Publications by authors named "Marine Vallet"

12 Publications

  • Page 1 of 1

Laminariales Host Does Impact Lipid Temperature Trajectories of the Fungal Endophyte (Sutherland.).

Mar Drugs 2020 Jul 22;18(8). Epub 2020 Jul 22.

Laboratoire de Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Muséum National d'Histoire Naturelle, IRD, SU, CNRS, UA, UCN, Station Marine de Concarneau, FR-29900 Concarneau, France.

Kelps are colonized by a wide range of microbial symbionts. Among them, endophytic fungi remain poorly studied, but recent studies evidenced yet their high diversity and their central role in algal defense against various pathogens. Thus, studying the metabolic expressions of kelp endophytes under different conditions is important to have a better understanding of their impacts on host performance. In this context, fatty acid composition is essential to a given algae fitness and of interest to food web studies either to measure its nutritional quality or to infer about its contribution to consumers diets. In the present study, , a fungal endophyte was isolated from (L.) and (Hudson.) and its fatty acid composition was assessed at increasing salinity and temperature conditions. Results showed that fungal composition in terms of fatty acids displayed algal-dependent trajectories in response to temperature increase. This highlights that C18 unsaturated fatty acids are key components in the host-dependant acclimation of to salinity and temperature changes.
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http://dx.doi.org/10.3390/md18080379DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7460085PMC
July 2020

Secondary Metabolites from the Culture of the Marine-derived Fungus PC 362H and Evaluation of the Anticancer Activity of Its Metabolite Hyalodendrin.

Mar Drugs 2020 Apr 3;18(4). Epub 2020 Apr 3.

Sorbonne Université, INSERM U938, Centre de Recherche Saint-Antoine, F-75012 Paris, France.

High-throughput screening assays have been designed to identify compounds capable of inhibiting phenotypes involved in cancer aggressiveness. However, most studies used commercially available chemical libraries. This prompted us to explore natural products isolated from marine-derived fungi as a new source of molecules. In this study, we established a chemical library from 99 strains corresponding to 45 molecular operational taxonomic units and evaluated their anticancer activity against the MCF7 epithelial cancer cell line and its invasive stem cell-like MCF7-Sh-WISP2 counterpart. We identified the marine fungal PC 362H strain, isolated from the brown alga (PC), as one of the most promising fungi which produce active compounds. Further chemical and biological characterizations of the culture of the PC 362H strain identified (-)-hyalodendrin as the active secondary metabolite responsible for the cytotoxic activity of the crude extract. The antitumor activity of (-)-hyalodendrin was not only limited to the MCF7 cell lines, but also prominent on cancer cells with invasive phenotypes including colorectal cancer cells resistant to chemotherapy. Further investigations showed that treatment of MCF7-Sh-WISP2 cells with (-)-hyalodendrin induced changes in the phosphorylation status of p53 and altered expression of HSP60, HSP70 and PRAS40 proteins. Altogether, our study reveals that this uninvestigated marine fungal crude extract possesses a strong therapeutic potential against tumor cells with aggressive phenotypes and confirms that members of the epidithiodioxopiperazines are interesting fungal toxins with anticancer activities.
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http://dx.doi.org/10.3390/md18040191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7230232PMC
April 2020

Author Correction: The oomycete Lagenisma coscinodisci hijacks host alkaloid synthesis during infection of a marine diatom.

Nat Commun 2020 Mar 31;11(1):1698. Epub 2020 Mar 31.

Research Group Plankton Community Interaction, Max Planck Institute for Chemical Ecology, Jena, Germany.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41467-020-15527-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7109102PMC
March 2020

Identification to species level of live single microalgal cells from plankton samples with matrix-free laser/desorption ionization mass spectrometry.

Metabolomics 2020 02 24;16(3):28. Epub 2020 Feb 24.

Max Planck Institute for Chemical Ecology, Max Planck Fellow Group On Plankton Community Interaction, Hans-Knöll-Str. 8, 07745, Jena, Germany.

Introduction: Marine planktonic communities are complex microbial consortia often dominated by microscopic algae. The taxonomic identification of individual phytoplankton cells usually relies on their morphology and demands expert knowledge. Recently, a live single-cell mass spectrometry (LSC-MS) pipeline was developed to generate metabolic profiles of microalgae.

Objective: Taxonomic identification of diverse microalgal single cells from collection strains and plankton samples based on the metabolic fingerprints analyzed with matrix-free laser desorption/ionization high-resolution mass spectrometry.

