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Zhang H, Li L, Wang S, Sun X, Luo C, Hou B. Construction of dentin-on-a-chip based on microfluidic technology and tissue engineering. J Dent 2024; 146:105028. [PMID: 38719135 DOI: 10.1016/j.jdent.2024.105028] [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: 02/05/2024] [Revised: 04/23/2024] [Accepted: 04/25/2024] [Indexed: 05/19/2024] Open
Abstract
AIM Three-dimensional (3D) cell culture systems perform better in resembling tissue or organism structures compared with traditional 2D models. Organs-on-chips (OoCs) are becoming more efficient 3D models. This study aimed to create a novel simplified dentin-on-a-chip using microfluidic chip technology and tissue engineering for screening dental materials. METHODOLOGY A microfluidic device with three channels was designed for creating 3D dental tissue constructs using stem cells from the apical papilla (SCAP) and gelatin methacrylate (GelMA). The study investigated the effect of varying cell densities and GelMA concentrations on the layer features formed within the microfluidic chip. Cell viability and distribution were evaluated through live/dead staining and nuclei/F-actin staining. The osteo/odontogenic potential was assessed through ALP staining and Alizarin red staining. The impact of GelMA concentrations (5 %, 10 %) on the osteo/odontogenic differentiation trajectory of SCAP was also studied. RESULTS The 3D tissue constructs maintained high viability and favorable spreading within the microfluidic chip for 3-7 days. A cell seeding density of 2 × 104 cells/μL was found to be the most optimal choice, ensuring favorable cell proliferation and even distribution. GelMA concentrations of 5 % and 10 % proved to be most effective for promoting cell growth and uniform distribution. Within the 5 % GelMA group, SCAP demonstrated higher osteo/odontogenic differentiation than that in the 10 % GelMA group. CONCLUSION In 3D culture, GelMA concentration was found to regulate the osteo/odontogenic differentiation of SCAP. The study recommends a seeding density of 2 × 104 cells/μL of SCAP within 5 % GelMA for constructing simplified dentin-on-a-chip. CLINICAL SIGNIFICANCE This study built up the 3D culture protocol, and induced odontogenic differentiation of SCAP, thus forming the simplified dentin-on-a-chip and paving the way to be used as a well-defined biological model for regenerative endodontics. It may serve as a potential testing platform for cell differentiation.
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Affiliation(s)
- Hexuan Zhang
- Center for Microscope Enhanced Dentistry, School of Stomatology, Capital Medical University, Beijing 100162, PR China; Department of Endodontics and Operative Dentistry, School of Stomatology, Capital Medical University, Beijing 100050, PR China
| | - Lingjun Li
- Wenzhou Institute University of Chinese Academy of Sciences, Wenzhou 325001, PR China.
| | - Shujing Wang
- Wenzhou Institute University of Chinese Academy of Sciences, Wenzhou 325001, PR China
| | - Xiaoqiang Sun
- Department of Endodontics and Operative Dentistry, School of Stomatology, Capital Medical University, Beijing 100050, PR China
| | - Chunxiong Luo
- Wenzhou Institute University of Chinese Academy of Sciences, Wenzhou 325001, PR China; The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, PR China.
| | - Benxiang Hou
- Center for Microscope Enhanced Dentistry, School of Stomatology, Capital Medical University, Beijing 100162, PR China.
