications for bacterial lifestyle and pathogenesis.
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Affiliation(s)
- Lisa Craig
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada.
| | - Katrina T Forest
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Berenike Maier
- Institute for Biological Physics, University of Cologne, Köln, Germany.
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19
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Mechanomicrobiology: how bacteria sense and respond to forces. Nat Rev Microbiol 2020; 18:227-240. [DOI: 10.1038/s41579-019-0314-2] [Citation(s) in RCA: 99] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2019] [Indexed: 12/26/2022]
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20
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Interspecies and Intraspecies Signals Synergistically Regulate Lysobacter enzymogenes Twitching Motility. Appl Environ Microbiol 2019; 85:AEM.01742-19. [PMID: 31540995 DOI: 10.1128/aem.01742-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 09/18/2019] [Indexed: 12/24/2022] Open
Abstract
The twitching motility of bacteria is closely related to environmental adaptability and pathogenic behaviors. Lysobacter is a good genus in which to study twitching motility because of the complex social activities and distinct movement patterns of its members. Regardless, the mechanism that induces twitching motility is largely unknown. In this study, we found that the interspecies signal indole caused Lysobacter to have irregular, random twitching motility with significantly enhanced speed. Deletion of qseC or qseB from the two-component system for indole signaling perception resulted in the disappearance of rapid, random movements and significantly decreased twitching activity. Indole-induced, rapid, random twitching was achieved through upregulation of expression of gene cluster pilE1-pilY11-pilX1-pilW1-pilV1-fimT1 In addition, under conditions of extremely low bacterial density, individual Lysobacter cells grew and divided in a stable manner in situ without any movement. The intraspecies quorum-sensing signaling factor 13-methyltetradecanoic acid, designated L. enzymogenes diffusible signaling factor (LeDSF), was essential for Lysobacter to produce twitching motility through indirect regulation of gene clusters pilM-pilN-pilO-pilP-pilQ and pilS1-pilR-pilA-pilB-pilC These results demonstrate that the motility of Lysobacter is induced and regulated by indole and LeDSF, which reveals a novel theory for future studies of the mechanisms of bacterial twitching activities.IMPORTANCE The mechanism underlying bacterial twitching motility is an important research area because it is closely related to social and pathogenic behaviors. The mechanism mediating cell-to-cell perception of twitching motility is largely unknown. Using Lysobacter as a model, we found in this study that the interspecies signal indole caused Lysobacter to exhibit irregular, random twitching motility via activation of gene cluster pilE1-pilY11-pilX1-pilW1-pilV1-fimT1 In addition, population-dependent behavior induced by 13-methyltetradecanoic acid, a quorum-sensing signaling molecule designated LeDSF, was involved in twitching motility by indirectly regulating gene clusters pilM-pilN-pilO-pilP-pilQ and pilS1-pilR-pilA-pilB-pilC The results demonstrate that the twitching motility of Lysobacter is regulated by these two signaling molecules, offering novel clues for exploring the mechanisms of twitching motility and population-dependent behaviors of bacteria.
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21
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Abstract
The motility mechanism of certain prokaryotes has long been a mystery, since their motion, known as gliding, involves no external appendages. The physical principles behind gliding still remain poorly understood. Using myxobacteria as an example of such organisms, we identify here the physical principles behind gliding motility and develop a theoretical model that predicts a 2-regime behavior of the gliding speed as a function of the substrate stiffness. Our theory describes the elasto-capillary-hydrodynamic interactions between the membrane of the bacteria, the slime it secretes, and the soft substrate underneath. Defining gliding as the horizontal translation under zero net force, we find the 2-regime behavior is due to 2 distinct mechanisms of motility thrust. On mildly soft substrates, the thrust arises from bacterial shape deformations creating a flow of slime that exerts a pressure along the bacterial length. This pressure in conjunction with the bacterial shape provides the necessary thrust for propulsion. On very soft substrates, however, we show that capillary effects must be considered that lead to the formation of a ridge at the slime-substrate-air interface, thereby creating a thrust in the form of a localized pressure gradient at the bacterial leading edge. To test our theory, we perform experiments with isolated cells on agar substrates of varying stiffness and find the measured gliding speeds in good agreement with the predictions from our elasto-capillary-hydrodynamic model. The mechanisms reported here serve as an important step toward an accurate theory of friction and substrate-mediated interactions between bacteria proliferating in soft media.
