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Dersch S, Graumann PL. Adaptation of Bacillus subtilis MreB Filaments to Osmotic Stress Depends on Influx of Potassium Ions. Microorganisms 2024; 12:1309. [PMID: 39065078 PMCID: PMC11279060 DOI: 10.3390/microorganisms12071309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Revised: 06/13/2024] [Accepted: 06/20/2024] [Indexed: 07/28/2024] Open
Abstract
The circumferential motion of MreB filaments plays a key role in cell shape maintenance in many bacteria. It has recently been shown that filament formation of MreB filaments in Bacillus subtilis is influenced by stress conditions. In response to osmotic upshift, MreB molecules were released from filaments, as seen by an increase in freely diffusive molecules, and the peptidoglycan synthesis pattern became less organized, concomitant with slowed-down cell extension. In this study, biotic and abiotic factors were analysed with respect to a possible function in the adaptation of MreB filaments to stress conditions. We show that parallel to MreB, its interactor RodZ becomes more diffusive following osmotic stress, but the remodeling of MreB filaments is not affected by a lack of RodZ. Conversely, mutant strains that prevent efficient potassium influx into cells following osmotic shock show a failure to disassemble MreB filaments, accompanied by less perturbed cell wall extension than is observed in wild type cells. Because potassium ions are known to negatively affect MreB polymerization in vitro, our data indicate that polymer disassembly is directly mediated by the physical consequences of the osmotic stress response. The lack of an early potassium influx response strongly decreases cell survival following stress application, suggesting that the disassembly of MreB filaments may ensure slowed-down cell wall extension to allow for efficient adaptation to new osmotic conditions.
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Affiliation(s)
| | - Peter L. Graumann
- Centre for Synthetic Microbiology (SYNMIKRO), Fachbereich Chemie, Philipps-Universität Marburg, 35032 Marburg, Germany;
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2
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Gulati A, Kokane S, Perez-Boerema A, Alleva C, Meier PF, Matsuoka R, Drew D. Structure and mechanism of the K +/H + exchanger KefC. Nat Commun 2024; 15:4751. [PMID: 38834573 PMCID: PMC11150392 DOI: 10.1038/s41467-024-49082-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 05/23/2024] [Indexed: 06/06/2024] Open
Abstract
Intracellular potassium (K+) homeostasis is fundamental to cell viability. In addition to channels, K+ levels are maintained by various ion transporters. One major family is the proton-driven K+ efflux transporters, which in gram-negative bacteria is important for detoxification and in plants is critical for efficient photosynthesis and growth. Despite their importance, the structure and molecular basis for K+-selectivity is poorly understood. Here, we report ~3.1 Å resolution cryo-EM structures of the Escherichia coli glutathione (GSH)-gated K+ efflux transporter KefC in complex with AMP, AMP/GSH and an ion-binding variant. KefC forms a homodimer similar to the inward-facing conformation of Na+/H+ antiporter NapA. By structural assignment of a coordinated K+ ion, MD simulations, and SSM-based electrophysiology, we demonstrate how ion-binding in KefC is adapted for binding a dehydrated K+ ion. KefC harbors C-terminal regulator of K+ conductance (RCK) domains, as present in some bacterial K+-ion channels. The domain-swapped helices in the RCK domains bind AMP and GSH and they inhibit transport by directly interacting with the ion-transporter module. Taken together, we propose that KefC is activated by detachment of the RCK domains and that ion selectivity exploits the biophysical properties likewise adapted by K+-ion-channels.
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Affiliation(s)
- Ashutosh Gulati
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Surabhi Kokane
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Annemarie Perez-Boerema
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Claudia Alleva
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Pascal F Meier
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Rei Matsuoka
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden
| | - David Drew
- Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
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3
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Rasmussen T. The Potassium Efflux System Kef: Bacterial Protection against Toxic Electrophilic Compounds. MEMBRANES 2023; 13:membranes13050465. [PMID: 37233526 DOI: 10.3390/membranes13050465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Revised: 04/21/2023] [Accepted: 04/23/2023] [Indexed: 05/27/2023]
Abstract
Kef couples the potassium efflux with proton influx in gram-negative bacteria. The resulting acidification of the cytosol efficiently prevents the killing of the bacteria by reactive electrophilic compounds. While other degradation pathways for electrophiles exist, Kef is a short-term response that is crucial for survival. It requires tight regulation since its activation comes with the burden of disturbed homeostasis. Electrophiles, entering the cell, react spontaneously or catalytically with glutathione, which is present at high concentrations in the cytosol. The resulting glutathione conjugates bind to the cytosolic regulatory domain of Kef and trigger activation while the binding of glutathione keeps the system closed. Furthermore, nucleotides can bind to this domain for stabilization or inhibition. The binding of an additional ancillary subunit, called KefF or KefG, to the cytosolic domain is required for full activation. The regulatory domain is termed K+ transport-nucleotide binding (KTN) or regulator of potassium conductance (RCK) domain, and it is also found in potassium uptake systems or channels in other oligomeric arrangements. Bacterial RosB-like transporters and K+ efflux antiporters (KEA) of plants are homologs of Kef but fulfill different functions. In summary, Kef provides an interesting and well-studied example of a highly regulated bacterial transport system.
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Affiliation(s)
- Tim Rasmussen
- Rudolf Virchow Center and Biocenter, Institute of Biochemistry II, Julius-Maximilians-Universität Würzburg, Josef-Schneider-Str. 2, 97080 Würzburg, Germany
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4
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Lee CE, Charmantier G, Lorin-Nebel C. Mechanisms of Na + uptake from freshwater habitats in animals. Front Physiol 2022; 13:1006113. [PMID: 36388090 PMCID: PMC9644288 DOI: 10.3389/fphys.2022.1006113] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/28/2022] [Indexed: 07/20/2023] Open
Abstract
Life in fresh water is osmotically and energetically challenging for living organisms, requiring increases in ion uptake from dilute environments. However, mechanisms of ion uptake from freshwater environments are still poorly understood and controversial, especially in arthropods, for which several hypothetical models have been proposed based on incomplete data. One compelling model involves the proton pump V-type H+ ATPase (VHA), which energizes the apical membrane, enabling the uptake of Na+ (and other cations) via an unknown Na+ transporter (referred to as the "Wieczorek Exchanger" in insects). What evidence exists for this model of ion uptake and what is this mystery exchanger or channel that cooperates with VHA? We present results from studies that explore this question in crustaceans, insects, and teleost fish. We argue that the Na+/H+ antiporter (NHA) is a likely candidate for the Wieczorek Exchanger in many crustaceans and insects; although, there is no evidence that this is the case for fish. NHA was discovered relatively recently in animals and its functions have not been well characterized. Teleost fish exhibit redundancy of Na+ uptake pathways at the gill level, performed by different ion transporter paralogs in diverse cell types, apparently enabling tolerance of low environmental salinity and various pH levels. We argue that much more research is needed on overall mechanisms of ion uptake from freshwater habitats, especially on NHA and other potential Wieczorek Exchangers. Such insights gained would contribute greatly to our general understanding of ionic regulation in diverse species across habitats.
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Affiliation(s)
- Carol Eunmi Lee
- Department of Integrative Biology, University of Wisconsin, Madison, WI, United States
- MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Montpellier, France
| | - Guy Charmantier
- MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Montpellier, France
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Azeem F, Zameer R, Rehman Rashid MA, Rasul I, Ul-Allah S, Siddique MH, Fiaz S, Raza A, Younas A, Rasool A, Ali MA, Anwar S, Siddiqui MH. Genome-wide analysis of potassium transport genes in Gossypium raimondii suggest a role of GrHAK/KUP/KT8, GrAKT2.1 and GrAKT1.1 in response to abiotic stress. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2022; 170:110-122. [PMID: 34864561 DOI: 10.1016/j.plaphy.2021.11.038] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 06/13/2023]
Abstract
Potassium (K+) is an important macro-nutrient for plants, which comprises almost 10% of plant's dry mass. It plays a crucial role in the growth of plants as well as other important processes related to metabolism and stress tolerance. Plants have a complex and well-organized potassium distribution system (channels and transporters). Cotton is the most important economic crop, which is the primary source of natural fiber. Soil deficiency in K+ can negatively affect yield and fiber quality of cotton. However, potassium transport system in cotton is poorly studied. Current study identified 43 Potassium Transport System (PTS) genes in Gossypium raimondii genome. Based on conserved domains, transmembrane domains, and motif structures, these genes were classified as K+ transporters (2 HKTs, 7 KEAs, and 16 KUP/HAK/KTs) and K+ channels (11 Shakers and 7 TPKs/KCO). The phylogenetic comparison of GrPTS genes from Arabidopsis thaliana, Glycine max, Oryza sativa, Medicago truncatula and Cicer arietinum revealed variations in PTS gene conservation. Evolutionary analysis predicted that most GrPTS genes were segmentally duplicated. Gene structure analysis showed that the intron/exon organization of these genes was conserved in specific-family. Chromosomal localization demonstrated a random distribution of PTS genes across all the thirteen chromosomes except chromosome six. Many stress responsive cis-regulatory elements were predicted in promoter regions of GrPTS genes. The RNA-seq data analysis followed by qRT-PCR validation demonstrated that PTS genes potentially work in groups against environmental factors. Moreover, a transporter gene (GrHAK/KUP/KT8) and two channel genes (GrAKT2.1 and GrAKT1.1) are important candidate genes for plant stress response. These results provide useful information for further functional characterization of PTS genes with the breeding aim of stress-resistant cultivars.