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2
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Ugolini GS, Wang M, Secchi E, Pioli R, Ackermann M, Stocker R. Microfluidic approaches in microbial ecology. LAB ON A CHIP 2024; 24:1394-1418. [PMID: 38344937 PMCID: PMC10898419 DOI: 10.1039/d3lc00784g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
Microbial life is at the heart of many diverse environments and regulates most natural processes, from the functioning of animal organs to the cycling of global carbon. Yet, the study of microbial ecology is often limited by challenges in visualizing microbial processes and replicating the environmental conditions under which they unfold. Microfluidics operates at the characteristic scale at which microorganisms live and perform their functions, thus allowing for the observation and quantification of behaviors such as growth, motility, and responses to external cues, often with greater detail than classical techniques. By enabling a high degree of control in space and time of environmental conditions such as nutrient gradients, pH levels, and fluid flow patterns, microfluidics further provides the opportunity to study microbial processes in conditions that mimic the natural settings harboring microbial life. In this review, we describe how recent applications of microfluidic systems to microbial ecology have enriched our understanding of microbial life and microbial communities. We highlight discoveries enabled by microfluidic approaches ranging from single-cell behaviors to the functioning of multi-cellular communities, and we indicate potential future opportunities to use microfluidics to further advance our understanding of microbial processes and their implications.
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Affiliation(s)
- Giovanni Stefano Ugolini
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zurich, Laura-Hezner-Weg 7, 8093 Zurich, Switzerland.
| | - Miaoxiao Wang
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
- Department of Environmental Microbiology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Duebendorf, Switzerland
| | - Eleonora Secchi
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zurich, Laura-Hezner-Weg 7, 8093 Zurich, Switzerland.
| | - Roberto Pioli
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zurich, Laura-Hezner-Weg 7, 8093 Zurich, Switzerland.
| | - Martin Ackermann
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
- Department of Environmental Microbiology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, Duebendorf, Switzerland
- Laboratory of Microbial Systems Ecology, School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédéral de Lausanne (EPFL), Lausanne, Switzerland
| | - Roman Stocker
- Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zurich, Laura-Hezner-Weg 7, 8093 Zurich, Switzerland.
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3
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Shoup D, Ursell T. Bacterial bioconvection confers context-dependent growth benefits and is robust under varying metabolic and genetic conditions. J Bacteriol 2023; 205:e0023223. [PMID: 37787517 PMCID: PMC10601612 DOI: 10.1128/jb.00232-23] [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: 07/26/2023] [Accepted: 08/17/2023] [Indexed: 10/04/2023] Open
Abstract
Microbes often respond to environmental cues by adopting collective behaviors-like biofilms or swarming-that benefit the population. During "bioconvection," microbes gather in dense groups and plume downward through fluid environments, driving flow and mixing on the scale of millions of cells. Though bioconvection was observed a century ago, the effects of differing physical and chemical inputs and its potential selective advantages for different species of microbes remain largely unexplored. In Bacillus subtilis, vertical oxygen gradients that originate from air-liquid interfaces create cell-density inversions that drive bioconvection. Here, we develop Escherichia coli as a complementary model for the study of bioconvection. In the context of a still fluid, we found that motile and chemotactic genotypes of both E. coli and B. subtilis bioconvect and show increased growth compared to immotile or non-chemotactic genotypes, whereas in a well-mixed fluid, there is no growth advantage to motility or chemotaxis. We found that fluid depth, cell concentration, and carbon availability affect the emergence and timing of bioconvective patterns. Also, whereas B. subtilis requires oxygen gradients to bioconvect, E. coli deficient in aerotaxis (Δaer) or energy-taxis (Δtsr) still bioconvects, as do cultures that lack an air-liquid interface. Thus, in two distantly related microbes, bioconvection may confer context-dependent growth benefits, and E. coli bioconvection is robustly elicited by multiple types of chemotaxis. These results greatly expand the set of physical and metabolic conditions in which this striking collective behavior can be expected and demonstrate its potential to be a generic force for behavioral selection across ecological contexts. IMPORTANCE Individual microorganisms frequently move in response to gradients in their fluid environment, with corresponding metabolic benefits. At a population level, such movements can create density variations in a fluid that couple to gravity and drive large-scale convection and mixing called bioconvection. In this work, we provide evidence that this collective behavior confers a selective benefit on two distantly related species of bacteria. We develop new methods for quantifying this behavior and show that bioconvection in Escherichia coli is surprisingly robust to changes in cell concentration, fluid depth, interface conditions, metabolic sensing, and carbon availability. These results greatly expand the set of conditions known to elicit this collective behavior and indicate its potential to be a selective pressure across ecological contexts.
