1
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Josephs-Spaulding J, Rajput A, Hefner Y, Szubin R, Balasubramanian A, Li G, Zielinski DC, Jahn L, Sommer M, Phaneuf P, Palsson BO. Reconstructing the transcriptional regulatory network of probiotic L. reuteri is enabled by transcriptomics and machine learning. mSystems 2024; 9:e0125723. [PMID: 38349131 PMCID: PMC10949432 DOI: 10.1128/msystems.01257-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 01/09/2024] [Indexed: 03/20/2024] Open
Abstract
Limosilactobacillus reuteri, a probiotic microbe instrumental to human health and sustainable food production, adapts to diverse environmental shifts via dynamic gene expression. We applied the independent component analysis (ICA) to 117 RNA-seq data sets to decode its transcriptional regulatory network (TRN), identifying 35 distinct signals that modulate specific gene sets. Our findings indicate that the ICA provides a qualitative advancement and captures nuanced relationships within gene clusters that other methods may miss. This study uncovers the fundamental properties of L. reuteri's TRN and deepens our understanding of its arginine metabolism and the co-regulation of riboflavin metabolism and fatty acid conversion. It also sheds light on conditions that regulate genes within a specific biosynthetic gene cluster and allows for the speculation of the potential role of isoprenoid biosynthesis in L. reuteri's adaptive response to environmental changes. By integrating transcriptomics and machine learning, we provide a system-level understanding of L. reuteri's response mechanism to environmental fluctuations, thus setting the stage for modeling the probiotic transcriptome for applications in microbial food production. IMPORTANCE We have studied Limosilactobacillus reuteri, a beneficial probiotic microbe that plays a significant role in our health and production of sustainable foods, a type of foods that are nutritionally dense and healthier and have low-carbon emissions compared to traditional foods. Similar to how humans adapt their lifestyles to different environments, this microbe adjusts its behavior by modulating the expression of genes. We applied machine learning to analyze large-scale data sets on how these genes behave across diverse conditions. From this, we identified 35 unique patterns demonstrating how L. reuteri adjusts its genes based on 50 unique environmental conditions (such as various sugars, salts, microbial cocultures, human milk, and fruit juice). This research helps us understand better how L. reuteri functions, especially in processes like breaking down certain nutrients and adapting to stressful changes. More importantly, with our findings, we become closer to using this knowledge to improve how we produce more sustainable and healthier foods with the help of microbes.
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Affiliation(s)
- Jonathan Josephs-Spaulding
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Copenhagen, Denmark
| | - Akanksha Rajput
- Department of Bioengineering, University of California, San Diego, California, USA
| | - Ying Hefner
- Department of Bioengineering, University of California, San Diego, California, USA
| | - Richard Szubin
- Department of Bioengineering, University of California, San Diego, California, USA
| | | | - Gaoyuan Li
- Department of Bioengineering, University of California, San Diego, California, USA
| | - Daniel C. Zielinski
- Department of Bioengineering, University of California, San Diego, California, USA
| | - Leonie Jahn
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Copenhagen, Denmark
| | - Morten Sommer
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Copenhagen, Denmark
| | - Patrick Phaneuf
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Copenhagen, Denmark
| | - Bernhard O. Palsson
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Copenhagen, Denmark
- Department of Bioengineering, University of California, San Diego, California, USA
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2
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Akabuogu E, Zhang L, Krašovec R, Roberts IS, Waigh TA. Electrical Impedance Spectroscopy with Bacterial Biofilms: Neuronal-like Behavior. NANO LETTERS 2024; 24:2234-2241. [PMID: 38320294 PMCID: PMC10885197 DOI: 10.1021/acs.nanolett.3c04446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 01/29/2024] [Accepted: 01/31/2024] [Indexed: 02/08/2024]
Abstract
Negative capacitance at low frequencies for spiking neurons was first demonstrated in 1941 (K. S. Cole) by using extracellular electrodes. The phenomenon subsequently was explained by using the Hodgkin-Huxley model and is due to the activity of voltage-gated potassium ion channels. We show that Escherichia coli (E. coli) biofilms exhibit significant stable negative capacitances at low frequencies when they experience a small DC bias voltage in electrical impedance spectroscopy experiments. Using a frequency domain Hodgkin-Huxley model, we characterize the conditions for the emergence of this feature and demonstrate that the negative capacitance exists only in biofilms containing living cells. Furthermore, we establish the importance of the voltage-gated potassium ion channel, Kch, using knock-down mutants. The experiments provide further evidence for voltage-gated ion channels in E. coli and a new, low-cost method to probe biofilm electrophysiology, e.g., to understand the efficacy of antibiotics. We expect that the majority of bacterial biofilms will demonstrate negative capacitances.
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Affiliation(s)
- Emmanuel
U. Akabuogu
- Division
of Infection, Lydia Becker Institute of Immunology and Inflammation,
School of Biological Sciences, University
of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
- Biological
Physics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Lin Zhang
- Biological
Physics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Rok Krašovec
- Division
of Evolution, Infection and Genomics, School of Biological Sciences,
Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, United
Kingdom
| | - Ian S. Roberts
- Division
of Infection, Lydia Becker Institute of Immunology and Inflammation,
School of Biological Sciences, University
of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Thomas A. Waigh
- Biological
Physics, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
- Photon
Science Institute, Alan
Turing Building, Oxford Road, Manchester, M13 9PY, United
Kingdom
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3
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Jung H. A pore-scale reactive transport modeling study for quorum sensing-driven biofilm dispersal in heterogeneous porous media. Math Biosci 2024; 367:109126. [PMID: 38070765 DOI: 10.1016/j.mbs.2023.109126] [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: 08/21/2023] [Revised: 10/26/2023] [Accepted: 12/06/2023] [Indexed: 12/17/2023]
Abstract
Microorganisms regulate the expression of energetically expensive phenotypes via a collective decision-making mechanism known as quorum sensing (QS). This study investigates the intricate dynamics of biofilm growth and QS-controlled biofilm dispersal in heterogeneous porous media, employing a pore-scale reactive transport modeling approach. Model simulations carried out under various fluid flow conditions and biofilm growth scenarios reveal that QS processes are influenced not only by the biomass density of biofilm colonies but also by a complex interplay between pore architecture, flow velocity, and the rates of biofilm growth and dispersal. This study demonstrates that pore architecture controls the initiation of QS processes and advection gives rise to oscillatory growth of biofilms. Such oscillation is suppressed if biofilm dynamics are in favor of sustaining a sufficiently high signal concentration, such as fast growth or slow dispersal rates. By establishing a mathematical framework, this study contributes to the fundamental understanding of QS-controlled biofilm dynamics in complex environments.