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Affiliation(s)
- Farrukh Azeem
- Department of Bioinformatics and Biotechnology, Govt. College University, Faisalabad, Pakistan
| | - Roshan Zameer
- Department of Bioinformatics and Biotechnology, Govt. College University, Faisalabad, Pakistan
| | | | - Ijaz Rasul
- Department of Bioinformatics and Biotechnology, Govt. College University, Faisalabad, Pakistan
| | - Sami Ul-Allah
- College of Agriculture, Bahauddin Zakariya University, Bahadur Sub-Campus, Layyah, Pakistan
| | | | - Sajid Fiaz
- Department of Plant Breeding and Genetics, The University of Haripur, 22620, Haripir, Pakistan.
| | - Ali Raza
- Fujian Provincial Key Laboratory of Crop Molecular and Cell Biology, Oil Crops Research Institute, Center of Legume Crop Genetics and Systems Biology/College of Agriculture, Fujian Agriculture and Forestry University (FAFU), Fuzhou, Fujian, 350002, China
| | - Afifa Younas
- Department of Botany, Lahore College for Women University, Lahore, Pakistan
| | - Asima Rasool
- Department of Bioinformatics and Biotechnology, Govt. College University, Faisalabad, Pakistan
| | - Muhammad Amjad Ali
- Department of Plant Pathology, University of Agriculture, Faisalabad, Pakistan
| | - Sultana Anwar
- Department of Agronomy, University of Florida, Gainesville, USA
| | - Manzer H Siddiqui
- Department of Botany and Microbiology, College of Science, King Saud University, Riyadh, Saudi Arabia
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Mondal R, Rimon A, Masrati G, Ben-Tal N, Friedler A, Padan E. Towards Molecular Understanding of the pH Dependence Characterizing NhaA of Which Structural Fold is Shared by Other Transporters. J Mol Biol 2021; 433:167156. [PMID: 34273399 DOI: 10.1016/j.jmb.2021.167156] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 06/19/2021] [Accepted: 07/08/2021] [Indexed: 11/25/2022]
Abstract
Na+/H+ antiporters comprise a super-family (CPA) of membrane proteins that are found in all kingdoms of life and are essential in cellular homeostasis of pH, Na+ and volume. Their activity is strictly dependent on pH, a property that underpins their role in pH homeostasis. While several human homologues have long been drug targets, NhaA of Escherichia coli has become the paradigm for this class of secondary active transporters as NhaA crystal structure provided insight into the architecture of this molecular machine. However, the mechanism of the strict pH dependence of NhaA is missing. Here, as a follow up of a recent evolutionary analysis that identified a 'CPA motif', we rationally designed three E. coli NhaA mutants: D133S, I134T, and the double mutant D133S-I134T. Exploring growth phenotype, transport activity and Li+-binding of the mutants, we revealed that Asp133 does not participate directly in proton binding, nor does it directly dictate the pH-dependent transport of NhaA. Strikingly, the variant I134T lost some of the pH control, and the D133S-Il134T double mutant retained Li+ binding in a pH independent fashion. Concurrent to loss of pH control, these mutants bound Li+ more strongly than the WT. Both positions are in close vicinity to the ion-binding site of the antiporter, attributing the results to electrostatic interaction between these residues and Asp164 of the ion-binding site. This is consistent with pH sensing resulting from direct coupling between cation binding and deprotonation in Asp164, which applies also to other CPA antiporters that are involved in human diseases.
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Affiliation(s)
- R Mondal
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - A Rimon
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - G Masrati
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978 Tel-Aviv, Israel
| | - N Ben-Tal
- Department of Biochemistry and Molecular Biology, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, 69978 Tel-Aviv, Israel
| | - A Friedler
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - E Padan
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel.
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7
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c-di-AMP, a likely master regulator of bacterial K + homeostasis machinery, activates a K + exporter. Proc Natl Acad Sci U S A 2021; 118:2020653118. [PMID: 33790011 DOI: 10.1073/pnas.2020653118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
bis-(3',5')-cyclic diadenosine monophosphate (c-di-AMP) is a second messenger with roles in virulence, cell wall and biofilm formation, and surveillance of DNA integrity in many bacterial species, including pathogens. Strikingly, it has also been proposed to coordinate the activity of the components of K+ homeostasis machinery, inhibiting K+ import, and activating K+ export. However, there is a lack of quantitative evidence supporting the direct functional impact of c-di-AMP on K+ transporters. To gain a detailed understanding of the role of c-di-AMP on the activity of a component of the K+ homeostasis machinery in B. subtilis, we have characterized the impact of c-di-AMP on the functional, biochemical, and physiological properties of KhtTU, a K+/H+ antiporter composed of the membrane protein KhtU and the cytosolic protein KhtT. We have confirmed c-di-AMP binding to KhtT and determined the crystal structure of this complex. We have characterized in vitro the functional properties of KhtTU and KhtU alone and quantified the impact of c-di-AMP and of pH on their activity, demonstrating that c-di-AMP activates KhtTU and that pH increases its sensitivity to this nucleotide. Based on our functional and structural data, we were able to propose a mechanism for the activation of KhtTU by c-di-AMP. In addition, we have analyzed the impact of KhtTU in its native bacterium, providing a physiological context for the regulatory function of c-di-AMP and pH. Overall, we provide unique information that supports the proposal that c-di-AMP is a master regulator of K+ homeostasis machinery.
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8
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Stautz J, Hellmich Y, Fuss MF, Silberberg JM, Devlin JR, Stockbridge RB, Hänelt I. Molecular Mechanisms for Bacterial Potassium Homeostasis. J Mol Biol 2021; 433:166968. [PMID: 33798529 DOI: 10.1016/j.jmb.2021.166968] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/11/2021] [Accepted: 03/22/2021] [Indexed: 10/21/2022]
Abstract
Potassium ion homeostasis is essential for bacterial survival, playing roles in osmoregulation, pH homeostasis, regulation of protein synthesis, enzyme activation, membrane potential adjustment and electrical signaling. To accomplish such diverse physiological tasks, it is not surprising that a single bacterium typically encodes several potassium uptake and release systems. To understand the role each individual protein fulfills and how these proteins work in concert, it is important to identify the molecular details of their function. One needs to understand whether the systems transport ions actively or passively, and what mechanisms or ligands lead to the activation or inactivation of individual systems. Combining mechanistic information with knowledge about the physiology under different stress situations, such as osmostress, pH stress or nutrient limitation, one can identify the task of each system and deduce how they are coordinated with each other. By reviewing the general principles of bacterial membrane physiology and describing the molecular architecture and function of several bacterial K+-transporting systems, we aim to provide a framework for microbiologists studying bacterial potassium homeostasis and the many K+-translocating systems that are still poorly understood.
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Affiliation(s)
- Janina Stautz
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Yvonne Hellmich
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Michael F Fuss
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Jakob M Silberberg
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Jason R Devlin
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States
| | - Randy B Stockbridge
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States.
| | - Inga Hänelt
- Institute of Biochemistry, Goethe University Frankfurt, Frankfurt am Main, Germany.
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Li Y, Feng Z, Wei H, Cheng S, Hao P, Yu S, Wang H. Silencing of GhKEA4 and GhKEA12 Revealed Their Potential Functions Under Salt and Potassium Stresses in Upland Cotton. FRONTIERS IN PLANT SCIENCE 2021; 12:789775. [PMID: 34950173 PMCID: PMC8689187 DOI: 10.3389/fpls.2021.789775] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 11/09/2021] [Indexed: 05/10/2023]
Abstract
The K+ efflux antiporter (KEA) mediates intracellular K+ and H+ homeostasis to improve salt tolerance in plants. However, the knowledge of KEA gene family in cotton is largely absent. In the present study, 8, 8, 15, and 16 putative KEA genes were identified in Gossypium arboreum, G. raimondii, G. hirsutum, and G. barbadense, respectively. These KEA genes were classified into three subfamilies, and members from the same subfamilies showed similar motif compositions and gene structure characteristics. Some hormone response elements and stress response elements were identified in the upstream 2000 bp sequence of GhKEAs. Transcriptome data showed that most of the GhKEAs were highly expressed in roots and stems. The quantificational real-time polymerase chain reaction (qRT-PCR) results showed that most of the GhKEAs responded to low potassium, salt and drought stresses. Virus-induced gene silencing (VIGS) experiments demonstrated that under salt stress, after silencing genes GhKEA4 and GhKEA12, the chlorophyll content, proline content, soluble sugar content, peroxidase (POD) activity and catalase (CAT) activity were significantly decreased, and the Na+/K+ ratio was extremely significantly increased in leaves, leading to greater salt sensitivity. Under high potassium stress, cotton plants silenced for the GhKEA4 could still maintain a more stable Na+ and K+ balance, and the activity of transporting potassium ions from roots into leaves was reduced silenced for GhKEA12. Under low potassium stress, silencing the GhKEA4 increased the activity of transporting potassium ions to shoots, and silencing the GhKEA12 increased the ability of absorbing potassium ions, but accumulated more Na+ in leaves. These results provided a basis for further studies on the biological roles of KEA genes in cotton development and adaptation to stress conditions.
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Affiliation(s)
- Yi Li
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of Chinese Academy of Agricultural Sciences, Anyang, China
| | - Zhen Feng
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of Chinese Academy of Agricultural Sciences, Anyang, China
| | - Hengling Wei
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of Chinese Academy of Agricultural Sciences, Anyang, China
| | - Shuaishuai Cheng
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of Chinese Academy of Agricultural Sciences, Anyang, China
| | - Pengbo Hao
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of Chinese Academy of Agricultural Sciences, Anyang, China
| | - Shuxun Yu
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of Chinese Academy of Agricultural Sciences, Anyang, China
- *Correspondence: Shuxun Yu,
| | - Hantao Wang
- State Key Laboratory of Cotton Biology, Institute of Cotton Research of Chinese Academy of Agricultural Sciences, Anyang, China
- Zhengzhou Research Base, State Key Laboratory of Cotton Biology, Zhengzhou University, Zhengzhou, China
- Hantao Wang,
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10
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The Many Roles of the Bacterial Second Messenger Cyclic di-AMP in Adapting to Stress Cues. J Bacteriol 2020; 203:JB.00348-20. [PMID: 32839175 DOI: 10.1128/jb.00348-20] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Bacteria respond to changes in environmental conditions through adaptation to external cues. Frequently, bacteria employ nucleotide signaling molecules to mediate a specific, rapid response. Cyclic di-AMP (c-di-AMP) was recently discovered to be a bacterial second messenger that is essential for viability in many species. In this review, we highlight recent work that has described the roles of c-di-AMP in bacterial responses to various stress conditions. These studies show that depending on the lifestyle and environmental niche of the bacterial species, the c-di-AMP signaling network results in diverse outcomes, such as regulating osmolyte transport, controlling plant attachment, or providing a checkpoint for spore formation. c-di-AMP achieves this signaling specificity through expression of different classes of synthesis and catabolic enzymes as well as receptor proteins and RNAs, which will be summarized.
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11
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Acanthamoeba spp. monoclonal antibody against a CPA2 transporter: a promising molecular tool for acanthamoebiasis diagnosis and encystment study. Parasitology 2020; 147:1678-1688. [PMID: 32951614 DOI: 10.1017/s0031182020001778] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Free-living amoeba of the genus Acanthamoeba are ubiquitous protozoa involved in opportunistic and non-opportunistic infection in humans, such as granulomatous amoebic encephalitis and amoebic keratitis. Both infections have challenging characteristics such as the formation of the resistant cysts in infected tissues, hampering the treatment and most usual diagnosis depending on time-consuming and/or low sensitivity techniques. The use of monoclonal antibodies presents itself as an opportunity for the development of more effective alternative diagnostic methods, as well as an important and useful tool in the search for new therapeutic targets. This study investigated the possibility of using a previously produced monoclonal antibody (mAb3), as a diagnostic tool for the detection of Acanthamoeba trophozoites by direct and indirect flow cytometry and immunofluorescence. Immunoprecipitation assay and mass spectrometry allowed the isolation of the antibody's target and suggested it is a transporter part of the CPA (cation: proton antiporter) superfamily. In vitro tests indicate an important role of this target in Acanthamoeba's encystment physiology. Our results support the importance of studying the role of CPA2 transporters in the context of acanthamoebiasis, as this may be a way to identify new therapeutic candidates.