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Affiliation(s)
- Daniel Shoup
- Department of Physics, University of Oregon, Eugene, Oregon, USA
- Rocky Mountain National Laboratories (NIH), Hamilton, Montana, USA
| | - Tristan Ursell
- Department of Physics, University of Oregon, Eugene, Oregon, USA
- Material Science Institute, Eugene, Oregon, USA
- Institute of Molecular Biology, University of Oregon, Eugene, Oregon, USA
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4
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Matilla MA, Gavira JA, Krell T. Accessing nutrients as the primary benefit arising from chemotaxis. Curr Opin Microbiol 2023; 75:102358. [PMID: 37459734 DOI: 10.1016/j.mib.2023.102358] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 06/19/2023] [Accepted: 06/19/2023] [Indexed: 09/17/2023]
Abstract
About half of the known bacterial species perform chemotaxis that gains them access to sites that are optimal for growth and survival. The motility apparatus and chemotaxis signaling pathway impose a large energetic and metabolic burden on the cell. There is almost no limit to the type of chemoeffectors that are recognized by bacterial chemoreceptors. For example, they include hormones, neurotransmitters, quorum-sensing molecules, and inorganic ions. However, the vast majority of chemoeffectors appear to be of metabolic value. We review here the experimental evidence indicating that accessing nutrients is the main selective force that led to the evolution of chemotaxis.
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Affiliation(s)
- Miguel A Matilla
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - José A Gavira
- Laboratory of Crystallographic Studies, IACT (CSIC-UGR), Armilla, Spain
| | - Tino Krell
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain.
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5
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The regulatory mechanism of the yeast osmoresponse under different glucose concentrations. iScience 2022; 26:105809. [PMID: 36636353 PMCID: PMC9830198 DOI: 10.1016/j.isci.2022.105809] [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: 02/18/2022] [Revised: 07/20/2022] [Accepted: 12/09/2022] [Indexed: 12/14/2022] Open
Abstract
Cells constantly respond to environmental changes by modulating gene expression programs. These responses may demand substantial costs and, thus, affect cell growth. Understanding the regulation of these processes represents a key question in biology and biotechnology. Here, we studied the responses to osmotic stress in glucose-limited environments. By analyzing seventeen osmotic stress-induced genes and stress-activated protein kinase Hog1, we found that cells exhibited stronger osmotic gene expression response and larger integral of Hog1 nuclear localization during adaptation to osmotic stress under glucose-limited conditions than under glucose-rich conditions. We proposed and verified that in glucose-limited environment, glycolysis intermediates (representing "reserve flux") were limited, which required cells to express more glycerol-production enzymes for stress adaptation. Consequently, the regulatory mechanism of osmoresponse was derived in the presence and absence of such reserve flux. Further experiments suggested that this reserve flux-dependent stress-defense strategy may be a general principle under nutrient-limited environments.
