1
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Livne N, Koler M, Vaknin A. Collective condensation and auto-aggregation of Escherichia coli in uniform acidic environments. Commun Biol 2024; 7:1028. [PMID: 39169072 PMCID: PMC11339372 DOI: 10.1038/s42003-024-06698-1] [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: 04/10/2024] [Accepted: 08/07/2024] [Indexed: 08/23/2024] Open
Abstract
Chemotaxis-the movement of cells along chemical gradients-leads to collective behaviors when cells coordinate their movements. Here, using Escherichia coli as a model, we demonstrate a distinct type of bacterial collective response in acidic environments containing organic acids. Bacterial populations immersed in such environments collectively condensed into millimeter-sized focal points. Furthermore, this bacterial condensation fostered the formation of small, tightly packed cell aggregates, resembling non-surface-attached biofilms. These cell aggregates were physically displaced by the free-swimming condensing cells, leading to the segregation of the two cell populations. Bacterial condensation relied on feedback between the tendency of these bacteria to neutralize the pH and their chemotactic repulsion from low pH. Sustained cell condensation occurred when the bacteria occupied only part of the acidic environment, either dynamically or due to physical constraints. Such condensed bacterial populations can mitigate acid stress more efficiently, a principle that may be applicable to other stress conditions.
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Affiliation(s)
- Nir Livne
- The Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
| | - Moriah Koler
- The Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
| | - Ady Vaknin
- The Racah Institute of Physics, The Hebrew University, Jerusalem, Israel.
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2
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Moore JP, Kamino K, Kottou R, Shimizu TS, Emonet T. Signal integration and adaptive sensory diversity tuning in Escherichia coli chemotaxis. Cell Syst 2024; 15:628-638.e8. [PMID: 38981486 PMCID: PMC11307269 DOI: 10.1016/j.cels.2024.06.003] [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: 11/11/2022] [Revised: 04/01/2024] [Accepted: 06/17/2024] [Indexed: 07/11/2024]
Abstract
In uncertain environments, phenotypic diversity can be advantageous for survival. However, as the environmental uncertainty decreases, the relative advantage of having diverse phenotypes decreases. Here, we show how populations of E. coli integrate multiple chemical signals to adjust sensory diversity in response to changes in the prevalence of each ligand in the environment. Measuring kinase activity in single cells, we quantified the sensitivity distribution to various chemoattractants in different mixtures of background stimuli. We found that when ligands bind uncompetitively, the population tunes sensory diversity to each signal independently, decreasing diversity when the signal's ambient concentration increases. However, among competitive ligands, the population can only decrease sensory diversity one ligand at a time. Mathematical modeling suggests that sensory diversity tuning benefits E. coli populations by modulating how many cells are committed to tracking each signal proportionally as their prevalence changes.
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Affiliation(s)
- Jeremy Philippe Moore
- Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06511, USA; Quantitative Biology Institute, Yale University, New Haven, CT 06511, USA
| | - Keita Kamino
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Rafaela Kottou
- Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06511, USA; Quantitative Biology Institute, Yale University, New Haven, CT 06511, USA
| | | | - Thierry Emonet
- Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06511, USA; Quantitative Biology Institute, Yale University, New Haven, CT 06511, USA; Department of Physics, Yale University, New Haven, CT 06511, USA.
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3
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Moore JP, Kamino K, Kottou R, Shimizu TS, Emonet T. Signal Integration and Adaptive Sensory Diversity Tuning in Escherichia coli Chemotaxis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.02.08.527720. [PMID: 36798398 PMCID: PMC9934624 DOI: 10.1101/2023.02.08.527720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
In uncertain environments, phenotypic diversity can be advantageous for survival. However, as the environmental uncertainty decreases, the relative advantage of having diverse phenotypes decreases. Here, we show how populations of E. coli integrate multiple chemical signals to adjust sensory diversity in response to changes in the prevalence of each ligand in the environment. Measuring kinase activity in single cells, we quantified the sensitivity distribution to various chemoattractants in different mixtures of background stimuli. We found that when ligands bind uncompetitively, the population tunes sensory diversity to each signal independently, decreasing diversity when the signal ambient concentration increases. However, amongst competitive ligands the population can only decrease sensory diversity one ligand at a time. Mathematical modeling suggests that sensory diversity tuning benefits E. coli populations by modulating how many cells are committed to tracking each signal proportionally as their prevalence changes.
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4
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Sherry DM, Graf IR, Bryant SJ, Emonet T, Machta BB. Lattice ultrasensitivity produces large gain in E. coli chemosensing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.28.596300. [PMID: 38854030 PMCID: PMC11160650 DOI: 10.1101/2024.05.28.596300] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2024]
Abstract
E. coli use a regular lattice of receptors and attached kinases to detect and amplify faint chemical signals. Kinase output is characterized by precise adaptation to a wide range of background ligand levels and large gain in response to small relative changes in ligand concentration. These characteristics are well described by models which achieve their gain through equilibrium cooperativity. But these models are challenged by two experimental results. First, neither adaptation nor large gain are present in receptor binding assays. Second, in cells lacking adaptation machinery, fluctuations can sometimes be enormous, with essentially all kinases transitioning together. Here we introduce a far-from equilibrium model in which receptors gate the spread of activity between neighboring kinases. This model achieves large gain through a mechanism we term lattice ultrasensitivity (LU). In our LU model, kinase and receptor states are separate degrees of freedom, and kinase kinetics are dominated by chemical rates far-from-equilibrium rather than by equilibrium allostery. The model recapitulates the successes of past models, but also matches the challenging experimental findings. Importantly, unlike past lattice critical models, our LU model does not require parameters to be fine tuned for function.
