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Mishra S, Welch N, Singh SS, Singh KD, Bellar A, Kumar A, Deutz LN, Hanlon MD, Kant S, Dastidar S, Patel H, Agrawal V, Attaway AH, Musich R, Stark GR, Tedesco FS, Truskey GA, Weiner ID, Karnik SS, Dasarathy S. Ammonia transporter RhBG initiates downstream signaling and functional responses by activating NFκB. Proc Natl Acad Sci U S A 2024; 121:e2314760121. [PMID: 39052834 PMCID: PMC11294993 DOI: 10.1073/pnas.2314760121] [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: 08/30/2023] [Accepted: 06/19/2024] [Indexed: 07/27/2024] Open
Abstract
Transceptors, solute transporters that facilitate intracellular entry of molecules and also initiate intracellular signaling events, have been primarily studied in lower-order species. Ammonia, a cytotoxic endogenous metabolite, is converted to urea in hepatocytes for urinary excretion in mammals. During hyperammonemia, when hepatic metabolism is impaired, nonureagenic ammonia disposal occurs primarily in skeletal muscle. Increased ammonia uptake in skeletal muscle is mediated by a membrane-bound, 12 transmembrane domain solute transporter, Rhesus blood group-associated B glycoprotein (RhBG). We show that in addition to its transport function, RhBG interacts with myeloid differentiation primary response-88 (MyD88) to initiate an intracellular signaling cascade that culminates in activation of NFκB. We also show that ammonia-induced MyD88 signaling is independent of the canonical toll-like receptor-initiated mechanism of MyD88-dependent NFκB activation. In silico, in vitro, and in situ experiments show that the conserved cytosolic J-domain of the RhBG protein interacts with the Toll-interleukin-1 receptor (TIR) domain of MyD88. In skeletal muscle from human patients, human-induced pluripotent stem cell-derived myotubes, and myobundles show an interaction of RhBG-MyD88 during hyperammonemia. Using complementary experimental and multiomics analyses in murine myotubes and mice with muscle-specific RhBG or MyD88 deletion, we show that the RhBG-MyD88 interaction is essential for the activation of NFkB but not ammonia transport. Our studies show a paradigm of substrate-dependent regulation of transceptor function with the potential for modulation of cellular responses in mammalian systems by decoupling transport and signaling functions of transceptors.
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Affiliation(s)
- Saurabh Mishra
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Nicole Welch
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
- Gastroenterology and Hepatology, Lerner Research Institute, Cleveland, OH44195
| | - Shashi Shekhar Singh
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | | | - Annette Bellar
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Avinash Kumar
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Lars N. Deutz
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Maxmillian D. Hanlon
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Sashi Kant
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Sumitava Dastidar
- Department of Cell and Developmental Biology, University College London & The Francis Crick Institute, LondonWC1E6DE, UK
| | - Hailee Patel
- Duke Biomedical Engineering, Duke University, Durham, NC27708
| | - Vandana Agrawal
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - Amy H. Attaway
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
- Pulmonary Medicine, Lerner Research Institute, Cleveland, OH44195
| | - Ryan Musich
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
| | - George R. Stark
- Cancer Biology, Lerner Research Institute, Cleveland, OH44195
| | - Francesco Saverio Tedesco
- Department of Cell and Developmental Biology, University College London & The Francis Crick Institute, LondonWC1E6DE, UK
| | | | - I. David Weiner
- Division of Nephrology Hypertension, and Renal Transplantation, University of Florida, Gainesville, FL32610
- Nephrology and Hypertension Section, Gainesville, FL32610
| | - Sadashiva S. Karnik
- Cardiovascular and Metabolic Diseases, Lerner Research Institute, Cleveland, OH44195
| | - Srinivasan Dasarathy
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland, OH44195
- Gastroenterology and Hepatology, Lerner Research Institute, Cleveland, OH44195
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Tribelhorn K, Twarużek M, Kosicki R, Straubinger RK, Ebel F, Ulrich S. A Chemically Defined Medium That Supports Mycotoxin Production by Stachybotrys chartarum Enabled Analysis of the Impact of Nitrogen and Carbon Sources on the Biosynthesis of Macrocyclic Trichothecenes and Stachybotrylactam. Appl Environ Microbiol 2023:e0016323. [PMID: 37338364 PMCID: PMC10370337 DOI: 10.1128/aem.00163-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 05/21/2023] [Indexed: 06/21/2023] Open
Abstract