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Affiliation(s)
- Heewon Jung
- Department of Geological Sciences, Chungnam National University, Daejeon 34134, South Korea.
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4
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Affiliation(s)
- Pamela Lyon
- Faculty of Arts, Business, Law and Economics, University of Adelaide, Adelaide, SA, 5000, Australia.
| | - Ken Cheng
- School of Natural Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
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5
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Martínez-Calvo A, Trenado-Yuste C, Lee H, Gore J, Wingreen NS, Datta SS. Interfacial morphodynamics of proliferating microbial communities. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.23.563665. [PMID: 37961366 PMCID: PMC10634769 DOI: 10.1101/2023.10.23.563665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
In microbial communities, various cell types often coexist by occupying distinct spatial domains. What determines the shape of the interface between such domains-which in turn influences the interactions between cells and overall community function? Here, we address this question by developing a continuum model of a 2D spatially-structured microbial community with two distinct cell types. We find that, depending on the balance of the different cell proliferation rates and substrate friction coefficients, the interface between domains is either stable and smooth, or unstable and develops finger-like protrusions. We establish quantitative principles describing when these different interfacial behaviors arise, and find good agreement both with the results of previous experimental reports as well as new experiments performed here. Our work thus helps to provide a biophysical basis for understanding the interfacial morphodynamics of proliferating microbial communities, as well as a broader range of proliferating active systems.
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6
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Jing X, Chen S, Liu X, Yang Y, Rensing C, Zhou S. Potassium channel mediates electroactive biofilm formation via recruiting planktonic Geobacter cells. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 850:158035. [PMID: 35981588 DOI: 10.1016/j.scitotenv.2022.158035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 07/31/2022] [Accepted: 08/11/2022] [Indexed: 06/15/2023]
Abstract
Potassium (K+)-channel-based electrical signaling can coordinate microbial actions at a distance that provides an evolutionary advantage to cell communities. Electroactive cells are usually cultured surrounded by an electric field which provided stronger electrical signaling than the K+-mediated electrical signaling. Whether the K+ signaling also plays a role in coordinating the behavior of electroactive microorganisms has not been accurately demonstrated. Thus, we constructed a K+-channel-deficient strain ΔgsuK of Geobacter sulfurreducens to directly investigate roles of K+ signaling in electroactive biofilm formation for the first time. The ΔgsuK strain exhibited significantly inferior biofilm formation (i.e., biomass, thickness and component) and consequently showed weaker electrical performance (i.e., start-up time, current output, electrochemical catalytic behavior and charge transfer resistance) than the wild-type strain. Individual electric generation capacity and the expression of genes involved in biofilm formation and electrical performance in the single cell did not significantly change with the deletion of gsuK, indicating that K+ signaling indeed influenced the recruiting behavior of planktonic cell but not the functioning of the single cell related to biofilm formation or electric generation. This study is intended to provide an in-depth understanding of electroactive biofilm formation and serve as a basis for optimizing its electrical performance via strengthening the recruitment behavior.
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Affiliation(s)
- Xianyue Jing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Shanshan Chen
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China.
| | - Xing Liu
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yuting Yang
- Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China
| | - Christopher Rensing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Shungui Zhou
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
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7
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Abstract
The morphogenesis of two-dimensional bacterial colonies has been well studied. However, little is known about the colony morphologies of bacteria growing in three dimensions, despite the prevalence of three-dimensional environments (e.g., soil, inside hosts) as natural bacterial habitats. Using experiments on bacteria in granular hydrogel matrices, we find that dense multicellular colonies growing in three dimensions undergo a common morphological instability and roughen, adopting a characteristic broccoli-like morphology when they exceed a critical size. Analysis of a continuum “active fluid” model of the expanding colony reveals that this behavior originates from an interplay of competition for nutrients with growth-driven colony expansion, both of which vary spatially. These results shed light on the fundamental biophysical principles underlying growth in three dimensions. How do growing bacterial colonies get their shapes? While colony morphogenesis is well studied in two dimensions, many bacteria grow as large colonies in three-dimensional (3D) environments, such as gels and tissues in the body or subsurface soils and sediments. Here, we describe the morphodynamics of large colonies of bacteria growing in three dimensions. Using experiments in transparent 3D granular hydrogel matrices, we show that dense colonies of four different species of bacteria generically become morphologically unstable and roughen as they consume nutrients and grow beyond a critical size—eventually adopting a characteristic branched, broccoli-like morphology independent of variations in the cell type and environmental conditions. This behavior reflects a key difference between two-dimensional (2D) and 3D colonies; while a 2D colony may access the nutrients needed for growth from the third dimension, a 3D colony inevitably becomes nutrient limited in its interior, driving a transition to unstable growth at its surface. We elucidate the onset of the instability using linear stability analysis and numerical simulations of a continuum model that treats the colony as an “active fluid” whose dynamics are driven by nutrient-dependent cellular growth. We find that when all dimensions of the colony substantially exceed the nutrient penetration length, nutrient-limited growth drives a 3D morphological instability that recapitulates essential features of the experimental observations. Our work thus provides a framework to predict and control the organization of growing colonies—as well as other forms of growing active matter, such as tumors and engineered living materials—in 3D environments.
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8
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Casani-Galdon P, Garcia-Ojalvo J. Signaling oscillations: Molecular mechanisms and functional roles. Curr Opin Cell Biol 2022; 78:102130. [PMID: 36130445 DOI: 10.1016/j.ceb.2022.102130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 07/21/2022] [Accepted: 08/19/2022] [Indexed: 01/31/2023]
Abstract
Mounting evidence shows that oscillatory activity is widespread in cell signaling. Here, we review some of this recent evidence, focusing on both the molecular mechanisms that potentially underlie such dynamical behavior, and the potential advantages that signaling oscillations might have in cell function. The biological processes considered include cellular differentiation and tissue maintenance, intermittent responses in pluripotent stem cells, and collective cell migration during wound healing. With the aid of mathematical modeling, we review recent examples in which delayed negative feedback has been seen to act as a unifying principle that underpins this wide variety of phenomena.
