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5 Publications visible to you, out of a total of 5
Frankobactin Metallophores Produced by Nitrogen-Fixing Frankia Actinobacteria Function in Toxic Metal Sequestration.

Abstract (Expand)

A series of new metallophores, referred to as frankobactins, were extracted from cultures of the symbiotic and nitrogen-fixing actinobacterium Frankia sp. CH37. Structure elucidation revealed a … 2-hydroxyphenyl-substituted oxazoline core and a chain composed of five proteinogenic and nonproteinogenic amino acids, suggesting nonribosomal peptide synthesis as the biosynthetic origin. By whole-genome sequencing, bioinformatic analysis, and comparison with other Frankia strains, the genetic locus responsible for the biosynthesis was detected. Spectrophotometric titration of frankobactin with Fe(III) and Cu(II) and mass spectrometry established the 1:1 (metal:frankobactin) coordination. Uptake experiments suggested that frankobactin A1 (1) did not serve to recruit iron, but to detoxify Cu(II). As frankobactin A1 prevents the cellular entry of Cu(II), it could play a crucial role in the symbiosis of Frankia sp. and its host in the reclamation of copper-contaminated soil.

Authors: J. F. Mohr, F. Baldeweg, M. Deicke, C. F. Morales-Reyes, D. Hoffmeister, T. Wichard

Date Published: 23rd Apr 2021

Publication Type: Journal

Macroalgal-bacterial interactions: identification and role of thallusin in morphogenesis of the seaweed Ulva (Chlorophyta).

Abstract (Expand)

Macroalgal microbiomes have core functions related to biofilm formation, growth, and morphogenesis of seaweeds. In particular, the growth and development of the sea lettuce Ulva spp. (Chlorophyta) … depend on bacteria releasing morphogenetic compounds. Under axenic conditions, the macroalga Ulva mutabilis develops a callus-like phenotype with cell wall protrusions. However, co-culturing with Roseovarius sp. (MS2) and Maribacter sp. (MS6), which produce various stimulatory chemical mediators, completely recovers morphogenesis. This ecological reconstruction forms a tripartite community which can be further studied for its role in cross-kingdom interactions. Hence, our study sought to identify algal growth- and morphogenesis-promoting factors (AGMPFs) capable of phenocopying the activity of Maribacter spp. We performed bioassay-guided solid-phase extraction in water samples collected from U. mutabilis aquaculture systems. We uncovered novel ecophysiological functions of thallusin, a sesquiterpenoid morphogen, identified for the first time in algal aquaculture. Thallusin, released by Maribacter sp., induced rhizoid and cell wall formation at a concentration of 11 pmol l-1. We demonstrated that gametes acquired the iron complex of thallusin, thereby linking morphogenetic processes with intracellular iron homeostasis. Understanding macroalgae-bacteria interactions permits further elucidation of the evolution of multicellularity and cellular differentiation, and development of new applications in microbiome-mediated aquaculture systems.

Authors: T. Alsufyani, G. Califano, M. Deicke, J. Grueneberg, A. Weiss, A. H. Engelen, M. Kwantes, J. F. Mohr, J. F. Ulrich, T. Wichard

Date Published: 11th Jun 2020

Publication Type: Journal

Metallophore profiling of nitrogen-fixing Frankia spp. to understand metal management in the rhizosphere of actinorhizal plants.

Abstract (Expand)

Frankia spp. are widespread nitrogen-fixing soil bacteria, which often live in symbiosis with a broad range of hosts. Metal homeostasis plays a crucial role in the success of the symbiosis regarding … the acquisition of essential trace metals and detoxification of potentially toxic elements. We have hypothesised that Frankia releases many organic ligands with a broad spectrum of affinity for essential and toxic metals. We coined the term 'ligandosphere' to describe the entirety of excreted metal complexing agents and ligands derived from the dissolved organic matter. Using metal isotope-coded profiling (MICP); metallophores of physiological important and toxic trace metals were identified by the addition of stable metal isotope pairs such as 54Fe/58Fe, 63Cu/65Cu, 66Zn/68Zn or 95Mo/98Mo. Liquid chromatography coupled to a mass spectrometer revealed strong variations of the metallophore profile in between the 14 test-strains. In total, about 83 organic ligands were identified as binding to one of the tested metals. The predicted sum formula of the major Fe binding ligands and MS/MS experiments suggested that several metallophore candidates have a similar molecular backbone. Growth experiments with a hyper-producer of metallophores revealed a positive relationship between metallophore production and the concentration of Cu in the growth medium. The present study provides the first comprehensive overview of the complexity of Frankia's ligandosphere. It opens a path to a deeper understanding of mechanisms that regulate metal homeostasis in frankiae. Deciphering these mechanisms is important since the fitness of actinorhizal plants and their potential in ecological restoration relies heavily on their symbiosis with frankiae.

Authors: M. Deicke, J. F. Mohr, S. Roy, P. Herzsprung, J. P. Bellenger, T. Wichard

Date Published: 17th Apr 2019

Publication Type: Journal

Gramibactin is a bacterial siderophore with a diazeniumdiolate ligand system.

Abstract (Expand)

Genome mining and chemical analyses revealed that rhizosphere bacteria (Paraburkholderia graminis) produce a new type of siderophore, gramibactin, a lipodepsipeptide that efficiently binds iron with a … logbeta value of 27.6. Complexation-induced proton NMR chemical shifts show that the unusual N-nitrosohydroxylamine (diazeniumdiolate) moieties participate in metal binding. Gramibactin biosynthesis genes are conserved in numerous plant-associated bacteria associated with rice, wheat, and maize, which may utilize iron from the complex.

Authors: R. Hermenau, K. Ishida, S. Gama, B. Hoffmann, M. Pfeifer-Leeg, W. Plass, J. F. Mohr, T. Wichard, H. P. Saluz, C. Hertweck

Date Published: 1st Aug 2018

Publication Type: Journal

DeltaMS: a tool to track isotopologues in GC- and LC-MS data

Abstract (Expand)

Introduction: Stable isotopic labeling experiments are powerful tools to study metabolic pathways, to follow tracers and fluxes in biotic and abiotic transformations and to elucidate molecules involved …d in metal complexing. Objective: To introduce a software tool for the identification of isotopologues from mass spectrometry data. Methods: DeltaMS relies on XCMS peak detection and X13CMS isotopologue grouping and then analyses data for specific isotope ratios and the relative error of these ratios. It provides pipelines for recognition of isotope patterns in three experiment types commonly used in isotopic labeling studies: (1) Search for isotope signatures with a specific mass shift and intensity ratio in one sample set. (2) Analyze two sample sets for a specific mass shift and, optionally, the isotope ratio, whereby one sample set is isotope-labeled, and one is not. (3) Analyze isotope-guided perturbation experiments with a setup described in X13CMS. Results: To illustrate the versatility of DeltaMS, we analyze data sets from case-studies that commonly pose challenges in evaluation of natural isotopes or isotopic signatures in labeling experiment. In these examples, the untargeted detection of sulfur, bromine and artificial metal isotopic patterns is enabled by the automated search for specific isotopes or isotope signatures. Conclusion: DeltaMS provides a platform for the identification of (pre-defined) isotopologues in MS data from single samples or comparative metabolomics data sets.

Authors: Tim U. H. Baumeister, Nico Ueberschaar, Wolfgang Schmidt-Heck, J. Frieder Mohr, Michael Deicke, Thomas Wichard, Reinhard Guthke, Georg Pohnert

Date Published: 27th Feb 2018

Publication Type: Not specified

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