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22
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Berry J, Ristić S, Zhou S, Park J, Srolovitz DJ. The MoSeS dynamic omnigami paradigm for smart shape and composition programmable 2D materials. Nat Commun 2019; 10:5210. [PMID: 31729363 PMCID: PMC6858317 DOI: 10.1038/s41467-019-12945-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 09/27/2019] [Indexed: 12/15/2022] Open
Abstract
The properties of 2D materials can be broadly tuned through alloying and phase and strain engineering. Shape programmable materials offer tremendous functionality, but sub-micron objects are typically unachievable with conventional thin films. Here we propose a new approach, combining phase/strain engineering with shape programming, to form 3D objects by patterned alloying of 2D transition metal dichalcogenide (TMD) monolayers. Conjugately, monolayers can be compositionally patterned using non-flat substrates. For concreteness, we focus on the TMD alloy MoSe[Formula: see text]S[Formula: see text]; i.e., MoSeS. These 2D materials down-scale shape/composition programming to nanoscale objects/patterns, provide control of both bending and stretching deformations, are reversibly actuatable with electric fields, and possess the extraordinary and diverse properties of TMDs. Utilizing a first principles-informed continuum model, we demonstrate how a variety of shapes/composition patterns can be programmed and reversibly modulated across length scales. The vast space of possible designs and scales enables novel material properties and thus new applications spanning flexible electronics/optics, catalysis, responsive coatings, and soft robotics.
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Affiliation(s)
- Joel Berry
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA.,Materials Science Division, Lawrence Livermore National Laboratory, Livermore, CA, 94550, USA
| | - Simeon Ristić
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Songsong Zhou
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Jiwoong Park
- Department of Chemistry, Institute for Molecular Engineering, James Franck Institute, University of Chicago, Chicago, IL, USA
| | - David J Srolovitz
- Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, PA, 19104, USA. .,Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, PA, 19104, USA. .,Department of Materials Science and Engineering, City University of Hong Kong, Hong Kong, SAR, P. R. China.
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23
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Bajpai A, Tong J, Qian W, Peng Y, Chen W. The Interplay Between Cell-Cell and Cell-Matrix Forces Regulates Cell Migration Dynamics. Biophys J 2019; 117:1795-1804. [PMID: 31706566 DOI: 10.1016/j.bpj.2019.10.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 09/18/2019] [Accepted: 10/08/2019] [Indexed: 12/18/2022] Open
Abstract
Cells in vivo encounter and exert forces as they interact with the extracellular matrix (ECM) and neighboring cells during migration. These mechanical forces play crucial roles in regulating cell migratory behaviors. Although a variety of studies have focused on describing single-cell or the collective cell migration behaviors, a fully mechanistic understanding of how the cell-cell (intercellular) and cell-ECM (extracellular) traction forces individually and cooperatively regulate single-cell migration and coordinate multicellular movement in a cellular monolayer is still lacking. Here, we developed an integrated experimental and analytical system to examine both the intercellular and extracellular traction forces acting on individual cells within an endothelial cell colony as well as their roles in guiding cell migratory behaviors (i.e., cell translation and rotation). Combined with force, multipole, and moment analysis, our results revealed that traction force dominates in regulating cell active translation, whereas intercellular force actively modulates cell rotation. Our findings advance the understanding of the intricacies of cell-cell and cell-ECM forces in regulating cellular migratory behaviors that occur during the monolayer development and may yield deeper insights into the single-cell dynamic behaviors during tissue development, embryogenesis, and wound healing.
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Affiliation(s)
| | - Jie Tong
- Department of Mechanical and Aerospace Engineering
| | - Weiyi Qian
- Department of Mechanical and Aerospace Engineering
| | - Yansong Peng
- Department of Mechanical and Aerospace Engineering
| | - Weiqiang Chen
- Department of Mechanical and Aerospace Engineering; Department of Biomedical Engineering, New York University, Brooklyn, New York.
