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  • 1
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    Online Resource
    Stable Fluorescent and Enzymatic Tagging of Bradyrhizobium diazoefficiens to Analyze Host-Plant Infection and Colonization
    Scientific Societies ; 2015
    In:  Molecular Plant-Microbe Interactions® Vol. 28, No. 9 ( 2015-09), p. 959-967
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 28, No. 9 ( 2015-09), p. 959-967
    Abstract: Bradyrhizobium diazoefficiens USDA 110 (formerly named Bradyrhizobium japonicum) can fix dinitrogen when living as an endosymbiont in root nodules of soybean and some other legumes. Formation of a functional symbiosis relies on a defined developmental program mediated by controlled gene expression in both symbiotic partners. In contrast to other well-studied Rhizobium-legume model systems that have been thoroughly examined by means of genetically tagged strains, analysis of B. diazoefficiens host infection has been impaired due to the lack of suitable tagging systems. Here, we describe the construction of B. diazoefficiens strains constitutively expressing single-copy genes for fluorescent proteins (eBFP2, mTurquoise2, GFP+, sYFP2, mCherry, HcRed) and enzymes (GusA, LacZ). For stable inheritance, the constructs were recombined into the chromosome. Effectiveness and versatility of the tagged strains was demonstrated in plant infection assays. (i) The infection process was followed from root-hair attachment to colonization of nodule cells with epifluorescent microscopy. (ii) Monitoring mixed infections with two strains producing different fluorescent proteins allowed rapid analysis of nodule occupancy and revealed that the majority of nodules contained clonal populations. (iii) Microscopic analysis of nodules induced by fluorescent strains provided evidence for host-dependent control of B. diazoefficiens bacteroid morphology in nodules of Aeschynomene afraspera and Arachis hypogaea (peanut), as deduced from their altered morphology compared with bacteroids in soybean nodules.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-03-15-0054-TA
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2015
    detail.hit.zdb_id: 2037108-1
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  • 2
    Online Resource
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    A Functional General Stress Response of Bradyrhizobium diazoefficiens Is Required for Early Stages of Host Plant Infection
    Scientific Societies ; 2018
    In:  Molecular Plant-Microbe Interactions® Vol. 31, No. 5 ( 2018-05), p. 537-547
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 31, No. 5 ( 2018-05), p. 537-547
    Abstract: Phylogenetically diverse bacteria respond to various stress conditions by mounting a general stress response (GSR) resulting in the induction of protection or damage repair functions. In α-proteobacteria, the GSR is induced by a regulatory cascade consisting of the extracytoplasmic function (ECF) σ factor σ EcfG , its anti-σ factor NepR, and the anti-anti-σ factor PhyR. We have reported previously that σ EcfG and PhyR of Bradyrhizobium diazoefficiens (formerly named Bradyrhizobium japonicum), the nitrogen-fixing root nodule symbiont of soybean and related legumes, are required for efficient symbiosis; however, the precise role of the GSR remained undefined. Here, we analyze the symbiotic defects of a B. diazoefficiens mutant lacking σ EcfG by comparing distinct infection stages of enzymatically or fluorescently tagged wild-type and mutant bacteria. Although root colonization and root hair curling were indistinguishable, the mutant was not competitive, and showed delayed development of emerging nodules and only a few infection threads. Consequently, many of the mutant-induced nodules were aborted, empty, or partially colonized. Congruent with these results, we found that σ EcfG was active in bacteria present in root-hair-entrapped microcolonies and infection threads but not in root-associated bacteria and nitrogen-fixing bacteroids. We conclude that GSR-controlled functions are crucial for synchronization of infection thread formation, colonization, and nodule development.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-11-17-0284-R
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2018
    detail.hit.zdb_id: 2037108-1
    SSG: 12
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  • 3
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    Salt- and Osmo-Responsive Sensor Histidine Kinases Activate the Bradyrhizobium diazoefficiens General Stress Response to Initiate Functional Symbiosis
    Scientific Societies ; 2022
    In:  Molecular Plant-Microbe Interactions® Vol. 35, No. 7 ( 2022-07), p. 604-615