Stachybotrys chartarum (Hypocreales, Ascomycota) is a toxigenic fungus that is frequently isolated from water-damaged buildings or improperly stored feed. The secondary metabolites formed by this mold have been associated with health problems in humans and animals. Several authors have studied the influence of environmental conditions on the production of mycotoxins, but these studies focused on undefined or complex substrates, such as building materials and media that impeded investigations of the influence of specific nutrients. In this study, a chemically defined cultivation medium was used to investigate the impact of several nitrogen and carbon sources on growth of S. chartarum and its production of macrocyclic trichothecenes (MTs) and stachybotrylactam (STLAC). Increasing concentrations of sodium nitrate were found to positively affect mycelial growth, the level of sporulation, and MT production, while ammonium nitrate and ammonium chloride had an inhibitory effect. Potato starch was the superior and most reliable carbon source tested. Additionally, we observed that the level of sporulation was correlated with the production of MTs but not with that of STLAC. In this study, we provide a chemically well-defined cultivation medium suitable for standardized in vitro testing of the capacity of S. chartarum isolates to produce macrocyclic trichothecenes. IMPORTANCE Macrocyclic trichothecenes (MTs) are highly toxic secondary metabolites that are produced by certain Stachybotrys chartarum strains, which consequently pose a risk for animals and humans. To identify hazardous, toxin-producing strains by analytical means, it is important to grow them under conditions that support MT production. Nutrients determine growth and development and thus the synthesis of secondary metabolites. Complex rich media are commonly used for diagnostics, but batch differences of supplements pose a risk for inconsistent data. We have established a chemically defined medium for S. chartarum and used it to analyze the impact of nitrogen and carbon sources. A key finding is that nitrate stimulates MT production, whereas ammonium suppresses it. Defining nutrients that support MT production will enable a more reliable identification of hazardous S. chartarum isolates. The new medium will also be instrumental in analyzing the biosynthetic pathways and regulatory mechanisms that control mycotoxin production in S. chartarum.
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Affiliation(s)
- Katharina Tribelhorn
- Chair of Bacteriology and Mycology, Department of Veterinary Sciences, Faculty of Veterinary Medicine, Institute for Infectious Diseases and Zoonosis, LMU Munich, Munich, Germany
| | - Magdalena Twarużek
- Department of Physiology and Toxicology, Faculty of Biological Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Robert Kosicki
- Department of Physiology and Toxicology, Faculty of Biological Sciences, Kazimierz Wielki University, Bydgoszcz, Poland
| | - Reinhard K Straubinger
- Chair of Bacteriology and Mycology, Department of Veterinary Sciences, Faculty of Veterinary Medicine, Institute for Infectious Diseases and Zoonosis, LMU Munich, Munich, Germany
| | - Frank Ebel
- Chair of Bacteriology and Mycology, Department of Veterinary Sciences, Faculty of Veterinary Medicine, Institute for Infectious Diseases and Zoonosis, LMU Munich, Munich, Germany
| | - Sebastian Ulrich
- Chair of Bacteriology and Mycology, Department of Veterinary Sciences, Faculty of Veterinary Medicine, Institute for Infectious Diseases and Zoonosis, LMU Munich, Munich, Germany
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Wang M, Mara P, Burgaud G, Edgcomb V, Long X, Yang H, Cai L, Li W. Metatranscriptomics and metabarcoding reveal spatiotemporal shifts in fungal communities and their activities in Chinese coastal waters. Mol Ecol 2023; 32:2750-2765. [PMID: 36852430 DOI: 10.1111/mec.16905] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 02/22/2023] [Accepted: 02/24/2023] [Indexed: 03/01/2023]
Abstract
Fungal communities are diverse and abundant in coastal waters, yet, their ecological roles and adaptations remain largely unknown. To address these gaps, ITS2 metabarcoding and metatranscriptomic analyses were used to capture the whole suite of fungal diversity and their metabolic potential in water column and sediments in the Yellow Sea during August and October 2019. ITS2 metabarcoding described successfully the abundance of Dikarya during August and October at the different examined habitats, but strongly underrepresented or failed to identify other fungal taxa, including zoosporic and early-diverging lineages, that were abundant in the mycobiome as uncovered by metatranscriptomes. Metatranscriptomics also revealed enriched expression of genes annotated to zoosporic fungi (e.g., chytrids) mainly in the surface water column in October. This enriched expression was correlated with the two-fold increase in chlorophyll-a intensity attributed to phytoplanktonic species which are known to be parasitized by chytrids. The concurrent high expression of genes related to calcium signalling and GTPase activity suggested that these metabolic traits facilitate the parasitic lifestyle of chytrids. Similarly, elevated expression of phagosome genes annotated to Rozellomycota, an early-diverging fungal phylum not fully detected with ITS2 metabarcoding, suggested that this taxon utilizes a suite of feeding modes, including phagotrophy in this coastal setting. Our data highlight the necessity of using combined approaches to accurately describe the community structure of coastal mycobiome. We also provide in-depth insights into the fungal ecological roles in coastal waters, and report potential metabolic mechanisms utilized by fungi to cope with environmental stresses that occur during distinct seasonal months in coastal ecosystems.
