1
|
Wang X, Cui Y, Wang Z, Jiang H, Ma L, Li W, Yang X, Zhang J, Zhao Y, Li G. NhaA: A promising adjuvant target for colistin against resistant Escherichia coli. Int J Biol Macromol 2024; 268:131833. [PMID: 38663703 DOI: 10.1016/j.ijbiomac.2024.131833] [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: 03/03/2024] [Revised: 04/15/2024] [Accepted: 04/22/2024] [Indexed: 04/30/2024]
Abstract
The emergence and widespread of multidrug-resistant Gram-negative bacteria have posed a severe threat to human health and environmental safety, escalating into a global medical crisis. Utilization of antibiotic adjuvants is a rapid approach to combat bacterial resistance effectively since the development of new antimicrobial agents is a formidable challenge. NhaA, driven by proton motive force, is a crucial secondary transporter on the cytoplasmic membrane of Escherichia coli. We found that 2-Aminoperimidine (2-AP), which is a specific inhibitor of NhaA, could enhance the activity of colistin against sensitive E. coli and reverse the resistance in mcr-1 positive E. coli. Mechanistic studies indicated that 2-AP induced dysfunction in cytoplasmic membrane through the suppression of NhaA, leading to metabolic inhibition and ultimately enhancing the sensitivity of E. coli to colistin. Moreover, 2-AP restored the efficacy of colistin against resistant E. coli in two animal infection models. Our findings reveal the potential of NhaA as a novel target for colistin adjuvants, providing new possibilities for the clinical application of colistin.
Collapse
Affiliation(s)
- Xuelin Wang
- School of Life Sciences and Biopharmaceutical Science, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, China
| | - Yong Cui
- School of Medical Devices, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Zhaohui Wang
- School of Life Sciences and Biopharmaceutical Science, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, China
| | - Huilin Jiang
- School of Life Sciences and Biopharmaceutical Science, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, China
| | - Lei Ma
- School of Life Sciences and Biopharmaceutical Science, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, China
| | - Wenwen Li
- School of Life Sciences and Biopharmaceutical Science, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, China
| | - Xinyi Yang
- Beijing Key Laboratory of Antimicrobial Agents, Laboratory of Pharmacology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China; Division for Medicinal Microorganisms Related Strains, CAMS Collection Center of Pathogenic Microorganisms, Beijing 100050, China; State Key Laboratory of Respiratory Health and Multimorbidity, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China
| | - Jinghai Zhang
- School of Medical Devices, Shenyang Pharmaceutical University, Shenyang 110016, China.
| | - Yongshan Zhao
- School of Life Sciences and Biopharmaceutical Science, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, China.
| | - Guoqing Li
- Beijing Key Laboratory of Antimicrobial Agents, Laboratory of Pharmacology, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China; Division for Medicinal Microorganisms Related Strains, CAMS Collection Center of Pathogenic Microorganisms, Beijing 100050, China; State Key Laboratory of Respiratory Health and Multimorbidity, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China.
| |
Collapse
|
2
|
Prokaryotic Na+/H+ Exchangers—Transport Mechanism and Essential Residues. Int J Mol Sci 2022; 23:ijms23169156. [PMID: 36012428 PMCID: PMC9408914 DOI: 10.3390/ijms23169156] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/09/2022] [Accepted: 08/13/2022] [Indexed: 11/16/2022] Open
Abstract
Na+/H+ exchangers are essential for Na+ and pH homeostasis in all organisms. Human Na+/H+ exchangers are of high medical interest, and insights into their structure and function are aided by the investigation of prokaryotic homologues. Most prokaryotic Na+/H+ exchangers belong to either the Cation/Proton Antiporter (CPA) superfamily, the Ion Transport (IT) superfamily, or the Na+-translocating Mrp transporter superfamily. Several structures have been solved so far for CPA and Mrp members, but none for the IT members. NhaA from E. coli has served as the prototype of Na+/H+ exchangers due to the high amount of structural and functional data available. Recent structures from other CPA exchangers, together with diverse functional information, have allowed elucidation of some common working principles shared by Na+/H+ exchangers from different families, such as the type of residues involved in the substrate binding and even a simple mechanism sufficient to explain the pH regulation in the CPA and IT superfamilies. Here, we review several aspects of prokaryotic Na+/H+ exchanger structure and function, discussing the similarities and differences between different transporters, with a focus on the CPA and IT exchangers. We also discuss the proposed transport mechanisms for Na+/H+ exchangers that explain their highly pH-regulated activity profile.
Collapse
|
3
|
Nguyen K, Kumar P. Morphological Phenotypes, Cell Division, and Gene Expression of Escherichia coli under High Concentration of Sodium Sulfate. Microorganisms 2022; 10:microorganisms10020274. [PMID: 35208727 PMCID: PMC8875244 DOI: 10.3390/microorganisms10020274] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/13/2022] [Accepted: 01/14/2022] [Indexed: 01/10/2023] Open
Abstract
Sodium and sulfate ions are among the suggested abundant ions on Europa, a moon of Jupiter. In order to investigate the potential habitability of Europa, we study the effects of sodium sulfate (Na2SO4) on a non-halophilic bacterium by subjecting Escherichia coli (E. coli) to a wide range of Na2SO4 concentrations (0–1.0 m). We discover that, as the concentration of sodium sulfate increases, the biomass doubling time increases and the cell growth is completely inhibited at 1.0 m Na2SO4. Furthermore, we find that E. coli exhibits three distinct morphological phenotypes—(i) shortened, (ii) normal, and (iii) elongated/filamented cells at 0.6 m and 0.8 m Na2SO4. We have examined the expression of different genes involved in sodium and sulfate transport (nhaA, nhaB, cysZ, sbp), osmotically driven transport of water (aqpZ), sulfate metabolism (cysN), fatty acid production (fabA), and a global transcriptional regulator (osmZ). Our results suggest that the expression of these genes is not affected significantly at high concentrations of sodium sulfate in the exponential growth phase. Using our experimental data and the existing data in the literature, we show that the osmotic pressure difference may play a major role in determining the growth inhibition of E. coli and B. subtilis at high concentrations of salt.
Collapse
|
4
|
Trautmann A, Schleicher L, Pfirrmann J, Boldt C, Steuber J, Seifert J. Na +-Coupled Respiration and Reshaping of Extracellular Polysaccharide Layer Counteract Monensin-Induced Cation Permeability in Prevotella bryantii B 14. Int J Mol Sci 2021; 22:ijms221910202. [PMID: 34638543 PMCID: PMC8508442 DOI: 10.3390/ijms221910202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 09/17/2021] [Accepted: 09/20/2021] [Indexed: 11/24/2022] Open
Abstract
Monensin is an ionophore for monovalent cations, which is frequently used to prevent ketosis and to enhance performance in dairy cows. Studies have shown the rumen bacteria Prevotella bryantii B14 being less affected by monensin. The present study aimed to reveal more information about the respective molecular mechanisms in P.bryantii, as there is still a lack of knowledge about defense mechanisms against monensin. Cell growth experiments applying increasing concentrations of monensin and incubations up to 72 h were done. Harvested cells were used for label-free quantitative proteomics, enzyme activity measurements, quantification of intracellular sodium and extracellular glucose concentrations and fluorescence microscopy. Our findings confirmed an active cell growth and fermentation activity of P.bryantii B14 despite monensin concentrations up to 60 µM. An elevated abundance and activity of the Na+-translocating NADH:quinone oxidoreductase counteracted sodium influx caused by monensin. Cell membranes and extracellular polysaccharides were highly influenced by monensin indicated by a reduced number of outer membrane proteins, an increased number of certain glucoside hydrolases and an elevated concentration of extracellular glucose. Thus, a reconstruction of extracellular polysaccharides in P.bryantii in response to monensin is proposed, which is expected to have a negative impact on the substrate binding capacities of this rumen bacterium.
Collapse
Affiliation(s)
- Andrej Trautmann
- HoLMiR-Hohenheim Center for Livestock Microbiome Research, University of Hohenheim, 70599 Stuttgart, Germany; (A.T.); (L.S.); (J.S.)
- Institute of Animal Science, University of Hohenheim, 70599 Stuttgart, Germany;
| | - Lena Schleicher
- HoLMiR-Hohenheim Center for Livestock Microbiome Research, University of Hohenheim, 70599 Stuttgart, Germany; (A.T.); (L.S.); (J.S.)
- Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Jana Pfirrmann
- Institute of Animal Science, University of Hohenheim, 70599 Stuttgart, Germany;
| | - Christin Boldt
- Institute of Bioscience, TU Bergakademie Freiberg, 09599 Freiberg, Germany;
| | - Julia Steuber
- HoLMiR-Hohenheim Center for Livestock Microbiome Research, University of Hohenheim, 70599 Stuttgart, Germany; (A.T.); (L.S.); (J.S.)
- Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Jana Seifert
- HoLMiR-Hohenheim Center for Livestock Microbiome Research, University of Hohenheim, 70599 Stuttgart, Germany; (A.T.); (L.S.); (J.S.)
- Institute of Animal Science, University of Hohenheim, 70599 Stuttgart, Germany;
- Correspondence: ; Tel.: +49-0711-459-24284
| |
Collapse
|
5
|
Wang KH, Zheng DH, Yuan GQ, Lin W, Li QQ. A yceI Gene Involves in the Adaptation of Ralstonia solanacearum to Methyl Gallate and Other Stresses. Microorganisms 2021; 9:microorganisms9091982. [PMID: 34576877 PMCID: PMC8472277 DOI: 10.3390/microorganisms9091982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 09/10/2021] [Accepted: 09/14/2021] [Indexed: 11/16/2022] Open
Abstract
Ralstonia solanacearum is a plant-pathogenic bacterium causing plant bacterial wilt, and can be strongly inhibited by methyl gallate (MG). Our previous transcriptome sequencing of MG-treated R. solanacearum showed that the yceI gene AVT05_RS03545 of Rs-T02 was up-regulated significantly under MG stress. In this study, a deletion mutant (named DM3545) and an over-expression strain (named OE3545) for yceI were constructed to confirm this hypothesis. No significant difference was observed among the growth of wild-type strain, DM3545 and OE3545 strains without MG treatment. Mutant DM3545 showed a lower growth ability than that of the wild type and OE3545 strains under MG treatment, non-optimal temperature, or 1% NaCl. The ability of DM3545 for rhizosphere colonization was lower than that of the wild-type and OE3545 strains. The DM3545 strain showed substantially reduced virulence toward tomato plants than its wild-type and OE3545 counterpart. Moreover, DM3545 was more sensitive to MG in plants than the wild-type and OE3545 strains. These results suggest that YceI is involved in the adaptability of R. solanacearum to the presence of MG and the effect of other tested abiotic stresses. This protein is also possibly engaged in the virulence potential of R. solanacearum.