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12
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Rath H, Sappa PK, Hoffmann T, Gesell Salazar M, Reder A, Steil L, Hecker M, Bremer E, Mäder U, Völker U. Impact of high salinity and the compatible solute glycine betaine on gene expression of Bacillus subtilis. Environ Microbiol 2020; 22:3266-3286. [PMID: 32419322 DOI: 10.1111/1462-2920.15087] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 04/30/2020] [Accepted: 05/13/2020] [Indexed: 12/15/2022]
Abstract
The Gram-positive bacterium Bacillus subtilis is frequently exposed to hyperosmotic conditions. In addition to the induction of genes involved in the accumulation of compatible solutes, high salinity exerts widespread effects on B. subtilis physiology, including changes in cell wall metabolism, induction of an iron limitation response, reduced motility and suppression of sporulation. We performed a combined whole-transcriptome and proteome analysis of B. subtilis 168 cells continuously cultivated at low or high (1.2 M NaCl) salinity. Our study revealed significant changes in the expression of more than one-fourth of the protein-coding genes and of numerous non-coding RNAs. New aspects in understanding the impact of high salinity on B. subtilis include a sustained low-level induction of the SigB-dependent general stress response and strong repression of biofilm formation under high-salinity conditions. The accumulation of compatible solutes such as glycine betaine aids the cells to cope with water stress by maintaining physiologically adequate levels of turgor and also affects multiple cellular processes through interactions with cellular components. Therefore, we additionally analysed the global effects of glycine betaine on the transcriptome and proteome of B. subtilis and revealed that it influences gene expression not only under high-salinity, but also under standard growth conditions.
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Affiliation(s)
- Hermann Rath
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Praveen K Sappa
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Tamara Hoffmann
- Laboratory for Microbiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Manuela Gesell Salazar
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Alexander Reder
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Leif Steil
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Michael Hecker
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany.,Institute of Marine Biotechnology e.V. (IMaB), Greifswald, Germany
| | - Erhard Bremer
- Laboratory for Microbiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Ulrike Mäder
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany
| | - Uwe Völker
- Interfaculty Institute for Genetics and Functional Genomics, University Medicine Greifswald, Greifswald, Germany.,Institute of Marine Biotechnology e.V. (IMaB), Greifswald, Germany
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13
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Tsujii M, Kera K, Hamamoto S, Kuromori T, Shikanai T, Uozumi N. Evidence for potassium transport activity of Arabidopsis KEA1-KEA6. Sci Rep 2019; 9:10040. [PMID: 31296940 PMCID: PMC6624313 DOI: 10.1038/s41598-019-46463-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 06/24/2019] [Indexed: 12/12/2022] Open
Abstract
Arabidopsis thaliana contains the putative K+ efflux transporters KEA1-KEA6, similar to KefB and KefC of Escherichia coli. KEA1-KEA3 are involved in the regulation of photosynthetic electron transport and chloroplast development. KEA4-KEA6 mediate pH regulation of the endomembrane network during salinity stress. However, the ion transport activities of KEA1-KEA6 have not been directly characterized. In this study, we used an E. coli expression system to examine KEA activity. KEA1-KEA3 and KEA5 showed bi-directional K+ transport activity, whereas KEA4 and KEA6 functioned as a K+ uptake system. The thylakoid membrane-localized Na+/H+ antiporter NhaS3 from the model cyanobacterium Synechocystis is the closest homolog of KEA3. Changing the putative Na+/H+ selective site of KEA3 (Gln-Asp) to that of NhaS3 (Asp-Asp) did not alter the ion selectivity without loss of K+ transport activity. The first residue in the conserved motif was not a determinant for K+ or Na+ selectivity. Deletion of the possible nucleotide-binding KTN domain from KEA3 lowered K+ transport activity, indicating that the KTN domain was important for this function. The KEA3-G422R mutation discovered in the Arabidopsis dpgr mutant increased K+ transport activity, consistent with the mutant phenotype. These results indicate that Arabidopsis KEA1-KEA6 act as K+ transport systems, and support the interpretation that KEA3 promotes dissipation of ΔpH in the thylakoid membrane.
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Affiliation(s)
- Masaru Tsujii
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Kota Kera
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Shin Hamamoto
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan
| | - Takashi Kuromori
- RIKEN Center for Sustainable Resource Science, Wako, Saitama, 351-0198, Japan
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Nobuyuki Uozumi
- Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Aobayama 6-6-07, Sendai, 980-8579, Japan.
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14
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Abstract
The cytoplasm of bacterial cells is a highly crowded cellular compartment that possesses considerable osmotic potential. As a result, and owing to the semipermeable nature of the cytoplasmic membrane and the semielastic properties of the cell wall, osmotically driven water influx will generate turgor, a hydrostatic pressure considered critical for growth and viability. Both increases and decreases in the external osmolarity inevitably trigger water fluxes across the cytoplasmic membrane, thus impinging on the degree of cellular hydration, molecular crowding, magnitude of turgor, and cellular integrity. Here, we assess mechanisms that permit the perception of osmotic stress by bacterial cells and provide an overview of the systems that allow them to genetically and physiologically cope with this ubiquitous environmental cue. We highlight recent developments implicating the secondary messenger c-di-AMP in cellular adjustment to osmotic stress and the role of osmotic forces in the life of bacteria-assembled in biofilms.
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Affiliation(s)
- Erhard Bremer
- Laboratory for Microbiology, Department of Biology; and Center for Synthetic Microbiology, Philipps-Universität Marburg, 35043 Marburg, Germany;
| | - Reinhard Krämer
- Institute of Biochemistry, University of Cologne, 50674 Cologne, Germany;
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15
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Gundlach J, Krüger L, Herzberg C, Turdiev A, Poehlein A, Tascón I, Weiss M, Hertel D, Daniel R, Hänelt I, Lee VT, Stülke J. Sustained sensing in potassium homeostasis: Cyclic di-AMP controls potassium uptake by KimA at the levels of expression and activity. J Biol Chem 2019; 294:9605-9614. [PMID: 31061098 DOI: 10.1074/jbc.ra119.008774] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Revised: 05/01/2019] [Indexed: 12/29/2022] Open
Abstract
The signaling nucleotide cyclic di-AMP (c-di-AMP) is the only known essential second messenger in bacteria. Recently, c-di-AMP has been identified as being essential for controlling potassium uptake in the model organism Bacillus subtilis and several other bacteria. A B. subtilis strain lacking c-di-AMP is not viable at high potassium concentrations, unless the bacteria acquire suppressor mutations. In this study, we isolated such suppressor mutants and found mutations that reduced the activities of the potassium transporters KtrCD and KimA. Although c-di-AMP-mediated control of KtrCD has previously been demonstrated, it is unknown how c-di-AMP affects KimA activity. Using the DRaCALA screening assay, we tested for any interactions of KimA and other potential target proteins in B. subtilis with c-di-AMP. This assay identified KimA, as well as the K+/H+ antiporter KhtT, the potassium exporter CpaA (YjbQ), the osmoprotectant transporter subunit OpuCA, the primary Mg2+ importer MgtE, and DarB (YkuL), a protein of unknown function, as bona fide c-di-AMP-binding proteins. Further, binding of c-di-AMP to KimA inhibited potassium uptake. Our results indicate that c-di-AMP controls KimA-mediated potassium transport at both kimA gene expression and KimA activity levels. Moreover, the discovery that potassium exporters are c-di-AMP targets indicates that this second messenger controls potassium homeostasis in B. subtilis at a global level by binding to riboswitches and to different classes of transport proteins involved in potassium uptake and export.
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Affiliation(s)
- Jan Gundlach
- From the Departments of General Microbiology and
| | | | | | - Asan Turdiev
- the Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, and
| | - Anja Poehlein
- Genomic and Applied Microbiology, Göttingen Center for Molecular Biosciences, Georg-August-University Göttingen, 37077 Göttingen, Germany, and
| | - Igor Tascón
- the Institute of Biochemistry, Goethe University Frankfurt, 60323 Frankfurt, Germany
| | - Martin Weiss
- From the Departments of General Microbiology and
| | - Dietrich Hertel
- the Department of Plant Ecology and Ecosystems Research, Georg-August-University Göttingen, 37077 Göttingen, Germany
| | - Rolf Daniel
- Genomic and Applied Microbiology, Göttingen Center for Molecular Biosciences, Georg-August-University Göttingen, 37077 Göttingen, Germany, and
| | - Inga Hänelt
- the Institute of Biochemistry, Goethe University Frankfurt, 60323 Frankfurt, Germany
| | - Vincent T Lee
- the Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, and
| | - Jörg Stülke
- From the Departments of General Microbiology and
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16
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Xu T, Chen H, Li J, Hong S, Shao L, Zheng X, Zou Q, Wang Y, Guo S, Jiang J. Implications for Cation Selectivity and Evolution by a Novel Cation Diffusion Facilitator Family Member From the Moderate Halophile Planococcus dechangensis. Front Microbiol 2019; 10:607. [PMID: 30967858 PMCID: PMC6440370 DOI: 10.3389/fmicb.2019.00607] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 03/11/2019] [Indexed: 11/28/2022] Open
Abstract
In the cation diffusion facilitator (CDF) family, the transported substrates are confined to divalent metal ions, such as Zn2+, Fe2+, and Mn2+. However, this study identifies a novel CDF member designated MceT from the moderate halophile Planococcus dechangensis. MceT functions as a Na+(Li+, K+)/H+ antiporter, together with its capability of facilitated Zn2+ diffusion into cells, which have not been reported in any identified CDF transporters as yet. MceT is proposed to represent a novel CDF group, Na-CDF, which shares significantly distant phylogenetic relationship with three known CDF groups including Mn-CDF, Fe/Zn-CDF, and Zn-CDF. Variation of key function-related residues to “Y44-S48-Q150” in two structural motifs explains a significant discrimination in cation selectivity between Na-CDF group and three major known CDF groups. Functional analysis via site-directed mutagenesis confirms that MceT employs Q150, S158, and D184 for the function of MceT as a Na+(Li+, K+)/H+ antiporter, and retains D41, D154, and D184 for its facilitated Zn2+ diffusion into cells. These presented findings imply that MceT has evolved from its native CDF family function to a Na+/H+ antiporter in an evolutionary strategy of the substitution of key conserved residues to “Q150-S158-D184” motif. More importantly, the discovery of MceT contributes to a typical transporter model of CDF family with the unique structural motifs, which will be utilized to explore the cation-selective mechanisms of secondary transporters.