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5
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Koler M, Parkinson JS, Vaknin A. Signal integration in chemoreceptor complexes. Proc Natl Acad Sci U S A 2024; 121:e2312064121. [PMID: 38530894 PMCID: PMC10998596 DOI: 10.1073/pnas.2312064121] [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: 07/15/2023] [Accepted: 03/01/2024] [Indexed: 03/28/2024] Open
Abstract
Motile bacteria use large receptor arrays to detect chemical and physical stimuli in their environment, process this complex information, and accordingly bias their swimming in a direction they deem favorable. The chemoreceptor molecules form tripod-like trimers of receptor dimers through direct contacts between their cytoplasmic tips. A pair of trimers, together with a dedicated kinase enzyme, form a core signaling complex. Hundreds of core complexes network to form extended arrays. While considerable progress has been made in revealing the hierarchical structure of the array, the molecular properties underlying signal processing in these structures remain largely unclear. Here we analyzed the signaling properties of nonnetworked core complexes in live cells by following both conformational and kinase control responses to attractant stimuli and to output-biasing lesions at various locations in the receptor molecule. Contrary to the prevailing view that individual receptors are binary two-state devices, we demonstrate that conformational coupling between the ligand binding and the kinase-control receptor domains is, in fact, only moderate. In addition, we demonstrate communication between neighboring receptors through their trimer-contact domains that biases them to adopt similar signaling states. Taken together, these data suggest a view of signaling in receptor trimers that allows significant signal integration to occur within individual core complexes.
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Affiliation(s)
- Moriah Koler
- The Racah Institute of Physics, The Hebrew University, Jerusalem91904, Israel
| | - John S. Parkinson
- School of Biological Sciences, University of Utah, Salt Lake City, UT84112
| | - Ady Vaknin
- The Racah Institute of Physics, The Hebrew University, Jerusalem91904, Israel
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6
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Hadjidemetriou K, Kaur S, Cassidy CK, Zhang P. Mechanisms of E. coli chemotaxis signaling pathways visualized using cryoET and computational approaches. Biochem Soc Trans 2022; 50:1595-1605. [PMID: 36421737 PMCID: PMC9788364 DOI: 10.1042/bst20220191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 11/08/2022] [Accepted: 11/11/2022] [Indexed: 11/25/2022]
Abstract
Chemotaxis signaling pathways enable bacteria to sense and respond to their chemical environment and, in some species, are critical for lifestyle processes such as biofilm formation and pathogenesis. The signal transduction underlying chemotaxis behavior is mediated by large, highly ordered protein complexes known as chemosensory arrays. For nearly two decades, cryo-electron tomography (cryoET) has been used to image chemosensory arrays, providing an increasingly detailed understanding of their structure and function. In this mini-review, we provide an overview of the use of cryoET to study chemosensory arrays, including imaging strategies, key results, and outstanding questions. We further discuss the application of molecular modeling and simulation techniques to complement structure determination efforts and provide insight into signaling mechanisms. We close the review with a brief outlook, highlighting promising future directions for the field.
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Affiliation(s)
| | - Satinder Kaur
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K
| | - C. Keith Cassidy
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K
| | - Peijun Zhang
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot OX11 0DE, U.K
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, U.K
- Chinese Academy of Medical Sciences Oxford Institute, University of Oxford, Oxford OX3 7BN, U.K
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7
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Smułek W, Kaczorek E. Factors Influencing the Bioavailability of Organic Molecules to Bacterial Cells-A Mini-Review. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27196579. [PMID: 36235114 PMCID: PMC9570905 DOI: 10.3390/molecules27196579] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/29/2022] [Accepted: 10/01/2022] [Indexed: 11/26/2022]
Abstract
The bioavailability of organic compounds to bacterial cells is crucial for their vital activities. This includes both compounds that are desirable to the cells (e.g., sources of energy, carbon, nitrogen, and other nutrients) and undesirable compounds that are toxic to the cells. For this reason, bioavailability is an issue of great importance in many areas of human activity that are related to bacteria, e.g., biotechnological production, bioremediation of organic pollutants, and the use of antibiotics. This article proposes a classification of factors determining bioavailability, dividing them into factors at the physicochemical level (i.e., those related to the solubility of a chemical compound and its transport in aqueous solution) and factors at the microbiological level (i.e., those related to adsorption on the cell surface and those related to transport into the cell). Awareness of the importance of and the mechanisms governing each of the factors described allows their use to change bioavailability in the desired direction.
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8
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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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9
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Piñas GE, DeSantis MD, Cassidy CK, Parkinson JS. Hexameric rings of the scaffolding protein CheW enhance response sensitivity and cooperativity in Escherichia coli chemoreceptor arrays. Sci Signal 2022; 15:eabj1737. [PMID: 35077199 DOI: 10.1126/scisignal.abj1737] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The Escherichia coli chemoreceptor array is a supramolecular assembly that enables cells to respond to extracellular cues dynamically and with great precision and sensitivity. In the array, transmembrane receptors organized as trimers of dimers are connected at their cytoplasmic tips by hexameric rings of alternating subunits of the kinase CheA and the scaffolding protein CheW (CheA-CheW rings). Interactions of CheW molecules with the members of receptor trimers not directly bound to CheA-CheW rings may lead to the formation of hexameric CheW rings in the chemoreceptor array. Here, we detected such CheW rings with a cellular cysteine-directed cross-linking assay and explored the requirements for their formation and their participation in array assembly. We found that CheW ring formation varied with cellular CheW abundance, depended on the presence of receptors capable of a trimer-of-dimers arrangement, and did not require CheA. Cross-linking studies of a CheA~CheW fusion protein incapable of forming homomeric CheW oligomers demonstrated that CheW rings were not essential for the assembly of CheA-containing arrays. Förster resonance energy transfer (FRET)-based kinase assays of arrays containing variable amounts of CheW rings revealed that CheW rings enhanced the cooperativity and the sensitivity of the responses to attractants. We propose that six-membered CheW rings provide the additional interconnectivity required for optimal signaling and gradient tracking performance by chemosensory arrays.
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Affiliation(s)
- Germán E Piñas
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - Michael D DeSantis
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
| | - C Keith Cassidy
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - John S Parkinson
- School of Biological Sciences, University of Utah, Salt Lake City, UT 84112, USA
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10
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Mandal SD, Chatterjee S. Effect of receptor cooperativity on methylation dynamics in bacterial chemotaxis with weak and strong gradient. Phys Rev E 2022; 105:014411. [PMID: 35193319 DOI: 10.1103/physreve.105.014411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 01/05/2022] [Indexed: 06/14/2023]
Abstract
We study methylation dynamics of the chemoreceptors as an Escherichia coli cell moves around in a spatially varying chemoattractant environment. We consider attractant concentration with strong and weak spatial gradient. During the uphill and downhill motion of the cell along the gradient, we measure the temporal variation of average methylation level of the receptor clusters. Our numerical simulations we show that the methylation dynamics depends sensitively on the size of the receptor clusters and also on the strength of the gradient. At short times after the beginning of a run, the methylation dynamics is mainly controlled by short runs which are generally associated with high receptor activity. This results in demethylation at short times. But for intermediate or large times, long runs play an important role and depending on receptor cooperativity or gradient strength, the qualitative variation of methylation can be completely different in this time regime. For weak gradient, both for uphill and downhill runs, after the initial demethylation, we find methylation level increases steadily with time for all cluster sizes. Similar qualitative behavior is observed for strong gradient during uphill runs as well. However, the methylation dynamics for downhill runs in strong gradient show highly nontrivial dependence on the receptor cluster size. We explain this behavior as a result of interplay between the sensing and adaptation modules of the signaling network.