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Affiliation(s)
- Pablo Casani-Galdon
- Department of Medicine and Life Sciences, Universitat Pompeu Fabra, Barcelona Biomedical Research Park, Dr. Aiguader 88, 08003 Barcelona, Spain
| | - Jordi Garcia-Ojalvo
- Department of Medicine and Life Sciences, Universitat Pompeu Fabra, Barcelona Biomedical Research Park, Dr. Aiguader 88, 08003 Barcelona, Spain.
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9
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Tang PC, Eriksson O, Sjögren J, Fatsis-Kavalopoulos N, Kreuger J, Andersson DI. A Microfluidic Chip for Studies of the Dynamics of Antibiotic Resistance Selection in Bacterial Biofilms. Front Cell Infect Microbiol 2022; 12:896149. [PMID: 35619647 PMCID: PMC9128571 DOI: 10.3389/fcimb.2022.896149] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 04/05/2022] [Indexed: 01/01/2023] Open
Abstract
Biofilms are arguably the most important mode of growth of bacteria, but how antibiotic resistance emerges and is selected in biofilms remains poorly understood. Several models to study evolution of antibiotic resistance have been developed, however, their usability varies depending on the nature of the biological question. Here, we developed and validated a microfluidic chip (Brimor) for studying the dynamics of enrichment of antibiotic-resistant bacteria in biofilms using real-time monitoring with confocal microscopy. In situ extracellular cellulose staining and physical disruption of the biomass confirmed Escherichia coli growth as biofilms in the chip. We showed that seven generations of growth occur in 16 h when biofilms were established in the growth chambers of Brimor, and that bacterial death and growth rates could be estimated under these conditions using a plasmid with a conditional replication origin. Additionally, competition experiments between antibiotic-susceptible and -resistant bacteria at sub-inhibitory concentrations demonstrated that the antibiotic ciprofloxacin selected for antibiotic resistance in bacterial biofilms at concentrations 17-fold below the minimal inhibitory concentration of susceptible planktonic bacteria. Overall, the microfluidic chip is easy to use and a relevant model for studying the dynamics of selection of antibiotic resistance in bacterial biofilms and we anticipate that the Brimor chip will facilitate basic research in this area.
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Affiliation(s)
- Po-Cheng Tang
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
| | - Olle Eriksson
- U-Print, Uppsala University 3D-Printing Facility, Uppsala University, Uppsala, Sweden
| | | | | | - Johan Kreuger
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
- *Correspondence: Dan I. Andersson, ; Johan Kreuger,
| | - Dan I. Andersson
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
- *Correspondence: Dan I. Andersson, ; Johan Kreuger,
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10
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Levin M. Technological Approach to Mind Everywhere: An Experimentally-Grounded Framework for Understanding Diverse Bodies and Minds. Front Syst Neurosci 2022; 16:768201. [PMID: 35401131 PMCID: PMC8988303 DOI: 10.3389/fnsys.2022.768201] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 01/24/2022] [Indexed: 12/11/2022] Open
Abstract
Synthetic biology and bioengineering provide the opportunity to create novel embodied cognitive systems (otherwise known as minds) in a very wide variety of chimeric architectures combining evolved and designed material and software. These advances are disrupting familiar concepts in the philosophy of mind, and require new ways of thinking about and comparing truly diverse intelligences, whose composition and origin are not like any of the available natural model species. In this Perspective, I introduce TAME-Technological Approach to Mind Everywhere-a framework for understanding and manipulating cognition in unconventional substrates. TAME formalizes a non-binary (continuous), empirically-based approach to strongly embodied agency. TAME provides a natural way to think about animal sentience as an instance of collective intelligence of cell groups, arising from dynamics that manifest in similar ways in numerous other substrates. When applied to regenerating/developmental systems, TAME suggests a perspective on morphogenesis as an example of basal cognition. The deep symmetry between problem-solving in anatomical, physiological, transcriptional, and 3D (traditional behavioral) spaces drives specific hypotheses by which cognitive capacities can increase during evolution. An important medium exploited by evolution for joining active subunits into greater agents is developmental bioelectricity, implemented by pre-neural use of ion channels and gap junctions to scale up cell-level feedback loops into anatomical homeostasis. This architecture of multi-scale competency of biological systems has important implications for plasticity of bodies and minds, greatly potentiating evolvability. Considering classical and recent data from the perspectives of computational science, evolutionary biology, and basal cognition, reveals a rich research program with many implications for cognitive science, evolutionary biology, regenerative medicine, and artificial intelligence.
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Affiliation(s)
- Michael Levin
- Allen Discovery Center at Tufts University, Medford, MA, United States
- Wyss Institute for Biologically Inspired Engineering at Harvard University, Cambridge, MA, United States
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11
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Ma Y, Budde MW, Mayalu MN, Zhu J, Lu AC, Murray RM, Elowitz MB. Synthetic mammalian signaling circuits for robust cell population control. Cell 2022; 185:967-979.e12. [PMID: 35235768 PMCID: PMC8995209 DOI: 10.1016/j.cell.2022.01.026] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 11/18/2021] [Accepted: 01/28/2022] [Indexed: 01/23/2023]
Abstract
In multicellular organisms, cells actively sense and control their own population density. Synthetic mammalian quorum-sensing circuits could provide insight into principles of population control and extend cell therapies. However, a key challenge is reducing their inherent sensitivity to "cheater" mutations that evade control. Here, we repurposed the plant hormone auxin to enable orthogonal mammalian cell-cell communication and quorum sensing. We designed a paradoxical population control circuit, termed "Paradaux," in which auxin stimulates and inhibits net cell growth at different concentrations. This circuit limited population size over extended timescales of up to 42 days of continuous culture. By contrast, when operating in a non-paradoxical regime, population control became more susceptible to mutational escape. These results establish auxin as a versatile "private" communication system and demonstrate that paradoxical circuit architectures can provide robust population control.
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Affiliation(s)
- Yitong Ma
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Mark W Budde
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Primordium Labs, Arcadia, CA 91006, USA
| | - Michaëlle N Mayalu
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA
| | - Junqin Zhu
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Andrew C Lu
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Richard M Murray
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA
| | - Michael B Elowitz
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA; Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA; Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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12
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Bavaharan A, Skilbeck C. Electrical signalling in prokaryotes and its convergence with quorum sensing in Bacillus. Bioessays 2022; 44:e2100193. [PMID: 35195292 DOI: 10.1002/bies.202100193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 12/15/2022]
Abstract
The importance of electrical signalling in bacteria is an emerging paradigm. Bacillus subtilis biofilms exhibit electrical communication that regulates metabolic activity and biofilm growth. Starving cells initiate oscillatory extracellular potassium signals that help even the distribution of nutrients within the biofilm and thus help regulate biofilm development. Quorum sensing also regulates biofilm growth and crucially there is convergence between electrical and quorum sensing signalling axes. This makes B. subtilis an interesting model for cell signalling research. SpoOF is predicted to act as a logic gate for signalling pathway convergence, raising interesting questions about the functional nature of this gate and the relative importance of these disparate signals on biofilm behaviour. How is an oscillating signal integrated with a quorum signal? The model presented offers rich opportunities for future experimental and theoretical modelling research. The importance of direct cell-to-cell electrical signalling in prokaryotes, so characteristic of multicellular eukaryotes, is also discussed.