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Affiliation(s)
- Tong Xu
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Huiwen Chen
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Jincheng Li
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Shan Hong
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Li Shao
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Xiutao Zheng
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Qiao Zou
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Yuting Wang
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Sijia Guo
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
| | - Juquan Jiang
- Department of Microbiology and Biotechnology, College of Life Sciences, Northeast Agricultural University, Harbin, China
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17
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León MJ, Hoffmann T, Sánchez-Porro C, Heider J, Ventosa A, Bremer E. Compatible Solute Synthesis and Import by the Moderate Halophile Spiribacter salinus: Physiology and Genomics. Front Microbiol 2018; 9:108. [PMID: 29497403 PMCID: PMC5818414 DOI: 10.3389/fmicb.2018.00108] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 01/17/2018] [Indexed: 11/13/2022] Open
Abstract
Members of the genus Spiribacter are found worldwide and are abundant in ecosystems possessing intermediate salinities between seawater and saturated salt concentrations. Spiribacter salinus M19-40 is the type species of this genus and its first cultivated representative. In the habitats of S. salinus M19-40, high salinity is a key determinant for growth and we therefore focused on the cellular adjustment strategy to this persistent environmental challenge. We coupled these experimental studies to the in silico mining of the genome sequence of this moderate halophile with respect to systems allowing this bacterium to control its potassium and sodium pools, and its ability to import and synthesize compatible solutes. S. salinus M19-40 produces enhanced levels of the compatible solute ectoine, both under optimal and growth-challenging salt concentrations, but the genes encoding the corresponding biosynthetic enzymes are not organized in a canonical ectABC operon. Instead, they are scrambled (ectAC; ectB) and are physically separated from each other on the S. salinus M19-40 genome. Genomes of many phylogenetically related bacteria also exhibit a non-canonical organization of the ect genes. S. salinus M19-40 also synthesizes trehalose, but this compatible solute seems to make only a minor contribution to the cytoplasmic solute pool under osmotic stress conditions. However, its cellular levels increase substantially in stationary phase cells grown under optimal salt concentrations. In silico genome mining revealed that S. salinus M19-40 possesses different types of uptake systems for compatible solutes. Among the set of compatible solutes tested in an osmostress protection growth assay, glycine betaine and arsenobetaine were the most effective. Transport studies with radiolabeled glycine betaine showed that S. salinus M19-40 increases the pool size of this osmolyte in a fashion that is sensitively tied to the prevalent salinity of the growth medium. It was amassed in salt-stressed cells in unmodified form and suppressed the synthesis of ectoine. In conclusion, the data presented here allow us to derive a genome-scale picture of the cellular adjustment strategy of a species that represents an environmentally abundant group of ecophysiologically important halophilic microorganisms.
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Affiliation(s)
- María J León
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Seville, Seville, Spain
| | - Tamara Hoffmann
- Laboratory for Microbiology, Department of Biology, Philipps University of Marburg, Marburg, Germany
| | - Cristina Sánchez-Porro
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Seville, Seville, Spain
| | - Johann Heider
- Laboratory for Microbiology, Department of Biology, Philipps University of Marburg, Marburg, Germany.,LOEWE-Center for Synthetic Microbiology, Philipps University of Marburg, Marburg, Germany
| | - Antonio Ventosa
- Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Seville, Seville, Spain
| | - Erhard Bremer
- Laboratory for Microbiology, Department of Biology, Philipps University of Marburg, Marburg, Germany.,LOEWE-Center for Synthetic Microbiology, Philipps University of Marburg, Marburg, Germany
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18
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Zhang M, Zhang X, Tong L, Wang Y, Ou D, Zhang J, Wu Q, Ye Y. Genes involved in tolerance to osmotic stress by random mutagenesis in Cronobacter malonaticus. J Dairy Sci 2018; 101:3851-3858. [PMID: 29454685 DOI: 10.3168/jds.2017-13995] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Accepted: 12/28/2017] [Indexed: 12/18/2022]
Abstract
Cronobacter malonaticus is one of the opportunistic food-borne pathogens in powdered infant formula and has unusual abilities to survive under environmental stresses such as osmotic conditions. However, the genes involved in osmotic stress have received little attention in C. malonaticus. Here, genes involved in osmotic stress were determined in C. malonaticus using a transposon mutagenesis approach. According to the growth of mutants (n = 215) under 5.0% NaCl concentration, the survival of 5 mutants under osmotic stress was significantly decreased compared with that of the wild type strain. Five mutating sites, including potassium efflux protein KefA, inner membrane protein YqjF, peptidylprolyl isomerase, Cys-tRNA(Pro)/Cys-tRNA(Cys) deacylase, and oligogalacturonate lyase were successfully identified. In addition, the biofilm formation of 5 mutants was determined using crystal violet staining, scanning electron microscopy, and confocal laser scanning microscopy, and the biofilms of 5 mutants significantly decreased within 72 h compared with that of wild type strain. This is the first report to determine the genes involved in osmotic tolerance in C. malonaticus. The findings provided valuable information for deep understanding of the mechanism of survival of C. malonaticus under osmotic stress, and a possible relationship between biofilm formation and tolerance to osmotic stress was also demonstrated in C. malonaticus.
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Affiliation(s)
- Maofeng Zhang
- School of Food Science and Engineering, Hefei University of Technology, Hefei 230009, China; State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou 510070, China
| | - Xiyan Zhang
- School of Food Science and Engineering, Hefei University of Technology, Hefei 230009, China
| | - Liaowang Tong
- School of Food Science and Engineering, Hefei University of Technology, Hefei 230009, China
| | - Yaping Wang
- School of Food Science and Engineering, Hefei University of Technology, Hefei 230009, China
| | - Dexin Ou
- School of Food Science and Engineering, Hefei University of Technology, Hefei 230009, China
| | - Jumei Zhang
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou 510070, China
| | - Qingping Wu
- State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou 510070, China.
| | - Yingwang Ye
- School of Food Science and Engineering, Hefei University of Technology, Hefei 230009, China; State Key Laboratory of Applied Microbiology Southern China, Guangdong Provincial Key Laboratory of Microbiology Culture Collection and Application, Guangdong Institute of Microbiology, Guangzhou 510070, China.
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19
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Spetea C, Herdean A, Allorent G, Carraretto L, Finazzi G, Szabo I. An update on the regulation of photosynthesis by thylakoid ion channels and transporters in Arabidopsis. PHYSIOLOGIA PLANTARUM 2017; 161:16-27. [PMID: 28332210 DOI: 10.1111/ppl.12568] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 02/08/2017] [Accepted: 02/20/2017] [Indexed: 05/07/2023]
Abstract
In natural, variable environments, plants rapidly adjust photosynthesis for optimal balance between light absorption and utilization. There is increasing evidence suggesting that ion fluxes across the chloroplast thylakoid membrane play an important role in this regulation by affecting the proton motive force and consequently photosynthesis and thylakoid membrane ultrastructure. This article presents an update on the thylakoid ion channels and transporters characterized in Arabidopsis thaliana as being involved in these processes, as well as an outlook at the evolutionary conservation of their functions in other photosynthetic organisms. This is a contribution to shed light on the thylakoid network of ion fluxes and how they help plants to adjust photosynthesis in variable light environments.
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Affiliation(s)
- Cornelia Spetea
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, 40530, Sweden
| | - Andrei Herdean
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, 40530, Sweden
| | - Guillaume Allorent
- Laboratoire de Physiologie Cellulaire et Végétale, UMR 5168, Centre National de la Recherche Scientifique (CNRS), Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Institut National Recherche Agronomique (INRA), Institut de Biosciences et Biotechnologie de Grenoble (BIG), Université Grenoble Alpes (UGA), Grenoble, 38100, France
| | - Luca Carraretto
- Department of Biology, University of Padova, Padova, Italy
- CNR Institute of Neuroscience, Padova, Italy
| | - Giovanni Finazzi
- Laboratoire de Physiologie Cellulaire et Végétale, UMR 5168, Centre National de la Recherche Scientifique (CNRS), Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Institut National Recherche Agronomique (INRA), Institut de Biosciences et Biotechnologie de Grenoble (BIG), Université Grenoble Alpes (UGA), Grenoble, 38100, France
| | - Ildikò Szabo
- Department of Biology, University of Padova, Padova, Italy
- CNR Institute of Neuroscience, Padova, Italy
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20
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Hoffmann T, Bremer E. Guardians in a stressful world: the Opu family of compatible solute transporters from Bacillus subtilis. Biol Chem 2017; 398:193-214. [PMID: 27935846 DOI: 10.1515/hsz-2016-0265] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Accepted: 08/29/2016] [Indexed: 01/09/2023]
Abstract
The development of a semi-permeable cytoplasmic membrane was a key event in the evolution of microbial proto-cells. As a result, changes in the external osmolarity will inevitably trigger water fluxes along the osmotic gradient. The ensuing osmotic stress has consequences for the magnitude of turgor and will negatively impact cell growth and integrity. No microorganism can actively pump water across the cytoplasmic membrane; hence, microorganisms have to actively adjust the osmotic potential of their cytoplasm to scale and direct water fluxes in order to prevent dehydration or rupture. They will accumulate ions and physiologically compliant organic osmolytes, the compatible solutes, when they face hyperosmotic conditions to retain cell water, and they rapidly expel these compounds through the transient opening of mechanosensitive channels to curb water efflux when exposed to hypo-osmotic circumstances. Here, we provide an overview on the salient features of the osmostress response systems of the ubiquitously distributed bacterium Bacillus subtilis with a special emphasis on the transport systems and channels mediating regulation of cellular hydration and turgor under fluctuating osmotic conditions. The uptake of osmostress protectants via the Opu family of transporters, systems of central importance for the management of osmotic stress by B. subtilis, will be particularly highlighted.
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21
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Szermer-Olearnik B, Drab M, Mąkosa M, Zembala M, Barbasz J, Dąbrowska K, Boratyński J. Aggregation/dispersion transitions of T4 phage triggered by environmental ion availability. J Nanobiotechnology 2017; 15:32. [PMID: 28438164 PMCID: PMC5404661 DOI: 10.1186/s12951-017-0266-5] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 04/10/2017] [Indexed: 11/24/2022] Open
Abstract
Background Bacteriophage survives in at least two extremes of ionic environments: bacterial host (high ionic-cytosol) and that of soil (low ionic-environmental water). The impact of ionic composition in the micro- and macro-environments has not so far been addressed in phage biology. Results Here, we discovered a novel mechanism of aggregation/disaggregation transitions by phage virions. When normal sodium levels in phage media (150 mM) were lowered to 10 mM, advanced imaging by scanning electron microscopy, atomic force microscopy and dynamic light scattering all revealed formation of viral packages, each containing 20–100 virions. When ionic strength was returned from low to high, the aggregated state of phage reversed to a dispersed state, and the change in ionic strength did not substantially affect infectivity of the phage. By providing the direct evidence, that lowering of the sodium ion below the threshold of 20 mM causes rapid aggregation of phage while returning Na+ concentration to the values above this threshold causes dispersion of phage, we identified a biophysical mechanism of phage aggregation. Conclusions Our results implicate operation of group behavior in phage and suggest a new kind of quorum sensing among its virions that is mediated by ions. Loss of ionic strength may act as a trigger in an evolutionary mechanism to improve the survival of bacteriophage by stimulating aggregation of phage when outside a bacterial host. Reversal of phage aggregation is also a promising breakthrough in biotechnological applications, since we demonstrated here the ability to retain viable virion aggregates on standard micro-filters.
