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Mao Z, Zhang H, Cai W, Yang Y, Zhang X, Jiang F, Li G. NhaA facilitates the maintenance of bacterial envelope integrity and the evasion of complement attack contributing to extraintestinal pathogenic Escherichia coli virulence. Infect Immun 2023; 91:e0003923. [PMID: 37815368 PMCID: PMC10652942 DOI: 10.1128/iai.00039-23] [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: 01/24/2023] [Accepted: 09/01/2023] [Indexed: 10/11/2023] Open
Abstract
Extraintestinal pathogenic Escherichia coli (ExPEC) is responsible for severe bloodstream infections in humans and animals. However, the mechanisms underlying ExPEC's serum resistance remain incompletely understood. Through the transposon-directed insertion-site sequencing approach, our previous study identified nhaA, the gene encoding a Na+/H+ antiporter, as a crucial factor for infection in vivo. In this study, we investigated the role of NhaA in ExPEC virulence utilizing both in vitro models and systemic infection models involving avian and mammalian animals. Genetic mutagenesis analysis revealed that nhaA deletion resulted in filamentous bacterial morphology and rendered the bacteria more susceptible to sodium dodecyl sulfate, suggesting the role of nhaA in maintaining cell envelope integrity. The nhaA mutant also displayed heightened sensitivity to complement-mediated killing compared to the wild-type strain, attributed to augmented deposition of complement components (C3b and C9). Remarkably, NhaA played a more crucial role in virulence compared to several well-known factors, including Iss, Prc, NlpI, and OmpA. Our findings revealed that NhaA significantly enhanced virulence across diverse human ExPEC prototype strains within B2 phylogroups, suggesting widespread involvement in virulence. Given its pivotal role, NhaA could serve as a potential drug target for tackling ExPEC infections.
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Affiliation(s)
- Zhao Mao
- Key Laboratory of Veterinary Public Health of Ministry of Agriculture, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Haobo Zhang
- National Animal Tuberculosis Reference Laboratory, Division of Zoonoses Surveillance, China Animal Health and Epidemiology Center, Qingdao, China
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA
| | - Wentong Cai
- Key Laboratory of Veterinary Public Health of Ministry of Agriculture, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Yan Yang
- Key Laboratory of Veterinary Public Health of Ministry of Agriculture, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Xinyang Zhang
- Key Laboratory of Veterinary Public Health of Ministry of Agriculture, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Fengwei Jiang
- Key Laboratory of Veterinary Public Health of Ministry of Agriculture, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
| | - Ganwu Li
- Key Laboratory of Veterinary Public Health of Ministry of Agriculture, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, China
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, USA
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Dai Y, Zhou Z, Kim K, Rivera N, Mohammed J, Hsu-Kim H, Chilkoti A, You L. Global control of cellular physiology by biomolecular condensates through modulation of electrochemical equilibria. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.19.563018. [PMID: 37904914 PMCID: PMC10614965 DOI: 10.1101/2023.10.19.563018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2023]
Abstract
Control of the electrochemical environment in living cells is typically attributed to ion channels. Here we show that the formation of biomolecular condensates can modulate the electrochemical environment in cells, which affects processes globally within the cell and interactions of the cell with its environment. Condensate formation results in the depletion or enrichment of certain ions, generating intracellular ion gradients. These gradients directly affect the electrochemical properties of a cell, including the cytoplasmic pH and hyperpolarization of the membrane potential. The modulation of the electrochemical equilibria between the intra- and extra-cellular environments by biomolecular condensates governs charge-dependent uptake of small molecules by cells, and thereby directly influences bacterial survival under antibiotic stress. The shift of the intracellular electrochemical equilibria by condensate formation also drives a global change of the gene expression profile. The control of the cytoplasmic environment by condensates is correlated with their volume fraction, which can be highly variable between cells due to the stochastic nature of gene expression at the single cell level. Thus, condensate formation can amplify cell-cell variability of the environmental effects induced by the shift of cellular electrochemical equilibria. Our work reveals new biochemical functions of condensates, which extend beyond the biomolecules driving and participating in condensate formation, and uncovers a new role of biomolecular condensates in cellular regulation.
