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153 Publications visible to you, out of a total of 153
A Chemical Perspective on Microalgal-Microbial Interactions

Abstract (Expand)

The exchange of chemical compounds is central to the interactions of microalgae with other microorganisms. Although foundational for many food webs, these interactions have been poorly studied compared … with higher plant-microbe interactions. Emerging insights have begun to reveal how these interactions and the participating chemical compounds shape microbial communities and broadly impact biogeochemical processes.

Authors: E. F. Hom, , , ,

Date Published: 28th Oct 2015

Publication Type: Not specified

A fast and direct liquid chromatography-mass spectrometry method to detect and quantify polyunsaturated aldehydes and polar oxylipins in diatoms

Abstract (Expand)

Polyunsaturated aldehydes (PUAs) are a group of microalgal metabolites that have attracted a lot of attention due to their biological activity. Determination of PUAs has become an important routine … procedure in plankton and biofilm investigations, especially those that deal with chemically mediated interactions. Here we introduce a fast and direct derivatization free method that allows quantifying PUAs in the nanomolar range, sufficient to undertake the analysis from cultures and field samples. The sample preparation requires one simple filtration step and the initiation of PUA formation by cell disruption. After centrifugation the samples are ready for measurement without any further handling. Within one chromatographic run this method additionally allows us to monitor the formation of the polar oxylipins arising from the cleavage of precursor fatty acids. The robust method is based on analyte separation and detection using ultra high performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (UHPLC-APCI MS) and enables high throughput investigations by employing an analysis time of only 5 min. Our protocol thus provides an alternative and extension to existing PUA determinations based on gas chromatography-mass spectrometry (GC-MS) with shorter run times and without any chemical derivatization. It also enables researchers with widely available LC-MS analytical platforms to monitor PUAs. Additionally, non-volatile oxylipins such as ω-oxo-acids and related compounds can be elucidated and monitored.

Authors: Constanze Kuhlisch, Michael Deicke, Nico Ueberschaar, Thomas Wichard, Georg Pohnert

Date Published: 15th Oct 2016

Publication Type: Not specified

A fivefold parallelized biosynthetic process secures chlorination of Armillaria mellea (honey mushroom) toxins

Abstract (Expand)

The basidiomycetous tree pathogen Armillaria mellea (honey mushroom) produces a large variety of structurally related antibiotically active and phytotoxic natural products, referred to as the melleolides. … During their biosynthesis, some members of the melleolide family of compounds undergo monochlorination of the aromatic moiety, whose biochemical and genetic basis was not known previously. This first study on basidiomycete halogenases presents the biochemical in vitro characterization of five flavin-dependent A. mellea enzymes (ArmH1-ArmH5) that were heterologously produced in Escherichia coli. We demonstrate that all five enzymes transfer a single chlorine atom to the melleolide backbone. A fivefold secured biosynthetic step during natural product assembly is unprecedented. Typically, flavin-dependent halogenases are categorized into enzymes acting on free compounds as opposed to those requiring a carrier protein-bound acceptor substrate. The enzymes characterized in this study clearly turned over free substrates. Phylogenetic clades of halogenases suggest that all fungal enzymes share a common ancestor and reflect a clear divergence between ascomycetes and basidiomycetes.

Authors: J. Wick, D. Heine, G. Lackner, M. Misiek, , H. Jagusch, ,

Date Published: 15th Dec 2015

Publication Type: Not specified

A giant type I polyketide synthase participates in zygospore maturation in Chlamydomonas reinhardtii.

Abstract (Expand)

Polyketide synthases (PKSs) occur in many bacteria, fungi and plants. They are highly versatile enzymes involved in the biosynthesis of a large variety of compounds including antimicrobial agents, … polymers associated with bacterial cell walls and plant pigments. While harmful algae are known to produce polyketide toxins, sequences of the genomes of non-toxic algae, including those of many green-algal species, have surprisingly revealed the presence of genes encoding type I PKSs. The genome of the model alga Chlamydomonas reinhardtii (Chlorophyta) contains a single type I PKS gene, designated PKS1 (Cre10.g449750), which encodes a giant PKS with a predicted mass of 2.3 MDa. Here, we show that PKS1 is induced in two-day old zygotes and is required for their development into zygospores, the dormant stage of the zygote. Wild-type zygospores contain knob-like structures (~50 nm diameter) that form at the cell surface and develop a central cell wall layer; both of these structures are absent from homozygous pks1 mutants. Additionally, in contrast to wild-type zygotes, chlorophyll degradation is delayed in homozygous pks1 mutant zygotes, indicating a disruption of zygospore development. In agreement with a role of the PKS in the formation of the highly resistant zygospore wall, mutant zygotes have lost the formidable desiccation tolerance of wild-type zygotes. Together, our results represent functional analyses of a PKS mutant in a photosynthetic eukaryotic microorganism, revealing a central function for polyketides in the sexual cycle and survival under stressful environmental conditions. This article is protected by copyright. All rights reserved.