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24
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Zöllner R, Cronenberg T, Maier B. Motor Properties of PilT-Independent Type 4 Pilus Retraction in Gonococci. J Bacteriol 2019; 201:e00778-18. [PMID: 30692169 PMCID: PMC6707916 DOI: 10.1128/jb.00778-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Accepted: 01/17/2019] [Indexed: 01/25/2023] Open
Abstract
Bacterial type 4 pili (T4P) belong to the strongest molecular machines. The gonococcal T4P retraction ATPase PilT supports forces exceeding 100 pN during T4P retraction. Here, we address the question of whether gonococcal T4P retract in the absence of PilT. We show that pilT deletion strains indeed retract their T4P, but the maximum force is reduced to 5 pN. Similarly, the speed of T4P retraction is lower by orders of magnitude compared to that of T4P retraction driven by PilT. Deleting the pilT paralogue pilT2 further reduces the speed of T4P retraction, yet T4P retraction is detectable in the absence of all three pilT paralogues. Furthermore, we show that depletion of proton motive force (PMF) slows but does not inhibit pilT-independent T4P retraction. We conclude that the retraction ATPase is not essential for gonococcal T4P retraction. However, the force generated in the absence of PilT is too low to support important functions of T4P, including twitching motility, fluidization of colonies, and induction of host cell response.IMPORTANCE Bacterial type 4 pili (T4P) have been termed the "Swiss Army knives" of bacteria because they perform numerous functions, including host cell interaction, twitching motility, colony formation, DNA uptake, protein secretion, and surface sensing. The pilus fiber continuously elongates or retracts, and these dynamics are functionally important. Curiously, only a subset of T4P systems employ T4P retraction ATPases to power T4P retraction. Here, we show that one of the strongest T4P machines, the gonococcal T4P, retracts without a retraction ATPase. Biophysical characterization reveals strongly reduced force and speed compared to retraction with ATPase. We propose that bacteria encode retraction ATPases when T4P have to generate high-force-supporting functions like twitching motility, triggering host cell response, or fluidizing colonies.
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Affiliation(s)
- Robert Zöllner
- University of Cologne, Institute for Biological Physics, Cologne, Germany
| | - Tom Cronenberg
- University of Cologne, Institute for Biological Physics, Cologne, Germany
| | - Berenike Maier
- University of Cologne, Institute for Biological Physics, Cologne, Germany
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25
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Simsek AN, Braeutigam A, Koch MD, Shaevitz JW, Huang Y, Gompper G, Sabass B. Substrate-rigidity dependent migration of an idealized twitching bacterium. SOFT MATTER 2019; 15:6224-6236. [PMID: 31334524 DOI: 10.1039/c9sm00541b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Mechanical properties of the extracellular matrix are important determinants of cellular migration in diverse processes, such as immune response, wound healing, and cancer metastasis. Moreover, recent studies indicate that even bacterial surface colonization can depend on the mechanics of the substrate. Here, we focus on physical mechanisms that can give rise to substrate-rigidity dependent migration. We study a "twitcher", a cell driven by extension-retraction cycles, to idealize bacteria and perhaps eukaryotic cells that employ a slip-stick mode of motion. The twitcher is asymmetric and always pulls itself forward at its front. Analytical calculations show that the migration speed of a twitcher depends non-linearly on substrate rigidity. For soft substrates, deformations do not lead to build-up of significant force and the migration speed is therefore determined by stochastic adhesion unbinding. For rigid substrates, forced adhesion rupture determines the migration speed. Depending on the force-sensitivity of front and rear adhesions, forced bond rupture implies an increase or a decrease of the migration speed. A requirement for the occurrence of rigidity-dependent stick-slip migration is a "sticky" substrate, with binding rates being an order of magnitude larger than unbinding rates in absence of force. Computer simulations show that small stall forces of the driving machinery lead to a reduced movement on high rigidities, regardless of force-sensitivities of bonds. The simulations also confirm the occurrence of rigidity-dependent migration speed in a generic model for slip-stick migration of cells on a sticky substrate.
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Affiliation(s)
- Ahmet Nihat Simsek
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
| | - Andrea Braeutigam
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
| | - Matthias D Koch
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, NJ 08544, USA
| | - Joshua W Shaevitz
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, NJ 08544, USA
| | - Yunfei Huang
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
| | - Benedikt Sabass
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich, Germany.