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Affiliation(s)
- Yifan Dai
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708
- Department of Biomedical Engineering, Center for Biomolecular Condensates, Washington University in St. Louis, Saint Louis, MO, 63130
| | - Zhengqing Zhou
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708
| | - Kyeri Kim
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708
| | - Nelson Rivera
- Department of Civil and Environmental Engineering, Duke University, Durham, NC, 27708
| | - Javid Mohammed
- Department of Immunology, Duke University, Durham, NC, 27705
| | - Heileen Hsu-Kim
- Department of Civil and Environmental Engineering, Duke University, Durham, NC, 27708
| | - Ashutosh Chilkoti
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708
- Center for Quantitative Biodesign, Duke University, Durham, NC 27708
| | - Lingchong You
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708
- Center for Quantitative Biodesign, Duke University, Durham, NC 27708
- Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC 27710
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Visualizing the pH in Escherichia coli Colonies via the Sensor Protein mCherryEA Allows High-Throughput Screening of Mutant Libraries. mSystems 2022; 7:e0021922. [PMID: 35430898 PMCID: PMC9238402 DOI: 10.1128/msystems.00219-22] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Cytoplasmic pH in bacteria is tightly regulated by diverse active mechanisms and interconnected regulatory processes. Many processes and regulators underlying pH homeostasis have been identified via phenotypic screening of strain libraries for nongrowth at low or high pH values. Direct screens with respect to changes of the internal pH in mutant strain collections are limited by laborious methods, which include fluorescent dyes and radioactive probes. Genetically encoded biosensors equip single organisms or strain libraries with an internal sensor molecule during the generation of the strain. Here, we used the pH-sensitive mCherry variant mCherryEA as a ratiometric pH biosensor. We visualized the internal pH of Escherichia coli colonies on agar plates by the use of a GelDoc imaging system. Combining this imaging technology with robot-assisted colony picking and spotting allowed us to screen and select mutants with altered internal pH values from a small transposon mutagenesis-derived E. coli library. Identification of the transposon (Tn) insertion sites in strains with altered internal pH levels revealed that the transposon was inserted into trkH (encoding a transmembrane protein of the potassium uptake system) or rssB (encoding the adaptor protein RssB, which mediates the proteolytic degradation of the general stress response regulator RpoS), two genes known to be associated with pH homeostasis and pH stress adaptation. This successful screening approach demonstrates that the pH sensor-based analysis of arrayed colonies on agar plates is a sensitive approach for the rapid identification of genes involved in pH homeostasis or pH stress adaptation in E. coli. IMPORTANCE Phenotypic screening of strain libraries on agar plates has become a versatile tool to understand gene functions and to optimize biotechnological platform organisms. Screening is supported by genetically encoded biosensors that allow to easily measure intracellular processes. For this purpose, transcription factor-based biosensors have emerged as the sensor type of choice. Here, the target stimulus initiates the activation of a response gene (e.g., a fluorescent protein), followed by transcription, translation, and maturation. Due to this mechanistic principle, biosensor readouts are delayed and cannot report the actual intracellular state of the cell in real time. To capture rapid intracellular processes adequately, fluorescent reporter proteins are extensively applied. However, these sensor types have not previously been used for phenotypic screenings. To take advantage of their properties, we established here an imaging method that allows application of a rapid ratiometric sensor protein for assessing the internal pH of colonies in a high-throughput manner.
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Du GF, Yin XF, Yang DH, He QY, Sun X. Proteomic Investigation of the Antibacterial Mechanism of trans-Cinnamaldehyde against Escherichia coli. J Proteome Res 2021; 20:2319-2328. [PMID: 33749271 DOI: 10.1021/acs.jproteome.0c00847] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Trans-Cinnamaldehyde (TC) is a widely used food additive, known for its sterilization, disinfection, and antiseptic properties. However, its antibacterial mechanism is not completely understood. In this study, quantitative proteomics was performed to investigate differentially expressed proteins (DEPs) in Escherichia coli in response to TC treatment. Bioinformatics analysis suggested aldehyde toxicity, acid stress, oxidative stress, interference of carbohydrate metabolism, energy metabolism, and protein translation as the bactericidal mechanism. E. coli BW25113ΔyqhD, ΔgldA, ΔbetB, ΔtktB, ΔgadA, ΔgadB, ΔgadC, and Δrmf were used to investigate the functions of DEPs through biochemical methods. The present study revealed that TC exerts its antibacterial effects by inducing the toxicity of its aldehyde group producing acid stress. These findings will contribute to the application of TC in the antibacterial field.