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13
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In vitro cell cycle oscillations exhibit a robust and hysteretic response to changes in cytoplasmic density. Proc Natl Acad Sci U S A 2022; 119:2109547119. [PMID: 35101974 PMCID: PMC8832984 DOI: 10.1073/pnas.2109547119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/17/2021] [Indexed: 12/25/2022] Open
Abstract
The cytoplasm, where most cellular reactions occur, has a variable density. We currently lack an understanding of how density variations affect cellular functions because of the challenge of controlling it experimentally. Here, we systematically modulate the density of an in vitro cytoplasm using microfluidics and analyze how the cell cycle behaves in turn. We found that mitotic cycles maintain their function across 0.2× to 1.2× of the natural density. Higher densities arrest cell cycles, and dilution recovers oscillations. However, the density at which cycles reappear is lower than the natural density. This behavior suggests a history-dependent mechanism called hysteresis, common in physics, chemistry, and engineering. Our approach paves the way for studying the responses of other processes to density changes. Cells control the properties of the cytoplasm to ensure proper functioning of biochemical processes. Recent studies showed that cytoplasmic density varies in both physiological and pathological states of cells undergoing growth, division, differentiation, apoptosis, senescence, and metabolic starvation. Little is known about how cellular processes cope with these cytoplasmic variations. Here, we study how a cell cycle oscillator comprising cyclin-dependent kinase (Cdk1) responds to changes in cytoplasmic density by systematically diluting or concentrating cycling Xenopus egg extracts in cell-like microfluidic droplets. We found that the cell cycle maintains robust oscillations over a wide range of deviations from the endogenous density: as low as 0.2× to more than 1.22× relative cytoplasmic density (RCD). A further dilution or concentration from these values arrested the system in a low or high steady state of Cdk1 activity, respectively. Interestingly, diluting an arrested cytoplasm of 1.22× RCD recovers oscillations at lower than 1× RCD. Thus, the cell cycle switches reversibly between oscillatory and stable steady states at distinct thresholds depending on the direction of tuning, forming a hysteresis loop. We propose a mathematical model which recapitulates these observations and predicts that the Cdk1/Wee1/Cdc25 positive feedback loops do not contribute to the observed robustness, supported by experiments. Our system can be applied to study how cytoplasmic density affects other cellular processes.
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14
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Moroz LL, Nikitin MA, Poličar PG, Kohn AB, Romanova DY. Evolution of glutamatergic signaling and synapses. Neuropharmacology 2021; 199:108740. [PMID: 34343611 DOI: 10.1016/j.neuropharm.2021.108740] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/28/2021] [Accepted: 07/29/2021] [Indexed: 12/13/2022]
Abstract
Glutamate (Glu) is the primary excitatory transmitter in the mammalian brain. But, we know little about the evolutionary history of this adaptation, including the selection of l-glutamate as a signaling molecule in the first place. Here, we used comparative metabolomics and genomic data to reconstruct the genealogy of glutamatergic signaling. The origin of Glu-mediated communications might be traced to primordial nitrogen and carbon metabolic pathways. The versatile chemistry of L-Glu placed this molecule at the crossroad of cellular biochemistry as one of the most abundant metabolites. From there, innovations multiplied. Many stress factors or injuries could increase extracellular glutamate concentration, which led to the development of modular molecular systems for its rapid sensing in bacteria and archaea. More than 20 evolutionarily distinct families of ionotropic glutamate receptors (iGluRs) have been identified in eukaryotes. The domain compositions of iGluRs correlate with the origins of multicellularity in eukaryotes. Although L-Glu was recruited as a neuro-muscular transmitter in the early-branching metazoans, it was predominantly a non-neuronal messenger, with a possibility that glutamatergic synapses evolved more than once. Furthermore, the molecular secretory complexity of glutamatergic synapses in invertebrates (e.g., Aplysia) can exceed their vertebrate counterparts. Comparative genomics also revealed 15+ subfamilies of iGluRs across Metazoa. However, most of this ancestral diversity had been lost in the vertebrate lineage, preserving AMPA, Kainate, Delta, and NMDA receptors. The widespread expansion of glutamate synapses in the cortical areas might be associated with the enhanced metabolic demands of the complex brain and compartmentalization of Glu signaling within modular neuronal ensembles.
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Affiliation(s)
- Leonid L Moroz
- Whitney Laboratory for Marine Biosciences, University of Florida, St. Augustine, FL, 32080, USA; Departments of Neuroscience and McKnight Brain Institute, University of Florida, Gainesville, FL, 32610, USA.
| | - Mikhail A Nikitin
- Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119991, Russia; Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, 127994, Russia
| | - Pavlin G Poličar
- Whitney Laboratory for Marine Biosciences, University of Florida, St. Augustine, FL, 32080, USA; Faculty of Computer and Information Science, University of Ljubljana, SI-1000, Ljubljana, Slovenia
| | - Andrea B Kohn
- Whitney Laboratory for Marine Biosciences, University of Florida, St. Augustine, FL, 32080, USA
| | - Daria Y Romanova
- Cellular Neurobiology of Learning Lab, Institute of Higher Nervous Activity and Neurophysiology, Moscow, 117485, Russia.