Authors: N. Heimerl, E. Hommel, M. Westermann, D. Meichsner, M. Lohr, C. Hertweck, A. R. Grossman, M. Mittag, S. Sasso

Date Published: No date defined

Publication Type: Not specified

A poly(A) ribonuclease controls the cellotriose-based interaction between Piriformospora indica and its host Arabidopsis.

Abstract (Expand)

Piriformospora indica, an endophytic root-colonizing fungus, efficiently promotes plant growth and induces resistance to abiotic stress and biotic diseases. The fungal cell wall extract induces cytoplasmic … calcium [Ca2+]cyt elevation in host plant roots. Here, we show that an elici-tor-active cell wall moiety, released by P. indica into the medium, is cellotriose (CT). CT in-duces a mild defense-like response including the production of reactive oxygen species, changes in membrane potentials and the expression of genes involved in growth regulation and root development. CT based [Ca2+]cyt elevation in Arabidopsis roots does not require BAK1 coreceptor, or the putative Ca2+ channels TPC1, GLR3.3, -2.4 and -2.5 and operates synergistically with the elicitor chitin. We identified an ethylmethane-sulfonate-induced mu-tant ([Ca2+]cyt elevation mutant, cycam) impaired in response to CT, cellooligomers (n = 2, 4-7), but not to chitooligomers (n = 4-8) in roots. The mutant contains a single nucleotide ex-change in the gene encoding for a poly(A) ribonuclease (AtPARN, At1g55870) which de-grades poly(A) tails of specific mRNAs. The wild-type PARN cDNA, expressed under the control of a 35S promoter, complements the mutant phenotype. Our finding of cellotriose as a novel chemical mediator might help to understand the complex P. indica-plant mutual rela-tionship in beneficial symbiosis.

Authors: J. M. Johnson, J. Thurich, E. K. Petutschnig, L. Altschmied, D. Meichsner, I. Sherameti, J. Dindas, A. Mrozinska, C. Paetz, S. S. Scholz, A. C. Furch, V. Lipka, R. Hedrich, B. Schneider, A. Svatos, R. Oelmuller

Date Published: No date defined

Publication Type: Not specified

A succinct access to omega-hydroxylated jasmonates via olefin metathesis.

Abstract (Expand)

In higher plants, jasmonates are lipid-derived signaling molecules that control many physiological processes, including responses to abiotic stress, defenses against insects and pathogens, and development. … Among jasmonates, omega-oxidized compounds form an important subfamily. The biological roles of these omega-modified derivatives are not fully understood, largely due to their limited availability. Herein, a brief (two-step), simple and efficient (>80% yield), versatile, gram-scalable, and environmentally friendly synthetic route to omega-oxidized jasmonates is described. The approach utilizes olefin cross-metathesis as the key step employing inexpensive, commercially available substrates and catalysts.

Authors: G. H. Jimenez-Aleman, S. Secinti, W. Boland

Date Published: 1st Jul 2017

Publication Type: Not specified

Algae induce siderophore biosynthesis in the freshwater bacterium Cupriavidus necator H16.

Abstract (Expand)

Cupriachelin is a photoreactive lipopeptide siderophore produced by the freshwater bacterium Cupriavidus necator H16. In the presence of sunlight, the iron-loaded siderophore undergoes photolytic … cleavage, thereby releasing solubilized iron into the environment. This iron is not only available to the siderophore producer, but also to the surrounding microbial community. In this study, the cupriachelin-based interaction between C. necator H16 and the freshwater diatom Navicula pelliculosa was investigated. A reporter strain of the bacterium was constructed to study differential expression levels of the cupriachelin biosynthesis gene cucJ in response to varying environmental conditions. Not only iron starvation, but also culture supernatants of N. pelliculosa were found to induce cupriachelin biosynthesis. The transcription factors involved in this differential gene expression were identified using DNA-protein pulldown assays. Besides the well-characterized ferric uptake regulator, a two-component system was found to tune the expression of cupriachelin biosynthesis genes in the presence of diatom supernatants.

