Search

Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales are highly diverse and widely distributed order whose species can serve as ecosystem engineers in intertidal habitats, including several notorious introduced species. The genusGracilariais cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole genome assemblies for two species (G. chilensisandG. gracilis), a draft genome assembly ofG. caudata, and genome annotation of the previously publishedG. vermiculophyllagenome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.

Haptophyte microalgae are key contributors to microbial communities in many environments. It has been proposed recently that members of this group would be virtually all dependent on vitamin B

One of the key tasks in MIDTAL (MIcroarrays for the Detection of Toxic ALgae) is to demonstrate the applicability of microarrays to monitor harmful algae across a broad range of ecological niches and toxic species responsible for harmful algal events. Water samples are collected from a series of sites used in national phytoplankton and biotoxin monitoring across Europe. The samples are filtered; rRNA is extracted, labelled with a fluorescent dye and applied to a microarray chip. The signal intensity from >120 probes previously spotted on the chip is measured and analysed. Preliminary results comparing microarray signal intensities with actual field counts are presented.

Ectocarpus subulatus depends on its associated bacteria for growth in fresh water, which stresses the significance of the “holobiont” during abiotic stress. The aim of my thesis is to elucidate the molecular mechanisms that underlie this phenomenon. Targeted co-culture experiments require cultivable organisms. Therefore, I have cultivated and characterized 388 Ectocarpus-associated bacteria, which belong to 33 different genera. None of the cultivated bacteria tested had a beneficial effect on algal growth in fresh water. For functional studies, I continued to work with mild antibiotic-treated holobionts that differed in their response to fresh water. The metatranscriptome and metabolome of these holobionts were analyzed during acclimation. In-depth analysis is ongoing, but first indications point towards a change in the microbiome regarding nitrogen assimilation and virulence. In parallel and complementary to the above, potentially beneficial algal-bacterial cross-talk was predicted in silico using metabolic network analysis on a subset of cultivated bacteria, and the predictions were experimentally verified using co-culture experiments. Together, these results contribute to a better understanding of how the Ectocarpus holobiont responds during abiotic stress and especially how bacteria are involved in this process.; Ectocarpus dépend de bactéries associées pour croitre en eau douce, ce qui souligne l'importance de l'holobionte lors de stress abiotique. Le but de ma thèse est d'élucider les mécanismes moléculaires qui sous-tendent ce phénomène. Les expériences de co-culture ciblées nécessitent des organismes cultivables. Par conséquent, j'ai caractérisé 388 bactéries associées à Ectocarpus, réparties en 33 genres. Aucune des bactéries cultivées testées n'a eu d'effet bénéfique sur la croissance des algues dans l'eau douce. J'ai continué à travailler avec des holobionts, traités aux antibiotiques doux, qui différaient dans leur réponse à l'eau douce. Le métatranscriptome/métabolome de ces holobionts ont été analysés pendant l'acclimatation. L'analyse approfondie est en cours, mais les premières indications indiquent un changement dans le microbiome en ce qui concerne l'assimilation de l'azote et la virulence. Concomitamment et complémentaire à ce qui précède, les interactions algues/bactéries potentiellement bénéfiques ont été prédites in silico à l'aide d'une analyse de réseau métabolique et les prédictions ont été vérifiées expérimentalement à l'aide de co-cultures. Ensemble, ces résultats contribuent à mieux comprendre comment l'holobiont d'Ectocarpus réagit au stress abiotique et surtout comment les bactéries sont impliquées dans ce processus.

Ectocarpus subulatus depends on its associated bacteria for growth in fresh water, which stresses the significance of the “holobiont” during abiotic stress. The aim of my thesis is to elucidate the molecular mechanisms that underlie this phenomenon. Targeted co-culture experiments require cultivable organisms. Therefore, I have cultivated and characterized 388 Ectocarpus-associated bacteria, which belong to 33 different genera. None of the cultivated bacteria tested had a beneficial effect on algal growth in fresh water. For functional studies, I continued to work with mild antibiotic-treated holobionts that differed in their response to fresh water. The metatranscriptome and metabolome of these holobionts were analyzed during acclimation. In-depth analysis is ongoing, but first indications point towards a change in the microbiome regarding nitrogen assimilation and virulence. In parallel and complementary to the above, potentially beneficial algal-bacterial cross-talk was predicted in silico using metabolic network analysis on a subset of cultivated bacteria, and the predictions were experimentally verified using co-culture experiments. Together, these results contribute to a better understanding of how the Ectocarpus holobiont responds during abiotic stress and especially how bacteria are involved in this process.; Ectocarpus dépend de bactéries associées pour croitre en eau douce, ce qui souligne l'importance de l'holobionte lors de stress abiotique. Le but de ma thèse est d'élucider les mécanismes moléculaires qui sous-tendent ce phénomène. Les expériences de co-culture ciblées nécessitent des organismes cultivables. Par conséquent, j'ai caractérisé 388 bactéries associées à Ectocarpus, réparties en 33 genres. Aucune des bactéries cultivées testées n'a eu d'effet bénéfique sur la croissance des algues dans l'eau douce. J'ai continué à travailler avec des holobionts, traités aux antibiotiques doux, qui différaient dans leur réponse à l'eau douce. Le métatranscriptome/métabolome de ces holobionts ont été analysés pendant l'acclimatation. L'analyse approfondie est en cours, mais les premières indications indiquent un changement dans le microbiome en ce qui concerne l'assimilation de l'azote et la virulence. Concomitamment et complémentaire à ce qui précède, les interactions algues/bactéries potentiellement bénéfiques ont été prédites in silico à l'aide d'une analyse de réseau métabolique et les prédictions ont été vérifiées expérimentalement à l'aide de co-cultures. Ensemble, ces résultats contribuent à mieux comprendre comment l'holobiont d'Ectocarpus réagit au stress abiotique et surtout comment les bactéries sont impliquées dans ce processus.