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Affiliation(s)
- Shobhan Dev Mandal
- Department of Theoretical Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector 3, Salt Lake, Kolkata 700106, India
| | - Sakuntala Chatterjee
- Department of Theoretical Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector 3, Salt Lake, Kolkata 700106, India
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11
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Gordon JB, Hoffman MC, Troiano JM, Li M, Hazelbauer GL, Schlau-Cohen GS. Concerted Differential Changes of Helical Dynamics and Packing upon Ligand Occupancy in a Bacterial Chemoreceptor. ACS Chem Biol 2021; 16:2472-2480. [PMID: 34647725 PMCID: PMC9990816 DOI: 10.1021/acschembio.1c00576] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Transmembrane receptors are central components of the chemosensory systems by which motile bacteria detect and respond to chemical gradients. An attractant bound to the receptor periplasmic domain generates conformational signals that regulate a histidine kinase interacting with its cytoplasmic domain. Ligand-induced signaling through the periplasmic and transmembrane domains of the receptor involves a piston-like helical displacement, but the nature of this signaling through the >200 Å four-helix coiled coil of the cytoplasmic domain had not yet been identified. We performed single-molecule Förster resonance energy transfer measurements on Escherichia coli aspartate receptor homodimers inserted into native phospholipid bilayers enclosed in nanodiscs. The receptors were labeled with fluorophores at diagnostic positions near the middle of the cytoplasmic coiled coil. At these positions, we found that the two N-helices of the homodimer were more distant, that is, less tightly packed and more dynamic than the companion C-helix pair, consistent with previous deductions that the C-helices form a stable scaffold and the N-helices are dynamic. Upon ligand binding, the scaffold pair compacted further, while separation and dynamics of the dynamic pair increased. Thus, ligand binding had asymmetric effects on the two helical pairs, shifting mean distances in opposite directions and increasing the dynamics of one pair. We suggest that this reflects a conformational change in which differential alterations to the packing and dynamics of the two helical pairs are coupled. These coupled changes could represent a previously unappreciated mode of conformational signaling that may well occur in other coiled-coil signaling proteins.
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Affiliation(s)
- Jesse B Gordon
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, 6-225, Cambridge, Massachusetts 02139, United States
| | - Mikaila C Hoffman
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, 6-225, Cambridge, Massachusetts 02139, United States
| | - Julianne M Troiano
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, 6-225, Cambridge, Massachusetts 02139, United States
| | - Mingshan Li
- Department of Biochemistry, University of Missouri, 117 Schweitzer Hall, Columbia, Missouri 65211, United States
| | - Gerald L Hazelbauer
- Department of Biochemistry, University of Missouri, 117 Schweitzer Hall, Columbia, Missouri 65211, United States
| | - Gabriela S Schlau-Cohen
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, 6-225, Cambridge, Massachusetts 02139, United States
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12
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Moore JP, Kamino K, Emonet T. Non-Genetic Diversity in Chemosensing and Chemotactic Behavior. Int J Mol Sci 2021; 22:6960. [PMID: 34203411 PMCID: PMC8268644 DOI: 10.3390/ijms22136960] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/21/2021] [Accepted: 06/22/2021] [Indexed: 01/18/2023] Open
Abstract
Non-genetic phenotypic diversity plays a significant role in the chemotactic behavior of bacteria, influencing how populations sense and respond to chemical stimuli. First, we review the molecular mechanisms that generate phenotypic diversity in bacterial chemotaxis. Next, we discuss the functional consequences of phenotypic diversity for the chemosensing and chemotactic performance of single cells and populations. Finally, we discuss mechanisms that modulate the amount of phenotypic diversity in chemosensory parameters in response to changes in the environment.
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Affiliation(s)
- Jeremy Philippe Moore
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06511, USA; (J.P.M.); (K.K.)
- Quantitative Biology Institute, Yale University, New Haven, CT 06511, USA
| | - Keita Kamino
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06511, USA; (J.P.M.); (K.K.)
- Quantitative Biology Institute, Yale University, New Haven, CT 06511, USA
| | - Thierry Emonet
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT 06511, USA; (J.P.M.); (K.K.)
- Quantitative Biology Institute, Yale University, New Haven, CT 06511, USA
- Department of Physics, Yale University, New Haven, CT 06511, USA
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13
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Burt A, Cassidy CK, Stansfeld PJ, Gutsche I. Alternative Architecture of the E. coli Chemosensory Array. Biomolecules 2021; 11:biom11040495. [PMID: 33806045 PMCID: PMC8064477 DOI: 10.3390/biom11040495] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 03/19/2021] [Accepted: 03/23/2021] [Indexed: 11/16/2022] Open
Abstract
Chemotactic responses in motile bacteria are the result of sophisticated signal transduction by large, highly organized arrays of sensory proteins. Despite tremendous progress in the understanding of chemosensory array structure and function, a structural basis for the heightened sensitivity of networked chemoreceptors is not yet complete. Here, we present cryo-electron tomography visualisations of native-state chemosensory arrays in E. coli minicells. Strikingly, these arrays appear to exhibit a p2-symmetric array architecture that differs markedly from the p6-symmetric architecture previously described in E. coli. Based on this data, we propose molecular models of this alternative architecture and the canonical p6-symmetric assembly. We evaluate our observations and each model in the context of previously published data, assessing the functional implications of an alternative architecture and effects for future studies.