Authors: C. Kurth, I. Wasmuth, T. Wichard, G. Pohnert, M. Nett

Date Published: 27th Nov 2018

Publication Type: Journal

Algal Oxylipins Mediate the Resistance of Diatoms against Algicidal Bacteria.

Abstract (Expand)

Algicidal bacteria can lyse microalgal blooms and trigger shifts within plankton communities. Resistant algal species can escape lysis, and have the opportunity to dominate the phytoplankton after a … bacterial infection. Despite their important function in ecosystem regulation, little is known about mechanisms of resistance. Here, we show that the diatom Chaetoceros didymus releases eicosanoid oxylipins into the medium, and that the lytic algicidal bacterium, Kordia algicida, induces the production of several wound-activated oxylipins in this resistant diatom. Neither releases nor an induction occurs in the susceptible diatom Skeletonema costatum that is lysed by the bacterium within a few days. Among the upregulated oxylipins, hydroxylated eicosapentaenoic acids (HEPEs) dominate. However, also, resolvins, known lipid mediators in mammals, increase upon exposure of the algae to the algicidal bacteria. The prevailing hydroxylated fatty acid, 15-HEPE, significantly inhibits growth of K. algicida at a concentration of approximately 1 microM. The oxylipin production may represent an independent line of defense of the resistant alga, acting in addition to the previously reported upregulation of proteases.

Authors: N. Meyer, J. Rettner, M. Werner, O. Werz, G. Pohnert

Date Published: No date defined

Publication Type: Not specified

An antifungal polyketide associated with horizontally acquired genes supports symbiont-mediated defense in Lagria villosa beetles.

Abstract (Expand)

Microbial symbionts are often a source of chemical novelty and can contribute to host defense against antagonists. However, the ecological relevance of chemical mediators remains unclear for most … systems. Lagria beetles live in symbiosis with multiple strains of Burkholderia bacteria that protect their offspring against pathogens. Here, we describe the antifungal polyketide lagriamide, and provide evidence supporting that it is produced by an uncultured symbiont, Burkholderia gladioli Lv-StB, which is dominant in field-collected Lagria villosa. Interestingly, lagriamide is structurally similar to bistramides, defensive compounds found in marine tunicates. We identify a gene cluster that is probably involved in lagriamide biosynthesis, provide evidence for horizontal acquisition of these genes, and show that the naturally occurring symbiont strains on the egg are protective in the soil environment. Our findings highlight the potential of microbial symbionts and horizontal gene transfer as influential sources of ecological innovation.

Authors: L. V. Florez, K. Scherlach, I. J. Miller, A. Rodrigues, J. C. Kwan, C. Hertweck, M. Kaltenpoth

Date Published: 26th Jun 2018

Publication Type: Journal

An Efficient Method To Generate Gene Deletion Mutants of the Rapamycin-Producing Bacterium Streptomyces iranensis HM 35

Abstract (Expand)

Streptomyces iranensis HM 35 is an alternative rapamycin producer to Streptomyces rapamycinicus Targeted genetic modification of rapamycin-producing actinomycetes is a powerful tool for the directed … production of rapamycin derivatives, and it has also revealed some key features of the molecular biology of rapamycin formation in S. rapamycinicus. The approach depends upon efficient conjugational plasmid transfer from Escherichia coli to Streptomyces, and the failure of this step has frustrated its application to Streptomyces iranensis HM 35. Here, by systematically optimizing the process of conjugational plasmid transfer, including screening of various media, and by defining optimal temperatures and concentrations of antibiotics and Ca(2+) ions in the conjugation media, we have achieved exconjugant formation for each of a series of gene deletions in S. iranensis HM 35. Among them were rapK, which generates the starter unit for rapamycin biosynthesis, and hutF, encoding a histidine catabolizing enzyme. The protocol that we have developed may allow efficient generation of targeted gene knockout mutants of Streptomyces species that are genetically difficult to manipulate. IMPORTANCE: The developed protocol of conjugational plasmid transfer from Escherichia coli to Streptomyces iranensis may allow efficient generation of targeted gene knockout mutants of other genetically difficult to manipulate, but valuable, Streptomyces species.

Authors: , , M. A. Gregory, M. Flak, M. K. Krespach, P. F. Leadlay,

Date Published: 15th Jun 2016

Publication Type: Not specified

An Iterative O-Methyltransferase Catalyzes 1,11-Dimethylation of Aspergillus fumigatus Fumaric Acid Amides.