Collapse
Affiliation(s)
| | | | | | | | - Qi-Qin Li
- Correspondence: (D.-H.Z.); (Q.-Q.L.)
| |
Collapse
|
6
|
Kumar S, Tiwari V, Doerrler WT. Cpx-dependent expression of YqjA requires cations at elevated pH. FEMS Microbiol Lett 2017; 364:3861960. [PMID: 28591809 DOI: 10.1093/femsle/fnx115] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2016] [Accepted: 06/06/2017] [Indexed: 11/13/2022] Open
Abstract
Under alkaline pH conditions, Escherichia coli must maintain a stable cytoplasmic pH of about 7.6 that is acidic relative to the environment. Bacteria employ various mechanisms to survive alkaline pH; however, membrane cation/H+ antiporters play a primary role by facilitating inward transport of protons. Escherichia coli YqjA belongs to the DedA/Tvp38 membrane protein family and, along with its paralog YghB, is required for growth at 42°C, proper cell division and antibiotic resistance. YqjA is required for viability at alkaline pH, requiring cations sodium or potassium to support growth under these conditions, suggesting it may be a transporter. We measured yqjA expression at different pHs and cation concentrations using a yqjA promoter-lacZ fusion. We found that yqjA promoter activity was highest at alkaline pH. Increased activity of the yqjA promoter required both the transcriptional regulator CpxR, in agreement with previous results, and sodium or potassium salts at alkaline pH. Extracellular cations are also required for activity of cpxP and degP promoters at alkaline pH, suggesting this is a general property of the Cpx regulon. To our knowledge, this is the first demonstration of cation-dependent expression of Cpx-regulated genes at alkaline pH.
Collapse
Affiliation(s)
- Sujeet Kumar
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Vijay Tiwari
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - William T Doerrler
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| |
Collapse
|
7
|
Soemphol W, Tatsuno M, Okada T, Matsutani M, Kataoka N, Yakushi T, Matsushita K. A novel Na(+)(K(+))/H(+) antiporter plays an important role in the growth of Acetobacter tropicalis SKU1100 at high temperatures via regulation of cation and pH homeostasis. J Biotechnol 2015; 211:46-55. [PMID: 26100236 DOI: 10.1016/j.jbiotec.2015.06.397] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 05/21/2015] [Accepted: 06/15/2015] [Indexed: 11/15/2022]
Abstract
A gene encoding a putative Na(+)/H(+) antiporter was previously proposed to be involved in the thermotolerance mechanism of Acetobacter tropicalis SKU 1100. The results of this study show that disruption of this antiporter gene impaired growth at high temperatures with an external pH>6.5. The growth impairment at high temperatures was much more severe in the absence of Na(+) (with only the presence of K(+)); under these conditions, cells failed to grow even at 30°C and neutral to alkaline pH values, suggesting that this protein is also important for K(+) tolerance. Functional analysis with inside-out membrane vesicles from wild type and mutant strains indicated that the antiporter, At-NhaK2 operates as an alkali cation/proton antiporter for ions such as Na(+), K(+), Li(+), and Rb(+) at acidic to neutral pH values (6.5-7.5). The membrane vesicles were also shown to contain a distinct pH-dependent Na(+)(specific)/H(+) antiporter(s) that might function at alkaline pH values. In addition, phylogenetic analysis showed that At-NhaK2 is a novel type of Na(+)/H(+) antiporter belonging to a phylogenetically distinct new clade. These data demonstrate that At-NhaK2 functions as a Na(+)(K(+))/H(+) antiporter and is essential for K(+) and pH homeostasis during the growth of A. tropicalis SKU1100, especially at higher temperatures.
Collapse
Affiliation(s)
- Wichai Soemphol
- Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan; Faculty of Applied Science and Engineering, Nong Khai Campus, Khon Kaen University, Nong Khai 43000, Thailand
| | - Maki Tatsuno
- Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan
| | - Takahiro Okada
- Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan
| | - Minenosuke Matsutani
- Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan
| | - Naoya Kataoka
- Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan
| | - Toshiharu Yakushi
- Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan
| | - Kazunobu Matsushita
- Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan.
| |
Collapse
|
8
|
Comparative genomics of Campylobacter concisus isolates reveals genetic diversity and provides insights into disease association. BMC Genomics 2013; 14:585. [PMID: 23984967 PMCID: PMC3765806 DOI: 10.1186/1471-2164-14-585] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 08/17/2013] [Indexed: 12/17/2022] Open
Abstract
Background In spite of its association with gastroenteritis and inflammatory bowel diseases, the isolation of Campylobacter concisus from both diseased and healthy individuals has led to controversy regarding its role as an intestinal pathogen. One proposed reason for this is the presence of high genetic diversity among the genomes of C. concisus strains. Results In this study the genomes of six C. concisus strains were sequenced, assembled and annotated including two strains isolated from Crohn’s disease patients (UNSW2 and UNSW3), three from gastroenteritis patients (UNSW1, UNSWCS and ATCC 51562) and one from a healthy individual (ATCC 51561). The genomes of C. concisus BAA-1457 and UNSWCD, available from NCBI, were included in subsequent comparative genomic analyses. The Pan and Core genomes for the sequenced C. concisus strains consisted of 3254 and 1556 protein coding genes, respectively. Conclusion Genes were identified with specific conservation in C. concisus strains grouped by phenotypes such as invasiveness, adherence, motility and diseased states. Phylogenetic trees based on ribosomal RNA sequences and concatenated host-related pathways for the eight C. concisus strains were generated using the neighbor-joining method, of which the 16S rRNA gene and peptidoglycan biosynthesis grouped the C. concisus strains according to their pathogenic phenotypes. Furthermore, 25 non-synonymous amino acid changes with 14 affecting functional domains, were identified within proteins of conserved host-related pathways, which had possible associations with the pathogenic potential of C. concisus strains. Finally, the genomes of the eight C. concisus strains were compared to the nine available genomes of the well-established pathogen Campylobacter jejuni, which identified several important differences in the respiration pathways of these two species. Our findings indicate that C. concisus strains are genetically diverse, and suggest the genomes of this bacterium contain respiration pathways and modifications in the peptidoglycan layer that may play an important role in its virulence.
Collapse
|
9
|
Lee Y, Seo H, Yeom J, Park W. Molecular characterization of the extracellular matrix in a Pseudomonas putida dsbA mutant: implications for acidic stress defense and plant growth promotion. Res Microbiol 2011; 162:302-10. [DOI: 10.1016/j.resmic.2010.11.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2010] [Accepted: 10/12/2010] [Indexed: 11/27/2022]
|
10
|
Pandey S, Saha P, Barai PK, Maiti TK. Characterization of a Cd2+-Resistant Strain of Ochrobactrum sp. Isolated from Slag Disposal Site of an Iron and Steel Factory. Curr Microbiol 2010; 61:106-11. [DOI: 10.1007/s00284-010-9583-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2009] [Accepted: 01/04/2010] [Indexed: 11/30/2022]
|
11
|
Kshatriya K, Singh JS, Singh DP. Salt tolerant mutant of Anabaena doliolum exhibiting efficient ammonium uptake and assimilation. PHYSIOLOGY AND MOLECULAR BIOLOGY OF PLANTS : AN INTERNATIONAL JOURNAL OF FUNCTIONAL PLANT BIOLOGY 2009; 15:377-81. [PMID: 23572949 PMCID: PMC3550349 DOI: 10.1007/s12298-009-0043-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Effect of salinity (NaCl, 100 mM) on growth, nitrate reductase (NR) and glutamine synthetase (GS) activities, and uptake of NH4 (+) was studied in the wild type (WT) and the NaCl-tolerant mutant type (MT) of cyanobacterium Anabaena doliolum. Results obtained in the presence of salt showed significant reduction in the growth rate of both WT and MT cells of A. doliolum by about 77.8 and 40 %, respectively over without NaCl. Similarly rate of NR activity in both WT and MT strains was reduced by 45.5 and 44.5 %, respectively. On the contrary, rate of GS activity of both the WT and MT strains in the presence 100 mM of NaCl increased by 34 and 159 %, respectively. The results of this study indicate that tolerance to NaCl in A. doliolum is more dependent on NH4 (+) assimilation rather than on nitrate assimilation in relation to N-metabolism. The increased GS activity in MT cells of the cyanobacterium is possibly because of high rate of energy dependent NH4 (+) uptake.
Collapse
Affiliation(s)
- K. Kshatriya
- />Department of Microbiology, Dr. RML Avadh University, Faizabad, 224 001 (U.P.) India
| | - Jay S. Singh
- />School for Environmental Sciences, Babasaheb Bhimrao Ambedkar University, Rae Bareli Road, Lucknow, 226 025 (U.P.) India
| | - D. P. Singh
- />School for Environmental Sciences, Babasaheb Bhimrao Ambedkar University, Rae Bareli Road, Lucknow, 226 025 (U.P.) India
| |
Collapse
|
12
|
Slonczewski JL, Fujisawa M, Dopson M, Krulwich TA. Cytoplasmic pH measurement and homeostasis in bacteria and archaea. Adv Microb Physiol 2009; 55:1-79, 317. [PMID: 19573695 DOI: 10.1016/s0065-2911(09)05501-5] [Citation(s) in RCA: 293] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Of all the molecular determinants for growth, the hydronium and hydroxide ions are found naturally in the widest concentration range, from acid mine drainage below pH 0 to soda lakes above pH 13. Most bacteria and archaea have mechanisms that maintain their internal, cytoplasmic pH within a narrower range than the pH outside the cell, termed "pH homeostasis." Some mechanisms of pH homeostasis are specific to particular species or groups of microorganisms while some common principles apply across the pH spectrum. The measurement of internal pH of microbes presents challenges, which are addressed by a range of techniques under varying growth conditions. This review compares and contrasts cytoplasmic pH homeostasis in acidophilic, neutralophilic, and alkaliphilic bacteria and archaea under conditions of growth, non-growth survival, and biofilms. We present diverse mechanisms of pH homeostasis including cell buffering, adaptations of membrane structure, active ion transport, and metabolic consumption of acids and bases.