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Affiliation(s)
- Alister Burt
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, IBS, 71 Avenue des Martyrs, F-38044 Grenoble, France;
| | - C. Keith Cassidy
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK;
| | - Phillip J. Stansfeld
- Department of Chemistry, School of Life Sciences, University of Warwick, Gibbet Hill Campus, Coventry CV4 7AL, UK;
| | - Irina Gutsche
- Institut de Biologie Structurale, Université Grenoble Alpes, CEA, CNRS, IBS, 71 Avenue des Martyrs, F-38044 Grenoble, France;
- Correspondence:
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14
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Mandal SD, Chatterjee S. Effect of receptor clustering on chemotactic performance of E. coli: Sensing versus adaptation. Phys Rev E 2021; 103:L030401. [PMID: 33862739 DOI: 10.1103/physreve.103.l030401] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 02/05/2021] [Indexed: 11/07/2022]
Abstract
We show how the competition between sensing and adaptation can result in a performance peak in Escherichia coli chemotaxis using extensive numerical simulations in a detailed theoretical model. Receptor clustering amplifies the input signal coming from ligand binding which enhances chemotactic efficiency. But large clusters also induce large fluctuations in total activity since the number of clusters goes down. The activity and hence the run-tumble motility now gets controlled by methylation levels which are part of adaptation module rather than ligand binding. This reduces chemotactic efficiency.
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Affiliation(s)
- Shobhan Dev Mandal
- Department of Theoretical Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector 3, Salt Lake, Kolkata 700106, India
| | - Sakuntala Chatterjee
- Department of Theoretical Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector 3, Salt Lake, Kolkata 700106, India
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15
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Muok AR, Chua TK, Srivastava M, Yang W, Maschmann Z, Borbat PP, Chong J, Zhang S, Freed JH, Briegel A, Crane BR. Engineered chemotaxis core signaling units indicate a constrained kinase-off state. Sci Signal 2020; 13:13/657/eabc1328. [PMID: 33172954 DOI: 10.1126/scisignal.abc1328] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Bacterial chemoreceptors, the histidine kinase CheA, and the coupling protein CheW form transmembrane molecular arrays with remarkable sensing properties. The receptors inhibit or stimulate CheA kinase activity depending on the presence of attractants or repellants, respectively. We engineered chemoreceptor cytoplasmic regions to assume a trimer of receptor dimers configuration that formed well-defined complexes with CheA and CheW and promoted a CheA kinase-off state. These mimics of core signaling units were assembled to homogeneity and investigated by site-directed spin-labeling with pulse-dipolar electron-spin resonance spectroscopy (PDS), small-angle x-ray scattering, targeted protein cross-linking, and cryo-electron microscopy. The kinase-off state was especially stable, had relatively low domain mobility, and associated the histidine substrate and docking domains with the kinase core, thus preventing catalytic activity. Together, these data provide an experimentally restrained model for the inhibited state of the core signaling unit and suggest that chemoreceptors indirectly sequester the kinase and substrate domains to limit histidine autophosphorylation.
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Affiliation(s)
- Alise R Muok
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.,Institute for Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, Netherlands
| | - Teck Khiang Chua
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Madhur Srivastava
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.,National Biomedical Center for Advanced ESR Technologies (ACERT), Cornell University, Ithaca, NY 14853, USA
| | - Wen Yang
- Institute for Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, Netherlands
| | - Zach Maschmann
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Petr P Borbat
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.,National Biomedical Center for Advanced ESR Technologies (ACERT), Cornell University, Ithaca, NY 14853, USA
| | - Jenna Chong
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Sheng Zhang
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.,National Biomedical Center for Advanced ESR Technologies (ACERT), Cornell University, Ithaca, NY 14853, USA
| | - Ariane Briegel
- Institute for Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, Netherlands
| | - Brian R Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
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16
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Frutos-Grilo E, Marsal M, Irazoki O, Barbé J, Campoy S. The Interaction of RecA With Both CheA and CheW Is Required for Chemotaxis. Front Microbiol 2020; 11:583. [PMID: 32318049 PMCID: PMC7154110 DOI: 10.3389/fmicb.2020.00583] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Accepted: 03/17/2020] [Indexed: 12/20/2022] Open
Abstract
Salmonella enterica is the most frequently reported cause of foodborne illness. As in other microorganisms, chemotaxis affords key physiological benefits, including enhanced access to growth substrates, but also plays an important role in infection and disease. Chemoreceptor signaling core complexes, consisting of CheA, CheW and methyl-accepting chemotaxis proteins (MCPs), modulate the switching of bacterial flagella rotation that drives cell motility. These complexes, through the formation of heterohexameric rings composed of CheA and CheW, form large clusters at the cell poles. RecA plays a key role in polar cluster formation, impairing the assembly when the SOS response is activated. In this study, we determined that RecA protein interacts with both CheW and CheA. The binding of these proteins to RecA is needed for wild-type polar cluster formation. In silico models showed that one RecA molecule, attached to one signaling unit, fits within a CheA-CheW ring without interfering with the complex formation or array assembly. Activation of the SOS response is followed by an increase in RecA, which rises up the number of signaling complexes associated with this protein. This suggests the presence of allosteric inhibition in the CheA-CheW interaction and thus of heterohexameric ring formation, impairing the array assembly. STED imaging demonstrated that all core unit components (CheA, CheW, and MPCs) have the same subcellular location as RecA. Activation of the SOS response promotes the RecA distribution along the cell instead of being at the cell poles. CheA- and CheW- RecA interactions are also crucial for chemotaxis, which is maintained when the SOS response is induced and the signaling units are dispersed. Our results provide new molecular-level insights into the function of RecA in chemoreceptor clustering and chemotaxis determining that the impaired chemoreceptor clustering not only inhibits swarming but also modulates chemotaxis in SOS-induced cells, thereby modifying bacterial motility in the presence of DNA-damaging compounds, such as antibiotics.