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Affiliation(s)
- Gao-Fei Du
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, China.,Medical Technology School, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Xing-Feng Yin
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, China
| | - Dong-Hong Yang
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, China
| | - Qing-Yu He
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, China
| | - Xuesong Sun
- MOE Key Laboratory of Tumor Molecular Biology and Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, China
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Huber MC, Schreiber A, von Olshausen P, Varga BR, Kretz O, Joch B, Barnert S, Schubert R, Eimer S, Kele P, Schiller SM. Designer amphiphilic proteins as building blocks for the intracellular formation of organelle-like compartments. NATURE MATERIALS 2015; 14:125-32. [PMID: 25362355 DOI: 10.1038/nmat4118] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 09/22/2014] [Indexed: 05/24/2023]
Abstract
Nanoscale biological materials formed by the assembly of defined block-domain proteins control the formation of cellular compartments such as organelles. Here, we introduce an approach to intentionally 'program' the de novo synthesis and self-assembly of genetically encoded amphiphilic proteins to form cellular compartments, or organelles, in Escherichia coli. These proteins serve as building blocks for the formation of artificial compartments in vivo in a similar way to lipid-based organelles. We investigated the formation of these organelles using epifluorescence microscopy, total internal reflection fluorescence microscopy and transmission electron microscopy. The in vivo modification of these protein-based de novo organelles, by means of site-specific incorporation of unnatural amino acids, allows the introduction of artificial chemical functionalities. Co-localization of membrane proteins results in the formation of functionalized artificial organelles combining artificial and natural cellular function. Adding these protein structures to the cellular machinery may have consequences in nanobiotechnology, synthetic biology and materials science, including the constitution of artificial cells and bio-based metamaterials.
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Affiliation(s)
- Matthias C Huber
- 1] Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Str. 31 D-79104 Freiburg, Germany [2] Institute for Pharmaceutical Sciences, University of Freiburg, Albertstr. 25 D-79104 Freiburg, Germany [3] Freiburg Institute for Advanced Studies (FRIAS), School of Soft Matter Research, University of Freiburg, Albertstr. 19 D-79104 Freiburg, Germany [4] Faculty of Chemistry and Pharmacy, University of Freiburg, Fahnenbergplatz D-79104 Freiburg, Germany
| | - Andreas Schreiber
- 1] Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Str. 31 D-79104 Freiburg, Germany [2] Institute for Pharmaceutical Sciences, University of Freiburg, Albertstr. 25 D-79104 Freiburg, Germany [3] Freiburg Institute for Advanced Studies (FRIAS), School of Soft Matter Research, University of Freiburg, Albertstr. 19 D-79104 Freiburg, Germany [4] Faculty of Biology, University of Freiburg, Schänzlestrasse 1 D-79085 Freiburg, Germany
| | - Philipp von Olshausen
- 1] Bio- and Nano-Photonics, Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 102 D-79110 Freiburg, Germany [2] BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestrasse 18 D-79104 Freiburg, Germany
| | - Balázs R Varga
- Chemical Biology Research Group, Hungarian Academy of Sciences, CNS, IOC, Magyar tudósok krt. 2 H-1117 Budapest, Hungary
| | - Oliver Kretz
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestrasse 18 D-79104 Freiburg, Germany
| | - Barbara Joch
- Institute for Neuroanatomy University of Freiburg, Albertstr. 17 D-79104 Freiburg, Germany
| | - Sabine Barnert
- 1] Faculty of Chemistry and Pharmacy, University of Freiburg, Fahnenbergplatz D-79104 Freiburg, Germany [2] Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology and Biopharmacy, University of Freiburg, Hermann-Herder-Str. 9 D-79104 Freiburg, Germany
| | - Rolf Schubert
- 1] Faculty of Chemistry and Pharmacy, University of Freiburg, Fahnenbergplatz D-79104 Freiburg, Germany [2] BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestrasse 18 D-79104 Freiburg, Germany [3] Institute of Pharmaceutical Sciences, Department of Pharmaceutical Technology and Biopharmacy, University of Freiburg, Hermann-Herder-Str. 9 D-79104 Freiburg, Germany
| | - Stefan Eimer
- BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestrasse 18 D-79104 Freiburg, Germany
| | - Péter Kele
- Chemical Biology Research Group, Hungarian Academy of Sciences, CNS, IOC, Magyar tudósok krt. 2 H-1117 Budapest, Hungary
| | - Stefan M Schiller
- 1] Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Str. 31 D-79104 Freiburg, Germany [2] Institute for Pharmaceutical Sciences, University of Freiburg, Albertstr. 25 D-79104 Freiburg, Germany [3] Freiburg Institute for Advanced Studies (FRIAS), School of Soft Matter Research, University of Freiburg, Albertstr. 19 D-79104 Freiburg, Germany [4] Faculty of Chemistry and Pharmacy, University of Freiburg, Fahnenbergplatz D-79104 Freiburg, Germany [5] Faculty of Biology, University of Freiburg, Schänzlestrasse 1 D-79085 Freiburg, Germany [6] BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestrasse 18 D-79104 Freiburg, Germany [7] IMTEK Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 103 D-79110 Freiburg, Germany [8] Center for Biosystems Analysis (ZBSA), University of Freiburg, Habsburger Str. 49 D-79104 Freiburg, Germany
