Thomas Wichard

Friedrich Schiller University Jena

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Georg Pohnert

Friedrich Schiller University Jena

Jean‐Philippe Bellenger

Université de Sherbrooke

Fatemeh Ghaderiardakani

Friedrich Schiller University Jena

Gianmaria Califano

University of Lisbon

Jan Mohr

Friedrich Schiller University Jena

Kirsten Küsel

German Centre for Integrative Biodiversity Research

Anne M. L. Kraepiel

Princeton University

Olivier De Clerck

Ghent University

Michael Deicke

Friedrich Schiller University Jena

Johann F. Ulrich

Friedrich Schiller University Jena

Cooperative Institutions

Friedrich Schiller University Jena

Centre National de la Recherche Scientifique

Sorbonne Université

Station Biologique de Roscoff

Ghent University

Leibniz-Institut für Naturstoff-Forschung und Infektionsbiologie e. V. - Hans-Knöll-Institut (HKI)

Stazione Zoologica Anton Dohrn

Ghent University Hospital

Max Planck Society

Leibniz Association

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Lipid and Fatty Acid Composition of Diatoms Revisited: Rapid Wound‐Activated Change of Food Quality Parameters Influences Herbivorous Copepod Reproductive Success

ChemBioChem (2007)

Thomas Wichard Andrea Gerecht Maarten Boersma Serge A. Poulet Karen Helen Wiltshire

Lipid and fatty acid composition are considered to be key parameters that determine the nutritive quality of phytoplankton diets for zooplanktonic herbivores. The fitness, reproduction and physiology of the grazers are influenced by these factors. The trophic transfer of lipids and fatty acids from algal cells has been typically studied by using simple extraction and quantification approaches, which, as we argue here, do not reflect the actual situation in the plankton. We show that cell disruption, as it occurs during a predator's grazing on diatoms can drastically change the lipid and fatty acid content of the food. In some algae, a rapid depletion of polyunsaturated fatty acids (PUFAs) is observed within the first minutes after cell disruption. This fatty acid depletion is directly linked to the production of PUFA-derived polyunsaturated aldehydes (PUA); these are molecules that are thought to be involved in the chemical defence of the algae. PUA-releasing diatoms are even capable of transforming lipids from other sources if these are available in the vicinity of the wounded cells. Fluorescent staining reveals that the enzymes involved in lipid transformation are active in the foregut of copepods, and therefore link the depletion processes directly to food uptake. Incubation experiments with the calanoid copepod Temora longicornis showed that PUFA depletion in PUA-producing diatoms is correlated to reduced hatching success, and can be compensated for by externally added single fatty acids.

10.1002/cbic.200700053

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Citations (97)

Age and nutrient limitation enhance polyunsaturated aldehyde production in marine diatoms

Phytochemistry (2007)

François Ribalet Thomas Wichard Georg Pohnert Adrianna Ianora Antonio Miralto

Bloom

10.1016/j.phytochem.2007.05.012

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Citations (133)

Ulva: An emerging green seaweed model for systems biology

Journal of Phycology (2023)

Jonas Blomme Thomas Wichard Thomas B. Jacobs Olivier De Clerck

Abstract Green seaweeds exhibit a wide range of morphologies and occupy various ecological niches, spanning from freshwater to marine and terrestrial habitats. These organisms, which predominantly belong to the class Ulvophyceae, showcase a remarkable instance of parallel evolution toward complex multicellularity and macroscopic thalli in the Viridiplantae lineage. Within the green seaweeds, several Ulva species (“sea lettuce”) are model organisms for studying carbon assimilation, interactions with bacteria, life cycle progression, and morphogenesis. Ulva species are also notorious for their fast growth and capacity to dominate nutrient‐rich, anthropogenically disturbed coastal ecosystems during “green tide” blooms. From an economic perspective, Ulva has garnered increasing attention as a promising feedstock for the production of food, feed, and biobased products, also as a means of removing excess nutrients from the environment. We propose that Ulva is poised to further develop as a model in green seaweed research. In this perspective, we focus explicitly on Ulva mutabilis/compressa as a model species and highlight the molecular data and tools that are currently available or in development. We discuss several areas that will benefit from future research or where exciting new developments have been reported in other Ulva species.