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15
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Bacterial hyperpolarization modulated by polyoxometalates for solutions of antibiotic resistance. J Inorg Biochem 2021; 220:111463. [PMID: 33894505 DOI: 10.1016/j.jinorgbio.2021.111463] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Revised: 04/06/2021] [Accepted: 04/08/2021] [Indexed: 01/02/2023]
Abstract
Developing strategies against the antibiotic resistance is a major global challenge for public health. Here, we report the synergy of the combination of Preyssler-type polyoxometalates (POMs) ([NaP5W30O110]14- or [AgP5W30O110]14-) and ribosome-targeting antibiotics for high antibacterial efficiency with low risk of antibiotic resistance. Due to their ultra-small sizes and active surface ligands, POM anions show strong affinity to bacterial cell membrane and impose hyperpolarization of the bacterial cells as well as the decrease of Mg2+ influx by blocking Mg2+ transporters, which finally lead to the structural perturbations of ribosomes and instability of bacterial structures. The bacterial growth can, therefore, be regulated by the presence of POMs: a fraction of Bacillus subtilis shifted to a 'dormant', slow-growing cellular state (an extended lag phase) upon the application of subinhibitory concentration of POMs. An approach to combat antibiotic resistant bacteria by applying POMs at their early growth phase followed by antibiotic exposure is validated, and its high efficiency for bacterial control is confirmed.
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16
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Ford N, Fisher G, Prindle A, Chopp D. A Two-Dimensional Model of Potassium Signaling and Oscillatory Growth in a Biofilm. Bull Math Biol 2021; 83:60. [PMID: 33856558 PMCID: PMC8857140 DOI: 10.1007/s11538-021-00887-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 03/11/2021] [Indexed: 12/01/2022]
Abstract
Biofilms are complex communities of bacteria that exhibit a variety of collective behaviors. These behaviors improve their ability to survive in many different environments. One of these collective behaviors seen in Bacillus subtilis is the ability for starving cells to stop the growth of other cells using potassium signaling and voltage changes. This signaling produces an oscillatory growth pattern so that during periods of low growth the nutrients diffuse deeper into the biofilm and reach the nutrient-starved, interior regions of the biomass. In this paper, we develop a mathematical model to describe this oscillatory behavior, and we use this model to develop a two-dimensional simulation that reproduces many of the important features seen in the experimental data. This simulation allows us to examine the spatial patterning of the oscillatory behavior to better understand the relationships between the various regions of the biofilm. Studying the spatial components of the metabolic and voltage oscillations could allow for the development of new control techniques for biofilms with complex shapes.
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Affiliation(s)
- Noah Ford
- Engineering Sciences and Applied Mathematics Department, Northwestern University, Evanston, IL, 60208, USA.
| | - Garth Fisher
- Department of Biochemistry and Molecular Genetics, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA.,Center for Synthetic Biology, Northwestern University, Evanston, IL, 60208, USA
| | - Arthur Prindle
- Department of Biochemistry and Molecular Genetics, Feinberg School of Medicine, Northwestern University, Chicago, IL, 60611, USA.,Center for Synthetic Biology, Northwestern University, Evanston, IL, 60208, USA.,Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - David Chopp
- Engineering Sciences and Applied Mathematics Department, Northwestern University, Evanston, IL, 60208, USA
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17
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Lyon P, Keijzer F, Arendt D, Levin M. Reframing cognition: getting down to biological basics. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190750. [PMID: 33487107 PMCID: PMC7935032 DOI: 10.1098/rstb.2019.0750] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/07/2020] [Indexed: 12/12/2022] Open
Abstract
The premise of this two-part theme issue is simple: the cognitive sciences should join the rest of the life sciences in how they approach the quarry within their research domain. Specifically, understanding how organisms on the lower branches of the phylogenetic tree become familiar with, value and exploit elements of an ecological niche while avoiding harm can be expected to aid understanding of how organisms that evolved later (including Homo sapiens) do the same or similar things. We call this approach basal cognition. In this introductory essay, we explain what the approach involves. Because no definition of cognition exists that reflects its biological basis, we advance a working definition that can be operationalized; introduce a behaviour-generating toolkit of capacities that comprise the function (e.g. sensing/perception, memory, valence, learning, decision making, communication), each element of which can be studied relatively independently; and identify a (necessarily incomplete) suite of common biophysical mechanisms found throughout the domains of life involved in implementing the toolkit. The articles in this collection illuminate different aspects of basal cognition across different forms of biological organization, from prokaryotes and single-celled eukaryotes-the focus of Part 1-to plants and finally to animals, without and with nervous systems, the focus of Part 2. By showcasing work in diverse, currently disconnected fields, we hope to sketch the outline of a new multidisciplinary approach for comprehending cognition, arguably the most fascinating and hard-to-fathom evolved function on this planet. Doing so has the potential to shed light on problems in a wide variety of research domains, including microbiology, immunology, zoology, biophysics, botany, developmental biology, neurobiology/science, regenerative medicine, computational biology, artificial life and synthetic bioengineering. This article is part of the theme issue 'Basal cognition: conceptual tools and the view from the single cell'.
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Affiliation(s)
- Pamela Lyon
- Southgate Institute for Health, Society and Equity, College of Medicine and Public Health, Flinders University, Adelaide, SA 5042, Australia
| | - Fred Keijzer
- Department of Theoretical Philosophy, Universityof Groningen, Oude Boteringestraat 52, Groningen 9712GL, The Netherlands
| | - Detlev Arendt
- Developmental Biology Unit, European Molecular Biology Laboratory, Meyerhofstraße 1, 69012 Heidelberg, Germany
- Centre for Organismal Studies, Heidelberg University, Im Neuenheimer Feld 230, 69120 Heidelberg, Germany
| | - Michael Levin
- Allen Discovery Center at Tufts University, Medford, MA 02155, USA
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18
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Fanesi A, Lavayssière M, Breton C, Bernard O, Briandet R, Lopes F. Shear stress affects the architecture and cohesion of Chlorella vulgaris biofilms. Sci Rep 2021; 11:4002. [PMID: 33597585 PMCID: PMC7889892 DOI: 10.1038/s41598-021-83523-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Accepted: 01/20/2021] [Indexed: 01/31/2023] Open
Abstract
The architecture of microalgae biofilms has been poorly investigated, in particular with respect to shear stress, which is a crucial factor in biofilm-based reactor design and operation. To investigate how microalgae biofilms respond to different hydrodynamic regimes, the architecture and cohesion of Chlorella vulgaris biofilms were studied in flow-cells at three shear stress: 1.0, 6.5 and 11.0 mPa. Biofilm physical properties and architecture dynamics were monitored using a set of microscopic techniques such as, fluorescence recovery after photobleaching (FRAP) and particle tracking. At low shear, biofilms cohesion was heterogeneous resulting in a strong basal (close to the substrate) layer and in more loose superficial ones. Higher shear (11.0 mPa) significantly increased the cohesion of the biofilms allowing them to grow thicker and to produce more biomass, likely due to a biological response to resist the shear stress. Interestingly, an acclimation strategy seemed also to occur which allowed the biofilms to preserve their growth rate at the different hydrodynamic regimes. Our results are in accordance with those previously reported for bacteria biofilms, revealing some general physical/mechanical rules that govern microalgae life on substrates. These results may bring new insights about how to improve productivity and stability of microalgae biofilm-based systems.