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6
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Kümmel A, Panke S, Heinemann M. Systematic assignment of thermodynamic constraints in metabolic network models. BMC Bioinformatics 2006; 7:512. [PMID: 17123434 PMCID: PMC1664590 DOI: 10.1186/1471-2105-7-512] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2006] [Accepted: 11/23/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The availability of genome sequences for many organisms enabled the reconstruction of several genome-scale metabolic network models. Currently, significant efforts are put into the automated reconstruction of such models. For this, several computational tools have been developed that particularly assist in identifying and compiling the organism-specific lists of metabolic reactions. In contrast, the last step of the model reconstruction process, which is the definition of the thermodynamic constraints in terms of reaction directionalities, still needs to be done manually. No computational method exists that allows for an automated and systematic assignment of reaction directions in genome-scale models. RESULTS We present an algorithm that - based on thermodynamics, network topology and heuristic rules - automatically assigns reaction directions in metabolic models such that the reaction network is thermodynamically feasible with respect to the production of energy equivalents. It first exploits all available experimentally derived Gibbs energies of formation to identify irreversible reactions. As these thermodynamic data are not available for all metabolites, in a next step, further reaction directions are assigned on the basis of network topology considerations and thermodynamics-based heuristic rules. Briefly, the algorithm identifies reaction subsets from the metabolic network that are able to convert low-energy co-substrates into their high-energy counterparts and thus net produce energy. Our algorithm aims at disabling such thermodynamically infeasible cyclic operation of reaction subnetworks by assigning reaction directions based on a set of thermodynamics-derived heuristic rules. We demonstrate our algorithm on a genome-scale metabolic model of E. coli. The introduced systematic direction assignment yielded 130 irreversible reactions (out of 920 total reactions), which corresponds to about 70% of all irreversible reactions that are required to disable thermodynamically infeasible energy production. CONCLUSION Although not being fully comprehensive, our algorithm for systematic reaction direction assignment could define a significant number of irreversible reactions automatically with low computational effort. We envision that the presented algorithm is a valuable part of a computational framework that assists the automated reconstruction of genome-scale metabolic models.
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Affiliation(s)
- Anne Kümmel
- Institute of Molecular Systems Biology, ETH Zurich, Wolfgang-Pauli-Str. 16, 8093 Zurich, Switzerland
| | - Sven Panke
- Bioprocess Laboratory, Institute of Process Engineering, ETH Zurich, Universitätsstr. 6, 8092 Zurich, Switzerland
| | - Matthias Heinemann
- Institute of Molecular Systems Biology, ETH Zurich, Wolfgang-Pauli-Str. 16, 8093 Zurich, Switzerland
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7
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Kümmel A, Panke S, Heinemann M. Putative regulatory sites unraveled by network-embedded thermodynamic analysis of metabolome data. Mol Syst Biol 2006; 2:2006.0034. [PMID: 16788595 PMCID: PMC1681506 DOI: 10.1038/msb4100074] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Accepted: 05/07/2006] [Indexed: 11/09/2022] Open
Abstract
As one of the most recent members of the omics family, large-scale quantitative metabolomics data are currently complementing our systems biology data pool and offer the chance to integrate the metabolite level into the functional analysis of cellular networks. Network-embedded thermodynamic analysis (NET analysis) is presented as a framework for mechanistic and model-based analysis of these data. By coupling the data to an operating metabolic network via the second law of thermodynamics and the metabolites' Gibbs energies of formation, NET analysis allows inferring functional principles from quantitative metabolite data; for example it identifies reactions that are subject to active allosteric or genetic regulation as exemplified with quantitative metabolite data from Escherichia coli and Saccharomyces cerevisiae. Moreover, the optimization framework of NET analysis was demonstrated to be a valuable tool to systematically investigate data sets for consistency, for the extension of sub-omic metabolome data sets and for resolving intracompartmental concentrations from cell-averaged metabolome data. Without requiring any kind of kinetic modeling, NET analysis represents a perfectly scalable and unbiased approach to uncover insights from quantitative metabolome data.