Collapse
|
13
|
Wu L, Lin XM, Peng XX. From Proteome to Genome for Functional Characterization of pH-Dependent Outer Membrane Proteins in Escherichia coli. J Proteome Res 2009; 8:1059-70. [DOI: 10.1021/pr800818r] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lina Wu
- Center for Proteomics, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xiang-min Lin
- Center for Proteomics, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xuan-xian Peng
- Center for Proteomics, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
| |
Collapse
|
14
|
Signal integration by the two-component signal transduction response regulator CpxR. J Bacteriol 2008; 190:2314-22. [PMID: 18223085 DOI: 10.1128/jb.01906-07] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The CpxAR two-component signal transduction system in Escherichia coli and other pathogens senses diverse envelope stresses and promotes the transcription of a variety of genes that remedy these stresses. An important member of the CpxAR regulon is cpxP. The CpxA-dependent transcription of cpxP has been linked to stresses such as misfolded proteins and alkaline pH. It also has been proposed that acetyl phosphate, the intermediate of the phosphotransacetylase (Pta)-acetate kinase (AckA) pathway, can activate the transcription of cpxP in a CpxA-independent manner by donating its phosphoryl group to CpxR. We tested this hypothesis by measuring the transcription of cpxP using mutants with mutations in the CpxAR pathway, mutants with mutations in the Pta-AckA pathway, and mutants with a combination of both types of mutations. From this epistasis analysis, we learned that CpxR integrates diverse stimuli. The stimuli that originate in the envelope depend on CpxA, while those associated with growth and central metabolism depend on the Pta-AckA pathway. While CpxR could receive a phosphoryl group from acetyl phosphate, this global signal was not the primary trigger for CpxR activation associated with the Pta-AckA pathway. On the strength of these results, we contend that the interactions between central metabolism and signal transduction can be quite complex and that successful investigations of such interactions must include a complete epistatic analysis.
Collapse
|
15
|
Richard H, Foster JW. Sodium regulates Escherichia coli acid resistance, and influences GadX- and GadW-dependent activation of gadE. MICROBIOLOGY-SGM 2007; 153:3154-3161. [PMID: 17768258 DOI: 10.1099/mic.0.2007/007575-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Enteric bacteria must survive the extreme acid of the stomach (pH 2 or less) before entering the intestine where they can colonize and cause disease. Escherichia coli is superior to most other Enterobacteriaceae in surviving pH 2 acid stress because it has four known acid-resistance systems, the most studied of which depends on glutamic acid. Glutamate-dependent acid resistance requires glutamate decarboxylase isozymes GadA and GadB, as well as a glutamate/gamma-aminobutyric acid antiporter encoded by gadC. The regulatory protein GadE is the essential activator of the gadA and gadBC genes. The transcription of gadE, however, is controlled by numerous proteins. Two of these proteins, GadX and GadW, are AraC-family regulators whose sensory input signals are not known. Since Na(+) and K(+) play important roles in pH homeostasis, the contribution of these ions toward the regulation of this acid-resistance system was examined. The results indicated that a decrease in Na(+), but not K(+), concentration coincided with diminished acid resistance, and decreased expression of the gadE, gadA and gadBC genes. However, Na(+)-dependent regulation of these genes dissipated in the absence of GadX and GadW. Since Na(+) levels did not regulate gadX or gadW transcription, it is proposed that GadX and GadW sense intracellular Na(+) concentration or some consequence of altered Na(+) levels.
Collapse
Affiliation(s)
- Hope Richard
- Department of Microbiology and Immunology, University of South Alabama, College of Medicine, Mobile, AL 36688, USA
| | - John W Foster
- Department of Microbiology and Immunology, University of South Alabama, College of Medicine, Mobile, AL 36688, USA
| |
Collapse
|
16
|
Han MJ, Lee SY. The Escherichia coli proteome: past, present, and future prospects. Microbiol Mol Biol Rev 2006; 70:362-439. [PMID: 16760308 PMCID: PMC1489533 DOI: 10.1128/mmbr.00036-05] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Proteomics has emerged as an indispensable methodology for large-scale protein analysis in functional genomics. The Escherichia coli proteome has been extensively studied and is well defined in terms of biochemical, biological, and biotechnological data. Even before the entire E. coli proteome was fully elucidated, the largest available data set had been integrated to decipher regulatory circuits and metabolic pathways, providing valuable insights into global cellular physiology and the development of metabolic and cellular engineering strategies. With the recent advent of advanced proteomic technologies, the E. coli proteome has been used for the validation of new technologies and methodologies such as sample prefractionation, protein enrichment, two-dimensional gel electrophoresis, protein detection, mass spectrometry (MS), combinatorial assays with n-dimensional chromatographies and MS, and image analysis software. These important technologies will not only provide a great amount of additional information on the E. coli proteome but also synergistically contribute to other proteomic studies. Here, we review the past development and current status of E. coli proteome research in terms of its biological, biotechnological, and methodological significance and suggest future prospects.
Collapse
Affiliation(s)
- Mee-Jung Han
- Metabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon 305-701, Republic of Korea
| | | |
Collapse
|
17
|
Kuroda T, Mizushima T, Tsuchiya T. Physiological roles of three Na+/H+ antiporters in the halophilic bacterium Vibrio parahaemolyticus. Microbiol Immunol 2005; 49:711-9. [PMID: 16113500 DOI: 10.1111/j.1348-0421.2005.tb03662.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Vibrio parahaemolyticus mutants lacking three Na+/H+ antiporters (NhaA, NhaB, NhaD) were constructed. The DeltanhaA strains showed significantly higher sensitivity to LiCl regarding their growth compared to the parental strain. The DeltanhaA and DeltanhaB strains exhibited higher sensitivities to LiCl. The mutant XACabd lacking all of the three antiporters could not grow in the presence of 500 mM LiCl at pH 7.0, or 50 mM at pH 8.5. The XACabd mutant was also sensitive to 1.0 M NaCl at pH 8.5. These results suggest that Na+/H+ antiporters, especially NhaA, are responsible for resistance to LiCl and to high concentrations of NaCl. Reduced Na+/H+ and Li+/H+ antiport activities were observed with everted membrane vesicles of DeltanhaB strains. However, Li+/H+ antiport activities of DeltanhaB strains were two times higher than those of DeltanhaA strains when cells were cultured at pH 8.5. It seems that expression of nhaA and nhaB is dependent on medium pH to some extent. In addition, HQNO (2-heptyl-4-hydroxyquinoline N-oxide), which is a potent inhibitor of the respiratory Na+ pump, inhibited growth of XACabd, but not of the wild type strain. Moreover, survival rate of XACabd under hypoosmotic stress was lower than that of wild type strain. It is likely that the Na+/H+ antiporters are involved in osmoregulation under hypoosmotic stress. Based on these findings, we propose that the Na+/H+ antiporters cooperate with the respiratory Na+ pump in ionic homeostasis in V. parahaemolyticus.
Collapse
Affiliation(s)
- Teruo Kuroda
- Department of Microbiology, Faculty of Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | | | | |
Collapse
|
18
|
Padan E, Bibi E, Ito M, Krulwich TA. Alkaline pH homeostasis in bacteria: new insights. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1717:67-88. [PMID: 16277975 PMCID: PMC3072713 DOI: 10.1016/j.bbamem.2005.09.010] [Citation(s) in RCA: 484] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2005] [Revised: 08/19/2005] [Accepted: 09/07/2005] [Indexed: 10/25/2022]
Abstract
The capacity of bacteria to survive and grow at alkaline pH values is of widespread importance in the epidemiology of pathogenic bacteria, in remediation and industrial settings, as well as in marine, plant-associated and extremely alkaline ecological niches. Alkali-tolerance and alkaliphily, in turn, strongly depend upon mechanisms for alkaline pH homeostasis, as shown in pH shift experiments and growth experiments in chemostats at different external pH values. Transcriptome and proteome analyses have recently complemented physiological and genetic studies, revealing numerous adaptations that contribute to alkaline pH homeostasis. These include elevated levels of transporters and enzymes that promote proton capture and retention (e.g., the ATP synthase and monovalent cation/proton antiporters), metabolic changes that lead to increased acid production, and changes in the cell surface layers that contribute to cytoplasmic proton retention. Targeted studies over the past decade have followed up the long-recognized importance of monovalent cations in active pH homeostasis. These studies show the centrality of monovalent cation/proton antiporters in this process while microbial genomics provides information about the constellation of such antiporters in individual strains. A comprehensive phylogenetic analysis of both eukaryotic and prokaryotic genome databases has identified orthologs from bacteria to humans that allow better understanding of the specific functions and physiological roles of the antiporters. Detailed information about the properties of multiple antiporters in individual strains is starting to explain how specific monovalent cation/proton antiporters play dominant roles in alkaline pH homeostasis in cells that have several additional antiporters catalyzing ostensibly similar reactions. New insights into the pH-dependent Na(+)/H(+) antiporter NhaA that plays an important role in Escherichia coli have recently emerged from the determination of the structure of NhaA. This review highlights the approaches, major findings and unresolved problems in alkaline pH homeostasis, focusing on the small number of well-characterized alkali-tolerant and extremely alkaliphilic bacteria.