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Affiliation(s)
- A. Fanesi
- grid.460789.40000 0004 4910 6535Laboratoire Génie des Procédés et Matériaux (LGPM), CentraleSupélec, Université Paris-Saclay, 91190 Gif-sur-Yvette, France
| | - M. Lavayssière
- grid.460789.40000 0004 4910 6535Laboratoire Génie des Procédés et Matériaux (LGPM), CentraleSupélec, Université Paris-Saclay, 91190 Gif-sur-Yvette, France
| | - C. Breton
- grid.460789.40000 0004 4910 6535Laboratoire Génie des Procédés et Matériaux (LGPM), CentraleSupélec, Université Paris-Saclay, 91190 Gif-sur-Yvette, France
| | - O. Bernard
- Biocore, INRIA, Université Côte d’Azur, 06902 Sophia Antipolis Cedex, France
| | - R. Briandet
- grid.507621.7Université Paris-Saclay, INRAE, AgroParisTech, Micalis Institute, 78350 Jouy-en-Josas, France
| | - F. Lopes
- grid.460789.40000 0004 4910 6535Laboratoire Génie des Procédés et Matériaux (LGPM), CentraleSupélec, Université Paris-Saclay, 91190 Gif-sur-Yvette, France
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19
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Wang Q, Zhang X, Yang Y. Effects of noise and harmonic excitation on the growth of Bacillus subtilis biofilm. Biosystems 2020; 201:104329. [PMID: 33359276 DOI: 10.1016/j.biosystems.2020.104329] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 12/13/2020] [Accepted: 12/13/2020] [Indexed: 11/25/2022]
Abstract
We study the dynamic growth behaviors of Bacillus subtilis biofilms by using a stochastic delay differential equation similar to the Mackey-Glass equation. We observe a wealth of dynamic behavior from a mathematical perspective. Firstly, the change of the time delay (i.e. the time that the growth state of the periphery to affect the stress of the interior cells needs and the time required for the stress signal coming from the interior to reach the peripheral cells) and the external excitation (i.e. the change in temperature) frequency will influence the size of Bacillus subtilis biofilm and the collective growth of the cell community. We also found the resonance phenomena in mathematics, which is of great help in understanding the behavior of stress levels in the biofilm periphery. Secondly, the direction of the Hopf bifurcation and the stability of the bifurcating periodic solutions are derived by using the normal form theory and the center manifold reduction. Numerical simulations are carried out to ensure theoretical results. Finally, the effects of noise on stress levels in the biofilm periphery are analyzed and reveal more complex dynamics of the system.
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Affiliation(s)
- Qiubao Wang
- Department of Mathematical and Physics, Shijiazhuang Tiedao University, 050043, China.
| | - Xing Zhang
- Department of Mathematical and Physics, Shijiazhuang Tiedao University, 050043, China
| | - Yuejuan Yang
- School of Mechanical Engineering, Tiangong University, 300380, China
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20
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All living cells are cognitive. Biochem Biophys Res Commun 2020; 564:134-149. [PMID: 32972747 DOI: 10.1016/j.bbrc.2020.08.120] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/28/2020] [Accepted: 08/19/2020] [Indexed: 12/24/2022]
Abstract
All living cells sense and respond to changes in external or internal conditions. Without that cognitive capacity, they could not obtain nutrition essential for growth, survive inevitable ecological changes, or correct accidents in the complex processes of reproduction. Wherever examined, even the smallest living cells (prokaryotes) display sophisticated regulatory networks establishing appropriate adaptations to stress conditions that maximize the probability of survival. Supposedly "simple" prokaryotic organisms also display remarkable capabilities for intercellular signalling and multicellular coordination. These observations indicate that all living cells are cognitive.
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21
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Bergkessel M. Regulation of protein biosynthetic activity during growth arrest. Curr Opin Microbiol 2020; 57:62-69. [PMID: 32858411 DOI: 10.1016/j.mib.2020.07.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 07/18/2020] [Accepted: 07/20/2020] [Indexed: 01/10/2023]
Abstract
Heterotrophic bacteria grow and divide rapidly when resources are abundant. Yet resources are finite, and environments fluctuate, so bacteria need strategies to survive when nutrients become scarce. In fact, many bacteria spend most of their time in such conditions of nutrient limitation, and hence they need to optimise gene regulation and protein biosynthesis during growth arrest. An optimal strategy in these conditions must mitigate the challenges and risks of making new proteins, while the cell is severely limited for energy and substrates. Recently, ribosome abundance and activity were measured in these conditions, revealing very low amounts of new protein synthesis, which is nevertheless vital for survival. The underlying mechanisms are only now starting to be explored. Improving our understanding of the regulation of protein production during bacterial growth arrest could have important implications for a wide range of challenges, including the identification of new targets for antibiotic development.
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Affiliation(s)
- Megan Bergkessel
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, UK.
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22
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Benarroch JM, Asally M. The Microbiologist’s Guide to Membrane Potential Dynamics. Trends Microbiol 2020; 28:304-314. [DOI: 10.1016/j.tim.2019.12.008] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 11/25/2019] [Accepted: 12/09/2019] [Indexed: 10/25/2022]
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23
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Garde R, Ibrahim B, Schuster S. Extending the minimal model of metabolic oscillations in Bacillus subtilis biofilms. Sci Rep 2020; 10:5579. [PMID: 32221356 PMCID: PMC7101430 DOI: 10.1038/s41598-020-62526-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 03/13/2020] [Indexed: 11/15/2022] Open
Abstract
Biofilms are composed of microorganisms attached to a solid surface or floating on top of a liquid surface. They pose challenges in the field of medicine but can also have useful applications in industry. Regulation of biofilm growth is complex and still largely elusive. Oscillations are thought to be advantageous for biofilms to cope with nutrient starvation and chemical attacks. Recently, a minimal mathematical model has been employed to describe the oscillations in Bacillus subtilis biofilms. In this paper, we investigate four different modifications to that minimal model in order to better understand the oscillations in biofilms. Our first modification is towards making a gradient of metabolites from the center of the biofilm to the periphery. We find that it does not improve the model and is therefore, unnecessary. We then use realistic Michaelis-Menten kinetics to replace the highly simple mass-action kinetics for one of the reactions. Further, we use reversible reactions to mimic the diffusion in biofilms. As the final modification, we check the combined effect of using Michaelis-Menten kinetics and reversible reactions on the model behavior. We find that these two modifications alone or in combination improve the description of the biological scenario.