Ulvophyceae

Green algae

10.1111/jpy.13341

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Citations (10)

Engineering bacteria-seaweed symbioses for modulating the photosynthate content of Ulva (Chlorophyta): Significant for the feedstock of bioethanol production

Algal Research (2020)

Mark Polikovsky Gianmaria Califano Nico Dunger Thomas Wichard Alexander Golberg

10.1016/j.algal.2020.101945

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Citations (31)

Supplementary data to "Changing microbial activities during low salinity acclimation in the brown alga Ectocarpus subulatus"

Zenodo (CERN European Organization for Nuclear Research) (2021)

Hetty KleinJan Gianmaria Caliafano Méziane Aïte Enora Fremy Clémence Frioux

This data set contains supplementary data related to the preprint: “Changing microbial activities during low salinity acclimation in the brown alga Ectocarpus subulatus”: https://www.biorxiv.org/content/10.1101/2021.04.13.439635v1 Metagenome.zip:
This archive contains the reconstructed genomes of the different bacterial bins. The ".gbk" file was used for the reconstruction of metabolic networks. The ".fsa" and ".gff" files were used for "read mapping". Metabolic_networks.zip:
This archive contains all bacterial networks in the "padmet" format (see Aite et al. 2018). Furthermore, there is one file containing all gene-reaction associations (for all bins). Expression_data.zip:
This file contains algal gene expression data, bacterial gene expression data (number of reads mapping to each feature in each sample), and, lastly, the summarized bacterial expression per metabolic reaction.

Brown seaweed

10.5281/zenodo.5589668

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Changing microbial activities during low salinity acclimation in the brown algaEctocarpus subulatus

bioRxiv (Cold Spring Harbor Laboratory) (2021)

Hetty KleinJan Gianmaria Caliafano Méziane Aïte Enora Fremy Clémence Frioux

Summary Ectocarpus subulatus is one of the few brown algae found in river habitats. Its ability to tolerate freshwater is due, in part, to its uncultivated microbiome. We investigated this phenomenon by modifying the microbiome of laboratory-grown E. subulatus using mild antibiotic treatments, which affected its ability to grow in low salinity. The acclimation to low salinity of fresh water-tolerant and intolerant holobionts was then compared. Salinity had a significant impact on bacterial gene expression as well as the expression of algae- and bacteria-associated viruses in all holobionts, albeit in different ways for each holobiont. On the other hand, gene expression of the algal host and metabolite profiles were affected almost exclusively in the fresh water intolerant holobiont. We found no evidence of bacterial protein production that would directly improve algal stress tolerance. However, we identified vitamin K synthesis as one possible bacterial service missing specifically in the fresh water-intolerant holobiont in low salinity. We also noticed an increase in bacterial transcriptomic activity and the induction of microbial genes involved in the biosynthesis of the autoinducer AI-1, a compound that regulates quorum sensing. This could have caused a shift in bacterial behavior in the intolerant holobiont, resulting in virulence or dysbiosis. Originality-Significance Statement The importance of symbiotic microbes for the health and stress resistance of multicellular eukaryotes is widely acknowledged, but understanding the mechanisms underlying these interactions is challenging. They are especially difficult to separate in systems with one or more uncultivable components. We bridge the gap between fully controlled, cultivable model systems and purely environmental studies through the use of a multi-omics approach and metabolic models on experimentally modified “holobiont” systems. This allows us to generate two promising working hypotheses on the mechanisms by which uncultivated bacteria influence their brown algal host’s fresh water tolerance.