Collapse
Affiliation(s)
- Etana Padan
- Alexander Silberman Institute of Life Sciences, Hebrew University, Jerusalem 91904, Israel.
| | | | | | | |
Collapse
|
19
|
Yohannes E, Barnhart DM, Slonczewski JL. pH-dependent catabolic protein expression during anaerobic growth of Escherichia coli K-12. J Bacteriol 2004; 186:192-9. [PMID: 14679238 PMCID: PMC303440 DOI: 10.1128/jb.186.1.192-199.2004] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During aerobic growth of Escherichia coli, expression of catabolic enzymes and envelope and periplasmic proteins is regulated by pH. Additional modes of pH regulation were revealed under anaerobiosis. E. coli K-12 strain W3110 was cultured anaerobically in broth medium buffered at pH 5.5 or 8.5 for protein identification on proteomic two-dimensional gels. A total of 32 proteins from anaerobic cultures show pH-dependent expression, and only four of these proteins (DsbA, TnaA, GatY, and HdeA) showed pH regulation in aerated cultures. The levels of 19 proteins were elevated at the high pH; these proteins included metabolic enzymes (DhaKLM, GapA, TnaA, HisC, and HisD), periplasmic proteins (ProX, OppA, DegQ, MalB, and MglB), and stress proteins (DsbA, Tig, and UspA). High-pH induction of the glycolytic enzymes DhaKLM and GapA suggested that there was increased fermentation to acids, which helped neutralize alkalinity. Reporter lac fusion constructs showed base induction of sdaA encoding serine deaminase under anaerobiosis; in addition, the glutamate decarboxylase genes gadA and gadB were induced at the high pH anaerobically but not with aeration. This result is consistent with the hypothesis that there is a connection between the gad system and GabT metabolism of 4-aminobutanoate. On the other hand, 13 other proteins were induced by acid; these proteins included metabolic enzymes (GatY and AckA), periplasmic proteins (TolC, HdeA, and OmpA), and redox enzymes (GuaB, HmpA, and Lpd). The acid induction of NikA (nickel transporter) is of interest because E. coli requires nickel for anaerobic fermentation. The position of the NikA spot coincided with the position of a small unidentified spot whose induction in aerobic cultures was reported previously; thus, NikA appeared to be induced slightly by acid during aeration but showed stronger induction under anaerobic conditions. Overall, anaerobic growth revealed several more pH-regulated proteins; in particular, anaerobiosis enabled induction of several additional catabolic enzymes and sugar transporters at the high pH, at which production of fermentation acids may be advantageous for the cell.
Collapse
|
20
|
Zuleta LFG, Italiani VCS, Marques MV. Isolation and characterization of NaCl-sensitive mutants of Caulobacter crescentus. Appl Environ Microbiol 2003; 69:3029-35. [PMID: 12788696 PMCID: PMC161536 DOI: 10.1128/aem.69.6.3029-3035.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An attempt to characterize Caulobacter crescentus genes important for the response to high concentrations of NaCl was initiated by the isolation of mutants defective in survival in the presence of 85 mM NaCl. A transposon Tn5 library was screened, and five strains which contained different genes disrupted by the transposon were isolated. Three of the mutants had the Tn5 in genes involved in lipopolysaccharide biosynthesis, one had the Tn5 in the nhaA gene, which encodes a Na(+)/H(+) antiporter, and one had the Tn5 in the ppiD gene, which encodes a peptidyl-prolyl cis-trans isomerase. All the mutant strains showed severe growth arrest in the presence of 85 mM NaCl, but only the nhaA mutant showed decreased viability under these conditions. All the mutants except the nhaA mutant showed a slightly reduced viability in the presence of 40 mM KCl, but all the strains showed a more severe reduction in viability in the presence of 150 mM sucrose, suggesting that they are defective in responding to osmotic shock. The promoter regions of each disrupted gene were cloned in lacZ reporter vectors, and the pattern of expression in response to NaCl and sucrose was determined; this showed that both agents induced ppiD and nhaA gene expression but did not induce the other genes. Furthermore, the ppiD gene was not induced by heat shock, indicating that it does not belong to the sigma(32) regulon, as opposed to what was observed for its Escherichia coli homolog.
Collapse
Affiliation(s)
- Luiz Fernando G Zuleta
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-900 São Paulo SP, Brazil
| | | | | |
Collapse
|
21
|
Shijuku T, Yamashino T, Ohashi H, Saito H, Kakegawa T, Ohta M, Kobayashi H. Expression of chaA, a sodium ion extrusion system of Escherichia coli, is regulated by osmolarity and pH. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1556:142-8. [PMID: 12460671 DOI: 10.1016/s0005-2728(02)00345-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
ChaA, one of the sodium ion extrusion systems of Escherichia coli, was found to function at high pH [Biochim. Biophys. Acta 1363 (1998) 231]. A chaA-lacZ transcriptional fusion gene was constructed using chaA of E. coli O157:H7 and its expression was observed in strains derived from E. coli K12. The fusion gene was expressed at high pH and was induced by the addition of NaCl, KCl or sucrose. The amount of chaA mRNA measured by reverse transcription-polymerase chain reaction (RT-PCR) was increased by the addition of sucrose to alkaline growth medium. These results suggested that chaA expression was regulated by medium osmolarity and pH.
Collapse
Affiliation(s)
- Toshiaki Shijuku
- Graduate School of Pharmaceutical Sciences, Chiba University, 1-33, Yayoi-cho, Inage-ku, 263-8522, Chiba, Japan
| | | | | | | | | | | | | |
Collapse
|
22
|
Stancik LM, Stancik DM, Schmidt B, Barnhart DM, Yoncheva YN, Slonczewski JL. pH-dependent expression of periplasmic proteins and amino acid catabolism in Escherichia coli. J Bacteriol 2002; 184:4246-58. [PMID: 12107143 PMCID: PMC135203 DOI: 10.1128/jb.184.15.4246-4258.2002] [Citation(s) in RCA: 238] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli grows over a wide range of pHs (pH 4.4 to 9.2), and its own metabolism shifts the external pH toward either extreme, depending on available nutrients and electron acceptors. Responses to pH values across the growth range were examined through two-dimensional electrophoresis (2-D gels) of the proteome and through lac gene fusions. Strain W3110 was grown to early log phase in complex broth buffered at pH 4.9, 6.0, 8.0, or 9.1. 2-D gel analysis revealed the pH dependence of 19 proteins not previously known to be pH dependent. At low pH, several acetate-induced proteins were elevated (LuxS, Tpx, and YfiD), whereas acetate-repressed proteins were lowered (Pta, TnaA, DksA, AroK, and MalE). These responses could be mediated by the reuptake of acetate driven by changes in pH. The amplified proton gradient could also be responsible for the acid induction of the tricarboxylic acid (TCA) enzymes SucB and SucC. In addition to the autoinducer LuxS, low pH induced another potential autoinducer component, the LuxH homolog RibB. pH modulated the expression of several periplasmic and outer membrane proteins: acid induced YcdO and YdiY; base induced OmpA, MalE, and YceI; and either acid or base induced OmpX relative to pH 7. Two pH-dependent periplasmic proteins were redox modulators: Tpx (acid-induced) and DsbA (base-induced). The locus alx, induced in extreme base, was identified as ygjT, whose product is a putative membrane-bound redox modulator. The cytoplasmic superoxide stress protein SodB was induced by acid, possibly in response to increased iron solubility. High pH induced amino acid metabolic enzymes (TnaA and CysK) as well as lac fusions to the genes encoding AstD and GabT. These enzymes participate in arginine and glutamate catabolic pathways that channel carbon into acids instead of producing alkaline amines. Overall, these data are consistent with a model in which E. coli modulates multiple transporters and pathways of amino acid consumption so as to minimize the shift of its external pH toward either acidic or alkaline extreme.
Collapse
|
23
|
Abstract
Enteric bacteria exposed to the marine environment simultaneously encounter a variety of abiotic and biotic challenges. Among the former, light appears to be critical in affecting seawater survival; previous growth history plays a major part in preadaptation of the cells, and stationary phase cells are generally more resistant than exponentially growing ones. Predation, mostly by protozoa, is probably the most significant biotic factor. Using Escherichia coli as a model, a surprisingly small number of genes was found that, when mutated, significantly affect seawater sensitivity of this bacterium. Most prominent among those is rpoS, which was also dominant among genes induced upon transfer to seawater.
Collapse
Affiliation(s)
- Y Rozen
- Environmental Sciences, Fredy and Nadine Herrmann Graduate School of Applied Science, Hebrew University of Jerusalem, 91904, Jerusalem, Israel
| | | |
Collapse
|
24
|
Shijuku T, Saito H, Kakegawa T, Kobayashi H. Expression of sodium/proton antiporter NhaA at various pH values in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1506:212-7. [PMID: 11779554 DOI: 10.1016/s0005-2728(01)00215-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It was reported that NhaA, one of sodium/proton antiporters in Escherichia coli, was expressed at alkaline pH [J. Biol. Chem. 266 (1991) 21753]. In disagreement with their results, expression of an nhaA-lacZ fusion gene was found to be very low in an E. coli strain derived from MC4100 within the wide pH range from 5 to 9. When nhaB was deleted, the fusion gene was expressed at pH values below 8, while the expression was observed at alkaline pH after chaA was deleted. The internal level of sodium ions was increased by deletion of nhaA in strains deficient in nhaB and chaA at low and high pH values, respectively. These results suggested that nhaA is induced only when a low level of internal sodium ions is not kept by NhaB and ChaA. Strains used in the previous study may have low active ChaA.
Collapse
Affiliation(s)
- T Shijuku
- Graduate School of Pharmaceutical Sciences, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
| | | | | | | |
Collapse
|
25
|
Kirkpatrick C, Maurer LM, Oyelakin NE, Yoncheva YN, Maurer R, Slonczewski JL. Acetate and formate stress: opposite responses in the proteome of Escherichia coli. J Bacteriol 2001; 183:6466-77. [PMID: 11591692 PMCID: PMC100143 DOI: 10.1128/jb.183.21.6466-6477.2001] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acetate and formate are major fermentation products of Escherichia coli. Below pH 7, the balance shifts to lactate; an oversupply of acetate or formate retards growth. E. coli W3110 was grown with aeration in potassium-modified Luria broth buffered at pH 6.7 in the presence or absence of added acetate or formate, and the protein profiles were compared by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Acetate increased the steady-state expression levels of 37 proteins, including periplasmic transporters for amino acids and peptides (ArtI, FliY, OppA, and ProX), metabolic enzymes (YfiD and GatY), the RpoS growth phase regulon, and the autoinducer synthesis protein LuxS. Acetate repressed 17 proteins, among them phosphotransferase (Pta). An ackA-pta deletion, which nearly eliminates interconversion between acetate and acetyl-coenzyme A (acetyl-CoA), led to elevated basal levels of 16 of the acetate-inducible proteins, including the RpoS regulon. Consistent with RpoS activation, the ackA-pta strain also showed constitutive extreme-acid resistance. Formate, however, repressed 10 of the acetate-inducible proteins, including the RpoS regulon. Ten of the proteins with elevated basal levels in the ackA-pta strain were repressed by growth of the mutant with formate; thus, the formate response took precedence over the loss of the ackA-pta pathway. The similar effects of exogenous acetate and the ackA-pta deletion, and the opposite effect of formate, could have several causes; one possibility is that the excess buildup of acetyl-CoA upregulates stress proteins but excess formate depletes acetyl-CoA and downregulates these proteins.