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 35, No. 7 ( 2022-07), p. 604-615
    Abstract: The general stress response (GSR) enables bacteria to sense and overcome a variety of environmental stresses. In alphaproteobacteria, stress-perceiving histidine kinases of the HWE and HisKA_2 families trigger a signaling cascade that leads to phosphorylation of the response regulator PhyR and, consequently, to activation of the GSR σ factor σ EcfG . In the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens, PhyR and σ EcfG are crucial for tolerance against a variety of stresses under free-living conditions and also for efficient infection of its symbiotic host soybean. However, the molecular players involved in stress perception and activation of the GSR remained largely unknown. In this work, we first showed that a mutant variant of PhyR where the conserved phosphorylatable aspartate residue D194 was replaced by alanine (PhyR D194A ) failed to complement the ΔphyR mutant in symbiosis, confirming that PhyR acts as a response regulator. To identify the PhyR-activating kinases in the nitrogen-fixing symbiont, we constructed in-frame deletion mutants lacking single, distinct combinations, or all of the 11 predicted HWE and HisKA_2 kinases, which we named HRXXN histidine kinases HhkA through HhkK. Phenotypic analysis of the mutants and complemented derivatives identified two functionally redundant kinases, HhkA and HhkE, that are required for nodulation competitiveness and during initiation of symbiosis. Using σ EcfG -activity reporter strains, we further showed that both HhkA and HhkE activate the GSR in free-living cells exposed to salt and hyperosmotic stress. In conclusion, our data suggest that HhkA and HhkE trigger GSR activation in response to osmotically stressful conditions which B. diazoefficiens encounters during soybean host infection. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI-02-22-0051-FI
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2022
    detail.hit.zdb_id: 2037108-1
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  • 4
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    Bradyrhizobium diazoefficiens Requires Chemical Chaperones To Cope with Osmotic Stress during Soybean Infection
    American Society for Microbiology ; 2021
    In:  mBio Vol. 12, No. 2 ( 2021-04-27)
    Details
    In: mBio, American Society for Microbiology, Vol. 12, No. 2 ( 2021-04-27)
    Abstract: When engaging in symbiosis with legume hosts, rhizobia are confronted with environmental changes, including nutrient availability and stress exposure. Genetic circuits allow responding to these environmental stimuli to optimize physiological adaptations during the switch from the free-living to the symbiotic life style. A pivotal regulatory system of the nitrogen-fixing soybean endosymbiont Bradyrhizobium diazoefficiens for efficient symbiosis is the general stress response (GSR), which relies on the alternative sigma factor σ EcfG . However, the GSR-controlled process required for symbiosis has not been identified. Here, we demonstrate that biosynthesis of trehalose is under GSR control, and mutants lacking the respective biosynthetic genes otsA and/or otsB phenocopy GSR-deficient mutants under symbiotic and selected free-living stress conditions. The role of trehalose as a cytoplasmic chemical chaperone and stress protectant can be functionally replaced in an otsA or otsB mutant by introducing heterologous genetic pathways for biosynthesis of the chemically unrelated compatible solutes glycine betaine and (hydroxy)ectoine. Alternatively, uptake of exogenously provided trehalose also restores efficient symbiosis and tolerance to hyperosmotic and hyperionic stress of otsA mutants. Hence, elevated cytoplasmic trehalose levels resulting from GSR-controlled biosynthesis are crucial for B. diazoefficiens cells to overcome adverse conditions during early stages of host infection and ensure synchronization with root nodule development. IMPORTANCE The Bradyrhizobium -soybean symbiosis is of great agricultural significance and serves as a model system for fundamental research in bacterium-plant interactions. While detailed molecular insight is available about mutual recognition and early nodule organogenesis, our understanding of the host-imposed conditions and the physiology of infecting rhizobia during the transition from a free-living state in the rhizosphere to endosymbiotic bacteroids is currently limited. In this study, we show that the requirement of the rhizobial general stress response (GSR) during host infection is attributable to GSR-controlled biosynthesis of trehalose. Specifically, trehalose is crucial for an efficient symbiosis by acting as a chemical chaperone to protect rhizobia from osmostress during host infection.