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6
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Zhao X, Ford RM. Escherichia coli chemotaxis to competing stimuli in a microfluidic device with a constant gradient. Biotechnol Bioeng 2022; 119:2564-2573. [PMID: 35716141 DOI: 10.1002/bit.28161] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 05/20/2022] [Accepted: 06/08/2022] [Indexed: 11/07/2022]
Abstract
In natural systems bacteria are exposed to many chemical stimulants; some attract chemotactic bacteria as they promote survival, while others repel bacteria because they inhibit survival. When faced with a mixture of chemoeffectors, it is not obvious which direction the population will migrate. Predicting this direction requires an understanding of how bacteria process information about their surroundings. We used a multiscale mathematical model to relate molecular level details of their two-component signaling system to the probability that an individual cell changes its swimming direction to the chemotactic velocity of a bacterial population. We used a microfluidic device designed to maintain a constant chemical gradient to compare model predictions to experimental observations. We obtained parameter values for the multiscale model of Escherichia coli chemotaxis to individual stimuli, α-methylaspartate and nickel ion, separately. Then without any additional fitting parameters, we predicted bacteria response to chemoeffector mixtures. Migration of E. coli toward α-methylaspartate was modulated by adding increasing concentrations of nickel ion. Thus, the migration direction was controlled by the relative concentrations of competing chemoeffectors in a predictable way. This study demonstrated the utility of a multiscale model to predict the migration direction of bacteria in the presence of competing chemoeffectors. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Xueying Zhao
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia
| | - Roseanne M Ford
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia
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7
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Livne N, Vaknin A. Collective responses of bacteria to a local source of conflicting effectors. Sci Rep 2022; 12:4928. [PMID: 35322063 PMCID: PMC8943191 DOI: 10.1038/s41598-022-08762-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 03/09/2022] [Indexed: 12/18/2022] Open
Abstract
To cope in complex environments, motile bacteria have developed a chemosensory system that integrates multiple cues and directs their motion toward regions that it deems favorable. However, we have a limited understanding of the principles that govern bacterial behavior in complex stimuli fields. Here, we followed the spatial redistribution of E. coli cells in perplexing environments created by a local source of both beneficial (nutrients) and hazardous (low pH or indole) effectors. We identified two fundamentally distinct collective responses: a ‘trade-off’ response, in which bacteria sharply accumulated at a distance from the source that reflected a trade-off between the propagating effectors, and a ‘bet-hedging’ response, in which part of the bacteria accumulated away from the source, avoiding the hazardous effector, while the other part evaded the repulsive force and accumulated at the source. In addition, we demonstrate that cells lacking the Tsr sensor swim toward both repellents and, surprisingly, even toward pH values well below 7. Using a numerical analysis, we could correlate the collective bacterial responses with fundamentally distinct chemotactic force fields created along the channel by the propagation of the effectors and their unique perception by the chemosensory system.
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Affiliation(s)
- Nir Livne
- The Racah Institute of Physics, The Hebrew University, Edmond J. Safra Campus, 91904, Jerusalem, Israel
| | - Ady Vaknin
- The Racah Institute of Physics, The Hebrew University, Edmond J. Safra Campus, 91904, Jerusalem, Israel.
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8
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Courcoubetis G, Gangan MS, Lim S, Guo X, Haas S, Boedicker JQ. Formation, collective motion, and merging of macroscopic bacterial aggregates. PLoS Comput Biol 2022; 18:e1009153. [PMID: 34982765 PMCID: PMC8759663 DOI: 10.1371/journal.pcbi.1009153] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 01/14/2022] [Accepted: 12/07/2021] [Indexed: 11/18/2022] Open
Abstract
Chemotactic bacteria form emergent spatial patterns of variable cell density within cultures that are initially spatially uniform. These patterns are the result of chemical gradients that are created from the directed movement and metabolic activity of billions of cells. A recent study on pattern formation in wild bacterial isolates has revealed unique collective behaviors of the bacteria Enterobacter cloacae. As in other bacterial species, Enterobacter cloacae form macroscopic aggregates. Once formed, these bacterial clusters can migrate several millimeters, sometimes resulting in the merging of two or more clusters. To better understand these phenomena, we examine the formation and dynamics of thousands of bacterial clusters that form within a 22 cm square culture dish filled with soft agar over two days. At the macroscale, the aggregates display spatial order at short length scales, and the migration of cell clusters is superdiffusive, with a merging acceleration that is correlated with aggregate size. At the microscale, aggregates are composed of immotile cells surrounded by low density regions of motile cells. The collective movement of the aggregates is the result of an asymmetric flux of bacteria at the boundary. An agent-based model is developed to examine how these phenomena are the result of both chemotactic movement and a change in motility at high cell density. These results identify and characterize a new mechanism for collective bacterial motility driven by a transient, density-dependent change in motility. Bacteria growing and swimming in soft agar often aggregate to form elaborate spatial patterns. Here we examine the patterns formed by the bacteria Enterobacter cloacae. An unusual behavior of these bacteria is the collective movement of cells after the initial aggregation into a tiny spot. Despite the majority of the cells within an aggregate being immotile at any point in the time, the flux of cells entering and leaving the aggregate, as motility is lost and regained in individual cells, led to a net, collective movement of the aggregate. These spots sometimes run into each other and combine. By looking at the cells within these spots under a microscope, we find that cells within each spot stop swimming. The process of switching back and forth between swimming and not swimming causes the movement and fusion of the spots. A numerical simulation shows that the migration and merging of these spots can be expected if the cells swim towards regions of space with high concentrations of attractant molecules and stop swimming in locations crowded with many cells. This work identifies a novel process through which populations of bacteria cooperate and control the movement of large groups of cells.