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26
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Huang Y, Schell C, Huber TB, Şimşek AN, Hersch N, Merkel R, Gompper G, Sabass B. Traction force microscopy with optimized regularization and automated Bayesian parameter selection for comparing cells. Sci Rep 2019; 9:539. [PMID: 30679578 PMCID: PMC6345967 DOI: 10.1038/s41598-018-36896-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Accepted: 11/27/2018] [Indexed: 12/12/2022] Open
Abstract
Adherent cells exert traction forces on to their environment which allows them to migrate, to maintain tissue integrity, and to form complex multicellular structures during developmental morphogenesis. Traction force microscopy (TFM) enables the measurement of traction forces on an elastic substrate and thereby provides quantitative information on cellular mechanics in a perturbation-free fashion. In TFM, traction is usually calculated via the solution of a linear system, which is complicated by undersampled input data, acquisition noise, and large condition numbers for some methods. Therefore, standard TFM algorithms either employ data filtering or regularization. However, these approaches require a manual selection of filter- or regularization parameters and consequently exhibit a substantial degree of subjectiveness. This shortcoming is particularly serious when cells in different conditions are to be compared because optimal noise suppression needs to be adapted for every situation, which invariably results in systematic errors. Here, we systematically test the performance of new methods from computer vision and Bayesian inference for solving the inverse problem in TFM. We compare two classical schemes, L1- and L2-regularization, with three previously untested schemes, namely Elastic Net regularization, Proximal Gradient Lasso, and Proximal Gradient Elastic Net. Overall, we find that Elastic Net regularization, which combines L1 and L2 regularization, outperforms all other methods with regard to accuracy of traction reconstruction. Next, we develop two methods, Bayesian L2 regularization and Advanced Bayesian L2 regularization, for automatic, optimal L2 regularization. Using artificial data and experimental data, we show that these methods enable robust reconstruction of traction without requiring a difficult selection of regularization parameters specifically for each data set. Thus, Bayesian methods can mitigate the considerable uncertainty inherent in comparing cellular tractions in different conditions.
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Affiliation(s)
- Yunfei Huang
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems-2 and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Christoph Schell
- Institut für Klinische Pathologie, Universitätsklinikum Freiburg, D-79002, Freiburg, Germany.,Berta-Ottenstein Programme, Faculty of Medicine, University of Freiburg, Freiburg, D-79106, Germany
| | - Tobias B Huber
- Department of Medicine IV, Faculty of Medicine, Medical Center - University of Freiburg, Freiburg, Germany.,BIOSS Center for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, Freiburg, Germany.,III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Ahmet Nihat Şimşek
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems-2 and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Nils Hersch
- Biomechanics, Institute of Complex Systems-7, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Rudolf Merkel
- Biomechanics, Institute of Complex Systems-7, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Gerhard Gompper
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems-2 and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425, Juelich, Germany
| | - Benedikt Sabass
- Theoretical Soft Matter and Biophysics, Institute of Complex Systems-2 and Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425, Juelich, Germany.
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27
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Gobbo P, Patil AJ, Li M, Harniman R, Briscoe WH, Mann S. Programmed assembly of synthetic protocells into thermoresponsive prototissues. NATURE MATERIALS 2018; 17:1145-1153. [PMID: 30297813 DOI: 10.1038/s41563-018-0183-5] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 08/30/2018] [Indexed: 06/08/2023]
Abstract
Although several new types of synthetic cell-like entities are now available, their structural integration into spatially interlinked prototissues that communicate and display coordinated functions remains a considerable challenge. Here we describe the programmed assembly of synthetic prototissue constructs based on the bio-orthogonal adhesion of a spatially confined binary community of protein-polymer protocells, termed proteinosomes. The thermoresponsive properties of the interlinked proteinosomes are used collectively to generate prototissue spheroids capable of reversible contractions that can be enzymatically modulated and exploited for mechanochemical transduction. Overall, our methodology opens up a route to the fabrication of artificial tissue-like materials capable of collective behaviours, and addresses important emerging challenges in bottom-up synthetic biology and bioinspired engineering.