Abstract (Expand)

S-adenosyl-l-methionine (SAM)-dependent methyltransfer is a common biosynthetic strategy to modify natural products. We investigated the previously uncharacterized Aspergillus fumigatus methyltransferase … FtpM, which is encoded next to the bimodular fumaric acid amide synthetase FtpA. Structure elucidation of two new A. fumigatus natural products, the 1,11-dimethyl esters of fumaryl-l-tyrosine and fumaryl-l-phenylalanine, together with ftpM gene disruption suggested that FtpM catalyzes iterative methylation. Final evidence that a single enzyme repeatedly acts on fumaric acid amides came from an in vitro biochemical investigation with recombinantly produced FtpM. Size-exclusion chromatography indicated that this methyltransferase is active as a dimer. As ftpA and ftpM homologues are found clustered in other fungi, we expect our work will help to identify and annotate natural product biosynthesis genes in various species.

Authors: D. Kalb, T. Heinekamp, S. Schieferdecker, M. Nett, A. A. Brakhage, D. Hoffmeister

Date Published: 22nd Jul 2016

Publication Type: Not specified

Analysis of basidiomycete pigments in situ by Raman spectroscopy.

Abstract (Expand)

Basidiomycetes, that is, mushroom-type fungi, are known to produce pigments in response to environmental impacts. As antioxidants with a high level of unsaturation, these compounds can neutralize highly … oxidative species. In the event of close contact with other microbes, the enzymatically controlled pigment production is triggered and pigment secretion is generated at the interaction zone. The identification and analysis of these pigments is important to understand the defense mechanism of fungi, which is essential to counteract an uncontrolled spread of harmful species. Usually, a detailed analysis of the pigments is time consuming as it depends on laborious sample preparation and isolation procedures. Furthermore, the applied protocols often influence the chemical integrity of the compound of interest. A possibility to noninvasively investigate the pigmentation is Raman microspectroscopy. The methodology has the potential to analyze the chemical composition of the sample spatially resolved at the interaction zone. After the acquisition of a representative spectroscopic library, the pigment production by basidiomycetes was monitored for during response to different fungi and bacteria. The presented results describe a very efficient noninvasive way of pigment analysis which can be applied with minimal sample preparation.

Authors: J. P. Tauber, C. Matthaus, C. Lenz, D. Hoffmeister, J. Popp

Date Published: 8th Feb 2018

Publication Type: Journal

Androgen-mediated sex bias impairs efficiency of leukotriene biosynthesis inhibitors in males.

Abstract (Expand)

Proinflammatory leukotrienes (LTs) are produced by 5-lipoxygenase (5-LO) aided by 5-LO-activating protein (FLAP). LT biosynthesis inhibitors are currently under clinical investigation as treatments for … respiratory and cardiovascular diseases. Here, we have revealed a sex bias in the efficiency of clinically relevant LT biosynthesis inhibitors, showing that their effects are superior in females. We found that androgens cause these sex differences by impeding the LT-biosynthetic 5-LO/FLAP complex assembly. Lower doses of the FLAP inhibitor MK886 were required to reduce LTB4 levels in exudates of female versus male mice and rats. Following platelet-activating factor-induced shock, MK886 increased survival exclusively in female mice, and this effect was abolished by testosterone administration. FLAP inhibitors and the novel-type 5-LO inhibitors licofelone and sulindac sulfide exhibited higher potencies in human blood from females, and bioactive 5-LO/FLAP complexes were formed in female, but not male, human and murine leukocytes. Supplementation of female blood or leukocytes with 5alpha-dihydrotestosterone abolished the observed sex differences. Our data suggest that females may benefit from anti-LT therapy to a greater extent than males, prompting consideration of sex issues in LT modifier development.

Authors: S. Pace, C. Pergola, F. Dehm, A. Rossi, J. Gerstmeier, F. Troisi, H. Pein, A. M. Schaible, C. Weinigel, S. Rummler, H. Northoff, S. Laufer, T. J. Maier, O. Radmark, B. Samuelsson, A. Koeberle, L. Sautebin, O. Werz

Date Published: 25th Jul 2017

Publication Type: Not specified

Antibiotic-producing symbionts dynamically transition between plant pathogenicity and insect-defensive mutualism

Abstract (Expand)