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Affiliation(s)
- George Courcoubetis
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California, United States of America
| | - Manasi S. Gangan
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California, United States of America
| | - Sean Lim
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California, United States of America
| | - Xiaokan Guo
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California, United States of America
| | - Stephan Haas
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California, United States of America
| | - James Q. Boedicker
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California, United States of America
- Department of Biological Sciences, University of Southern California, Los Angeles, California, United States of America
- * E-mail:
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9
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Colin R, Ni B, Laganenka L, Sourjik V. Multiple functions of flagellar motility and chemotaxis in bacterial physiology. FEMS Microbiol Rev 2021; 45:fuab038. [PMID: 34227665 PMCID: PMC8632791 DOI: 10.1093/femsre/fuab038] [Citation(s) in RCA: 113] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 07/02/2021] [Indexed: 12/13/2022] Open
Abstract
Most swimming bacteria are capable of following gradients of nutrients, signaling molecules and other environmental factors that affect bacterial physiology. This tactic behavior became one of the most-studied model systems for signal transduction and quantitative biology, and underlying molecular mechanisms are well characterized in Escherichia coli and several other model bacteria. In this review, we focus primarily on less understood aspect of bacterial chemotaxis, namely its physiological relevance for individual bacterial cells and for bacterial populations. As evident from multiple recent studies, even for the same bacterial species flagellar motility and chemotaxis might serve multiple roles, depending on the physiological and environmental conditions. Among these, finding sources of nutrients and more generally locating niches that are optimal for growth appear to be one of the major functions of bacterial chemotaxis, which could explain many chemoeffector preferences as well as flagellar gene regulation. Chemotaxis might also generally enhance efficiency of environmental colonization by motile bacteria, which involves intricate interplay between individual and collective behaviors and trade-offs between growth and motility. Finally, motility and chemotaxis play multiple roles in collective behaviors of bacteria including swarming, biofilm formation and autoaggregation, as well as in their interactions with animal and plant hosts.