Collapse
Affiliation(s)
- C Kirkpatrick
- Department of Biology, Kenyon College, Gambier, Ohio 43022, USA
| | | | | | | | | | | |
Collapse
|
26
|
Toesca I, Perard C, Bouvier J, Gutierrez C, Conter A. The transcriptional activator NhaR is responsible for the osmotic induction of osmC(p1), a promoter of the stress-inducible gene osmC in Escherichia coli. MICROBIOLOGY (READING, ENGLAND) 2001; 147:2795-2803. [PMID: 11577158 DOI: 10.1099/00221287-147-10-2795] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Two overlapping promoters, osmC(p1) and osmC(p2), direct the transcription of the osmC gene of Escherichia coli. The proximal promoter, osmC(p2), is induced upon entry into stationary phase under the control of Esigma(s), the RNA polymerase that uses the sigma(s) (RpoS) sigma factor. Transcription from the distal promoter, osmC(p1), is independent of sigma(s). Previous analysis demonstrated that the osmolarity of the growth medium modulates expression of both promoters. The use of an E. coli genomic library showed that the cloned nhaR gene was able to stimulate transcription of an osmC-lac reporter fusion. NhaR is a positive regulator of the LysR family, previously identified as an activator of nhaA, a gene encoding a Na+/H+ antiporter involved in adaptation to Na+ and alkaline pH in E. coli and other enteric bacteria. NhaR was shown to activate only the expression of osmC(p1) and to be necessary for the induction of this promoter by LiCl, NaCl and sucrose. Therefore, activation by NhaR is responsible for the osmotic induction of osmC(p1). In contrast to its action on nhaA, NhaR activation of osmC(p1) is independent of H-NS. Activation of osmC(p1) by NhaR requires a site located just upstream of the atypical -35 region of the promoter.
Collapse
Affiliation(s)
- Isabelle Toesca
- Laboratoire de Microbiologie et Génétique Moléculaire, UMR 5100 CNRS - Université Toulouse III, 118 Route de Narbonne, F-31062, Toulouse Cedex, France1
| | - Catherine Perard
- Laboratoire de Microbiologie et Génétique Moléculaire, UMR 5100 CNRS - Université Toulouse III, 118 Route de Narbonne, F-31062, Toulouse Cedex, France1
| | - Jean Bouvier
- Laboratoire de Microbiologie et Génétique Moléculaire, UMR 5100 CNRS - Université Toulouse III, 118 Route de Narbonne, F-31062, Toulouse Cedex, France1
| | - Claude Gutierrez
- Laboratoire de Microbiologie et Génétique Moléculaire, UMR 5100 CNRS - Université Toulouse III, 118 Route de Narbonne, F-31062, Toulouse Cedex, France1
| | - Annie Conter
- Laboratoire de Microbiologie et Génétique Moléculaire, UMR 5100 CNRS - Université Toulouse III, 118 Route de Narbonne, F-31062, Toulouse Cedex, France1
| |
Collapse
|
27
|
Häse CC, Fedorova ND, Galperin MY, Dibrov PA. Sodium ion cycle in bacterial pathogens: evidence from cross-genome comparisons. Microbiol Mol Biol Rev 2001; 65:353-70, table of contents. [PMID: 11528000 PMCID: PMC99031 DOI: 10.1128/mmbr.65.3.353-370.2001] [Citation(s) in RCA: 189] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Analysis of the bacterial genome sequences shows that many human and animal pathogens encode primary membrane Na+ pumps, Na+-transporting dicarboxylate decarboxylases or Na+ translocating NADH:ubiquinone oxidoreductase, and a number of Na+ -dependent permeases. This indicates that these bacteria can utilize Na+ as a coupling ion instead of or in addition to the H+ cycle. This capability to use a Na+ cycle might be an important virulence factor for such pathogens as Vibrio cholerae, Neisseria meningitidis, Salmonella enterica serovar Typhi, and Yersinia pestis. In Treponema pallidum, Chlamydia trachomatis, and Chlamydia pneumoniae, the Na+ gradient may well be the only energy source for secondary transport. A survey of preliminary genome sequences of Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, and Treponema denticola indicates that these oral pathogens also rely on the Na+ cycle for at least part of their energy metabolism. The possible roles of the Na+ cycling in the energy metabolism and pathogenicity of these organisms are reviewed. The recent discovery of an effective natural antibiotic, korormicin, targeted against the Na+ -translocating NADH:ubiquinone oxidoreductase, suggests a potential use of Na+ pumps as drug targets and/or vaccine candidates. The antimicrobial potential of other inhibitors of the Na+ cycle, such as monensin, Li+ and Ag+ ions, and amiloride derivatives, is discussed.
Collapse
Affiliation(s)
- C C Häse
- Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
| | | | | | | |
Collapse
|
28
|
Abstract
Na(+)/H(+) antiporters are membrane proteins that play a major role in pH and Na(+) homeostasis of cells throughout the biological kingdom, from bacteria to humans and higher plants. The emerging genomic sequence projects already have started to reveal that the Na(+)/H(+) antiporters cluster in several families. Structure and function studies of a purified antiporter protein have as yet been conducted mainly with NhaA, the key Na(+)/H(+) antiporter of Escherichia coli. This antiporter has been overexpressed, purified and reconstituted in a functional form in proteoliposomes. It has recently been crystallized in both 3D as well as 2D crystals. The NhaA 2D crystals were analyzed by cryoelectron microscopy and a density map at 4 A resolution was obtained and a 3D map was reconstructed. NhaA is shown to exist in the 2D crystals as a dimer of monomers each composed of 12 transmembrane segments with an asymmetric helix packing. This is the first insight into the structure of a polytopic membrane protein. Many Na(+)/H(+) antiporters are characterized by very dramatic sensitivity to pH, a property that corroborates their role in pH homeostasis. The molecular mechanism underlying this pH sensitivity has been studied in NhaA. Amino acid residues involved in the pH response have been identified. Conformational changes transducing the pH change into a change in activity were found in loop VIII-IX and at the N-terminus by probing trypsin digestion or binding of a specific monoclonal antibody respectively. Regulation by pH of the eukaryotic Na(+)/H(+) antiporters involves an intricate signal transduction pathway (recently reviewed by Yun et al., Am. J. Physiol. 269 (1995) G1-G11). The transcription of NhaA has been shown to be regulated by a novel Na(+)-specific regulatory network. It is envisaged that interdisciplinary approaches combining structure, molecular and cell biology as well as genomics should be applied in the future to the study of this important group of transporters.
Collapse
Affiliation(s)
- E Padan
- Department of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University of Jerusalem, Israel.
| | | | | | | |
Collapse
|
29
|
Dover N, Padan E. Transcription of nhaA, the main Na(+)/H(+) antiporter of Escherichia coli, is regulated by Na(+) and growth phase. J Bacteriol 2001; 183:644-53. [PMID: 11133959 PMCID: PMC94921 DOI: 10.1128/jb.183.2.644-653.2001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The transcription of nhaA, encoding the main Na(+)/H(+) antiporter of Escherichia coli, is induced by Na(+), regulated by NhaR, and affected by H-NS. In this work the roles of the two nhaA promoters (P1 and P2) were studied by analysis of transcription both in vivo and in vitro and promoter mutations. We found that P1 is an NhaR-dependent, Na(+)-induced, and H-NS-affected promoter both in the exponential and stationary phases. An in vitro transcription assay demonstrated that P1 is activated by sigma(70)-RNA polymerase and both NhaR and H-NS increase the specificity of P1. Remarkably, in marked contrast to P1, P2 exhibits very low activity during the exponential phase but is induced in the stationary phase to become the major promoter. Furthermore, P2 is activated by sigma(S) and is neither induced by Na(+) nor dependent on NhaR or affected by H-NS. Hence, this work establishes that nhaA has a dual mode of regulation, each involving a different promoter, and reveals that P2 and sigma(S) together are responsible for the survival of stationary-phase cells in the presence of high Na(+), alkaline pH, and the combination of high Na(+) and alkaline pH, the most stressful condition.
Collapse
Affiliation(s)
- N Dover
- Division of Microbial and Molecular Ecology, Institute of Life Sciences, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | | |
Collapse
|
30
|
Sharma PK, Balkwill DL, Frenkel A, Vairavamurthy MA. A new Klebsiella planticola strain (Cd-1) grows anaerobically at high cadmium concentrations and precipitates cadmium sulfide. Appl Environ Microbiol 2000; 66:3083-7. [PMID: 10877810 PMCID: PMC92115 DOI: 10.1128/aem.66.7.3083-3087.2000] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2000] [Accepted: 04/25/2000] [Indexed: 11/20/2022] Open
Abstract
Heavy metal resistance by bacteria is a topic of much importance to the bioremediation of contaminated soils and sediments. We report here the isolation of a highly cadmium-resistant Klebsiella planticola strain, Cd-1, from reducing salt marsh sediments. The strain grows in up to 15 mM CdCl(2) under a wide range of NaCl concentrations and at acidic or neutral pH. In growth medium amended with thiosulfate, it precipitated significant amounts of cadmium sulfide (CdS), as confirmed by x-absorption spectroscopy. In comparison with various other strains tested, Cd-1 is superior for precipitating CdS in cultures containing thiosulfate. Thus, our results suggest that Cd-1 is a good candidate for the accelerated bioremediation of systems contaminated by high levels of cadmium.
Collapse
Affiliation(s)
- P K Sharma
- Department of Applied Science, Brookhaven National Laboratory, Upton, New York 11973, USA
| | | | | | | |
Collapse
|
31
|
Vimont S, Berche P. NhaA, an Na(+)/H(+) antiporter involved in environmental survival of Vibrio cholerae. J Bacteriol 2000; 182:2937-44. [PMID: 10781565 PMCID: PMC102005 DOI: 10.1128/jb.182.10.2937-2944.2000] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae, the agent of cholera, is a normal inhabitant of aquatic environments, in which it survives under a wide range of conditions of pH and salinity. In this work, we identified the nhaA gene in a wild-type epidemic strain of V. cholerae O1. nhaA encodes a protein of 382 amino acids that is very similar to the proteins NhaA of Vibrio parahaemolyticus, Vibrio alginolyticus ( approximately 87% identity), and Escherichia coli (56% identity). V. cholerae NhaA complements an E. coli nhaA mutant, enabling it to grow in 700 mM NaCl, pH 7.5, indicating functional homology to E. coli NhaA. However, unlike E. coli, the growth of a nhaA-inactivated mutant of V. cholerae was not restricted at various pH and NaCl concentrations, although it was inhibited in the presence of 120 mM LiCl at pH 8.5. Nevertheless, using a nhaA'-lacZ transcriptional fusion, we observed induction of nhaA transcription by Na(+), Li(+), and K(+). These results strongly suggest that NhaA is an Na(+)/H(+) antiporter contributing to the Na(+)/H(+) homeostasis of V. cholerae. nhaA-related sequences were detected in all strains of V. cholerae from the various serogroups. This gene is presumably involved in the survival and persistence of free-living bacteria in their natural habitat.