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Affiliation(s)
- Pierangelo Gobbo
- Centre for Protolife Research and Centre for Organized Matter Chemistry, School of Chemistry, University of Bristol, Bristol, UK
| | - Avinash J Patil
- Centre for Protolife Research and Centre for Organized Matter Chemistry, School of Chemistry, University of Bristol, Bristol, UK
| | - Mei Li
- Centre for Protolife Research and Centre for Organized Matter Chemistry, School of Chemistry, University of Bristol, Bristol, UK
| | - Robert Harniman
- Centre for Protolife Research and Centre for Organized Matter Chemistry, School of Chemistry, University of Bristol, Bristol, UK
| | - Wuge H Briscoe
- Centre for Protolife Research and Centre for Organized Matter Chemistry, School of Chemistry, University of Bristol, Bristol, UK
| | - Stephen Mann
- Centre for Protolife Research and Centre for Organized Matter Chemistry, School of Chemistry, University of Bristol, Bristol, UK.
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Asymmetric adhesion of rod-shaped bacteria controls microcolony morphogenesis. Nat Commun 2018; 9:1120. [PMID: 29549338 PMCID: PMC5856753 DOI: 10.1038/s41467-018-03446-y] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 02/14/2018] [Indexed: 12/29/2022] Open
Abstract
Surface colonization underpins microbial ecology on terrestrial environments. Although factors that mediate bacteria–substrate adhesion have been extensively studied, their spatiotemporal dynamics during the establishment of microcolonies remains largely unexplored. Here, we use laser ablation and force microscopy to monitor single-cell adhesion during the course of microcolony formation. We find that adhesion forces of the rod-shaped bacteria Escherichia coli and Pseudomonas aeruginosa are polar. This asymmetry induces mechanical tension, and drives daughter cell rearrangements, which eventually determine the shape of the microcolonies. Informed by experimental data, we develop a quantitative model of microcolony morphogenesis that enables the prediction of bacterial adhesion strength from simple time-lapse measurements. Our results demonstrate how patterns of surface colonization derive from the spatial distribution of adhesive factors on the cell envelope. It is unclear how cell adhesion and elongation coordinate during formation of bacterial microcolonies. Here, Duvernoy et al. monitor microcolony formation in rod-shaped bacteria, and show that patterns of surface colonization derive from the spatial distribution of adhesive factors on the cell envelope.
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Rodesney CA, Roman B, Dhamani N, Cooley BJ, Katira P, Touhami A, Gordon VD. Mechanosensing of shear by Pseudomonas aeruginosa leads to increased levels of the cyclic-di-GMP signal initiating biofilm development. Proc Natl Acad Sci U S A 2017; 114:5906-5911. [PMID: 28533383 PMCID: PMC5468607 DOI: 10.1073/pnas.1703255114] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Biofilms are communities of sessile microbes that are phenotypically distinct from their genetically identical, free-swimming counterparts. Biofilms initiate when bacteria attach to a solid surface. Attachment triggers intracellular signaling to change gene expression from the planktonic to the biofilm phenotype. For Pseudomonas aeruginosa, it has long been known that intracellular levels of the signal cyclic-di-GMP increase upon surface adhesion and that this is required to begin biofilm development. However, what cue is sensed to notify bacteria that they are attached to the surface has not been known. Here, we show that mechanical shear acts as a cue for surface adhesion and activates cyclic-di-GMP signaling. The magnitude of the shear force, and thereby the corresponding activation of cyclic-di-GMP signaling, can be adjusted both by varying the strength of the adhesion that binds bacteria to the surface and by varying the rate of fluid flow over surface-bound bacteria. We show that the envelope protein PilY1 and functional type IV pili are required mechanosensory elements. An analytic model that accounts for the feedback between mechanosensors, cyclic-di-GMP signaling, and production of adhesive polysaccharides describes our data well.
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Affiliation(s)
- Christopher A Rodesney
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX 78712
| | - Brian Roman
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX 78712
| | - Numa Dhamani
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX 78712
| | - Benjamin J Cooley
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX 78712
| | | | - Ahmed Touhami
- Department of Physics, The University of Texas Rio Grande Valley, Brownsville, TX 78520
| | - Vernita D Gordon
- Department of Physics, Center for Nonlinear Dynamics, The University of Texas at Austin, Austin, TX 78712;
- Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, TX 78712
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