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Affiliation(s)
- Remy Colin
- Max Planck Institute for Terrestrial Microbiology & Center for Synthetic Microbiology (SYNMIKRO), Karl-von-Frisch Strasse 16, Marburg D-35043, Germany
| | - Bin Ni
- Max Planck Institute for Terrestrial Microbiology & Center for Synthetic Microbiology (SYNMIKRO), Karl-von-Frisch Strasse 16, Marburg D-35043, Germany
- College of Resources and Environmental Science, National Academy of Agriculture Green Development, China Agricultural University, Yuanmingyuan Xilu No. 2, Beijing 100193, China
| | - Leanid Laganenka
- Institute of Microbiology, D-BIOL, ETH Zürich, Vladimir-Prelog-Weg 4, Zürich 8093, Switzerland
| | - Victor Sourjik
- Max Planck Institute for Terrestrial Microbiology & Center for Synthetic Microbiology (SYNMIKRO), Karl-von-Frisch Strasse 16, Marburg D-35043, Germany
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10
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Chen K, Rong N, Wang S, Luo C. A novel two-layer-integrated microfluidic device for high-throughput yeast proteomic dynamics analysis at the single-cell level. Integr Biol (Camb) 2021; 12:241-249. [PMID: 32995887 DOI: 10.1093/intbio/zyaa018] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 08/12/2020] [Accepted: 08/31/2020] [Indexed: 11/14/2022]
Abstract
Current microfluidic methods for studying multicell strains (e.g., m-types) with multienvironments (e.g., n-types) require large numbers of inlets/outlets (m*n), a complicated procedure or expensive machinery. Here, we developed a novel two-layer-integrated method to combine different PDMS microchannel layers with different functions into one chip by a PDMS through-hole array, which improved the design of a PDMS-based microfluidic system. Using this method, we succeeded in converting 2 × m × n inlets/outlets into m + n inlets/outlets and reduced the time cost of loading processing (from m × n to m) of the device for studying multicell strains (e.g., m-types) in varied multitemporal environments (i.e., n-types). Using this device, the dynamic behavior of the cell-stress-response proteins was studied when the glucose concentration decreased from 2% to a series of lower concentrations. Our device could also be widely used in high-throughput studies of various stress responses, and the new concept of a multilayer-integrated fabrication method could greatly improve the design of PDMS-based microfluidic systems.
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Affiliation(s)
- Kaiyue Chen
- The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, China.,Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, China
| | - Nan Rong
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, China
| | - Shujing Wang
- The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, China.,Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, China
| | - Chunxiong Luo
- The State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, School of Physics, Peking University, China.,Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, China
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11
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Middlebrooks SA, Zhao X, Ford RM, Cummings PT. A mathematical model for Escherichia coli chemotaxis to competing stimuli. Biotechnol Bioeng 2021; 118:4678-4686. [PMID: 34463958 DOI: 10.1002/bit.27930] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 08/19/2021] [Accepted: 08/21/2021] [Indexed: 11/12/2022]
Abstract
Chemotactic bacteria sense and respond to temporal and spatial gradients of chemical cues in their surroundings. This phenomenon plays a critical role in many microbial processes such as groundwater bioremediation, microbially enhanced oil recovery, nitrogen fixation in legumes, and pathogenesis of the disease. Chemical heterogeneity in these natural systems may produce numerous competing signals from various directions. Predicting the migration behavior of bacterial populations under such conditions is necessary for designing effective treatment schemes. In this study, experimental studies and mathematical models are reported for the chemotactic response of Escherichia coli to a combination of attractant (α-methylaspartate) and repellent (NiCl2 ), which bind to the same transmembrane receptor complex. The model describes the binding of chemoeffectors and phosphorylation of the kinase in the signal transduction mechanism. Chemotactic parameters of E. coli (signaling efficiency σ , stimuli sensitivity coefficient γ , and repellent sensitivity coefficient κ ) were determined by fitting the model with experimental results for individual stimuli. Interestingly, our model naturally identifies NiCl2 as a repellent for κ > 1 . The model is capable of describing quantitatively the response to the individual attractant and repellent, and correctly predicts the change in direction of bacterial population migration for competing stimuli with a twofold increase in repellent concentration.