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Affiliation(s)
- Ravindra Garde
- Department of Bioinformatics, Matthias Schleiden Institute, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, 07743, Jena, Germany
- Max Planck Institute for Chemical Ecology Hans-Knöll Str. 8, 07745, Jena, Germany
| | - Bashar Ibrahim
- Department of Bioinformatics, Matthias Schleiden Institute, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, 07743, Jena, Germany.
- Centre for Applied Mathematics and Bioinformatics, and Department of Mathematics and Natural Sciences Gulf University for Science and Technology, Hawally, 32093, Kuwait.
| | - Stefan Schuster
- Department of Bioinformatics, Matthias Schleiden Institute, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, 07743, Jena, Germany.
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24
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Wacquier B, Combettes L, Dupont G. Dual dynamics of mitochondrial permeability transition pore opening. Sci Rep 2020; 10:3924. [PMID: 32127570 PMCID: PMC7054270 DOI: 10.1038/s41598-020-60177-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 02/06/2020] [Indexed: 11/09/2022] Open
Abstract
Mitochondria play an essential role in bioenergetics and cellular Ca\documentclass[12pt]{minimal}
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\begin{document}$${}^{2+}$$\end{document}2+ handling. The mitochondrial permeability transition pore (mPTP) is a non-specific channel located in the inner mitochondrial membrane. Long-lasting openings of the pore allow the rapid passage of ions and large molecules, which can result in cell death. The mPTP also exhibits transient, low conductance openings that contribute to Ca\documentclass[12pt]{minimal}
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\begin{document}$${}^{2+}$$\end{document}2+ homeostasis. Although many regulators of the pore have been identified, none of them uniquely governs the passage between the two operating modes, which thus probably relies on a still unidentified network of interactions. By developing a core computational model for mPTP opening under the control of mitochondrial voltage and Ca\documentclass[12pt]{minimal}
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\begin{document}$${}^{2+}$$\end{document}2+, we uncovered the existence of a positive feedback loop leading to bistability. The characteristics of the two stable steady-states correspond to those of the two opening states. When inserted in a full model of Ca\documentclass[12pt]{minimal}
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\begin{document}$${}^{2+}$$\end{document}2+ handling by mitochondria, our description of the pore reproduces observations in mitochondrial suspensions. Moreover, the model predicted the occurrence of hysteresis in the switching between the two modes, upon addition and removal of free Ca\documentclass[12pt]{minimal}
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\begin{document}$${}^{2+}$$\end{document}2+ in the extra-mitochondrial medium. Stochastic simulations then confirmed that the pore can undergo transient openings resembling those observed in intact cells.
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Affiliation(s)
- Benjamin Wacquier
- Unit of Theoretical Chronobiology, Faculté des Sciences, Université Libre de Bruxelles (ULB) CP231, B1050, Brussels, Belgium
| | | | - Geneviève Dupont
- Unit of Theoretical Chronobiology, Faculté des Sciences, Université Libre de Bruxelles (ULB) CP231, B1050, Brussels, Belgium.
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25
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Garde R, Ibrahim B, Kovács ÁT, Schuster S. Differential equation-based minimal model describing metabolic oscillations in Bacillus subtilis biofilms. ROYAL SOCIETY OPEN SCIENCE 2020; 7:190810. [PMID: 32257302 PMCID: PMC7062081 DOI: 10.1098/rsos.190810] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 01/15/2020] [Indexed: 06/11/2023]
Abstract
Biofilms offer an excellent example of ecological interaction among bacteria. Temporal and spatial oscillations in biofilms are an emerging topic. In this paper, we describe the metabolic oscillations in Bacillus subtilis biofilms by applying the smallest theoretical chemical reaction system showing Hopf bifurcation proposed by Wilhelm and Heinrich in 1995. The system involves three differential equations and a single bilinear term. We specifically select parameters that are suitable for the biological scenario of biofilm oscillations. We perform computer simulations and a detailed analysis of the system including bifurcation analysis and quasi-steady-state approximation. We also discuss the feedback structure of the system and the correspondence of the simulations to biological observations. Our theoretical work suggests potential scenarios about the oscillatory behaviour of biofilms and also serves as an application of a previously described chemical oscillator to a biological system.
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Affiliation(s)
- Ravindra Garde
- Department of Bioinformatics, Matthias Schleiden Institute, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, 07743 Jena, Germany
- Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745 Jena, Germany
| | - Bashar Ibrahim
- Department of Bioinformatics, Matthias Schleiden Institute, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, 07743 Jena, Germany
- Centre for Applied Mathematics and Bioinformatics, Gulf University for Science and Technology, Hawally 32093, Kuwait
- Department of Mathematics and Natural Sciences, Gulf University for Science and Technology, Hawally 32093, Kuwait
| | - Ákos T. Kovács
- Bacterial Interactions and Evolution Group, DTU Bioengineering, Technical University of Denmark, Søltofts Plads Building 221, 2800 Kgs. Lyngby, Denmark
| | - Stefan Schuster
- Department of Bioinformatics, Matthias Schleiden Institute, Friedrich Schiller University Jena, Ernst-Abbe-Platz 2, 07743 Jena, Germany
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26
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Choudhary SK, Baskaran A, Sharma P. Reentrant Efficiency of Phototaxis in Chlamydomonas reinhardtii Cells. Biophys J 2019; 117:1508-1513. [PMID: 31586523 PMCID: PMC6817637 DOI: 10.1016/j.bpj.2019.09.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 08/08/2019] [Accepted: 09/09/2019] [Indexed: 11/16/2022] Open
Abstract
Phototaxis is one of the most fundamental stimulus-response behaviors in biology wherein motile microorganisms sense light gradients to swim toward the light source. Apart from single-cell survival and growth, it plays a major role at the global scale of aquatic ecosystems and bioreactors. We study phototaxis of single-celled algae Chlamydomonas reinhardtii as a function of cell number density and light stimulus using high spatiotemporal video microscopy. Surprisingly, the phototactic efficiency has a minimum at a well-defined number density, for a given light gradient, above which the phototaxis behavior of a collection of cells can even exceed the performance obtainable from single isolated cells. We show that the origin of enhancement of performance above the critical concentration lies in the slowing down of the cells, which enables them to sense light more effectively. We also show that this steady-state phenomenology is well captured by modeling the phototactic response as a density-dependent torque acting on an active Brownian particle.