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Affiliation(s)
- Anne Kümmel
- Bioprocess Laboratory, Institute of Process Engineering, ETH Zurich, Zurich, Switzerland
- Present address: Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
| | - Sven Panke
- Bioprocess Laboratory, Institute of Process Engineering, ETH Zurich, Zurich, Switzerland
| | - Matthias Heinemann
- Bioprocess Laboratory, Institute of Process Engineering, ETH Zurich, Zurich, Switzerland
- Present address: Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland
- Institute of Molecular Systems Biology, ETH Zurich, Wolfgang-Pauli-Strasse 16, 8093 Zurich, Switzerland. Tel.: +41 44 632 63 66; Fax: +41 44 633 10 51; E-mail:
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8
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Wood JM, Bremer E, Csonka LN, Kraemer R, Poolman B, van der Heide T, Smith LT. Osmosensing and osmoregulatory compatible solute accumulation by bacteria. Comp Biochem Physiol A Mol Integr Physiol 2001; 130:437-60. [PMID: 11913457 DOI: 10.1016/s1095-6433(01)00442-1] [Citation(s) in RCA: 337] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Bacteria inhabit natural and artificial environments with diverse and fluctuating osmolalities, salinities and temperatures. Many maintain cytoplasmic hydration, growth and survival most effectively by accumulating kosmotropic organic solutes (compatible solutes) when medium osmolality is high or temperature is low (above freezing). They release these solutes into their environment when the medium osmolality drops. Solutes accumulate either by synthesis or by transport from the extracellular medium. Responses to growth in high osmolality medium, including biosynthetic accumulation of trehalose, also protect Salmonella typhimurium from heat shock. Osmotically regulated transporters and mechanosensitive channels modulate cytoplasmic solute levels in Bacillus subtilis, Corynebacterium glutamicum, Escherichia coli, Lactobacillus plantarum, Lactococcus lactis, Listeria monocytogenes and Salmonella typhimurium. Each organism harbours multiple osmoregulatory transporters with overlapping substrate specificities. Membrane proteins that can act as both osmosensors and osmoregulatory transporters have been identified (secondary transporters ProP of E. coli and BetP of C. glutamicum as well as ABC transporter OpuA of L. lactis). The molecular bases for the modulation of gene expression and transport activity by temperature and medium osmolality are under intensive investigation with emphasis on the role of the membrane as an antenna for osmo- and/or thermosensors.
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Affiliation(s)
- J M Wood
- Department of Microbiology and Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, University of Guelph, Canada.
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Katsu T, Nakagawa H, Kanamori T, Kamo N, Tsuchiya T. Ion-selective electrode for transmembrane pH difference measurements. Anal Chem 2001; 73:1849-54. [PMID: 11338601 DOI: 10.1021/ac001090t] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A triethylammonium-sensitive electrode was constructed using sodium tetrakis[3,5-bis(2-methoxyhexafluoro-2-propyl)phenyl]borate as an ion-exchanger and benzyl 2-nitrophenyl ether as a solvent mediator in a poly(vinylchloride) membrane matrix and was used to determine the pH difference across a cell membrane. The method is based on monitoring of the pH gradient-induced uptake of triethylammonium in situ. The triethylammonium electrode exhibited a near-Nernstian response to triethylammonium in the concentration range of 5 x 10(-6)-1 x 10(-2) M with a slope of 58.5 mV per concentration decade in a buffer solution composed of 150 mM NaCl and 10 mM NaH2PO4/Na2HPO4 (pH 7.5). The limit of detection was 1 microM. In experiments using liposomes, the uptake of triethylammonium into liposomes was quantitatively induced according to the pH difference across the liposomal membrane. The transmembrane pH differences in Escherichia coli cells and the light-induced pH differences across the envelope vesicles of Halobacterium halobium were successfully determined by the present method.
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Affiliation(s)
- T Katsu
- Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530, Japan.