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Affiliation(s)
- Elisabet Frutos-Grilo
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Maria Marsal
- ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, Barcelona, Spain
| | - Oihane Irazoki
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Jordi Barbé
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Susana Campoy
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, Barcelona, Spain
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17
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Abstract
Prokaryotic organisms occupy the most diverse set of environments and conditions on our planet. Their ability to sense and respond to a broad range of external cues remain key research areas in modern microbiology, central to behaviors that underlie beneficial and pathogenic interactions of bacteria with multicellular organisms and within complex ecosystems. Advances in our understanding of the one- and two-component signal transduction systems that underlie these sensing pathways have been driven by advances in imaging the behavior of many individual bacterial cells, as well as visualizing individual proteins and protein arrays within living cells. Cryo-electron tomography continues to provide new insights into the structure and function of chemosensory receptors and flagellar motors, while advances in protein labeling and tracking are applied to understand information flow between receptor and motor. Sophisticated microfluidics allow simultaneous analysis of the behavior of thousands of individual cells, increasing our understanding of how variance between individuals is generated, regulated and employed to maximize fitness of a population. In vitro experiments have been complemented by the study of signal transduction and motility in complex in vivo models, allowing investigators to directly address the contribution of motility, chemotaxis and aggregation/adhesion on virulence during infection. Finally, systems biology approaches have demonstrated previously uncharted areas of protein space in which novel two-component signal transduction pathways can be designed and constructed de novo These exciting experimental advances were just some of the many novel findings presented at the 15th Bacterial Locomotion and Signal Transduction conference (BLAST XV) in January 2019.
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18
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Muok AR, Briegel A, Crane BR. Regulation of the chemotaxis histidine kinase CheA: A structural perspective. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183030. [PMID: 31374212 DOI: 10.1016/j.bbamem.2019.183030] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 07/24/2019] [Accepted: 07/25/2019] [Indexed: 02/06/2023]
Abstract
Bacteria sense and respond to their environment through a highly conserved assembly of transmembrane chemoreceptors (MCPs), the histidine kinase CheA, and the coupling protein CheW, hereafter termed "the chemosensory array". In recent years, great strides have been made in understanding the architecture of the chemosensory array and how this assembly engenders sensitive and cooperative responses. Nonetheless, a central outstanding question surrounds how receptors modulate the activity of the CheA kinase, the enzymatic output of the sensory system. With a focus on recent advances, we summarize the current understanding of array structure and function to comment on the molecular mechanism by which CheA, receptors and CheW generate the high sensitivity, gain and dynamic range emblematic of bacterial chemotaxis. The complexity of the chemosensory arrays has motivated investigation with many different approaches. In particular, structural methods, genetics, cellular activity assays, nanodisc technology and cryo-electron tomography have provided advances that bridge length scales and connect molecular mechanism to cellular function. Given the high degree of component integration in the chemosensory arrays, we ultimately aim to understand how such networked molecular interactions generate a whole that is truly greater than the sum of its parts. This article is part of a Special Issue entitled: Molecular biophysics of membranes and membrane proteins.
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Affiliation(s)
- Alise R Muok
- Institute for Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, the Netherlands
| | - Ariane Briegel
- Institute for Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden, the Netherlands
| | - Brian R Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14850, United States of America.
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19
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Conformational shifts in a chemoreceptor helical hairpin control kinase signaling in Escherichia coli. Proc Natl Acad Sci U S A 2019; 116:15651-15660. [PMID: 31315979 PMCID: PMC6681711 DOI: 10.1073/pnas.1902521116] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Motile bacteria use chemoreceptor signaling arrays to track chemical gradients with high precision. The Escherichia coli chemotaxis system offers an ideal model for probing the molecular mechanisms of transmembrane and intracellular signaling. In this study, we characterized the signaling properties of mutant E. coli receptors that had amino acid replacements in residues that form a salt-bridge connection between the cytoplasmic tips of receptor molecules. The mutant signaling defects suggested that the chemoreceptor tip operates as a two-state device with discrete active and inactive conformations and that the level of output activity modulates connections between receptor signaling units that produce highly cooperative responses to attractant stimuli. These findings shed important light on the nature and control of receptor signaling states. Motile Escherichia coli cells use chemoreceptor signaling arrays to track chemical gradients with exquisite precision. Highly conserved residues in the cytoplasmic hairpin tip of chemoreceptor molecules promote assembly of trimer-based signaling complexes and modulate the activity of their CheA kinase partners. To explore hairpin tip output states in the serine receptor Tsr, we characterized the signaling consequences of amino acid replacements at the salt-bridge residue pair E385-R388. All mutant receptors assembled trimers and signaling complexes, but most failed to support serine chemotaxis in soft agar assays. Small side-chain replacements at either residue produced OFF- or ON-shifted outputs that responded to serine stimuli in wild-type fashion, suggesting that these receptors, like the wild-type, operate as two-state signaling devices. Larger aliphatic or aromatic side chains caused slow or partial kinase control responses that proved dependent on the connections between core signaling units that promote array cooperativity. In a mutant lacking one of two key adapter-kinase contacts (interface 2), those mutant receptors exhibited more wild-type behaviors. Lastly, mutant receptors with charged amino acid replacements assembled signaling complexes that were locked in kinase-ON (E385K|R) or kinase-OFF (R388D|E) output. The hairpin tips of mutant receptors with these more aberrant signaling properties probably have nonnative structures or dynamic behaviors. Our results suggest that chemoeffector stimuli and adaptational modifications influence the cooperative connections between core signaling units. This array remodeling process may involve activity-dependent changes in the relative strengths of interface 1 and 2 interactions between the CheW and CheA.P5 components of receptor core signaling complexes.