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Affiliation(s)
- Mengmeng Wang
- College of Science, Shantou University, Shantou, China.,State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Paraskevi Mara
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
| | - Gaëtan Burgaud
- University of Brest, INRAE, Laboratoire Universitaire de Biodiversité et Écologie Microbienne, Plouzané, France
| | - Virginia Edgcomb
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
| | - Xuedan Long
- College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Haiping Yang
- College of Marine Life Sciences, Ocean University of China, Qingdao, China
| | - Lei Cai
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Wei Li
- College of Science, Shantou University, Shantou, China
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Densi A, Iyer RS, Bhat PJ. Synonymous and Nonsynonymous Substitutions in Dictyostelium discoideum Ammonium Transporter amtA Are Necessary for Functional Complementation in Saccharomyces cerevisiae. Microbiol Spectr 2023; 11:e0384722. [PMID: 36840598 PMCID: PMC10100761 DOI: 10.1128/spectrum.03847-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 01/24/2023] [Indexed: 02/24/2023] Open
Abstract
Ammonium transporters are present in all three domains of life. They have undergone extensive horizontal gene transfer (HGT), gene duplication, and functional diversification and therefore offer an excellent paradigm to study protein evolution. We attempted to complement a mep1Δmep2Δmep3Δ strain of Saccharomyces cerevisiae (triple-deletion strain), which otherwise cannot grow on ammonium as a sole nitrogen source at concentrations of <3 mM, with amtA of Dictyostelium discoideum, an orthologue of S. cerevisiae MEP2. We observed that amtA did not complement the triple-deletion strain of S. cerevisiae for growth on low-ammonium medium. We isolated two mutant derivatives of amtA (amtA M1 and amtA M2) from a PCR-generated mutant plasmid library that complemented the triple-deletion strain of S. cerevisiae. amtA M1 bears three nonsynonymous and two synonymous substitutions, which are necessary for its functionality. amtA M2 bears two nonsynonymous substitutions and one synonymous substitution, all of which are necessary for functionality. Interestingly, AmtA M1 transports ammonium but does not confer methylamine toxicity, while AmtA M2 transports ammonium and confers methylamine toxicity, demonstrating functional diversification. Preliminary biochemical analyses indicated that the mutants differ in their conformations as well as their mechanisms of ammonium transport. These intriguing results clearly point out that protein evolution cannot be fathomed by studying nonsynonymous and synonymous substitutions in isolation. The above-described observations have significant implications for various facets of biological processes and are discussed in detail. IMPORTANCE Functional diversification following gene duplication is one of the major driving forces of protein evolution. While the role of nonsynonymous substitutions in the functional diversification of proteins is well recognized, knowledge of the role of synonymous substitutions in protein evolution is in its infancy. Using functional complementation, we isolated two functional alleles of the D. discoideum ammonium transporter gene (amtA), which otherwise does not function in S. cerevisiae as an ammonium transporters. One of them is an ammonium transporter, while the other is an ammonium transporter that also confers methylammonium (ammonium analogue) toxicity, suggesting functional diversification. Surprisingly, both alleles require a combination of synonymous and nonsynonymous substitutions for their functionality. These results bring out a hitherto-unknown pathway of protein evolution and pave the way for not only understanding protein evolution but also interpreting single nucleotide polymorphisms (SNPs).