Holobiont

10.1101/2021.04.13.439635

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Citations (3)

Flow cytometric measurements as a proxy for sporulation intensity in the cultured macroalga Ulva (Chlorophyta)

Botanica Marina (2021)

Omri Nahor Cristina F. Morales‐Reyes Gianmaria Califano Thomas Wichard Alexander Golberg

Abstract Controlling the life cycle of the green macroalga Ulva (Chlorophyta) is essential to maintain its efficient aquaculture. A fundamental shift in cultivation occurs by transforming the thallus cells into gametangia and sporangia (sporulation), with the subsequent release of gametes and zoids. Sporulation occurrence depends on algal age and abiotic stimuli and is controlled by sporulation inhibitors. Thus, quantification of sporulation intensity is critical for identifying the biotic and abiotic factors that influence the transition to reproductive growth. Here, we propose to determine the sporulation index by measuring the number of released gametes using flow cytometry, in proportion to the total number of thallus cells present before the occurrence of the sporulation event. The flow cytometric measurements were validated by manually counting the number of released gametes. We observed a variation in the autofluorescence levels of the gametes which were released from the gametangia. High autofluorescence level correlated to phototactically active behaviour of the gametes. As autofluorescence levels varied between different groups of gametes related to their mobility, flow cytometry can also determine the physiological status of the gametes used as feedstock in seaweed cultivation.

Thallus

Heterosigma akashiwo

10.1515/bot-2020-0050

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Citations (5)

Supplementary material to "Modeling the growth and sporulation dynamics of the macroalga Ulva in mixed-age populations in cultivation and the formation of green tides"

Uri Obolski Thomas Wichard Álvaro Israel Alexander Golberg Alex Liberzon

Dynamics

10.5194/bg-2021-183-supplement

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Hydroxypyridinones in nitrogen-fixing bacterial cultures: a metal buffer for molybdenum and simulation of natural conditions

Metallomics (2022)

Jan Mohr Sofia Gama Sébastien Roy Jean‐Philippe Bellenger Winfried Plass

Abstract Organic matter regulates the availability of important trace elements in aquatic and terrestrial ecosystems by acting as a source and container for microbes. To overcome the limitation of trace elements, nitrogen-fixing bacteria, e.g. release low-molecular-weight chelators (metallophores), which scavenge the essential cofactors of the nitrogenase, iron, and molybdenum (Mo), via complexation and subsequent uptake. The formation of metallophores is triggered by limiting conditions, which must be replicated in the laboratory in order to study metallophores as a mediator in metal cycling. While ethylenediaminetetraacetic acid (EDTA)-based buffer systems for metal cations are well established, there is limited knowledge regarding the buffering of oxoanions such as molybdate in a bacterial growth medium. To mimic the availability of molybdenum in nature under laboratory conditions, this study created a Mo-buffer system for bacterial growth media of the model organisms Azotobacter vinelandii and Frankia sp. CH37. We investigated selected hydroxypyridinones (HPs) as potential molybdenum-chelating agents, determining the amount required for efficient molybdenum complexation by calculating speciation plots of the various candidate complexes in artificial growth media at various pH values. The Mo–maltol system was identified as an ideal, nontoxic molybdenum-buffer system. In the presence of the Mo–maltol system, the growth of Frankia sp. was limited under diazotrophic conditions, whereas A. vinelandii could acquire molybdenum through the release of protochelin and subsequent molybdenum uptake. The study paves the way for unravelling molybdenum recruitment and homeostasis under limiting conditions in bacteria.

Azotobacter vinelandii

10.1093/mtomcs/mfac055

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Citations (2)

Collapse of Calanus chilensis reproduction in a marine environment with high diatom concentration

Journal of Experimental Marine Biology and Ecology (2007)

S. A. Poulet Rubén Escribano Pamela Hidalgo Anne Cueff Thomas Wichard

Calanus

Dinoflagellate

Bloom

Acartia tonsa

10.1016/j.jembe.2007.07.019

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Citations (42)