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20
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Yang W, Cassidy CK, Ames P, Diebolder CA, Schulten K, Luthey-Schulten Z, Parkinson JS, Briegel A. In Situ Conformational Changes of the Escherichia coli Serine Chemoreceptor in Different Signaling States. mBio 2019; 10:e00973-19. [PMID: 31266867 PMCID: PMC6606802 DOI: 10.1128/mbio.00973-19] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 05/31/2019] [Indexed: 11/20/2022] Open
Abstract
Tsr, the serine chemoreceptor in Escherichia coli, transduces signals from a periplasmic ligand-binding site to its cytoplasmic tip, where it controls the activity of the CheA kinase. To function, Tsr forms trimers of homodimers (TODs), which associate in vivo with the CheA kinase and CheW coupling protein. Together, these proteins assemble into extended hexagonal arrays. Here, we use cryo-electron tomography and molecular dynamics simulation to study Tsr in the context of a near-native array, characterizing its signaling-related conformational changes at both the individual dimer and the trimer level. In particular, we show that individual Tsr dimers within a trimer exhibit asymmetric flexibilities that are a function of the signaling state, highlighting the effect of their different protein interactions at the receptor tips. We further reveal that the dimer compactness of the Tsr trimer changes between signaling states, transitioning at the glycine hinge from a compact conformation in the kinase-OFF state to an expanded conformation in the kinase-ON state. Hence, our results support a crucial role for the glycine hinge: to allow the receptor flexibility necessary to achieve different signaling states while also maintaining structural constraints imposed by the membrane and extended array architecture.IMPORTANCE In Escherichia coli, membrane-bound chemoreceptors, the histidine kinase CheA, and coupling protein CheW form highly ordered chemosensory arrays. In core signaling complexes, chemoreceptor trimers of dimers undergo conformational changes, induced by ligand binding and sensory adaptation, which regulate kinase activation. Here, we characterize by cryo-electron tomography the kinase-ON and kinase-OFF conformations of the E. coli serine receptor in its native array context. We found distinctive structural differences between the members of a receptor trimer, which contact different partners in the signaling unit, and structural differences between the ON and OFF signaling complexes. Our results provide new insights into the signaling mechanism of chemoreceptor arrays and suggest an important functional role for a previously postulated flexible region and glycine hinge in the receptor molecule.
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Affiliation(s)
- Wen Yang
- Institute of Biology, Leiden University, Leiden, The Netherlands
| | - C Keith Cassidy
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- Department of Physics and Beckman Institute, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - Peter Ames
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, USA
| | | | - Klaus Schulten
- Department of Physics and Beckman Institute, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - Zaida Luthey-Schulten
- Department of Chemistry and Center for the Physics of Living Cells, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - John S Parkinson
- School of Biological Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Ariane Briegel
- Institute of Biology, Leiden University, Leiden, The Netherlands
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21
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Chai L, Ding C, Li J, Yang Z, Shi Y. Multi-omics response of Pannonibacter phragmitetus BB to hexavalent chromium. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 249:63-73. [PMID: 30878863 DOI: 10.1016/j.envpol.2019.03.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 02/25/2019] [Accepted: 03/03/2019] [Indexed: 05/27/2023]
Abstract
The release of hexavalent chromium [Cr(VI)] into water bodies poses a major threat to the environment and human health. However, studies of the biological response to Cr(VI) are limited. In this study, a toxic bacterial mechanism of Cr(VI) was investigated using Pannonibacter phragmitetus BB (hereafter BB), which was isolated from chromate slag. The maximum Cr(VI) concentrations with respect to the resistance and reduction by BB are 4000 mg L-1 and 2500 mg L-1, respectively. In the BB genome, more genes responsible for Cr(VI) resistance and reduction are observed compared with other P. phragmitetus strains. A total of 361 proteins were upregulated to respond to Cr(VI) exposure, including enzymes for Cr(VI) uptake, intracellular reduction, ROS detoxification, DNA repair, and Cr(VI) efflux and proteins associated with novel mechanisms involving extracellular reduction mediated by electron transfer, quorum sensing, and chemotaxis. Based on metabolomic analysis, 174 metabolites were identified. Most of the upregulated metabolites are involved in amino acid, glucose, lipid, and energy metabolisms. The results show that Cr(VI) induces metabolite production, while metabolites promote Cr(VI) reduction. Overall, multi-enzyme expression and metabolite production by BB contribute to its high ability to resist/reduce Cr(VI). This study provides details supporting the theory of Cr(VI) reduction and a theoretical basis for the efficient bioremoval of Cr(VI) from the environment.
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Affiliation(s)
- Liyuan Chai
- Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University, 410083, Changsha, China; National Engineering Research Center for Heavy Metals Pollution Control and Treatment, 410083, Changsha, China
| | - Chunlian Ding
- Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University, 410083, Changsha, China
| | - Jiawei Li
- Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University, 410083, Changsha, China
| | - Zhihui Yang
- Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University, 410083, Changsha, China; National Engineering Research Center for Heavy Metals Pollution Control and Treatment, 410083, Changsha, China
| | - Yan Shi
- Institute of Environmental Science and Engineering, School of Metallurgy and Environment, Central South University, 410083, Changsha, China; National Engineering Research Center for Heavy Metals Pollution Control and Treatment, 410083, Changsha, China.
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22
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King D, Başağaoğlu H, Nguyen H, Healy F, Whitman M, Succi S. Effects of Advective-Diffusive Transport of Multiple Chemoattractants on Motility of Engineered Chemosensory Particles in Fluidic Environments. ENTROPY 2019; 21:e21050465. [PMID: 33267179 PMCID: PMC7514954 DOI: 10.3390/e21050465] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Revised: 04/30/2019] [Accepted: 05/01/2019] [Indexed: 11/25/2022]
Abstract
Motility behavior of an engineered chemosensory particle (ECP) in fluidic environments is driven by its responses to chemical stimuli. One of the challenges to understanding such behaviors lies in tracking changes in chemical signal gradients of chemoattractants and ECP-fluid dynamics as the fluid is continuously disturbed by ECP motion. To address this challenge, we introduce a new multiscale numerical model to simulate chemotactic swimming of an ECP in confined fluidic environments by accounting for motility-induced disturbances in spatiotemporal chemoattractant distributions. The model accommodates advective-diffusive transport of unmixed chemoattractants, ECP-fluid hydrodynamics at the ECP-fluid interface, and spatiotemporal disturbances in the chemoattractant concentrations due to particle motion. Demonstrative simulations are presented with an ECP, mimicking Escherichia coli (E. coli) chemotaxis, released into initially quiescent fluids with different source configurations of the chemoattractants N-methyl-L-aspartate and L-serine. Simulations demonstrate that initial distributions and temporal evolution of chemoattractants and their release modes (instantaneous vs. continuous, point source vs. distributed) dictate time histories of chemotactic motility of an ECP. Chemotactic motility is shown to be largely determined by spatiotemporal variation in chemoattractant concentration gradients due to transient disturbances imposed by ECP-fluid hydrodynamics, an observation not captured in previous numerical studies that relied on static chemoattractant concentration fields.