Methods: Matrix-free atmospheric pressure laser-desorption ionization mass spectrometry was performed to acquire single-cell mass spectra from collection strains and prior identified environmental isolates. The computational identification of microalgal species was performed by spectral pattern matching (SPM). Three similarity scores and a bootstrap-derived confidence score were evaluated in terms of their classification performance. The effects of high and low-mass resolutions on the classification success were evaluated.

Results: Several hundred single-cell mass spectra from nine genera and nine species of marine microalgae were obtained. SPM enabled the identification of single cells at the genus and species level with high accuracies. The receiver operating characteristic (ROC) curves indicated a good performance of the similarity measures but were outperformed by the bootstrap-derived confidence scores.

Conclusion: This is the first study to solve taxonomic identification of microalgae based on the metabolic fingerprints of the individual cell using an SPM approach.
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http://dx.doi.org/10.1007/s11306-020-1646-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7036359PMC
February 2020

Biocontrol Potential of a Novel Endophytic Bacterium From Mulberry () Tree.

Front Bioeng Biotechnol 2019 23;7:488. Epub 2020 Jan 23.

Institute of Sericulture and Apiculture, College of Animal Sciences, Zhejiang University, Hangzhou, China.

Mulberry () is an economically important woody tree that is suitable for use in sericulture as forage and in medicine. However, this broad-leaved tree is facing multiple threats ranging from phytopathogens to insect pests. Here, a Gram-positive, endospore-forming bacterium (ZJU1) was frequently isolated from healthy mulberry plants by screening for foliar endophytes showing antagonism against pathogens and pests. Whole-genome sequencing and annotation resulted in a genome size of 4.06 Mb and classified the bacterium as a novel strain of that has rarely been identified from tree leaves. An integrative approach combining traditional natural product chemistry, activity bioassays, and high-resolution mass spectrometry confirmed that strain ZJU1 uses a blend of antimicrobials including peptides and volatile organic compounds to oppose , a major phytopathogenic fungus causing mulberry gray mold disease. We showed that the inoculation of endophyte-free plants with ZJU1 significantly decreased both leaf necrosis and mortality under field conditions. In addition to the direct interactions of endophytes with foliar pathogens, studies suggested that the inoculation of endophytes also induced plant systemic defense, including high expression levels of mulberry disease resistance genes. Moreover, when applied to the generalist herbivore , ZJU1 was sufficient to reduce the pest survival rate below 50%. A previously undiscovered crystal toxin (Cry10Aa) could contribute to this insecticidal effect against notorious lepidopteran pests. These unique traits clearly demonstrate that ZJU1 is promising for the development of successful strategies for biocontrol applications. The search for new plant-beneficial microbes and engineering microbiomes is therefore of great significance for sustainably improving plant performance.
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http://dx.doi.org/10.3389/fbioe.2019.00488DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6990687PMC
January 2020

The oomycete Lagenisma coscinodisci hijacks host alkaloid synthesis during infection of a marine diatom.

Nat Commun 2019 10 30;10(1):4938. Epub 2019 Oct 30.

Research Group Plankton Community Interaction, Max Planck Institute for Chemical Ecology, Jena, Germany.

Flagellated oomycetes frequently infect unicellular algae, thus limiting their proliferation. Here we show that the marine oomycete Lagenisma coscinodisci rewires the metabolome of the bloom-forming diatom Coscinodiscus granii, thereby promoting infection success. The algal alkaloids β-carboline and 4-carboxy-2,3,4,9-tetrahydro-1H-β-carboline are induced during infection. Single-cell profiling with AP-MALDI-MS and confocal laser scanning microscopy reveals that algal carbolines accumulate in the reproductive form of the parasite. The compounds arrest the algal cell division, increase the infection rate and induce plasmolysis in the host. Our results indicate that the oomycete manipulates the host metabolome to support its own multiplication.
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http://dx.doi.org/10.1038/s41467-019-12908-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6821873PMC
October 2019

Bacterial-Fungal Interactions in the Kelp Endomicrobiota Drive Autoinducer-2 Quorum Sensing.

Front Microbiol 2019 31;10:1693. Epub 2019 Jul 31.

Unité Molécules de Communication et Adaptation des Microorganismes (MCAM), Muséum National d'Histoire Naturelle (MNHN), Centre National de la Recherche Scientifique (CNRS), CP 54, Paris, France.