Collapse
Affiliation(s)
- S Vimont
- Institut National de la Santé et de la Recherche Médicale (INSERM U411), CHU Necker-Enfants-Malades, 75730 Paris Cedex 15, France
| | | |
Collapse
|
32
|
Venturi M, Rimon A, Gerchman Y, Hunte C, Padan E, Michel H. The monoclonal antibody 1F6 identifies a pH-dependent conformational change in the hydrophilic NH(2) terminus of NhaA Na(+)/H(+) antiporter of Escherichia coli. J Biol Chem 2000; 275:4734-42. [PMID: 10671505 DOI: 10.1074/jbc.275.7.4734] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
One of the most interesting properties of the NhaA Na(+)/H(+) antiporter of Escherichia coli is the strong regulation of its activity by pH. This regulation is accompanied by a conformational change that can be probed by digestion with trypsin and involves the hydrophilic loop connecting the transmembrane helices VIII-IX. In the present work we show that a monoclonal antibody (mAb), 1F6, recognizes yet another domain of NhaA in a pH-dependent manner. This antibody binds NhaA at pH 8.5 but not at pH 4.5, whereas two other mAbs bind to NhaA independently of pH. The epitope of mAb 1F6 was located at the NH(2) terminus of NhaA by probing proteolytic fragments in Western blot analysis and amino acid sequencing. The antibody bound to the peptide HLHRFFSS, starting at the third amino acid of NhaA. A synthetic peptide with this sequence was shown to bind mAb 1F6 both at acidic and alkaline pH suggesting that this peptide is accessible to mAb 1F6 in the native protein only at alkaline pH. Although slightly shifted to acidic pH, the pH profile of the binding of mAb 1F6 to the antiporter is similar to that of both the Na(+)/H(+) antiporter activity as well as to its sensitivity to trypsin. We thus suggest that these pH profiles reflect a pH-dependent conformational change, which leads to activation of the antiporter. Indeed, a replacement of Gly-338 by Ser (G338S), which alleviates the pH dependence of both the NhaA activity as well as its sensitivity to trypsin, affects in a similar pattern the binding of mAb 1F6 to NhaA. Furthermore, the binding site of mAb 1F6 is involved in the functioning of the antiporter as follows: a double Cys replacement H3C/H5C causes an acidic shift by half a pH unit in the pH dependence of the antiporter; N-ethylmaleimide, which does not inhibit the wild-type protein, inhibits H3C/H5C antiporter to an extent similar to that exerted by mAb 1F6.
Collapse
Affiliation(s)
- M Venturi
- Max-Planck Institut für Biophysik, Abteilung Molekulare Membranbiologie, Heinrich-Hoffmann Strasse 7, D-60528 Frankfurt/Main, Germany.
| | | | | | | | | | | |
Collapse
|
33
|
Gerchman Y, Rimon A, Padan E. A pH-dependent conformational change of NhaA Na(+)/H(+) antiporter of Escherichia coli involves loop VIII-IX, plays a role in the pH response of the protein, and is maintained by the pure protein in dodecyl maltoside. J Biol Chem 1999; 274:24617-24. [PMID: 10455127 DOI: 10.1074/jbc.274.35.24617] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Digestion with trypsin of purified His-tagged NhaA in a solution of dodecyl maltoside yields two fragments at alkaline pH but only one fragment at acidic pH. Determination of the amino acid sequence of the N terminus of the cleavage products show that the pH-sensitive cleavage site of NhaA, both in isolated everted membrane vesicles as well as in the pure protein in detergent, is Lys-249 in loop VIII-IX, which connects transmembrane segment VIII to IX. Interestingly, the two polypeptide products of the split antiporter remain complexed and co-purify on Ni(2+)-NTA column. Loop VIII-IX has also been found to play a role in the pH regulation of NhaA; three mutations introduced into the loop shift the pH profile of the Na(+)/H(+) antiporter activity as measured in everted membrane vesicles. An insertion mutation introducing Ile-Glu-Gly between residues Lys-249 and Arg-250 (K249-IEG-R250) and Cys replacement of either Val-254 (V254C) or Glu-241 (E241C) cause acidic shift of the pH profile of the antiporter by 0.5, 1, and 0.3 pH units, respectively. Interestingly, the double mutant E241C/V254C introduces a basic shift of more than 1 pH unit with respect to the single mutation V254C. Taken together these results imply the involvement of loop VIII-IX in the pH-induced conformational change, which leads to activation of NhaA at alkaline pH.
Collapse
Affiliation(s)
- Y Gerchman
- Division of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | | | | |
Collapse
|
34
|
Ryu JH, Deng Y, Beuchat L. Survival of Escherichia coli O157:H7 in dried beef powder as affected by water activity, sodium chloride content and temperature. Food Microbiol 1999. [DOI: 10.1006/fmic.1998.0233] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
35
|
Padan E, Gerchman Y, Rimon A, Rothman A, Dover N, Carmel-Harel O. The molecular mechanism of regulation of the NhaA Na+/H+ antiporter of Escherichia coli, a key transporter in the adaptation to Na+ and H+. NOVARTIS FOUNDATION SYMPOSIUM 1999; 221:183-96; discussion 196-9. [PMID: 10207920 DOI: 10.1002/9780470515631.ch12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The NhaA Na+/H+ antiporter is the main system responsible for adaptation to Na+ and alkaline pH (in the presence of Na+) in Escherichia coli and many other enteric bacteria. It is under intricate control. At the protein level it is regulated directly by pH, one of its regulatory signals. A pH shift from 7 to 8.5 activates the antiporter and, in a fashion correlated with the activity change, confers a conformation change that, in isolated membrane vesicles, is reflected in the exposure of trypsin-cleavable sites. H225 and G338 are essential for the pH response of NhaA. nhaA transcription is dependent on NhaR, a positive regulator of the LysR family, and is regulated by Na+, the other environmental signal. Na+ affects the NhaR/nhaA interaction directly by changing the footprint of NhaR on nhaA in a pH-dependent fashion. The expression of nhaA is also under global regulation of H-NS. We suggest that the pattern of regulation of nhaA found in E. coli is a paradigm for the response of proteins and genes to H+ and Na+, the most common ions that challenge every cell.
Collapse
Affiliation(s)
- E Padan
- Hebrew University of Jerusalem, Department of Microbial and Molecular Ecology, Jerusalem, Israel
| | | | | | | | | | | |
Collapse
|
36
|
Slonczewski JL, Blankenhorn D. Acid and base regulation in the proteome of Escherichia coli. NOVARTIS FOUNDATION SYMPOSIUM 1999; 221:75-83; discussions 83-92. [PMID: 10207914 DOI: 10.1002/9780470515631.ch6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Acid and base conditions have many significant effects on the growth of Escherichia coli. External and internal pH perturbations induce different classes of genes. pH-dependent regulation of genes intersects with other regulatory responses, e.g. oxygen level or osmolarity. 2D electrophoretic gels were used to compare global patterns of protein induction in Escherichia coli grown in complex media buffered at the acid or alkaline ends of the pH range for growth (pH 4.4 vs. pH 9.1). Preliminary results indicate new classes of acid- and base-dependent regulation, in some cases highly dependent on oxygen level. Other proteins are induced strongly at both extremes of pH, compared to pH 7. Current work continues to dissect the relationship between effects of pH, oxygen level and osmolarity.
Collapse
Affiliation(s)
- J L Slonczewski
- Department of Biology, Kenyon College, Gambier, OH 43022, USA
| | | |
Collapse
|
37
|
Blankenhorn D, Phillips J, Slonczewski JL. Acid- and base-induced proteins during aerobic and anaerobic growth of Escherichia coli revealed by two-dimensional gel electrophoresis. J Bacteriol 1999; 181:2209-16. [PMID: 10094700 PMCID: PMC93635 DOI: 10.1128/jb.181.7.2209-2216.1999] [Citation(s) in RCA: 167] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Proteins induced by acid or base, during long-term aerobic or anaerobic growth in complex medium, were identified in Escherichia coli. Two-dimensional gel electrophoresis revealed pH-dependent induction of 18 proteins, nine of which were identified by N-terminal sequencing. At pH 9, tryptophan deaminase (TnaA) was induced to a high level, becoming one of the most abundant proteins observed. TnaA may reverse alkalinization by metabolizing amino acids to produce acidic products. Also induced at high pH, but only in anaerobiosis, was glutamate decarboxylase (GadA). The gad system (GadA/GadBC) neutralizes acidity and enhances survival in extreme acid; its induction during anaerobic growth may help protect alkaline-grown cells from the acidification resulting from anaerobic fermentation. To investigate possible responses to internal acidification, cultures were grown in propionate, a membrane-permeant weak acid which acidifies the cytoplasm. YfiD, a homologue of pyruvate formate lyase, was induced to high levels at pH 4.4 and induced twofold more by propionate at pH 6; both of these conditions cause internal acidification. At neutral or alkaline pH, YfiD was virtually absent. YfiD is therefore a strong candidate for response to internal acidification. Acid or propionate also increased the expression of alkyl hydroperoxide reductase (AhpC) but only during aerobic growth. At neutral or high pH, AhpC showed no significant difference between aerobic and anaerobic growth. The increase of AhpC in acid may help protect the cell from the greater concentrations of oxidizing intermediates at low pH. Isocitrate lyase (AceA) was induced by oxygen across the pH range but showed substantially greater induction in acid or in base than at pH 7. Additional responses observed included the induction of MalE at high pH and induction of several enzymes of sugar metabolism at low pH: the phosphotransferase system components ManX and PtsH and the galactitol fermentation enzyme GatY. Overall, our results indicate complex relationships between pH and oxygen and a novel permeant acid-inducible gene, YfiD.