Pathogenic and mutualistic bacteria associated with eukaryotic hosts often lack distinctive genomic features, suggesting regular transitions between these lifestyles. Here we present evidence supporting … a dynamic transition from plant pathogenicity to insect-defensive mutualism in symbiotic Burkholderia gladioli bacteria. In a group of herbivorous beetles, these symbionts protect the vulnerable egg stage against detrimental microbes. The production of a blend of antibiotics by B. gladioli, including toxoflavin, caryoynencin and two new antimicrobial compounds, the macrolide lagriene and the isothiocyanate sinapigladioside, likely mediate this defensive role. In addition to vertical transmission, these insect symbionts can be exchanged via the host plant and retain the ability to initiate systemic plant infection at the expense of the plant's fitness. Our findings provide a paradigm for the transition between pathogenic and mutualistic lifestyles and shed light on the evolution and chemical ecology of this defensive mutualism.

Authors: L. V. Florez, K. Scherlach, P. Gaube, C. Ross, E. Sitte, C. Hermes, A. Rodrigues, C. Hertweck, M. Kaltenpoth

Date Published: 30th Apr 2017

Publication Type: Not specified

Antifungal potential of secondary metabolites involved in the interaction between citrus pathogens.

Abstract (Expand)

Numerous postharvest diseases have been reported that cause substantial losses of citrus fruits worldwide. Penicillium digitatum is responsible for up to 90% of production losses, and represent a problem … for worldwide economy. In order to control phytopathogens, chemical fungicides have been extensively used. Yet, the use of some artificial fungicides cause concerns about environmental risks and fungal resistance. Therefore, studies focusing on new approaches, such as the use of natural products, are getting attention. Co-culture strategy can be applied to discover new bioactive compounds and to understand microbial ecology. Mass Spectrometry Imaging (MSI) was used to screen for potential antifungal metabolites involved in the interaction between Penicillium digitatum and Penicillium citrinum. MSI revealed a chemical warfare between the fungi: two tetrapeptides, deoxycitrinadin A, citrinadin A, chrysogenamide A and tryptoquialanines are produced in the fungi confrontation zone. Antimicrobial assays confirmed the antifungal activity of the investigated metabolites. Also, tryptoquialanines inhibited sporulation of P. citrinum. The fungal metabolites reported here were never described as antimicrobials until this date, demonstrating that co-cultures involving phytopathogens that compete for the same host is a positive strategy to discover new antifungal agents. However, the use of these natural products on the environment, as a safer strategy, needs further investigation. This paper aimed to contribute to the protection of agriculture, considering health and ecological risks.

Authors: J. H. Costa, C. I. Wassano, C. F. F. Angolini, K. Scherlach, C. Hertweck, T. Pacheco Fill

Date Published: 9th Dec 2019

Publication Type: Journal

Antimicrobial discovery inspired by ecological interactions

Abstract

Not specified

Author: C. Hertweck

Date Published: No date defined

Publication Type: Not specified

antiSMASH 4.0-improvements in chemistry prediction and gene cluster boundary identification.

Abstract (Expand)

Many antibiotics, chemotherapeutics, crop protection agents and food preservatives originate from molecules produced by bacteria, fungi or plants. In recent years, genome mining methodologies have been … widely adopted to identify and characterize the biosynthetic gene clusters encoding the production of such compounds. Since 2011, the 'antibiotics and secondary metabolite analysis shell-antiSMASH' has assisted researchers in efficiently performing this, both as a web server and a standalone tool. Here, we present the thoroughly updated antiSMASH version 4, which adds several novel features, including prediction of gene cluster boundaries using the ClusterFinder method or the newly integrated CASSIS algorithm, improved substrate specificity prediction for non-ribosomal peptide synthetase adenylation domains based on the new SANDPUMA algorithm, improved predictions for terpene and ribosomally synthesized and post-translationally modified peptides cluster products, reporting of sequence similarity to proteins encoded in experimentally characterized gene clusters on a per-protein basis and a domain-level alignment tool for comparative analysis of trans-AT polyketide synthase assembly line architectures. Additionally, several usability features have been updated and improved. Together, these improvements make antiSMASH up-to-date with the latest developments in natural product research and will further facilitate computational genome mining for the discovery of novel bioactive molecules.

Authors: K. Blin, T. Wolf, M. G. Chevrette, X. Lu, C. J. Schwalen, S. A. Kautsar, H. G. Suarez Duran, E. L. C. de Los Santos, H. U. Kim, M. Nave, J. S. Dickschat, D. A. Mitchell, E. Shelest, R. Breitling, E. Takano, S. Y. Lee, T. Weber, M. H. Medema

Date Published: 2nd May 2017

Publication Type: Not specified

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