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Affiliation(s)
- Bożena Szermer-Olearnik
- Laboratory of Biomedical Chemistry-"Neolek". Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, R. Weigla 12, 53-114, Wroclaw, Poland
| | - Marek Drab
- USI, Unit of Nanostructural Bio-Interactions, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, R. Weigla 12, 53-114, Wrocław, Poland
| | - Mateusz Mąkosa
- Laboratory of Biomedical Chemistry-"Neolek". Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, R. Weigla 12, 53-114, Wroclaw, Poland
| | - Maria Zembala
- Institute of Biology, Pedagogical University of Cracow, Podchorążych 2, 30-084, Cracow, Poland
| | - Jakub Barbasz
- Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239, Cracow, Poland
| | - Krystyna Dąbrowska
- Bacteriophage Laboratory, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, R. Weigla 12, 53-114, Wrocław, Poland
| | - Janusz Boratyński
- Laboratory of Biomedical Chemistry-"Neolek". Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, R. Weigla 12, 53-114, Wroclaw, Poland. .,Institute of Chemistry, Environmental Protection and Biotechnology, Jan Długosz University, 42-200, Częstochowa, Poland.
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22
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Wang C, Yamamoto H, Narumiya F, Munekage YN, Finazzi G, Szabo I, Shikanai T. Fine-tuned regulation of the K + /H + antiporter KEA3 is required to optimize photosynthesis during induction. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 89:540-553. [PMID: 27783435 DOI: 10.1111/tpj.13405] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 10/17/2016] [Accepted: 10/17/2016] [Indexed: 05/22/2023]
Abstract
KEA3 is a thylakoid membrane localized K+ /H+ antiporter that regulates photosynthesis by modulating two components of proton motive force (pmf), the proton gradient (∆pH) and the electric potential (∆ψ). We identified a mutant allele of KEA3, disturbed proton gradient regulation (dpgr) based on its reduced non-photochemical quenching (NPQ) in artificial (CO2 -free with low O2 ) air. This phenotype was enhanced in the mutant backgrounds of PSI cyclic electron transport (pgr5 and crr2-1). In ambient air, reduced NPQ was observed during induction of photosynthesis in dpgr, the phenotype that was enhanced after overnight dark adaptation. In contrast, the knockout allele of kea3-1 exhibited a high-NPQ phenotype during steady state in ambient air. Consistent with this kea3-1 phenotype in ambient air, the membrane topology of KEA3 indicated a proton efflux from the thylakoid lumen to the stroma. The dpgr heterozygotes showed a semidominant and dominant phenotype in artificial and ambient air, respectively. In dpgr, the protein level of KEA3 was unaffected but the downregulation of its activity was probably disturbed. Our findings suggest that fine regulation of KEA3 activity is necessary for optimizing photosynthesis.
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Affiliation(s)
- Caijuan Wang
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Hiroshi Yamamoto
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
- CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo, 102-0076, Japan
| | - Fumika Narumiya
- Graduate School of Sciences, Nara Institute of Science and Technology, Ikoma, Nara, 630-0101, Japan
- Sakai City Institute of Public Health, Sakai, Osaka, 590-0953, Japan
| | - Yuri Nakajima Munekage
- Graduate School of Sciences, Nara Institute of Science and Technology, Ikoma, Nara, 630-0101, Japan
- Department of Bioscience, School of Science and Technology, Kwansei Gakuin University, Sandan, Hyogo, 669-1337, Japan
| | - Giovanni Finazzi
- UMR 5168 Laboratoire de Physiologie Cellulaire Végétale (LPCV) CNRS/UJF/INRA/CEA, Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), CEA Grenoble, 38054, Grenoble, France
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padova, 35121, Italy
| | - Toshiharu Shikanai
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
- CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo, 102-0076, Japan
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23
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Smirnova GV, Tyulenev AV, Muzyka NG, Peters MA, Oktyabrsky ON. Ciprofloxacin provokes SOS-dependent changes in respiration and membrane potential and causes alterations in the redox status of Escherichia coli. Res Microbiol 2016; 168:64-73. [PMID: 27498196 DOI: 10.1016/j.resmic.2016.07.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/25/2016] [Accepted: 07/27/2016] [Indexed: 10/21/2022]
Abstract
An in-depth understanding of the physiological response of bacteria to antibiotic-induced stress is needed for development of new approaches to combatting microbial infections. Fluoroquinolone ciprofloxacin causes phase alterations in Escherichia coli respiration and membrane potential that strongly depend on its concentration. Concentrations lower than the optimal bactericidal concentration (OBC) do not inhibit respiration during the first phase. A dose higher than the OBC provokes immediate SOS-independent inhibition of respiration and growth that can contribute to a decreased SOS response and lowered susceptibility to high concentrations of ciprofloxacin. Cells retain their metabolic activity, membrane potential and accelerated K+ uptake and produce low levels of superoxide and H2O2 during the first phase. The time before initiation of the second phase is inversely correlated with the ciprofloxacin concentration. The second phase is SOS-dependent and characterized by respiratory inhibition, membrane depolarization, K+ and glutathione leakage and cessation of glucose consumption and may be considered as cell death. atpA, gshA and kefBkefC knockouts, which perturb fluxes of protons and K+, can modify the degree and duration of respiratory inhibition and potassium retention. Loss of K+ efflux channels KefB and KefC enhances the susceptibility of E. coli to ciprofloxacin.
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Affiliation(s)
- Galina V Smirnova
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Aleksey V Tyulenev
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Nadezda G Muzyka
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Mikhail A Peters
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia.
| | - Oleg N Oktyabrsky
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul. Goleva 13, Perm, 614081, Russia; Department of Chemistry and Biotechnology, Perm National Research Polytechnic University, Komsomolsky pr., 29, Perm, 614990, Russia.
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Smirnova GV, Muzyka NG, Ushakov VY, Tyulenev AV, Oktyabrsky ON. Extracellular superoxide provokes glutathione efflux from Escherichia coli cells. Res Microbiol 2015; 166:609-17. [DOI: 10.1016/j.resmic.2015.07.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 06/23/2015] [Accepted: 07/06/2015] [Indexed: 11/28/2022]
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Ma Y, Wang J, Zhong Y, Geng F, Cramer GR, Cheng ZM(M. Subfunctionalization of cation/proton antiporter 1 genes in grapevine in response to salt stress in different organs. HORTICULTURE RESEARCH 2015; 2:15031. [PMID: 26504576 PMCID: PMC4591679 DOI: 10.1038/hortres.2015.31] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 06/04/2015] [Accepted: 06/04/2015] [Indexed: 05/20/2023]
Abstract
Cation/proton antiporter 1 (CPA1) proteins function as regulators of monovalent ions, pH homeostasis, and other developmental processes in plants. Better understanding of the expression and regulation of CPA1 in plant responses to salinity would help the development of scientific practices in crops worldwide. In this report, we characterized all seven CPA1 family genes in grapevine (Vitis vinifera) in response to short-term osmotic and NaCl stresses. We found that two of the seven genes have subfunctionalized to be differentially expressed in response to NaCl stress in the early stage in different organs, whereas the other five members seem to play little or no role in this response. Specifically, VIT_19s0090g01480 may control Na(+) compartmentalization in grapevine roots; and VIT_05s0020g01960 may influence Na(+) transfer in stems. Based on the dynamics of ion concentrations, electrolyte leakage rates, and CPA1 gene expression in root, stem, and leaf tissues under osmotic and NaCl stresses, we suggest how grapevine responds physiologically and molecularly to the osmotic and ion toxicity of NaCl stress in the short term. This work lays a foundation for future research on the CPA1 gene family regarding its evolutionary history and biological functions for modulating salt responses in grapevine.
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Affiliation(s)
- Yuanchun Ma
- The Laboratory of Fruit Crop Systems Biology, College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, The People’s Republic of China
| | - Jiaoyang Wang
- The Laboratory of Fruit Crop Systems Biology, College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, The People’s Republic of China
| | - Yan Zhong
- The Laboratory of Fruit Crop Systems Biology, College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, The People’s Republic of China
| | - Fang Geng
- The Laboratory of Fruit Crop Systems Biology, College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, The People’s Republic of China
| | - Grant R Cramer
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV 89557, USA
| | - Zong-Ming (Max) Cheng
- The Laboratory of Fruit Crop Systems Biology, College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, The People’s Republic of China
- Department of Plant Sciences, University of Tennessee, Knoxville, TN 37996, USA
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Ion antiport accelerates photosynthetic acclimation in fluctuating light environments. Nat Commun 2014; 5:5439. [PMID: 25451040 PMCID: PMC4243252 DOI: 10.1038/ncomms6439] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 10/01/2014] [Indexed: 12/19/2022] Open
Abstract
Many photosynthetic organisms globally, including crops, forests and algae, must grow in environments where the availability of light energy fluctuates dramatically. How photosynthesis maintains high efficiency despite such fluctuations in its energy source remains poorly understood. Here we show that Arabidopsis thaliana K+ efflux antiporter (KEA3) is critical for high photosynthetic efficiency under fluctuating light. On a shift from dark to low light, or high to low light, kea3 mutants show prolonged dissipation of absorbed light energy as heat. KEA3 localizes to the thylakoid membrane, and allows proton efflux from the thylakoid lumen by proton/potassium antiport. KEA3’s activity accelerates the downregulation of pH-dependent energy dissipation after transitions to low light, leading to faster recovery of high photosystem II quantum efficiency and increased CO2 assimilation. Our results reveal a mechanism that increases the efficiency of photosynthesis under fluctuating light. Plants must respond rapidly to unpredictable variations in light intensity to maximize photosynthetic efficiency. Here Armbruster et al. identify a potassium antiporter that is critical for accelerating proton fluxes across thylakoid membranes and minimizing energy loss in fluctuating light conditions.
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Plastidial transporters KEA1, -2, and -3 are essential for chloroplast osmoregulation, integrity, and pH regulation in Arabidopsis. Proc Natl Acad Sci U S A 2014; 111:7480-5. [PMID: 24794527 DOI: 10.1073/pnas.1323899111] [Citation(s) in RCA: 175] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Multiple K(+) transporters and channels and the corresponding mutants have been described and studied in the plasma membrane and organelle membranes of plant cells. However, knowledge about the molecular identity of chloroplast K(+) transporters is limited. Potassium transport and a well-balanced K(+) homeostasis were suggested to play important roles in chloroplast function. Because no loss-of-function mutants have been identified, the importance of K(+) transporters for chloroplast function and photosynthesis remains to be determined. Here, we report single and higher-order loss-of-function mutants in members of the cation/proton antiporters-2 antiporter superfamily KEA1, KEA2, and KEA3. KEA1 and KEA2 proteins are targeted to the inner envelope membrane of chloroplasts, whereas KEA3 is targeted to the thylakoid membrane. Higher-order but not single mutants showed increasingly impaired photosynthesis along with pale green leaves and severely stunted growth. The pH component of the proton motive force across the thylakoid membrane was significantly decreased in the kea1kea2 mutants, but increased in the kea3 mutant, indicating an altered chloroplast pH homeostasis. Electron microscopy of kea1kea2 leaf cells revealed dramatically swollen chloroplasts with disrupted envelope membranes and reduced thylakoid membrane density. Unexpectedly, exogenous NaCl application reversed the observed phenotypes. Furthermore, the kea1kea2 background enables genetic analyses of the functional significance of other chloroplast transporters as exemplified here in kea1kea2Na(+)/H(+) antiporter1 (nhd1) triple mutants. Taken together, the presented data demonstrate a fundamental role of inner envelope KEA1 and KEA2 and thylakoid KEA3 transporters in chloroplast osmoregulation, integrity, and ion and pH homeostasis.