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SMITH G, SMITH L, GERHARDT P, KO R. SOLUTE TRANSPORT ENZYMES RELATED TO STRESS TOLERANCE IN LISTERIA MONOCYTOGENES: A REVIEW. J Food Biochem 1998. [DOI: 10.1111/j.1745-4514.1998.tb00244.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Sakuma T, Yamada N, Saito H, Kakegawa T, Kobayashi H. pH dependence of the function of sodium ion extrusion systems in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1363:231-7. [PMID: 9518629 DOI: 10.1016/s0005-2728(97)00102-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Escherichia coli has three systems for sodium ion extrusion, NhaA, NhaB and ChaA. In this study, we examined the effect of pH on the function of these transporters using mutants having one of them, and found that (1) a mutant having NhaB excreted sodium ions at pH 7.5 but not at pH 8.5, (2) the efflux of sodium ions from mutant cells having ChaA was observed at both pH 7.5 and 8.5, but the activity was lower at pH 7.5, and (3) sodium ions were excreted from mutant cells having NhaA at pH 6.5 to 8.5. The extrusion activity of cells having NhaA was higher than that of cells having NhaB or ChaA. These results indicate that NhaB functions at a pH below 8, and ChaA extrudes sodium ions mainly at an alkaline pH above 8. It was also suggested that the activity of NhaB and ChaA is not enough to maintain a low level of internal sodium ions when the external concentration of sodium ions is high, and NhaA is induced within a wide range of medium pH under such conditions.
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Affiliation(s)
- T Sakuma
- Faculty of Pharmaceutical Sciences, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263, Japan
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12
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Nakamura T, Enomoto H, Unemoto T. Cloning and sequencing of nhaB gene encoding an Na+/H+ antiporter from Vibrio alginolyticus. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1275:157-60. [PMID: 8695633 DOI: 10.1016/0005-2728(96)00034-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A gene has been cloned from the marine bacterium Vibrio alginolyticus that functionally complements a mutant strain of Escherichia coli, TO114, defective in three Na+/H+ antiport genes (nhaA, nhaB, chaA). The nucleotide sequence of the cloned fragment revealed an open reading frame, which encodes a protein with a predicted 528 amino acid sequence and molecular mass of 57212 Da. This gene has 62% identity to nhaB gene at the DNA level from Escherichia coli and the deduced amino acid sequence is 67% identical with E. coli NhaB. This gene is presumably the V. alginolyticus nhaB gene and will be named nhaBv.
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Affiliation(s)
- T Nakamura
- Laboratory of Membrane Biochemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
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13
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Verkhovskaya ML, Verkhovsky MI, Wikström M. K+-dependent Na+ transport driven by respiration in Escherichia coli cells and membrane vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1273:207-16. [PMID: 8616158 DOI: 10.1016/0005-2728(95)00142-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Respiration-driven Na+ transport from Escherichia coli cells and right-side-out membrane vesicles is strictly dependent on K+. Cells from an E. colic mutant deficient in three major K+ transport systems were incapable of accumulating K+ or expelling Na+ unless valinomycin was added. Membrane vesicles from an E. coli mutant from which the genes encoding the two known electrogenic Na+/nH+ antiporters nhaA and nhaB were deleted transported Na+ as well as did vesicles from wild-type cells. Quantitative analysis of Delta psi and Delta pH showed a high driving force for electrogenic Na+/nH+ antiport whether K+ was present or not, although Na+ transport occurred only in its presence. These results suggest that an Na+/nH+ antiporter is not responsible for the Na+ transport. Respiration-driven efflux of Na+ from vesicles was found to be accompanied by primary uphill efflux of K+. Also, no respiration-dependent efflux of K+ was observed in the absence of Na+. Such coupling between Na+ and K+ fluxes may be explained by the operation of an Na+, K+/H+ antiporter previously described in E. coli membrane vesicles (Verkhovskay, M.L., Verkhovsky, M.I. and Wikström, M. (1995) FEBS Lett. 363, 46-48). Active Na+ transport is abolished when delta mu H+ is eliminated by a protonophore, but at low concentrations the protonophore actually accelerated Na+ transport. Such an effect may be expected if the Na+, K+/H+ antiporter normally operates in tight conjunction with respiratory chain complexes, thus exhibiting some phenomenological properties of a primary redox-linked sodium pump.
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Affiliation(s)
- M L Verkhovskaya
- Helsinki Bioenergetics Group, Institute of Biomedical Sciences, Department of Medical Chemistry, University of Helsinki, Finland
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Chapter 22 Bacterial Na+/H+ antiporters — Molecular biology, biochemistry and physiology. HANDBOOK OF BIOLOGICAL PHYSICS 1996. [DOI: 10.1016/s1383-8121(96)80063-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Affiliation(s)
- H K Hall
- Department of Microbiology and Immunology, College of Medicine, University of South Alabama, Mobile 36688, USA
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