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Affiliation(s)
| | - Aparna Baskaran
- Martin A. Fisher School of Physics, Brandeis University, Waltham, Massachusetts
| | - Prerna Sharma
- Department of Physics, Indian Institute of Science, Bengaluru, Karnataka, India.
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27
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Martinez-Corral R, Liu J, Prindle A, Süel GM, Garcia-Ojalvo J. Metabolic basis of brain-like electrical signalling in bacterial communities. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180382. [PMID: 31006362 PMCID: PMC6553584 DOI: 10.1098/rstb.2018.0382] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2019] [Indexed: 12/20/2022] Open
Abstract
Information processing in the mammalian brain relies on a careful regulation of the membrane potential dynamics of its constituent neurons, which propagates across the neuronal tissue via electrical signalling. We recently reported the existence of electrical signalling in a much simpler organism, the bacterium Bacillus subtilis. In dense bacterial communities known as biofilms, nutrient-deprived B. subtilis cells in the interior of the colony use electrical communication to transmit stress signals to the periphery, which interfere with the growth of peripheral cells and reduce nutrient consumption, thereby relieving stress from the interior. Here, we explicitly address the interplay between metabolism and electrophysiology in bacterial biofilms, by introducing a spatially extended mathematical model that combines the metabolic and electrical components of the phenomenon in a discretized reaction-diffusion scheme. The model is experimentally validated by environmental and genetic perturbations, and confirms that metabolic stress is transmitted through the bacterial population via a potassium wave. Interestingly, this behaviour is reminiscent of cortical spreading depression in the brain, characterized by a wave of electrical activity mediated by potassium diffusion that has been linked to various neurological disorders, calling for future studies on the evolutionary link between the two phenomena. This article is part of the theme issue 'Liquid brains, solid brains: How distributed cognitive architectures process information'.
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Affiliation(s)
- Rosa Martinez-Corral
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona Biomedical Research Park, Barcelona 08003, Spain
| | - Jintao Liu
- Center for Infectious Diseases Research and Tsinghua-Peking Center for Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, People's Republic of China
| | - Arthur Prindle
- Department of Biochemistry and Molecular Genetics, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Center for Synthetic Biology, Northwestern University, Evanston, IL 60208, USA
| | - Gürol M. Süel
- Division of Biological Sciences, San Diego Center for Systems Biology and Center for Microbiome Innovation, University of California San Diego, La Jolla, CA 92093, USA
| | - Jordi Garcia-Ojalvo
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona Biomedical Research Park, Barcelona 08003, Spain
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28
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Banerjee J, Sasmal SK, Layek RK. Supercritical and subcritical Hopf-bifurcations in a two-delayed prey–predator system with density-dependent mortality of predator and strong Allee effect in prey. Biosystems 2019; 180:19-37. [DOI: 10.1016/j.biosystems.2019.02.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Revised: 12/31/2018] [Accepted: 02/26/2019] [Indexed: 11/26/2022]
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29
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Emergence of active nematics in chaining bacterial biofilms. Nat Commun 2019; 10:2285. [PMID: 31123251 PMCID: PMC6533293 DOI: 10.1038/s41467-019-10311-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Accepted: 05/01/2019] [Indexed: 01/06/2023] Open
Abstract
Growing tissue and bacterial colonies are active matter systems where cell divisions and cellular motion generate active stress. Although they operate in the non-equilibrium regime, these biological systems can form large-scale ordered structures. How mechanical instabilities drive the dynamics of active matter systems and form ordered structures are not well understood. Here, we use chaining Bacillus subtilis, also known as a biofilm, to study the relation between mechanical instabilities and nematic ordering. We find that bacterial biofilms have intrinsic length scales above which a series of mechanical instabilities occur. Localized stress and friction drive buckling and edge instabilities which further create nematically aligned structures and topological defects. We also observe that topological defects control stress distribution and initiate the formation of sporulation sites by creating three-dimensional structures. In this study we propose an alternative active matter platform to study the essential roles of mechanics in growing biological tissue.
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30
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Lee DYD, Galera-Laporta L, Bialecka-Fornal M, Moon EC, Shen Z, Briggs SP, Garcia-Ojalvo J, Süel GM. Magnesium Flux Modulates Ribosomes to Increase Bacterial Survival. Cell 2019; 177:352-360.e13. [PMID: 30853217 PMCID: PMC6814349 DOI: 10.1016/j.cell.2019.01.042] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2018] [Revised: 12/03/2018] [Accepted: 01/24/2019] [Indexed: 01/30/2023]
Abstract
Bacteria exhibit cell-to-cell variability in their resilience to stress, for example, following antibiotic exposure. Higher resilience is typically ascribed to "dormant" non-growing cellular states. Here, by measuring membrane potential dynamics of Bacillus subtilis cells, we show that actively growing bacteria can cope with ribosome-targeting antibiotics through an alternative mechanism based on ion flux modulation. Specifically, we observed two types of cellular behavior: growth-defective cells exhibited a mathematically predicted transient increase in membrane potential (hyperpolarization), followed by cell death, whereas growing cells lacked hyperpolarization events and showed elevated survival. Using structural perturbations of the ribosome and proteomic analysis, we uncovered that stress resilience arises from magnesium influx, which prevents hyperpolarization. Thus, ion flux modulation provides a distinct mechanism to cope with ribosomal stress. These results suggest new approaches to increase the effectiveness of ribosome-targeting antibiotics and reveal an intriguing connection between ribosomes and the membrane potential, two fundamental properties of cells.
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Affiliation(s)
- Dong-Yeon D Lee
- Molecular Biology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Leticia Galera-Laporta
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Maja Bialecka-Fornal
- Molecular Biology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Eun Chae Moon
- Molecular Biology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Zhouxin Shen
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, 92093-0380, USA
| | - Steven P Briggs
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, 92093-0380, USA
| | - Jordi Garcia-Ojalvo
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, 08003 Barcelona, Spain
| | - Gürol M Süel
- Molecular Biology Section, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA; San Diego Center for Systems Biology, University of California, San Diego, La Jolla, CA 92093-0380, USA; Center for Microbiome Innovation, University of California, San Diego, La Jolla, CA 92093-0380, USA.
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