    Type of Medium: Online Resource
    ISSN: 2150-7511
    URL: Article
    DOI: 10.1128/mBio.00390-21
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2021
    detail.hit.zdb_id: 2557172-2
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  • 5
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    Fractional Flow Reserve to Guide Treatment of Patients With Multivessel Coronary Artery Disease
    Elsevier BV ; 2021
    In:  Journal of the American College of Cardiology Vol. 78, No. 19 ( 2021-11), p. 1875-1885
    Details
    In: Journal of the American College of Cardiology, Elsevier BV, Vol. 78, No. 19 ( 2021-11), p. 1875-1885
    Type of Medium: Online Resource
    ISSN: 0735-1097
    URL: Article
    DOI: 10.1016/j.jacc.2021.08.061
    RVK:
    XA 17760
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2021
    detail.hit.zdb_id: 1468327-1
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  • 6
    Online Resource
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    Conditional sanctioning in a legume– Rhizobium mutualism
    Proceedings of the National Academy of Sciences ; 2021
    In:  Proceedings of the National Academy of Sciences Vol. 118, No. 19 ( 2021-05-11)
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 118, No. 19 ( 2021-05-11)
    Abstract: Legumes are high in protein and form a valuable part of human diets due to their interaction with symbiotic nitrogen-fixing bacteria known as rhizobia. Plants house rhizobia in specialized root nodules and provide the rhizobia with carbon in return for nitrogen. However, plants usually house multiple rhizobial strains that vary in their fixation ability, so the plant faces an investment dilemma. Plants are known to sanction strains that do not fix nitrogen, but nonfixers are rare in field settings, while intermediate fixers are common. Here, we modeled how plants should respond to an intermediate fixer that was otherwise isogenic and tested model predictions using pea plants. Intermediate fixers were only tolerated when a better strain was not available. In agreement with model predictions, nodules containing the intermediate-fixing strain were large and healthy when the only alternative was a nonfixer, but nodules of the intermediate-fixing strain were small and white when the plant was coinoculated with a more effective strain. The reduction in nodule size was preceded by a lower carbon supply to the nodule even before differences in nodule size could be observed. Sanctioned nodules had reduced rates of nitrogen fixation, and in later developmental stages, sanctioned nodules contained fewer viable bacteria than nonsanctioned nodules. This indicates that legumes can make conditional decisions, most likely by comparing a local nodule-dependent cue of nitrogen output with a global cue, giving them remarkable control over their symbiotic partners.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.2025760118
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2021
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 7
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    Antiviral immune responses in gene-targeted mice expressing the immunoglobulin heavy chain of virus-neutralizing antibodies
    Proceedings of the National Academy of Sciences ; 2003
    In:  Proceedings of the National Academy of Sciences Vol. 100, No. 22 ( 2003-10-28), p. 12883-12888
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 100, No. 22 ( 2003-10-28), p. 12883-12888
    Abstract: Two gene-targeted immunoglobulin heavy chain transgenic mouse strains, TgH(KL25) and TgH(VI10), expressing neutralizing specificities for lymphocytic choriomeningitis virus and vesicular stomatitis virus, respectively, have been generated. Three days after lymphocytic choriomeningitis virus infection, TgH(KL25) mice showed a thymus-independent neutralizing IgM response followed by thymus-dependent (TD) IgG. In contrast, WT mice mounted only a TD IgG response around day 80. These observations indicated that not only structural properties of the virus but also immunological parameters such as the frequency of B cells were indicative for the induction of thymus-independent versus TD Ig responses. Naïve vesicular stomatitis virusspecific Ig heavy chain transgenic mice displayed greatly elevated natural antibody titers. However, despite these high naïve titers, de novo activation of naïve CD4 + T and B cells was not blocked. Therefore, B cells giving rise to natural antibodies do not participate in virus-induced antibody responses.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.2135542100
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2003