Collapse
Affiliation(s)
- D Blankenhorn
- Department of Biology, Kenyon College, Gambier, Ohio 43022, USA
| | | | | |
Collapse
|
38
|
Vasseur C, Baverel L, Hébraud M, Labadie J. Effect of osmotic, alkaline, acid or thermal stresses on the growth and inhibition of Listeria monocytogenes. J Appl Microbiol 1999; 86:469-76. [PMID: 10196752 DOI: 10.1046/j.1365-2672.1999.00686.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Five strains of Listeria monocytogenes (a, b, c, d and e) isolated from industrial plants have been subjected to different osmotic, alkaline, acid or thermal stresses. The effects of these treatments on lag-phase (L) and growth rate (mu) of cells in mid-log phase have been followed using an automated optical density monitoring system. Increasing the osmotic pressure by the addition of different amounts of NaCl increased the lag phase and decreased the growth rate. The same phenomena were observed after decreasing the pH of the medium to 5.8, 5.6 or 5.4 by addition of acetic, lactic or hydrochloric acids. The inhibitory effect was: acetic acid > lactic acid > hydrochloric acid. The addition of NaOH to attain pH values of 9.5, 10.0, 10.5 or 11.0 in the medium produced a dramatic increase of the lag phase at pH 10.5 and 11. Growth rates were also decreased while the maximal population increased with high pH values. These effects varied according to strains. Strains d and e were the most resistant to acidic and alkaline stresses, and e was the most affected by the addition of NaCl. A cold shock of 30 min at 0 degree C had limited effects on growth parameters. On the other hand, hyperthermal shocks (55 or 63 degrees C, 30 min) led to similar increased lag phases and to significant increases of the maximal population in all five strains.
Collapse
Affiliation(s)
- C Vasseur
- Station de Recherches sur la Viande, Unité de Recherches de Microbiologie, INRA de Theix, Saint-Genès-Champanelle, France
| | | | | | | |
Collapse
|
39
|
Lease RA, Cusick ME, Belfort M. Riboregulation in Escherichia coli: DsrA RNA acts by RNA:RNA interactions at multiple loci. Proc Natl Acad Sci U S A 1998; 95:12456-61. [PMID: 9770507 PMCID: PMC22852 DOI: 10.1073/pnas.95.21.12456] [Citation(s) in RCA: 211] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DsrA is an 87-nt untranslated RNA that regulates both the global transcriptional silencer and nucleoid protein H-NS and the stationary phase and stress response sigma factor RpoS (sigmas). We demonstrate that DsrA acts via specific RNA:RNA base pairing interactions at the hns locus to antagonize H-NS translation. We also give evidence that supports a role for RNA:RNA interactions at the rpoS locus to enhance RpoS translation. Negative regulation of hns by DsrA is achieved by the RNA:RNA interaction blocking translation of hns RNA. In contrast, results suggest that positive regulation of rpoS by DsrA occurs by formation of an RNA structure that activates a cis-acting translational operator. Sequences within DsrA complementary to three additional genes, argR, ilvIH, and rbsD, suggest that DsrA is a riboregulator of gene expression that acts coordinately via RNA:RNA interactions at multiple loci.
Collapse
Affiliation(s)
- R A Lease
- Molecular Genetics Program, Wadsworth Center, New York State Department of Health, and School of Public Health, State University of New York at Albany, P.O. Box 22002, Albany, New York 12201-2002, USA
| | | | | |
Collapse
|
40
|
Rimon A, Gerchman Y, Kariv Z, Padan E. A point mutation (G338S) and its suppressor mutations affect both the pH response of the NhaA-Na+/H+ antiporter as well as the growth phenotype of Escherichia coli. J Biol Chem 1998; 273:26470-6. [PMID: 9756882 DOI: 10.1074/jbc.273.41.26470] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
pH controls the activity of the NhaA Na+/H+ antiporter of Escherichia coli. In the present work we show that replacement of glycine 338 of NhaA with serine (G338S) alleviates the pH control of the antiporter. Monitoring Na+-dependent collapse of DeltapH, to assess antiporter activity in isolated membrane vesicles, shows that the mutant protein is practically independent of pH, between pH 7 and 9, and even at pH 6 is 70% active. Similarly the purified reconstituted mutant protein catalyzes pH-independent passive efflux of 22Na from proteoliposomes as well as DeltapH-driven influx. Whereas the native NhaA in isolated membrane vesicles is exposed to digestion by trypsin only above pH 7, the mutated protein is degraded already at pH 6.5. DeltanhaA DeltanhaB cells transformed with a plasmid encoding the pH-independent antiporter are sensitive to Na+ but not to K+ at alkaline pH, while growing in the presence of both ions at neutral pH. Several possibilities that could explain the Na+ sensitivity of the mutant at alkaline pH were excluded; Western analysis and measurement of Na+/H+ antiporter activity in membrane vesicles, isolated from cells shifted to the non-permissive growth conditions, showed neither reduced expression of G338S-NhaA nor defective activity. The finding that the mutated protein is electrogenic led to the retraction of the idea that the protein is active in vitro but not in vivo at alkaline pH, when only Deltapsi exists in the cells. The Na+ concentration needed for half-maximal activity of G338S in isolated everted membrane vesicles is similar to that of the wild type. Therefore an increase in intracellular Na+ due to a reduced antiporter affinity could not explain the results. It is suggested that the loss of growth at alkaline pH in the presence of Na+ is due to the loss of the pH control of the mutated NhaA. Indeed, in the four mutations suppressing G338S phenotype, growth at alkaline pH was restored together with the pH regulation of NhaA. Three of the four suppressor mutations cluster in helix IV, whereas the original mutation is in helix XI, suggesting that the two helixes interact.
Collapse
Affiliation(s)
- A Rimon
- Division of Microbial and Molecular Ecology, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | | | | | | |
Collapse
|
41
|
Abstract
This map is an update of the edition 9 map by Berlyn et al. (M. K. B. Berlyn, K. B. Low, and K. E. Rudd, p. 1715-1902, in F. C. Neidhardt et al., ed., Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed., vol. 2, 1996). It uses coordinates established by the completed sequence, expressed as 100 minutes for the entire circular map, and adds new genes discovered and established since 1996 and eliminates those shown to correspond to other known genes. The latter are included as synonyms. An alphabetical list of genes showing map location, synonyms, the protein or RNA product of the gene, phenotypes of mutants, and reference citations is provided. In addition to genes known to correspond to gene sequences, other genes, often older, that are described by phenotype and older mapping techniques and that have not been correlated with sequences are included.
Collapse
Affiliation(s)
- M K Berlyn
- Department of Biology and School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06520-8104, USA.
| |
Collapse
|
42
|
Evidence for the existence of a novel component of biological water stress (anhydrotic stress) inEscherichia coli. J Genet 1998. [DOI: 10.1007/bf02933035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
43
|
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.
Collapse
Affiliation(s)
- T Sakuma
- Faculty of Pharmaceutical Sciences, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263, Japan
| | | | | | | | | |
Collapse
|
44
|
Williams SG, Carmel-Harel O, Manning PA. A functional homolog of Escherichia coli NhaR in Vibrio cholerae. J Bacteriol 1998; 180:762-5. [PMID: 9457888 PMCID: PMC106952 DOI: 10.1128/jb.180.3.762-765.1998] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Escherichia coli NhaR controls expression of a sodium/proton (Na+/H+) antiporter, NhaA. The Vibrio cholerae NhaR protein shows over 60% identity to those of Escherichia coli and Salmonella enteritidis. V. cholerae NhaR complements an E. coli nhaR mutant for growth in 100 mM LiCl-33 mM NaCl, pH 7.6, and enhances the Na+-dependent induction of an E. coli chromosomal nhaA::lacZ fusion. These findings indicate functional homology to E. coli NhaR. Two V. cholerae nhaR mutants were constructed by using kanamycin resistance cartridge insertion at different sites to disrupt the gene. Both mutants showed sensitivity to growth in 120 mM LiCl, pH 9.2, compared with the wild-type strain and could be complemented by the introduction of V. cholerae nhaR on a low-copy-number plasmid. An nhaR mutation had no detectable effect on the virulence of the V. cholerae strain in the infant mouse model, suggesting that the antiporter system involved is not required in vivo, at least in this animal model.
Collapse
Affiliation(s)
- S G Williams
- Department of Microbiology and Immunology, University of Adelaide, South Australia, Australia.
| | | | | |
Collapse
|
45
|
Rothman A, Gerchman Y, Padan E, Schuldiner S. Probing the conformation of NhaA, a Na+/H+ antiporter from Escherichia coli, with trypsin. Biochemistry 1997; 36:14572-6. [PMID: 9398175 DOI: 10.1021/bi971800y] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
One of the most striking features of NhaA, an Escherichia coli Na+/H+ antiporter, is its extreme sensitivity to pH. The activity of NhaA increases 2000-fold between pH 6.5 and 8.5. In this work, we investigated whether the activation of NhaA by pH is accompanied by conformational changes which can be detected using trypsin as a probe. We have found that NhaA is susceptible to proteolytic digestion at the pH range where it is activated, suggesting that these two events may be related; at alkaline pH, the protein becomes active and adopts an "open" conformational state in which more domains are exposed to the enzyme. This idea was further supported by results from two mutants of NhaA in which His-225, a residue involved in pH sensing, has been replaced by either Arg or Asp. The mutant H225R is activated at more acidic pH values, while H225D at more alkaline pH. In accordance with the results described for the wild-type protein, H225R was susceptible to digestion by trypsin at the pH at which it undergoes main activation. NhaA has many potential tryptic cleavage sites. However, analysis of the tryptic digestion fragments suggests that at alkaline pH, the protein is exposed to cleavage mainly at hydrophilic loops 6, 7, and 8. Thus, upon activation, NhaA appears to undergo a change in conformation that is reflected in specific regions of the protein.