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Affiliation(s)
- Scott A Middlebrooks
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia, USA
| | - Xueying Zhao
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia, USA
| | - Roseanne M Ford
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia, USA
| | - Peter T Cummings
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia, USA.,Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee, USA
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12
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How an unusual chemosensory system forms arrays on the bacterial nucleoid. Biochem Soc Trans 2021; 48:347-356. [PMID: 32129822 DOI: 10.1042/bst20180450] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 02/04/2020] [Accepted: 02/05/2020] [Indexed: 11/17/2022]
Abstract
Chemosensory systems are signaling pathways elegantly organized in hexagonal arrays that confer unique functional features to these systems such as signal amplification. Chemosensory arrays adopt different subcellular localizations from one bacterial species to another, yet keeping their supramolecular organization unmodified. In the gliding bacterium Myxococcus xanthus, a cytoplasmic chemosensory system, Frz, forms multiple clusters on the nucleoid through the direct binding of the FrzCD receptor to DNA. A small CheW-like protein, FrzB, might be responsible for the formation of multiple (instead of just one) Frz arrays. In this review, we summarize what is known on Frz array formation on the bacterial chromosome and discuss hypotheses on how FrzB might contribute to the nucleation of multiple clusters. Finally, we will propose some possible biological explanations for this type of localization pattern.
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13
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Li Z, Lou Y, Ding J, Liu BF, Xie GJ, Ren NQ, Xing D. Metabolic regulation of ethanol-type fermentation of anaerobic acidogenesis at different pH based on transcriptome analysis of Ethanoligenens harbinense. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:101. [PMID: 32518589 PMCID: PMC7268672 DOI: 10.1186/s13068-020-01740-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 05/25/2020] [Indexed: 05/04/2023]
Abstract
BACKGROUND Ethanol-type fermentation, one of the fermentation types in mixed cultures of acidogenesis with obvious advantages such as low pH tolerance and high efficiency of H2 production, has attracted widespread attentions. pH level greatly influences the establishment of the fermentation of carbohydrate acidogenesis by shaping community assembly and the metabolic activity of keystone populations. To explore the adaptation mechanisms of ethanol-type fermentation to low pH, we report the effects of initial pH on the physiological metabolism and transcriptomes of Ethanoligenens harbinense-a representative species of ethanol-type fermentation. RESULTS Different initial pH levels significantly changed the cell growth and fermentation products of E. harbinense. Using transcriptomic analysis, we identified and functionally categorized 1753 differentially expressed genes (DEGs). By mining information on metabolic pathways, we probed the transcriptional regulation of ethanol-H2 metabolism relating to pH responses. Multiple pathways of E. harbinense were co-regulated by changing gene expression patterns. Low initial pH down-regulated the expression of cell growth- and acidogenesis-related genes but did not affect the expression of H2 evolution-related hydrogenase and ferredoxin genes. High pH down-regulated the expression of H2 evolution- and acidogenesis-related genes. Multiple resistance mechanisms, including chemotaxis, the phosphotransferase system (PTS), and the antioxidant system, were regulated at the transcriptional level under pH stress. CONCLUSIONS Ethanoligenens adapted to low pH by regulating the gene expression networks of cell growth, basic metabolism, chemotaxis and resistance but not H2 evolution-related genes. Regulation based on pH shifts can represent an important approach to establish and enhance ethanol-type fermentation. The complete gene expression network of ethanol fermentative bacteria for pH response provides valuable insights into the acidogenic fermentation, and offers an effective regulation strategy for the sustainable energy recovery from wastewater and solid waste.
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Affiliation(s)
- Zhen Li
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, P.O. Box 2614, Harbin, Heilongjiang 150090 China
| | - Yu Lou
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, P.O. Box 2614, Harbin, Heilongjiang 150090 China
| | - Jie Ding
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, P.O. Box 2614, Harbin, Heilongjiang 150090 China
| | - Bing-Feng Liu
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, P.O. Box 2614, Harbin, Heilongjiang 150090 China
| | - Guo-Jun Xie
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, P.O. Box 2614, Harbin, Heilongjiang 150090 China
| | - Nan-Qi Ren
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, P.O. Box 2614, Harbin, Heilongjiang 150090 China
| | - Defeng Xing
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, 73 Huanghe Road, Nangang District, P.O. Box 2614, Harbin, Heilongjiang 150090 China
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