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Affiliation(s)
- Asha Densi
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Revathi S. Iyer
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Paike Jayadeva Bhat
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
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5
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The Exploring Functional Role of Ammonium Transporters of Aspergillus oryzae in Nitrogen Metabolism: Challenges towards Cell Biomass Production. Int J Mol Sci 2022; 23:ijms23147567. [PMID: 35886914 PMCID: PMC9319855 DOI: 10.3390/ijms23147567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 07/04/2022] [Accepted: 07/04/2022] [Indexed: 11/30/2022] Open
Abstract
Ammonium is a source of fermentable inorganic nitrogen essential for the growth and development of filamentous fungi. It is involved in several cellular metabolic pathways underlying nitrogen transport and assimilation. Ammonium can be transferred into the cell by an ammonium transporter. This study explored the role of ammonium transporters in nitrogen metabolism and cell biomass production in Aspergillus oryzae strain BCC 7051. Specific sequences encoding ammonium transporters (Amts) in A. oryzae were identified using genomic analysis. Four of the identified ammonium transporter genes, aoamt1-aoamt4, showed similarity in deduced amino acid sequences to the proteins in the ammonium transporter/methylammonium permease (AMT/MEP) family. Transcriptional analysis showed that the expression of aoamt2 and aoamt3 was ammonium-dependent, and was highly upregulated under ammonium-limited conditions. Their functional roles are characterized by genetic perturbations. The gene disruption and overexpression of aoamt3 indicated that the protein encoded by it was a crucial ammonium transporter associated with nitrogen metabolism and was required for filamentous growth. Compared with the wild type, the aoamt3-overexpressing strain showed superior growth performance, high biomass yield, and low glucose consumption. These results shed light on further improvements in the production of potent bioproducts by A. oryzae by manipulating the ammonium uptake capacity and nitrogen metabolism.
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6
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McDonald TR, Rizvi MF, Ruiter BL, Roy R, Reinders A, Ward JM. Posttranslational regulation of transporters important for symbiotic interactions. PLANT PHYSIOLOGY 2022; 188:941-954. [PMID: 34850211 PMCID: PMC8825328 DOI: 10.1093/plphys/kiab544] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 10/27/2021] [Indexed: 05/20/2023]
Abstract
Coordinated sharing of nutritional resources is a central feature of symbiotic interactions, and, despite the importance of this topic, many questions remain concerning the identification, activity, and regulation of transporter proteins involved. Recent progress in obtaining genome and transcriptome sequences for symbiotic organisms provides a wealth of information on plant, fungal, and bacterial transporters that can be applied to these questions. In this update, we focus on legume-rhizobia and mycorrhizal symbioses and how transporters at the symbiotic interfaces can be regulated at the protein level. We point out areas where more research is needed and ways that an understanding of transporter mechanism and energetics can focus hypotheses. Protein phosphorylation is a predominant mechanism of posttranslational regulation of transporters in general and at the symbiotic interface specifically. Other mechanisms of transporter regulation, such as protein-protein interaction, including transporter multimerization, polar localization, and regulation by pH and membrane potential are also important at the symbiotic interface. Most of the transporters that function in the symbiotic interface are members of transporter families; we bring in relevant information on posttranslational regulation within transporter families to help generate hypotheses for transporter regulation at the symbiotic interface.
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Affiliation(s)
- Tami R McDonald
- Department of Biology, St Catherine University, St Paul, Minnesota, USA
| | - Madeeha F Rizvi
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Bretton L Ruiter
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Rahul Roy
- Department of Biology, St Catherine University, St Paul, Minnesota, USA
| | - Anke Reinders
- College of Continuing and Professional Studies, University of Minnesota, St. Paul, Minnesota, USA
| | - John M Ward
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
- Author for communication:
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Hettiarachchige IK, Vander Jagt CJ, Mann RC, Sawbridge TI, Spangenberg GC, Guthridge KM. Global Changes in Asexual Epichloë Transcriptomes during the Early Stages, from Seed to Seedling, of Symbiotum Establishment. Microorganisms 2021; 9:microorganisms9050991. [PMID: 34064362 PMCID: PMC8147782 DOI: 10.3390/microorganisms9050991] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 04/30/2021] [Accepted: 04/30/2021] [Indexed: 11/16/2022] Open
Abstract
Asexual Epichloë fungi are strictly seed-transmitted endophytic symbionts of cool-season grasses and spend their entire life cycle within the host plant. Endophyte infection can confer protective benefits to its host through the production of bioprotective compounds. Inversely, plants provide nourishment and shelter to the resident endophyte in return. Current understanding of the changes in global gene expression of asexual Epichloë endophytes during the early stages of host-endophyte symbiotum is limited. A time-course study using a deep RNA-sequencing approach was performed at six stages of germination, using seeds infected with one of three endophyte strains belonging to different representative taxa. Analysis of the most abundantly expressed endophyte genes identified that most were predicted to have a role in stress and defence responses. The number of differentially expressed genes observed at early time points was greater than those detected at later time points, suggesting an active transcriptional reprogramming of endophytes at the onset of seed germination. Gene ontology enrichment analysis revealed dynamic changes in global gene expression consistent with the developmental processes of symbiotic relationships. Expression of pathway genes for biosynthesis of key secondary metabolites was studied comprehensively and fuzzy clustering identified some unique expression patterns. Furthermore, comparisons of the transcriptomes from three endophyte strains in planta identified genes unique to each strain, including genes predicted to be associated with secondary metabolism. Findings from this study highlight the importance of better understanding the unique properties of individual endophyte strains and will serve as an excellent resource for future studies of host-endophyte interactions.