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Chandrangsu P, Dusi R, Hamilton CJ, Helmann JD. Methylglyoxal resistance in Bacillus subtilis: contributions of bacillithiol-dependent and independent pathways. Mol Microbiol 2014; 91:706-15. [PMID: 24330391 DOI: 10.1111/mmi.12489] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2013] [Indexed: 11/27/2022]
Abstract
Methylglyoxal (MG) is a toxic by-product of glycolysis that damages DNA and proteins ultimately leading to cell death. Protection from MG is often conferred by a glutathione-dependent glyoxalase pathway. However, glutathione is absent from the low-GC Gram-positive Firmicutes, such as Bacillus subtilis. The identification of bacillithiol (BSH) as the major low-molecular-weight thiol in the Firmicutes raises the possibility that BSH is involved in MG detoxification. Here, we demonstrate that MG can rapidly and specifically deplete BSH in cells, and we identify both BSH-dependent and BSH-independent MG resistance pathways. The BSH-dependent pathway utilizes glyoxalase I (GlxA, formerly YwbC) and glyoxalase II (GlxB, formerly YurT) to convert MG to d-lactate. The critical step in this pathway is the activation of the KhtSTU K(+) efflux pump by the S-lactoyl-BSH intermediate, which leads to cytoplasmic acidification. We show that cytoplasmic acidification is both necessary and sufficient for maximal protection from MG. Two additional MG detoxification pathways operate independent of BSH. The first involves three enzymes (YdeA, YraA and YfkM) which are predicted to be homologues of glyoxalase III that converts MG to d-lactate, and the second involves YhdN, previously shown to be a broad specificity aldo-keto reductase that converts MG to acetol.
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Affiliation(s)
- Pete Chandrangsu
- Department of Microbiology, Cornell University, Ithaca, NY, 14853-8101, USA
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Zheng S, Pan T, Fan L, Qiu QS. A novel AtKEA gene family, homolog of bacterial K+/H+ antiporters, plays potential roles in K+ homeostasis and osmotic adjustment in Arabidopsis. PLoS One 2013; 8:e81463. [PMID: 24278440 PMCID: PMC3835744 DOI: 10.1371/journal.pone.0081463] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2013] [Accepted: 10/13/2013] [Indexed: 12/28/2022] Open
Abstract
AtKEAs, homologs of bacterial KefB/KefC, are predicted to encode K+/H+ antiporters in Arabidopsis. The AtKEA family contains six genes forming two subgroups in the cladogram: AtKEA1-3 and AtKEA4-6. AtKEA1 and AtKEA2 have a long N-terminal domain; the full-length AtKEA1 was inactive in yeast. The transport activity was analyzed by expressing the AtKEA genes in yeast mutants lacking multiple ion carriers. AtKEAs conferred resistance to high K+ and hygromycin B but not to salt and Li+ stress. AtKEAs expressed in both the shoot and root of Arabidopsis. The expression of AtKEA1, -3 and -4 was enhanced under low K+ stress, whereas AtKEA2 and AtKEA5 were induced by sorbitol and ABA treatments. However, osmotic induction of AtKEA2 and AtKEA5 was not observed in aba2-3 mutants, suggesting an ABA regulated mechanism for their osmotic response. AtKEAs’ expression may not be regulated by the SOS pathway since their expression was not affected in sos mutants. The GFP tagging analysis showed that AtKEAs distributed diversely in yeast. The Golgi localization of AtKEA3 was demonstrated by both the stably transformed seedlings and the transient expression in protoplasts. Overall, AtKEAs expressed and localized diversely, and may play roles in K+ homeostasis and osmotic adjustment in Arabidopsis.
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Affiliation(s)
- Sheng Zheng
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, China
| | - Ting Pan
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, China
| | - Ligang Fan
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, China
| | - Quan-Sheng Qiu
- MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, China
- *
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Repeated triggering of sporulation in Bacillus subtilis selects against a protein that affects the timing of cell division. ISME JOURNAL 2013; 8:77-87. [PMID: 23924781 DOI: 10.1038/ismej.2013.128] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 06/10/2013] [Accepted: 07/03/2013] [Indexed: 11/08/2022]
Abstract
Bacillus subtilis sporulation is a last-resort phenotypical adaptation in response to starvation. The regulatory network underlying this developmental pathway has been studied extensively. However, how sporulation initiation is concerted in relation to the environmental nutrient availability is poorly understood. In a fed-batch fermentation set-up, in which sporulation of ultraviolet (UV)-mutagenized B. subtilis is repeatedly triggered by periods of starvation, fitter strains with mutated tagE evolved. These mutants display altered timing of phenotypical differentiation. The substrate for the wall teichoic acid (WTA)-modifying enzyme TagE, UDP-glucose, has recently been shown to be an intracellular proxy for nutrient availability, and influences the timing of cell division. Here we suggest that UDP-glucose also influences timing of cellular differentiation.
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Ozyamak E, de Almeida C, de Moura APS, Miller S, Booth IR. Integrated stress response of Escherichia coli to methylglyoxal: transcriptional readthrough from the nemRA operon enhances protection through increased expression of glyoxalase I. Mol Microbiol 2013; 88:936-50. [PMID: 23646895 PMCID: PMC3739934 DOI: 10.1111/mmi.12234] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/09/2013] [Indexed: 12/02/2022]
Abstract
Methylglyoxal (MG) elicits activation of K+ efflux systems to protect cells against the toxicity of the electrophile. ChIP-chip targeting RNA polymerase, supported by a range of other biochemical measurements and mutant creation, was used to identify genes transcribed in response to MG and which complement this rapid response. The SOS DNA repair regulon is induced at cytotoxic levels of MG, even when exposure to MG is transient. Glyoxalase I alone among the core MG protective systems is induced in response to MG exposure. Increased expression is an indirect consequence of induction of the upstream nemRA operon, encoding an enzyme system that itself does not contribute to MG detoxification. Moreover, this induction, via nemRA only occurs when cells are exposed to growth inhibitory concentrations of MG. We show that the kdpFABCDE genes are induced and that this expression occurs as a result of depletion of cytoplasmic K+ consequent upon activation of the KefGB K+ efflux system. Finally, our analysis suggests that the transcriptional changes in response to MG are a culmination of the damage to DNA and proteins, but that some integrate specific functions, such as DNA repair, to augment the allosteric activation of the main protective system, KefGB.
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Affiliation(s)
- Ertan Ozyamak
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen, AB25 2ZD, UK.
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Abstract
Recent research suggests that in addition to their role as soluble electron carriers, pyridine nucleotides [NAD(P)(H)] also regulate ion transport mechanisms. This mode of regulation seems to have been conserved through evolution. Several bacterial ion-transporting proteins or their auxiliary subunits possess nucleotide-binding domains. In eukaryotes, the Kv1 and Kv4 channels interact with pyridine nucleotide-binding β-subunits that belong to the aldo-keto reductase superfamily. Binding of NADP(+) to Kvβ removes N-type inactivation of Kv currents, whereas NADPH stabilizes channel inactivation. Pyridine nucleotides also regulate Slo channels by interacting with their cytosolic regulator of potassium conductance domains that show high sequence homology to the bacterial TrkA family of K(+) transporters. These nucleotides also have been shown to modify the activity of the plasma membrane K(ATP) channels, the cystic fibrosis transmembrane conductance regulator, the transient receptor potential M2 channel, and the intracellular ryanodine receptor calcium release channels. In addition, pyridine nucleotides also modulate the voltage-gated sodium channel by supporting the activity of its ancillary subunit-the glycerol-3-phosphate dehydrogenase-like protein. Moreover, the NADP(+) metabolite, NAADP(+), regulates intracellular calcium homeostasis via the 2-pore channel, ryanodine receptor, or transient receptor potential M2 channels. Regulation of ion channels by pyridine nucleotides may be required for integrating cell ion transport to energetics and for sensing oxygen levels or metabolite availability. This mechanism also may be an important component of hypoxic pulmonary vasoconstriction, memory, and circadian rhythms, and disruption of this regulatory axis may be linked to dysregulation of calcium homeostasis and cardiac arrhythmias.
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Affiliation(s)
- Peter J Kilfoil
- Diabetes Obesity Center, University of Louisville, Louisville, KY 40202, USA
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Hoffmann T, Wensing A, Brosius M, Steil L, Völker U, Bremer E. Osmotic control of opuA expression in Bacillus subtilis and its modulation in response to intracellular glycine betaine and proline pools. J Bacteriol 2013; 195:510-22. [PMID: 23175650 PMCID: PMC3554007 DOI: 10.1128/jb.01505-12] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Accepted: 11/14/2012] [Indexed: 11/20/2022] Open
Abstract
Glycine betaine is an effective osmoprotectant for Bacillus subtilis. Its import into osmotically stressed cells led to the buildup of large pools, whose size was sensitively determined by the degree of the osmotic stress imposed. The amassing of glycine betaine caused repression of the formation of an osmostress-adaptive pool of proline, the only osmoprotectant that B. subtilis can synthesize de novo. The ABC transporter OpuA is the main glycine betaine uptake system of B. subtilis. Expression of opuA was upregulated in response to both sudden and sustained increases in the external osmolarity. Nonionic osmolytes exerted a stronger inducing effect on transcription than ionic osmolytes, and this was reflected in the development of corresponding OpuA-mediated glycine betaine pools. Primer extension analysis and site-directed mutagenesis pinpointed the osmotically controlled opuA promoter. Deviations from the consensus sequence of SigA-type promoters serve to keep the transcriptional activity of the opuA promoter low in the absence of osmotic stress. opuA expression was downregulated in a finely tuned manner in response to increases in the intracellular glycine betaine pool, regardless of whether this osmoprotectant was imported or was newly synthesized from choline. Such an effect was also exerted by carnitine, an effective osmoprotectant for B. subtilis that is not a substrate for the OpuA transporter. opuA expression was upregulated in a B. subtilis mutant that was unable to synthesize proline in response to osmotic stress. Collectively, our data suggest that the intracellular solute pool is a key determinant for the osmotic control of opuA expression.
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Affiliation(s)
- Tamara Hoffmann
- Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, Marburg, Germany
| | - Annette Wensing
- Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, Marburg, Germany
| | - Margot Brosius
- Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, Marburg, Germany
| | - Leif Steil
- Interfaculty Institute for Genetics and Functional Genomics, Department of Functional Genomics, Ernst-Moritz-Arndt University, Greifswald, Germany
| | - Uwe Völker
- Interfaculty Institute for Genetics and Functional Genomics, Department of Functional Genomics, Ernst-Moritz-Arndt University, Greifswald, Germany
| | - Erhard Bremer
- Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, Marburg, Germany
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Smirnova G, Muzyka N, Oktyabrsky O. Transmembrane glutathione cycling in growing Escherichia coli cells. Microbiol Res 2012; 167:166-72. [PMID: 21689911 DOI: 10.1016/j.micres.2011.05.005] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 05/17/2011] [Accepted: 05/22/2011] [Indexed: 10/18/2022]
Abstract
Glutathione (GSH) plays an important role in bacterial cells, participating in maintenance of redox balance in the cytoplasm and in defense against many toxic compounds and stresses. In this study we demonstrate that in aerobic, exponentially growing Escherichia coli culture endogenous reduced glutathione undergoes continuous transmembrane cycling between the cells and medium. As a result of an establishment of a dynamic balance between GSH efflux and uptake, a constant extracellular concentration of GSH counting per biomass unit is maintained. The magnitude of this concentration strictly depends on external pH. GSH cycling is carried out in respiring cells and disturbed by influences, which change the level of ΔμH(+) and ATP. Export of GSH is modified by phosphate deficiency in the medium.