Brown macroalgae are an essential component of temperate coastal ecosystems and a growing economic sector. They harbor diverse microbial communities that regulate algal development and health. This algal holobiont is dynamic and achieves equilibrium a complex network of microbial and host interactions. We now report that bacterial and fungal endophytes associated with four brown algae (, , , and produce metabolites that interfere with bacterial autoinducer-2 quorum sensing, a signaling system implicated in virulence and host colonization. Additionally, we performed co-culture experiments combined to a metabolomic approach and demonstrated that microbial interactions influence production of metabolites, including metabolites involved in quorum sensing. Collectively, the data highlight autoinducer-2 quorum sensing as a key metabolite in the complex network of interactions within the algal holobiont.
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http://dx.doi.org/10.3389/fmicb.2019.01693DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6685064PMC
July 2019

Live Single-Cell Metabolomics With Matrix-Free Laser/Desorption Ionization Mass Spectrometry to Address Microalgal Physiology.

Front Plant Sci 2019 18;10:172. Epub 2019 Feb 18.

Max Planck Fellow Group on Plankton Community Interaction, Max Planck Institute for Chemical Ecology, Jena, Germany.

Unicellular phototrophic algae can form massive blooms with up to millions of individual cells per milliliter in freshwater and marine ecosystems. Despite the temporal dominance of bloom formers many algal species can co-exist and compete for nutrients and space, creating a complex and diverse community. While microscopy and single cell genomics can address the taxonomic inventory, the cellular metabolome has yet to be thoroughly explored to determine the physiological status of microalgae. This might, however, provide a key to understand the observed species diversity in the homogeneous environment. Here, we introduce an effective, rapid and versatile method to analyze living single cells from aqueous substrata with laser-desorption/ionization mass spectrometry (LDI-MS) using a simple and inexpensive matrix-free support. The cells deposited on a cultivation-medium wetted support are analyzed with minimal disturbance as they remain in their natural viable state until their disruption during LDI-MS. Metabolites desorbed from single cells are analyzed on High-Resolution Mass Spectrometry (HR-MS) using the Orbitrap FT-MS technology to fingerprint cellular chemistry. This live single-cell mass spectrometry (LSC-MS) allows assessing the physiological status and strain-specifics of different microalgae, including marine diatoms and freshwater chlorophytes, at the single-cell level. We further report a reliable and robust data treatment pipeline to perform multivariate statistics on the replicated LSC-MS data. Comparing single cell MS spectra from natural phytoplankton samples and from laboratory strains allows the identification and discrimination of inter and intra-specific metabolic variability and thereby has promising applications in addressing highly complex phytoplankton communities. Notably, the herein described matrix-free live-single-cell LDI-HR-MS approach enables monitoring dynamics of the plankton and might explain why key-players survive, thrive, avoid selective feeding or pathogenic virus and bacteria, while others are overcome and die.
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http://dx.doi.org/10.3389/fpls.2019.00172DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6387974PMC
February 2019

Chemically-Mediated Interactions Between Macroalgae, Their Fungal Endophytes, and Protistan Pathogens.

Front Microbiol 2018 21;9:3161. Epub 2018 Dec 21.

Muséum National d'Histoire Naturelle, Unité Molécules de Communication et Adaptation des Micro-organismes, UMR 7245, CP 54, Paris, France.

Filamentous fungi asymptomatically colonize the inner tissues of macroalgae, yet their ecological roles remain largely underexplored. Here, we tested if metabolites produced by fungal endophytes might protect their host against a phylogenetically broad spectrum of protistan pathogens. Accordingly, the cultivable fungal endophytes of four brown algal species were isolated and identified based on LSU and SSU sequencing. The fungal metabolomes were tested for their ability to reduce the infection by protistan pathogens in the algal model . The most active metabolomes effective against the oomycetes and , and the phytomixid were further characterized chemically. Several pyrenocines isolated from sp. AN596H efficiently inhibited the infection by all abovementioned pathogens. Strikingly, these compounds also inhibited the infection of () against its two most devastating oomycete pathogens, , and . We thus demonstrate that fungal endophytes associated with brown algae produce bioactive metabolites which might confer protection against pathogen infection. These results highlight the potential of metabolites to finely-tune the outcome of molecular interactions between algae, their endophytes, and protistan pathogens. This also provide proof-of-concept toward the applicability of such metabolites in marine aquaculture to control otherwise untreatable diseases.
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http://dx.doi.org/10.3389/fmicb.2018.03161DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6309705PMC
December 2018

An Integrative Approach to Decipher the Chemical Antagonism between the Competing Endophytes Paraconiothyrium variabile and Bacillus subtilis.