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Affiliation(s)
- Inoka K. Hettiarachchige
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, VIC 3083, Australia; (I.K.H.); (C.J.V.J.); (R.C.M.); (T.I.S.); (G.C.S.)
| | - Christy J. Vander Jagt
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, VIC 3083, Australia; (I.K.H.); (C.J.V.J.); (R.C.M.); (T.I.S.); (G.C.S.)
| | - Ross C. Mann
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, VIC 3083, Australia; (I.K.H.); (C.J.V.J.); (R.C.M.); (T.I.S.); (G.C.S.)
| | - Timothy I. Sawbridge
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, VIC 3083, Australia; (I.K.H.); (C.J.V.J.); (R.C.M.); (T.I.S.); (G.C.S.)
- School of Applied Systems Biology, La Trobe University, Bundoora, VIC 3086, Australia
| | - German C. Spangenberg
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, VIC 3083, Australia; (I.K.H.); (C.J.V.J.); (R.C.M.); (T.I.S.); (G.C.S.)
- School of Applied Systems Biology, La Trobe University, Bundoora, VIC 3086, Australia
| | - Kathryn M. Guthridge
- Agriculture Victoria, AgriBio, Centre for AgriBioscience, Bundoora, VIC 3083, Australia; (I.K.H.); (C.J.V.J.); (R.C.M.); (T.I.S.); (G.C.S.)
- Correspondence:
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8
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Grishin D, Kasap E, Izotov A, Lisitsa A. Multifaceted ammonia transporters. ALL LIFE 2020. [DOI: 10.1080/26895293.2020.1812443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Affiliation(s)
- D.V. Grishin
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - E.Y. Kasap
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - A.A. Izotov
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
| | - A.V. Lisitsa
- Institute of Biomedical Chemistry (IBMC), Moscow, Russia
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Smeulders MJ, Peeters SH, van Alen T, de Bruijckere D, Nuijten GHL, op den Camp HJM, Jetten MSM, van Niftrik L. Nutrient Limitation Causes Differential Expression of Transport- and Metabolism Genes in the Compartmentalized Anammox Bacterium Kuenenia stuttgartiensis. Front Microbiol 2020; 11:1959. [PMID: 32903544 PMCID: PMC7438415 DOI: 10.3389/fmicb.2020.01959] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 07/24/2020] [Indexed: 12/11/2022] Open
Abstract
Anaerobic ammonium-oxidizing (anammox) bacteria, members of the "Candidatus Brocadiaceae" family, play an important role in the nitrogen cycle and are estimated to be responsible for about half of the oceanic nitrogen loss to the atmosphere. Anammox bacteria combine ammonium with nitrite and produce dinitrogen gas via the intermediates nitric oxide and hydrazine (anammox reaction) while nitrate is formed as a by-product. These reactions take place in a specialized, membrane-enclosed compartment called the anammoxosome. Therefore, the substrates ammonium, nitrite and product nitrate have to cross the outer-, cytoplasmic-, and anammoxosome membranes to enter or exit the anammoxosome. The genomes of all anammox species harbor multiple copies of ammonium-, nitrite-, and nitrate transporter genes. Here we investigated how the distinct genes for ammonium-, nitrite-, and nitrate- transport were expressed during substrate limitation in membrane bioreactors. Transcriptome analysis of Kuenenia stuttgartiensis planktonic cells showed that four of the seven ammonium transporter homologs and two of the nine nitrite transporter homologs were significantly upregulated during ammonium-limited growth, while another ammonium transporter- and four nitrite transporter homologs were upregulated in nitrite limited growth conditions. The two nitrate transporters were expressed to similar levels in both conditions. In addition, genes encoding enzymes involved in the anammox reaction were differentially expressed, with those using nitrite as a substrate being upregulated under nitrite limited growth and those using ammonium as a substrate being upregulated during ammonium limitation. Taken together, these results give a first insight in the potential role of the multiple nutrient transporters in regulating transport of substrates and products in and out of the compartmentalized anammox cell.
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Affiliation(s)
| | | | | | | | | | | | | | - Laura van Niftrik
- Department of Microbiology, Institute for Water and Wetland Research, Faculty of Science, Radboud University Nijmegen, Nijmegen, Netherlands
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