Collapse
Affiliation(s)
- A Rothman
- Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Israel
| | | | | | | |
Collapse
|
46
|
Ito M, Guffanti AA, Zemsky J, Ivey DM, Krulwich TA. Role of the nhaC-encoded Na+/H+ antiporter of alkaliphilic Bacillus firmus OF4. J Bacteriol 1997; 179:3851-7. [PMID: 9190799 PMCID: PMC179192 DOI: 10.1128/jb.179.12.3851-3857.1997] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Application of protoplast transformation and single- and double-crossover mutagenesis protocols to alkaliphilic Bacillus firmus OF4811M (an auxotrophic strain of B. firmus OF4) facilitated the extension of the sequence of the previously cloned nhaC gene, which encodes an Na+/H+ antiporter, and the surrounding region. The nhaC gene is part of a likely 2-gene operon encompassing nhaC and a small gene that was designated nhaS; the operon is preceded by novel direct repeats. The predicted alkaliphile NhaC, based on the extended sequence analysis, would be a membrane protein with 462 amino acid residues and 12 transmembrane segments that is highly homologous to the deduced products of homologous genes of unknown function from Bacillus subtilis and Haemophilus influenzae. The full-length version of nhaC complemented the Na+-sensitive phenotype of an antiporter-deficient mutant strain of Escherichia coli but not the alkali-sensitive growth phenotypes of Na+/H+-deficient mutants of either alkaliphilic B. firmus OF4811M or B. subtilis. Indeed, NhaC has no required role in alkaliphily, inasmuch as the nhaC deletion strain of B. firmus OF4811M, N13, grew well at pH 10.5 at Na+ concentrations equal to or greater than 10 mM. Even at lower Na+ concentrations, N13 exhibited only a modest growth defect at pH 10.5. This was accompanied by a reduced capacity to acidify the cytoplasm relative to the medium compared to the wild-type strain or to N13 complemented by cloned nhaC. The most notable deficiency observed in N13 was its poor growth at pH 7.5 and Na+ concentrations up to 25 mM. During growth at pH 7.5, NhaC is apparently a major component of the relatively high affinity Na+/H+ antiport activity available to extrude the Na+ and to confer some initial protection in the face of a sudden upshift in external pH, i.e., before full induction of additional antiporters. Consistent with the inference that NhaC is a relatively high affinity, electrogenic Na+/H+ antiporter, N13 exhibited a defect in diffusion potential-energized efflux of 22Na+ from right-side-out membrane vesicles from cells that were preloaded with 2 mM Na+ and energized at pH 7.5. When the experiment was conducted with vesicles loaded with 25 mM Na+, comparable efflux was observed in preparations from all the strains.
Collapse
Affiliation(s)
- M Ito
- Department of Biochemistry, Mount Sinai School of Medicine of the City University of New York, New York 10029, USA
| | | | | | | | | |
Collapse
|
47
|
Olami Y, Rimon A, Gerchman Y, Rothman A, Padan E. Histidine 225, a residue of the NhaA-Na+/H+ antiporter of Escherichia coli is exposed and faces the cell exterior. J Biol Chem 1997; 272:1761-8. [PMID: 8999858 DOI: 10.1074/jbc.272.3.1761] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Cysteine residues were found nonessential in the mechanism of the NhaA antiporter activity of Escherichia coli. The functional C-less NhaA has provided the groundwork to study further histidine 225 of NhaA which has previously been suggested to play an important role in the activation of NhaA at alkaline pH (Rimon, A., Gerchman, Y., Olami, Y., Schuldiner, S. and Padan, E. (1995) J. Biol. Chem. 270, 26813-26817). C-less H225C was constructed and shown to possess an antiporter activity 60% of that of C-less antiporter and a pH profile similar to that of both the C-less or wild-type antiporters. Remarkably, whereas neither the wild-type nor the C-less antiporters were affected by N-ethylmaleimide, C-less H225C was inhibited by this reagent. To determine the degree of alkylation of the antiporter protein by N-ethylmaleimide, antiporter derivatives tagged at their C termini with six histidines residues were constructed. Alkylation of C-less H225C was measured by labeling of everted membrane vesicles with [14C]N-ethylmaleimide, affinity purification of the His-tagged antiporter, and determination of the radioactivity of the purified protein. This assay showed that H225C is alkylated to a much higher level than any of the native cysteinyl residues of NhaA reaching saturation at alkyl/NhaA stoichiometry of 1. The wild-type derivative showed at least 10-fold less alkylation even at higher concentrations, suggesting that H225C resides in a domain that is much more exposed to N-ethylmaleimide than the native cysteinyl residues of NhaA. Since H225C residues both in right-side out and inside-out membrane vesicles were quantitatively alkylated by N-ethylmaleimide, this assay was used to determine the accessibility of H225C to other SH reagents by titrating the H225C left free to react with N-ethylmaleimide, following exposure of the membranes to the reagents. Furthermore, since membrane-impermeant probes can react with residues in membrane-embedded protein only if accessible to the medium containing the reagent, the assay was used to determine the membrane topology of H225C. As expected for a membrane-permeant probe, p-chloromercuribenzoate reacted with H225C as efficiently as N-ethylmaleimide in both membrane orientations. Similar results were obtained with methanethiosulfonate ethylammonium supporting the recent observations that this probe is membrane-permeant. On the other hand, both membrane-impermeant reagents p-chloromercuribenzosulfonate and methanethiosulfonate ethyl-trimethyl ammonium bromide reacted with H225C 10-fold more in right-side out than in inside-out vesicles, and p-chloromercuribenzosulfonate also blocked completely the H225C in intact cells. These results strongly suggest that H225C is exposed at the periplasmic face of the membrane.
Collapse
Affiliation(s)
- Y Olami
- Division of Microbial and Molecular Ecology, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | | | | | | | | |
Collapse
|
48
|
Rothman A, Padan E, Schuldiner S. Topological analysis of NhaA, a Na+/H+ antiporter from Escherichia coli. J Biol Chem 1996; 271:32288-92. [PMID: 8943289 DOI: 10.1074/jbc.271.50.32288] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Analysis of the hydropathic profile of the amino acid sequence of NhaA, a Na+/H+ antiporter from Escherichia coli has previously suggested the existence of 11 putative transmembrane segments (Taglicht, D., Padan, E., and Schuldiner, S. (1991) J. Biol. Chem. 266, 11289-11294). In the present work to test the location of the C terminus, right-side-out and inside-out membrane vesicles were digested with carboxypeptidase B and probed with an antibody raised against a synthetic peptide whose sequence was based on the C terminus sequence. The results demonstrate that the C terminus is facing the cell interior because it is available for digestion only from the inside. Previous evidence from an NhaA-beta-galactosidase fusion to loop 5 of NhaA indicated that this loop is also facing the cytoplasm (Karpel, R., Alon, T., Glaser, G., Schuldiner, S., and Padan, E. (1991) J. Biol. Chem. 266, 21753-21759) and therefore was not consistent with the position of the C terminus in an 11-transmembrane segment model. Therefore, the model was re-evaluated. For this purpose, 10 nhaA'-'phoA gene fusions were constructed and assayed for alkaline phosphatase activity. The results support a 12-transmembrane segment model with the N and C termini located in the cytoplasm. The evidence indicates that two very short segments, 14 and 16 amino acids long, must cross the membrane in an unknown conformation.
Collapse
Affiliation(s)
- A Rothman
- Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
| | | | | |
Collapse
|
49
|
Dover N, Higgins CF, Carmel O, Rimon A, Pinner E, Padan E. Na+-induced transcription of nhaA, which encodes an Na+/H+ antiporter in Escherichia coli, is positively regulated by nhaR and affected by hns. J Bacteriol 1996; 178:6508-17. [PMID: 8932307 PMCID: PMC178537 DOI: 10.1128/jb.178.22.6508-6517.1996] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
nhaA encodes an Na+/H+ antiporter in Escherichia coli which is essential for adaptation to high salinity and alkaline pH in the presence of Na+. We used Northern (RNA) analysis to measure directly the cellular levels of nhaA mRNA. NhaR belongs to the LysR family of regulatory proteins. Consistent with our previous data with an nhaA'-'lacZ fusion, NhaR was found to be a positive regulator and Na+ was found to be a specific inducer of nhaA transcription. In the nhaA'-'lacZ fusion, maximal induction was observed at alkaline pH. In contrast, in the nhaA+ strain both the level of nhaA expression and the induction ratio were lower at alkaline pH. This difference may be due to the activity of NhaA in the wild-type strain as NhaA efficiently excreted Na+ at alkaline pH and reduced the intracellular concentration of Na+, the signal for induction. We also showed that although the global regulator rpoS was not involved in nhaA regulation, the global regulator hns played a role. Thus, the expression of nhaA'-'lacZ was derepressed in strains bearing hns mutations and transformation with a low-copy-number plasmid carrying hns repressed expression and restored Na+ induction. The derepression in hns strains was nhaR independent. Most interestingly, multicopy nhaR, which in an hns+ background acted only as an Na+-dependent positive regulator, acted as a repressor in an hns strain in the absence of Na+ but was activated in the presence of the ion. Hence, an interplay between nhaR and hns in the regulation of nhaA was suggested.
Collapse
Affiliation(s)
- N Dover
- Division of Microbial and Molecular Ecology, Institute of Life Sciences, Hebrew University of Jerusalem, Israel
| | | | | | | | | | | |
Collapse
|
50
|
Murata T, Yamato I, Igarashi K, Kakinuma Y. Intracellular Na+ regulates transcription of the ntp operon encoding a vacuolar-type Na+-translocating ATPase in Enterococcus hirae. J Biol Chem 1996; 271:23661-6. [PMID: 8798587 DOI: 10.1074/jbc.271.39.23661] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The Gram-positive bacterium Enterococcus hirae has a vacuolar-type Na+-translocating ATPase that is encoded by the ntp operon (ntpFIKECGABDHJ) (Takase, K., Kakinuma, S., Yamato, I., Konishi, K., Igarashi, K., and Kakinuma, Y. (1994) J. Biol. Chem. 269, 11037-11044). Primer extension experiments identified the start site of transcription of this operon upstream of the ntpF gene. In parallel with the increases of both Na+-pumping activity in whole cells and Na+-stimulated ATPase activity in the membranes, the amounts of the two major subunits (A and B) of this enzyme increased remarkably in cells grown on medium containing high concentrations of NaCl but not on medium containing KCl or sorbitol. Chloramphenicol completely abolished the increases of the enzyme activity and the amounts of A and B subunits, suggesting that the Na+-ATPase level increased by de novo synthesis of the enzyme with the stimulation of high concentrations of the external sodium ions. Finally, Western blot and Northern blot experiments revealed that the increase in the Na+-ATPase level with the external Na+ was further accelerated by addition of an ionophore, such as monensin, which rendered the cell membrane permeable to Na+. These results suggest that the transcription of the Na+-ATPase operon is regulated by the intracellular concentration of sodium ions.
Collapse
Affiliation(s)
- T Murata
- Department of Biological Science and Technology, Science University of Tokyo, 2641 Yamazaki, Noda-shi, Chiba 278, Japan
| | | | | | | |
Collapse
|