J Nat Prod 2017 11 15;80(11):2863-2873. Epub 2017 Nov 15.

Unité Molécules de Communication et Adaptation des Micro-organismes (UMR 7245), Sorbonne Université, Muséum National d'Histoire Naturelle, CNRS , CP 54, 57 rue Cuvier, 75005 Paris, France.

An integrative approach combining traditional natural products chemistry, molecular networking, and mass spectrometry imaging has been undertaken to decipher the molecular dialogue between the fungus Paraconiothyrium variabile and the bacterium Bacillus subtilis, which were isolated as endophytes from the conifer Cephalotaxus harringtonia and are characterized by a strong and mutual antibiosis. From this study, we highlight that bacterial surfactins and a fungal tetronic acid are involved in such competition and that the fungus is able to hydrolyze surfactins to fight against the bacterial partner.
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http://dx.doi.org/10.1021/acs.jnatprod.6b01185DOI Listing
November 2017

A Reactive Eremophilane and Its Antibacterial 2(1H)-Naphthalenone Rearrangement Product, Witnesses of a Microbial Chemical Warfare.

Org Lett 2017 08 24;19(15):4038-4041. Epub 2017 Jul 24.

Muséum National d'Histoire Naturelle , CNRS (UMR 7245 MCAM), Sorbonne Universités, 57 rue Cuvier (CP 54), 75005 Paris, France.

Two sesquiterpenes, 4-epi-microsphaeropsisin (1) and a dihydrofurano-2(1H)-naphthalenone (variabilone, 2) which represents a new skeleton, were isolated from endophytic fungus Paraconiothyrium variabile. Reactivity studies showed that eremophilane 1 is a precursor of 2 through acid-promoted methyl 1,2-migration and aromatization. An electrophilic intermediate of this transformation was intercepted by N-acetylcysteamine, a biomimetic nucleophile. Only compound 2 was antibacterial against endophytic bacterium Bacillus subtilis (coisolated with P. variabile), suggesting a role in the microbial competition in plants.
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http://dx.doi.org/10.1021/acs.orglett.7b01788DOI Listing
August 2017

Molecular Analysis of the embCAB Locus and embR Gene Involved in Ethambutol Resistance in Clinical Isolates of Mycobacterium tuberculosis in France.

Antimicrob Agents Chemother 2015 Aug 1;59(8):4800-8. Epub 2015 Jun 1.

AP-HP, Hôpital Pitié-Salpêtrière, Centre National de Référence des Mycobactéries et de la Résistance des Mycobactéries aux Antituberculeux, Paris, France Sorbonne Universités, UPMC Université Paris 06, UMRS1135, Centre d'Immunologie et des Maladies Infectieuses, CIMI-Paris, Team 13 (Bacteriology), Paris, France INSERM, U1135, Centre d'Immunologie et des Maladies Infectieuses, CIMI-Paris, Team 13 (Bacteriology), Paris, France.

Modification of codon 306 in embB is regarded as the main mechanism leading to ethambutol (ETB) resistance in clinical isolates of Mycobacterium tuberculosis. However, numerous mutations elsewhere in the embCAB locus and in embR, a putative transcriptional activator of this locus, have been reported to be involved in ETB resistance. Here, we investigated the diversity of nucleotide variations observed in embCAB and embR in M. tuberculosis complex isolates from France. These regions were sequenced in 71 ETB-resistant (ETB-R) and 60 ETB-susceptible (ETB-S) clinical isolates of known phylogenetic lineages. The 131 isolates had 12 mutations corresponding to phylogenetic markers. Among the 60 ETB-S isolates, only 3 (5%) had nonsynonymous mutations that were not phylogenetic markers. Among the 71 ETB-R isolates, 98% had mutations in embCAB that likely contribute to ETB resistance: 70% had mutations located in embB codon 306, 406, or 497; 13% had mutations located outside these three positions between codons 296 and 426; and 15% had mutations corresponding to mutations in the embC-embA intergenic region. We found a strong association between resistance to ETB and the presence of mutations in embB and the embC-embA intergenic region (P < 0.001). In contrast, the mutations detected in embC and embA were not involved in ETB resistance, and no mutation was detected in embR. These results strongly suggest that the sensitivity of diagnostic assays for detecting ETB resistance based on testing of embB codon 306 can be increased by testing of the embB region between codons 296 and 497 and by including the embC-embA intergenic region between positions -8 and -21.
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http://dx.doi.org/10.1128/AAC.00150-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4505224PMC
August 2015