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Affiliation(s)
- Danielle King
- Department of Mathematics, The University of Texas, Austin, TX 78712-1202, USA
- Correspondence:
| | - Hakan Başağaoğlu
- Mechanical Engineering Division, Southwest Research Institute, San Antonio, TX 78238-5166, USA
| | - Hoa Nguyen
- Department of Mathematics, Trinity University, One Trinity Place, San Antonio, TX 78212-7200, USA
| | - Frank Healy
- Department of Biology, Trinity University, One Trinity Place, San Antonio, TX 78212-7200, USA
| | - Melissa Whitman
- Department of Biology, Trinity University, One Trinity Place, San Antonio, TX 78212-7200, USA
| | - Sauro Succi
- Fondazione Istituto Italiano di Tecnologia, Center for Life Nanoscience at la Sapienza, vle Regina Margherita, 00165 Rome, Italy
- Istituto Applicazioni del Calcolo, Via dei Taurini 19, 00185 Roma, Italy
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23
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O'Neal L, Akhter S, Alexandre G. A PilZ-Containing Chemotaxis Receptor Mediates Oxygen and Wheat Root Sensing in Azospirillum brasilense. Front Microbiol 2019; 10:312. [PMID: 30881352 PMCID: PMC6406031 DOI: 10.3389/fmicb.2019.00312] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 02/05/2019] [Indexed: 01/14/2023] Open
Abstract
Chemotactic bacteria sense environmental changes via dedicated receptors that bind to extra- or intracellular cues and relay this signal to ultimately alter direction of movement toward beneficial cues and away from harmful environments. In complex environments, such as the rhizosphere, bacteria must be able to sense and integrate diverse cues. Azospirillum brasilense is a microaerophilic motile bacterium that promotes growth of cereals and grains. Root surface colonization is a prerequisite for the beneficial effects on plant growth but how motile A. brasilense navigates the rhizosphere is poorly studied. Previously only 2 out of 51 A. brasilense chemotaxis receptors have been characterized, AerC and Tlp1, and only Tlp1 was found to be essential for wheat root colonization. Here we describe another chemotaxis receptor, named Aer, that is homologous to the Escherichia coli Aer receptor, likely possesses an FAD cofactor and is involved in aerotaxis (taxis in an air gradient). We also found that the A. brasilense Aer contributes to sensing chemical gradients originating from wheat roots. In addition to A. brasilense Aer having a putative N-terminal FAD-binding PAS domain, it possesses a C-terminal PilZ domain that contains all the conserved residues for binding c-di-GMP. Mutants lacking the PilZ domain of Aer are altered in aerotaxis and are completely null in wheat root colonization and they also fail to sense gradients originating from wheat roots. The PilZ domain of Aer is also vital in integrating Aer signaling with signaling from other chemotaxis receptors to sense gradients from wheat root surfaces and colonizing wheat root surfaces.
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Affiliation(s)
- Lindsey O'Neal
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Shehroze Akhter
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Gladys Alexandre
- Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, Knoxville, TN, United States
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24
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Koler M, Peretz E, Aditya C, Shimizu TS, Vaknin A. Long-term positioning and polar preference of chemoreceptor clusters in E. coli. Nat Commun 2018; 9:4444. [PMID: 30361683 PMCID: PMC6202326 DOI: 10.1038/s41467-018-06835-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 09/26/2018] [Indexed: 11/09/2022] Open
Abstract
The bacterial chemosensory arrays are a notable model for studying the basic principles of receptor clustering and cellular organization. Here, we provide a new perspective regarding the long-term dynamics of these clusters in growing E. coli cells. We demonstrate that pre-existing lateral clusters tend to avoid translocation to pole regions and, therefore, continually shuttle between the cell poles for many generations while being static relative to the local cell-wall matrix. We also show that the polar preference of clusters results fundamentally from reduced clustering efficiency in the lateral region, rather than a developmental-like progression of clusters. Furthermore, polar preference is surprisingly robust to structural alterations designed to probe preference due to curvature sorting, perturbing the cell envelope physiology affects the cluster-size distribution, and the size-dependent mobility of receptor complexes differs between polar and lateral regions. Thus, distinct envelope physiology in the polar and lateral cell regions may contribute to polar preference. Bacterial chemoreceptors form clusters, preferably at the cell poles. Here, Koler et al. show that polar and lateral clusters exhibit distinct long-term positional dynamics and that polar bias may be due to differences in mobility of receptor complexes between the polar and lateral cell regions.
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Affiliation(s)
- Moriah Koler
- The Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel
| | - Eliran Peretz
- The Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel
| | | | | | - Ady Vaknin
- The Racah Institute of Physics, The Hebrew University, Jerusalem, 91904, Israel.
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25
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Bi S, Sourjik V. Stimulus sensing and signal processing in bacterial chemotaxis. Curr Opin Microbiol 2018; 45:22-29. [PMID: 29459288 DOI: 10.1016/j.mib.2018.02.002] [Citation(s) in RCA: 136] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 01/30/2018] [Accepted: 02/02/2018] [Indexed: 11/25/2022]
Abstract
Motile bacteria use chemotaxis to migrate towards environments that are favorable for growth and survival. The signaling pathway that mediates this behavior is largely conserved among prokaryotes, with Escherichia coli chemotaxis system being one of the simplest and the best studied. At the core of this pathway are the arrays of clustered chemoreceptors that detect, amplify and integrate various stimuli. Recent work provided deeper understanding of spatial organization and signal processing by these clusters and uncovered the variety of sensory mechanisms used to detect environmental stimuli. Moreover, studies of bacteria with different lifestyles have led to new insights into the diversity and evolutionary conservation of the chemotaxis pathway, as well as the physiological relevance of chemotactic behavior in different environments.
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Affiliation(s)
- Shuangyu Bi
- Max Planck Institute for Terrestrial Microbiology and LOEWE Center for Synthetic Microbiology, Karl-von-Frisch-Strasse 16, 35043 Marburg, Germany
| | - Victor Sourjik
- Max Planck Institute for Terrestrial Microbiology and LOEWE Center for Synthetic Microbiology, Karl-von-Frisch-Strasse 16, 35043 Marburg, Germany.