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
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  • 8
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    Molecular basis for the reversible ADP-ribosylation of guanosine bases
    Elsevier BV ; 2023
    In:  Molecular Cell Vol. 83, No. 13 ( 2023-07), p. 2303-2315.e6
    Details
    In: Molecular Cell, Elsevier BV, Vol. 83, No. 13 ( 2023-07), p. 2303-2315.e6
    Type of Medium: Online Resource
    ISSN: 1097-2765
    URL: Article
    DOI: 10.1016/j.molcel.2023.06.013
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2023
    detail.hit.zdb_id: 2001948-8
    SSG: 12
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  • 9
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    Nodulation and nitrogen fixation in Medicago truncatula strongly alters the abundance of its root microbiota and subtly affects its structure
    Wiley ; 2022
    In:  Environmental Microbiology Vol. 24, No. 11 ( 2022-11), p. 5524-5533
    Details
    In: Environmental Microbiology, Wiley, Vol. 24, No. 11 ( 2022-11), p. 5524-5533
    Abstract: The plant common symbiosis signalling (SYM) pathway has shared function between interactions with rhizobia and arbuscular mycorrhizal fungi, the two most important symbiotic interactions between plants and microorganisms that are crucial in plant and agricultural yields. Here, we determine the role of the plant SYM pathway in the structure and abundance of the microbiota in the model legume Medicago truncatula and whether this is controlled by the nitrogen or phosphorus status of the plant. We show that SYM mutants ( dmi3 ) differ substantially from the wild type (WT) in the absolute abundance of the root microbiota, especially under nitrogen limitation. Changes in the structure of the microbiota were less pronounced and depended on both plant genotype and nutrient status. Thus, the SYM pathway has a major impact on microbial abundance in M . truncatula and also subtly alters the composition of the microbiota.
    Type of Medium: Online Resource
    ISSN: 1462-2912 , 1462-2920
    URL: Issue
    URL: Article
    DOI: 10.1111/emi.v24.11
    DOI: 10.1111/1462-2920.16164
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2020213-1
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  • 10
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    Use of the Bruker MALDI Biotyper for Identification of Molds in the Clinical Mycology Laboratory
    American Society for Microbiology ; 2014
    In:  Journal of Clinical Microbiology Vol. 52, No. 8 ( 2014-08), p. 2797-2803
    Details
    In: Journal of Clinical Microbiology, American Society for Microbiology, Vol. 52, No. 8 ( 2014-08), p. 2797-2803
    Abstract: Matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) is increasingly used for the identification of bacteria and fungi in the diagnostic laboratory. We evaluated the mold database of Bruker Daltonik (Bremen, Germany), the Filamentous Fungi Library 1.0. First, we studied 83 phenotypically and molecularly well-characterized, nondermatophyte, nondematiaceous molds from a clinical strain collection. Using the manufacturer-recommended interpretation criteria, genus and species identification rates were 78.3% and 54.2%, respectively. Reducing the species cutoff from 2.0 to 1.7 significantly increased species identification to 71.1% without increasing misidentifications. In a subsequent prospective study, 200 consecutive clinical mold isolates were identified by the MALDI Biotyper and our conventional identification algorithm. Discrepancies were resolved by ribosomal DNA (rDNA) internal transcribed spacer region sequence analysis. For the MALDI Biotyper, genus and species identification rates were 83.5% and 79.0%, respectively, when using a species cutoff of 1.7. Not identified were 16.5% of the isolates. Concordant genus and species assignments of MALDI-TOF MS and the conventional identification algorithm were observed for 98.2% and 64.2% of the isolates, respectively. Four erroneous species assignments were observed using the MALDI Biotyper. The MALDI Biotyper seems highly reliable for the identification of molds when using the Filamentous Fungi Library 1.0 and a species cutoff of 1.7. However, expansion of the database is required to reduce the number of nonidentified isolates.
    Type of Medium: Online Resource
    ISSN: 0095-1137 , 1098-660X
    URL: Article
    DOI: 10.1128/JCM.00049-14
    RVK:
    XA 10000
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 2014
    detail.hit.zdb_id: 1498353-9
    SSG: 12
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