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Affiliation(s)
- Galina Smirnova
- Institute of Ecology and Genetics of Microorganisms, Russian Academy of Sciences, ul.Goleva 13, Perm 614081, Russia.
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Aranda-Sicilia MN, Cagnac O, Chanroj S, Sze H, Rodríguez-Rosales MP, Venema K. Arabidopsis KEA2, a homolog of bacterial KefC, encodes a K(+)/H(+) antiporter with a chloroplast transit peptide. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2362-71. [PMID: 22551943 DOI: 10.1016/j.bbamem.2012.04.011] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/10/2012] [Accepted: 04/16/2012] [Indexed: 01/10/2023]
Abstract
KEA genes encode putative K(+) efflux antiporters that are predominantly found in algae and plants but are rare in metazoa; however, nothing is known about their functions in eukaryotic cells. Plant KEA proteins show homology to bacterial K(+) efflux (Kef) transporters, though two members in the Arabidopsis thaliana family, AtKEA1 and AtKEA2, have acquired an extra hydrophilic domain of over 500 residues at the amino terminus. We show that AtKEA2 is highly expressed in leaves, stems and flowers, but not in roots, and that an N-terminal peptide of the protein is targeted to chloroplasts in Arabidopsis cotyledons. The full-length AtKEA2 protein was inactive when expressed in yeast; however, a truncated AtKEA2 protein (AtsKEA2) lacking the N-terminal domain complemented disruption of the Na(+)(K(+))/H(+) antiporter Nhx1p to confer hygromycin resistance and tolerance to Na(+) or K(+) stress. To test transport activity, purified truncated AtKEA2 was reconstituted in proteoliposomes containing the fluorescent probe pyranine. Monovalent cations reduced an imposed pH gradient (acid inside) indicating AtsKEA2 mediated cation/H(+) exchange with preference for K(+)=Cs(+)>Li(+)>Na(+). When a conserved Asp(721) in transmembrane helix 6 that aligns to the cation binding Asp(164) of Escherichia coli NhaA was replaced with Ala, AtsKEA2 was completely inactivated. Mutation of a Glu(835) between transmembrane helix 8 and 9 in AtsKEA2 also resulted in loss of activity suggesting this region has a regulatory role. Thus, AtKEA2 represents the founding member of a novel group of eukaryote K(+)/H(+) antiporters that modulate monovalent cation and pH homeostasis in plant chloroplasts or plastids.
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Chanroj S, Wang G, Venema K, Zhang MW, Delwiche CF, Sze H. Conserved and diversified gene families of monovalent cation/h(+) antiporters from algae to flowering plants. FRONTIERS IN PLANT SCIENCE 2012; 3:25. [PMID: 22639643 PMCID: PMC3355601 DOI: 10.3389/fpls.2012.00025] [Citation(s) in RCA: 143] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Accepted: 01/21/2012] [Indexed: 05/18/2023]
Abstract
All organisms have evolved strategies to regulate ion and pH homeostasis in response to developmental and environmental cues. One strategy is mediated by monovalent cation-proton antiporters (CPA) that are classified in two superfamilies. Many CPA1 genes from bacteria, fungi, metazoa, and plants have been functionally characterized; though roles of plant CPA2 genes encoding K(+)-efflux antiporter (KEA) and cation/H(+) exchanger (CHX) families are largely unknown. Phylogenetic analysis showed that three clades of the CPA1 Na(+)-H(+) exchanger (NHX) family have been conserved from single-celled algae to Arabidopsis. These are (i) plasma membrane-bound SOS1/AtNHX7 that share ancestry with prokaryote NhaP, (ii) endosomal AtNHX5/6 that is part of the eukaryote Intracellular-NHE clade, and (iii) a vacuolar NHX clade (AtNHX1-4) specific to plants. Early diversification of KEA genes possibly from an ancestral cyanobacterium gene is suggested by three types seen in all plants. Intriguingly, CHX genes diversified from three to four members in one subclade of early land plants to 28 genes in eight subclades of Arabidopsis. Homologs from Spirogyra or Physcomitrella share high similarity with AtCHX20, suggesting that guard cell-specific AtCHX20 and its closest relatives are founders of the family, and pollen-expressed CHX genes appeared later in monocots and early eudicots. AtCHX proteins mediate K(+) transport and pH homeostasis, and have been localized to intracellular and plasma membrane. Thus KEA genes are conserved from green algae to angiosperms, and their presence in red algae and secondary endosymbionts suggest a role in plastids. In contrast, AtNHX1-4 subtype evolved in plant cells to handle ion homeostasis of vacuoles. The great diversity of CHX genes in land plants compared to metazoa, fungi, or algae would imply a significant role of ion and pH homeostasis at dynamic endomembranes in the vegetative and reproductive success of flowering plants.
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Affiliation(s)
- Salil Chanroj
- Department of Cell Biology and Molecular Genetics, Maryland Agricultural Experiment Station, University of MarylandCollege Park, MD, USA
| | - Guoying Wang
- Department of Cell Biology and Molecular Genetics, Maryland Agricultural Experiment Station, University of MarylandCollege Park, MD, USA
| | - Kees Venema
- Departmento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, Consejo Superior de Investigaciones CientíficasGranada, Spain
| | - Muren Warren Zhang
- Department of Cell Biology and Molecular Genetics, Maryland Agricultural Experiment Station, University of MarylandCollege Park, MD, USA
| | - Charles F. Delwiche
- Department of Cell Biology and Molecular Genetics, Maryland Agricultural Experiment Station, University of MarylandCollege Park, MD, USA
| | - Heven Sze
- Department of Cell Biology and Molecular Genetics, Maryland Agricultural Experiment Station, University of MarylandCollege Park, MD, USA
- *Correspondence: Heven Sze, Department of Cell Biology and Molecular Genetics, Maryland Agricultural Experiment Station, University of Maryland, Bioscience Research Building # 413, College Park, MD 20742, USA. e-mail:
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Brill J, Hoffmann T, Bleisteiner M, Bremer E. Osmotically controlled synthesis of the compatible solute proline is critical for cellular defense of Bacillus subtilis against high osmolarity. J Bacteriol 2011; 193:5335-46. [PMID: 21784929 PMCID: PMC3187420 DOI: 10.1128/jb.05490-11] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 07/13/2011] [Indexed: 11/20/2022] Open
Abstract
Bacillus subtilis is known to accumulate large amounts of the compatible solute proline via de novo synthesis as a stress protectant when it faces high-salinity environments. We elucidated the genetic determinants required for the osmoadaptive proline production from the precursor glutamate. This proline biosynthesis route relies on the proJ-encoded γ-glutamyl kinase, the proA-encoded γ-glutamyl phosphate reductase, and the proH-encoded Δ1-pyrroline-5-caboxylate reductase. Disruption of the proHJ operon abolished osmoadaptive proline production and strongly impaired the ability of B. subtilis to cope with high-osmolarity growth conditions. Disruption of the proA gene also abolished osmoadaptive proline biosynthesis but caused, in contrast to the disruption of proHJ, proline auxotrophy. Northern blot analysis demonstrated that the transcription of the proHJ operon is osmotically inducible, whereas that of the proBA operon is not. Reporter gene fusion studies showed that proHJ expression is rapidly induced upon an osmotic upshift. Increased expression is maintained as long as the osmotic stimulus persists and is sensitively linked to the prevalent osmolarity of the growth medium. Primer extension analysis revealed the osmotically controlled proHJ promoter, a promoter that resembles typical SigA-type promoters of B. subtilis. Deletion analysis of the proHJ promoter region identified a 126-bp DNA segment carrying all sequences required in cis for osmoregulated transcription. Our data disclose the presence of ProA-interlinked anabolic and osmoadaptive proline biosynthetic routes in B. subtilis and demonstrate that the synthesis of the compatible solute proline is a central facet of the cellular defense to high-osmolarity surroundings for this soil bacterium.
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Affiliation(s)
| | | | - Monika Bleisteiner
- Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, Karl-von-Frisch-Str. 8, D-35032 Marburg, Germany
| | - Erhard Bremer
- Philipps-University Marburg, Department of Biology, Laboratory for Microbiology, Karl-von-Frisch-Str. 8, D-35032 Marburg, Germany
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Chanroj S, Lu Y, Padmanaban S, Nanatani K, Uozumi N, Rao R, Sze H. Plant-specific cation/H+ exchanger 17 and its homologs are endomembrane K+ transporters with roles in protein sorting. J Biol Chem 2011; 286:33931-41. [PMID: 21795714 PMCID: PMC3190763 DOI: 10.1074/jbc.m111.252650] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Revised: 07/08/2011] [Indexed: 11/30/2022] Open
Abstract
The complexity of intracellular compartments in eukaryotic cells evolved to provide distinct environments to regulate processes necessary for cell proliferation and survival. A large family of predicted cation/proton exchangers (CHX), represented by 28 genes in Arabidopsis thaliana, are associated with diverse endomembrane compartments and tissues in plants, although their roles are poorly understood. We expressed a phylogenetically related cluster of CHX genes, encoded by CHX15-CHX20, in yeast and bacterial cells engineered to lack multiple cation-handling mechanisms. Of these, CHX16-CHX20 were implicated in pH homeostasis because their expression rescued the alkaline pH-sensitive growth phenotype of the host yeast strain. A smaller subset, CHX17-CHX19, also conferred tolerance to hygromycin B. Further differences were observed in K(+)- and low pH-dependent growth phenotypes. Although CHX17 did not alter cytoplasmic or vacuolar pH in yeast, CHX20 elicited acidification and alkalization of the cytosol and vacuole, respectively. Using heterologous expression in Escherichia coli strains lacking K(+) uptake systems, we provide evidence for K(+) ((86)Rb) transport mediated by CHX17 and CHX20. Finally, we show that CHX17 and CHX20 affected protein sorting as measured by carboxypeptidase Y secretion in yeast mutants grown at alkaline pH. In plant cells, CHX20-RFP co-localized with an endoplasmic reticulum marker, whereas RFP-tagged CHX17-CHX19 co-localized with prevacuolar compartment and endosome markers. Together, these results suggest that in response to environmental cues, multiple CHX transporters differentially modulate K(+) and pH homeostasis of distinct intracellular compartments, which alter membrane trafficking events likely to be critical for adaptation and survival.