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26
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Bacterial Chemoreceptor Imaging at High Spatiotemporal Resolution Using Photoconvertible Fluorescent Proteins. Methods Mol Biol 2018; 1729:203-231. [PMID: 29429094 DOI: 10.1007/978-1-4939-7577-8_18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
We describe two methods for high-resolution fluorescence imaging of the positioning and mobility of E. coli chemoreceptors fused to photoconvertible fluorescent proteins. Chemoreceptors such as Tar and Tsr are transmembrane proteins expressed at high levels (thousands of copies per cell). Together with their cognate cytosolic signaling proteins, they form clusters on the plasma membrane. Theoretical models imply that the size of these clusters is an important parameter for signaling, and recent PALM imaging has revealed a broad distribution of cluster sizes. We describe experimental setups and protocols for PALM imaging in fixed cells with ~10 nm spatial precision, which allows analysis of cluster-size distributions, and localized-photoactivation single-particle tracking (LPA-SPT) in live cells at ~10 ms temporal resolution, which allows for analysis of cluster mobility.
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27
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Colin R, Rosazza C, Vaknin A, Sourjik V. Multiple sources of slow activity fluctuations in a bacterial chemosensory network. eLife 2017; 6:26796. [PMID: 29231168 PMCID: PMC5809148 DOI: 10.7554/elife.26796] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 12/02/2017] [Indexed: 12/31/2022] Open
Abstract
Cellular networks are intrinsically subject to stochastic fluctuations, but analysis of the resulting noise remained largely limited to gene expression. The pathway controlling chemotaxis of Escherichia coli provides one example where posttranslational signaling noise has been deduced from cellular behavior. This noise was proposed to result from stochasticity in chemoreceptor methylation, and it is believed to enhance environment exploration by bacteria. Here we combined single-cell FRET measurements with analysis based on the fluctuation-dissipation theorem (FDT) to characterize origins of activity fluctuations within the chemotaxis pathway. We observed surprisingly large methylation-independent thermal fluctuations of receptor activity, which contribute to noise comparably to the energy-consuming methylation dynamics. Interactions between clustered receptors involved in amplification of chemotactic signals are also necessary to produce the observed large activity fluctuations. Our work thus shows that the high response sensitivity of this cellular pathway also increases its susceptibility to noise, from thermal and out-of-equilibrium processes.
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Affiliation(s)
- Remy Colin
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.,LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Christelle Rosazza
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.,LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
| | - Ady Vaknin
- The Racah Institute of Physics, The Hebrew University, Jerusalem, Israel
| | - Victor Sourjik
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.,LOEWE Center for Synthetic Microbiology (SYNMIKRO), Marburg, Germany
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28
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Moine A, Espinosa L, Martineau E, Yaikhomba M, Jazleena PJ, Byrne D, Biondi EG, Notomista E, Brilli M, Molle V, Gayathri P, Mignot T, Mauriello EMF. The nucleoid as a scaffold for the assembly of bacterial signaling complexes. PLoS Genet 2017; 13:e1007103. [PMID: 29161263 PMCID: PMC5716589 DOI: 10.1371/journal.pgen.1007103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 12/05/2017] [Accepted: 11/05/2017] [Indexed: 11/17/2022] Open
Abstract
The FrzCD chemoreceptor from the gliding bacterium Myxococcus xanthus forms cytoplasmic clusters that occupy a large central region of the cell body also occupied by the nucleoid. In this work, we show that FrzCD directly binds to the nucleoid with its N-terminal positively charged tail and recruits active signaling complexes at this location. The FrzCD binding to the nucleoid occur in a DNA-sequence independent manner and leads to the formation of multiple distributed clusters that explore constrained areas. This organization might be required for cooperative interactions between clustered receptors as observed in membrane-bound chemosensory arrays.
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Affiliation(s)
- Audrey Moine
- Laboratoire de Chimie Bactérienne, CNRS-Université Aix-Marseille, Marseille, France
| | - Leon Espinosa
- Laboratoire de Chimie Bactérienne, CNRS-Université Aix-Marseille, Marseille, France
| | - Eugenie Martineau
- Laboratoire de Chimie Bactérienne, CNRS-Université Aix-Marseille, Marseille, France
| | - Mutum Yaikhomba
- Biology Division, Indian Institute of Science Education and Research, Pune, India
| | - P. J. Jazleena
- Biology Division, Indian Institute of Science Education and Research, Pune, India
| | - Deborah Byrne
- Protein Purification Platform, Institut de Microbiologie de la Méditerranée, CNRS, Marseille, France
| | - Emanuele G. Biondi
- Laboratoire de Chimie Bactérienne, CNRS-Université Aix-Marseille, Marseille, France
| | - Eugenio Notomista
- Dipartimento di Biologia, Università degli Studi di Napoli “Federico II”, Naples, Italy
| | - Matteo Brilli
- DAFNAE, Department of Agronomy, Food, Natural Resources, Animals and Environment, University of Padova, Legnano, Italy
| | - Virginie Molle
- Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, CNRS-Universités de Montpellier II et I, Montpellier, France
| | - Pananghat Gayathri
- Biology Division, Indian Institute of Science Education and Research, Pune, India
| | - Tâm Mignot
- Laboratoire de Chimie Bactérienne, CNRS-Université Aix-Marseille, Marseille, France
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Colin R, Sourjik V. Emergent properties of bacterial chemotaxis pathway. Curr Opin Microbiol 2017; 39:24-33. [PMID: 28822274 DOI: 10.1016/j.mib.2017.07.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Accepted: 07/27/2017] [Indexed: 11/17/2022]
Abstract
The chemotaxis pathway of Escherichia coli is the most studied sensory system in prokaryotes. The highly conserved general architecture of this pathway consists of two modules which mediate signal transduction and adaptation. The signal transduction module detects and amplifies changes in environmental conditions and rapidly transmits these signals to control bacterial swimming behavior. The adaptation module gradually resets the activity and sensitivity of the first module after initial stimulation and thereby enables the temporal comparisons necessary for bacterial chemotaxis. Recent experimental and theoretical work has unraveled multiple quantitative features emerging from the interplay between these two modules. This has laid the groundwork for rationalization of these emerging properties in the context of the evolutionary optimization of the chemotactic behavior.
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Affiliation(s)
- Remy Colin
- Max Planck Institute for Terrestrial Microbiology and LOEWE Center for Synthetic Microbiology, Karl-von-Frisch-strasse 16, 35043 Marburg, Germany
| | - Victor Sourjik
- Max Planck Institute for Terrestrial Microbiology and LOEWE Center for Synthetic Microbiology, Karl-von-Frisch-strasse 16, 35043 Marburg, Germany.
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