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Affiliation(s)
- Salil Chanroj
- From the Department of Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, Maryland 20742
| | - Yongxian Lu
- From the Department of Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, Maryland 20742
| | - Senthilkumar Padmanaban
- From the Department of Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, Maryland 20742
| | - Kei Nanatani
- the Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| | - Nobuyuki Uozumi
- the Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| | - Rajini Rao
- the Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and
| | - Heven Sze
- From the Department of Cell Biology and Molecular Genetics and the Maryland Agricultural Experiment Station, University of Maryland, College Park, Maryland 20742
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KefF, the regulatory subunit of the potassium efflux system KefC, shows quinone oxidoreductase activity. J Bacteriol 2011; 193:4925-32. [PMID: 21742892 DOI: 10.1128/jb.05272-11] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Escherichia coli and many other Gram-negative pathogenic bacteria protect themselves from the toxic effects of electrophilic compounds by using a potassium efflux system (Kef). Potassium efflux is coupled to the influx of protons, which lowers the internal pH and results in immediate protection. The activity of the Kef system is subject to complex regulation by glutathione and its S conjugates. Full activation of KefC requires a soluble ancillary protein, KefF. This protein has structural similarities to oxidoreductases, including human quinone reductases 1 and 2. Here, we show that KefF has enzymatic activity as an oxidoreductase, in addition to its role as the KefC activator. It accepts NADH and NADPH as electron donors and quinones and ferricyanide (in addition to other compounds) as acceptors. However, typical electrophilic activators of the Kef system, e.g., N-ethyl maleimide, are not substrates. If the enzymatic activity is disrupted by site-directed mutagenesis while retaining structural integrity, KefF is still able to activate the Kef system, showing that the role as an activator is independent of the enzyme activity. Potassium efflux assays show that electrophilic quinones are able to activate the Kef system by forming S conjugates with glutathione. Therefore, it appears that the enzymatic activity of KefF diminishes the redox toxicity of quinones, in parallel with the protection afforded by activation of the Kef system.
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40
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Nhe1 is essential for potassium but not calcium facilitation of cell motility and the monovalent cation requirement for chemotactic orientation in Dictyostelium discoideum. EUKARYOTIC CELL 2011; 10:320-31. [PMID: 21239624 DOI: 10.1128/ec.00255-10] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In Dictyostelium discoideum, extracellular K+ or Ca2+ at a concentration of 40 or 20 mM, respectively, facilitates motility in the absence or presence of a spatial gradient of chemoattractant. Facilitation results in maximum velocity, cellular elongation, persistent translocation, suppression of lateral pseudopod formation, and myosin II localization in the posterior cortex. A lower threshold concentration of 15 mM K+ or Na or 5 mM Ca2+ is required for chemotactic orientation. Although the common buffer solutions used by D. discoideum researchers to study chemotaxis contain sufficient concentrations of cations for chemotactic orientation, the majority contain insufficient levels to facilitate motility. Here it has been demonstrated that Nhe1, a plasma membrane protein, is required for K+ but not Ca2+ facilitation of cell motility and for the lower K+ but not Ca2+ requirement for chemotactic orientation.
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41
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A comprehensive proteomics and transcriptomics analysis of Bacillus subtilis salt stress adaptation. J Bacteriol 2009; 192:870-82. [PMID: 19948795 DOI: 10.1128/jb.01106-09] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
In its natural habitats, Bacillus subtilis is exposed to changing osmolarity, necessitating adaptive stress responses. Transcriptomic and proteomic approaches can provide a picture of the dynamic changes occurring in salt-stressed B. subtilis cultures because these studies provide an unbiased view of cells coping with high salinity. We applied whole-genome microarray technology and metabolic labeling, combined with state-of-the-art proteomic techniques, to provide a global and time-resolved picture of the physiological response of B. subtilis cells exposed to a severe and sudden osmotic upshift. This combined experimental approach provided quantitative data for 3,961 mRNA transcription profiles, 590 expression profiles of proteins detected in the cytosol, and 383 expression profiles of proteins detected in the membrane fraction. Our study uncovered a well-coordinated induction of gene expression subsequent to an osmotic upshift that involves large parts of the SigB, SigW, SigM, and SigX regulons. Additionally osmotic upregulation of a large number of genes that do not belong to these regulons was observed. In total, osmotic upregulation of about 500 B. subtilis genes was detected. Our data provide an unprecedented rich basis for further in-depth investigation of the physiological and genetic responses of B. subtilis to hyperosmotic stress.
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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.
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Roosild TP, Castronovo S, Miller S, Li C, Rasmussen T, Bartlett W, Gunasekera B, Choe S, Booth IR. KTN (RCK) domains regulate K+ channels and transporters by controlling the dimer-hinge conformation. Structure 2009; 17:893-903. [PMID: 19523906 PMCID: PMC2920069 DOI: 10.1016/j.str.2009.03.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 03/16/2009] [Accepted: 03/30/2009] [Indexed: 01/13/2023]
Abstract
KTN (RCK) domains are nucleotide-binding folds that form the cytoplasmic regulatory complexes of various K+ channels and transporters. The mechanisms these proteins use to control their transmembrane pore-forming counterparts remains unclear despite numerous electrophysiological and structural studies. KTN (RCK) domains consistently crystallize as dimers within the asymmetric unit, forming a pronounced hinge between two Rossmann folds. We have previously proposed that modification of the hinge angle plays an important role in activating the associated membrane-integrated components of the channel or transporter. Here we report the structure of the C-terminal, KTN-bearing domain of the E. coli KefC K+ efflux system in association with the ancillary subunit, KefF, which is known to stabilize the conductive state. The structure of the complex and functional analysis of KefC variants reveal that control of the conformational flexibility inherent in the KTN dimer hinge is modulated by KefF and essential for regulation of KefC ion flux.
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Affiliation(s)
- Tarmo P. Roosild
- Drug Development Department, Nevada Cancer Institute, Las Vegas, NV 89135, USA
| | - Samantha Castronovo
- Drug Development Department, Nevada Cancer Institute, Las Vegas, NV 89135, USA
| | - Samantha Miller
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
| | - Chan Li
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
| | - Tim Rasmussen
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
| | - Wendy Bartlett
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
| | - Banuri Gunasekera
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
| | - Senyon Choe
- Structural Biology Laboratory, Salk Institute, La Jolla, San Diego, CA 92037, USA
| | - Ian R. Booth
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
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Acid and base stress and transcriptomic responses in Bacillus subtilis. Appl Environ Microbiol 2008; 75:981-90. [PMID: 19114526 DOI: 10.1128/aem.01652-08] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K(+)/H(+) antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids.
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The Bacillus cereus GerN and GerT protein homologs have distinct roles in spore germination and outgrowth, respectively. J Bacteriol 2008; 190:6148-52. [PMID: 18641133 DOI: 10.1128/jb.00789-08] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The GerT protein of Bacillus cereus shares 74% amino acid identity with its homolog GerN. The latter is a Na(+)/H(+)-K(+) antiporter that is required for normal spore germination in inosine. The germination properties of single and double mutants of B. cereus ATCC 10876 reveal that unlike GerN, which is required for all germination responses that involve the GerI germinant receptor, the GerT protein does not have a significant role in germination, although it is required for the residual GerI-mediated inosine germination response of a gerN mutant. In contrast, GerT has a significant role in outgrowth; gerT mutant spores do not outgrow efficiently under alkaline conditions and outgrow more slowly than the wild type in the presence of high NaCl concentrations. The GerT protein in B. cereus therefore contributes to the success of spore outgrowth from the germinated state during alkaline or Na(+) stress.
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46
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Single gene deletions of mrpA to mrpG and mrpE point mutations affect activity of the Mrp Na+/H+ antiporter of alkaliphilic Bacillus and formation of hetero-oligomeric Mrp complexes. J Bacteriol 2008; 190:4162-72. [PMID: 18408029 DOI: 10.1128/jb.00294-08] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Mrp antiporters catalyze secondary Na(+)(Li(+))/H(+) antiport and/or K(+)/H(+) antiport that is physiologically important in diverse bacteria. An additional capacity for anion flux has been observed for a few systems. Mrp is unique among antiporters in that it requires all six or seven hydrophobic gene products (MrpA to MrpG) of the mrp operon for full antiporter activity, but MrpE has been reported to be dispensable. Here, the membrane complexes formed by Mrp proteins were examined using a cloned mrp operon from alkaliphilic Bacillus pseudofirmus OF4. The operon was engineered so that the seven Mrp proteins could be detected in single samples. Membrane extracts of an antiporter-deficient Escherichia coli strain expressing this construct were analyzed by blue native-sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Mrp complexes of two sizes were identified containing all seven Mrp proteins. Studies of the single nonpolar mrp gene deletions in the construct showed that a subcomplex of MrpA, MrpB, MrpC, and MrpD was formed in the absence of MrpE, MrpF, or MrpG. By contrast, MrpE, MrpF, and MrpG were not observed in membranes lacking MrpA, MrpB, MrpC, or MrpD. Although MrpA and MrpD have been hypothesized to be the antiporter proteins, the MrpA-to-D complex was inactive. Every Mrp protein was required for an activity level near that of the wild-type Na(+)/H(+) antiporter, but a very low activity level was observed in the absence of MrpE. The introduction of an MrpE(P114G) mutation into the full Mrp complex led to antiport activity with a greatly increased apparent K(m) value for Na(+). The results suggested that interactions among the proteins of heterooligomeric Mrp complexes strongly impact antiporter properties.
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Liu J, Krulwich TA, Hicks DB. Purification of two putative type II NADH dehydrogenases with different substrate specificities from alkaliphilic Bacillus pseudofirmus OF4. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:453-61. [PMID: 18359284 DOI: 10.1016/j.bbabio.2008.02.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 02/26/2008] [Accepted: 02/27/2008] [Indexed: 11/17/2022]
Abstract
A putative Type II NADH dehydrogenase from Halobacillus dabanensis was recently reported to have Na+/H+ antiport activity (and called Nap), raising the possibility of direct coupling of respiration to antiport-dependent pH homeostasis. This study characterized a homologous type II NADH dehydrogenase of genetically tractable alkaliphilic Bacillus pseudofirmus OF4, in which evidence supports antiport-based pH homeostasis that is mediated entirely by secondary antiport. Two candidate type II NADH dehydrogenase genes with canonical GXGXXG motifs were identified in a draft genome sequence of B. pseudofirmus OF4. The gene product designated NDH-2A exhibited homology to enzymes from Bacillus subtilis and Escherichia coli whereas NDH-2B exhibited homology to the H. dabanensis Nap protein and its alkaliphilic Bacillus halodurans C-125 homologue. The ndh-2A, but not the ndh-2B, gene complemented the growth defect of an NADH dehydrogenase-deficient E. coli mutant. Neither gene conferred Na+-resistance on an antiporter-deficient E. coli strain, nor did they confer Na+/H+ antiport activity in vesicle assays. The purified hexa-histidine-tagged gene products were approximately 50 kDa, contained noncovalently bound FAD and oxidized NADH. They were predominantly cytoplasmic in E. coli, consonant with the absence of antiport activity. The catalytic properties of NDH-2A were more consistent with a major respiratory role than those of NDH-2B.
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Affiliation(s)
- Jun Liu
- Department of Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA
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