Fucoid brown algae inject fucoidan carbon into the ocean

Peer reviewe

Monosaccharide concentrations of particulate organic matter in samples collected during RV MARIA S. MERIAN cruise MSM95 to the Fram Strait, Arctic Ocean

During the Maria S. Merian cruise MSM95 to the Fram Strait in 2020, water samples were collected from nine stations using a CTD rosette sampler (SeaBird SBE 911Plus). Samples were collected at several depths. From each sample, 4 L of seawater was filtered onto a 0.7 µm GF/F filter using a peristaltic pump. The filters were immediately stored at -80 °C. From each of the filters, 2 x 11.2 mm circular pieces were removed and subject to acid hydrolysis (1 M HCI for 24 h at 100 °C). The aliquots were run in a speed vac before resuspension in MilliQ. Measurements of monosaccharides were obtained using High-performance anion exchange chromatography with pulsed amperometric detection along with standards

Polysaccharide structures in HMWDOM and POM at the North Sea detected by carbohydrate microarray analysis

Here, we traced the abundance of 27 polysaccharide epitopes in dissolved and particulate organic matter along a three month diatom bloom period in the North Sea. We used a bioanalytic approach based on carbohydrate microarrays and monoclonal antibodies (mAbs). Details describing the data: Carbohydrate microarray data show the relative polysaccharide abundance (antibody signal intensity) detected in samples harvested during a spring phytoplankton bloom period (21 sampling dates) in the North Sea (54˚11.3'N, 7˚54.0'E). Samples include high molecular weight dissolved organic matter (HMWDOM) and particulate organic matter (POM). Polysaccharides from all samples were sequentially extracted with the solvents H2O, 50 mM EDTA pH 7.5 and 4 M NaOH with 0.1% w/v NaBH4. A library of identical microarrays was created, each populated with the same time-series of extracted polysaccharides. These microarrays were then individually incubated with polysaccharide-specific mAbs or carbohydrate binding modules (CBMs) as probes, which specifically bind to a single polysaccharide epitope. The binding of probes to polysaccharide epitopes on the microarrays was detected using a secondary antibody coupled to alkaline phosphatase, which converts its substrate into a coloured product, the amount of which correlates with polysaccharide concentration. Antibody signal intensity was quantified and the highest signal value in the data set for HMWDOM and for POM was set to 100 and all other values were normalised accordingly. The temporal dynamics but not the absolute number should be compared between HMWDOM and POM pools as they required independent normalisation since their sampling was different. A cut-off of 5 arbitrary units was applied and all probe profiles where in at least one date an antibody positive signal (value ≥ 5) was detected are included in the data set. The epitope recognised by each probe is shown at the top of each column and the name of the corresponding mAb or CBM is depicted in parentheses. Size fractions correspond to: POM 10 µm, over 10 µm; POM 3 µm, between 10 and 3 µm; POM 0.2 µm, between 3 and 0.2 µm; HMWDOM, between 0.2 µm and 1 kDa. HG, homogalacturonan; DE, degree of esterification; AGP, arabinogalactan protein; GlcA, glucuronic acid. This microarray data set reveals the temporal dynamics of 27 polysaccharide epitopes in HMWDOM and POM

Monosaccharide composition in HMWDOM during a microalgae bloom period in the North Sea

We analysed the monosaccharide composition in high molecular weight dissolved organic matter (HMWDOM) during a three month diatom bloom period in the North Sea (54˚11.3'N, 7˚54.0'E). HMWDOM samples were concentrated by tangential flow filtration (TFF). These were hydrolysed with acid into monomers and quantified by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). Details describing the data: A total of 19 samples were analysed including two technical replicates. Each sample corresponds to 100 L of 0.2 μm-filtered seawater that were concentrated to a final volume of 0.5 L by TFF with 1 kDa cassettes. Therefore samples contain the size fraction between 0.2 µm and 1 kDa. The TFF-concentrated HMWDOM samples were analysed and data show their monosaccharide composition as mean relative abundance (in molarity)

Polysaccharides present in HMWDOM and POM during a microalgae bloom period in the North Sea

High molecular weight dissolved organic matter (HMWDOM) and particulate organic matter (POM) samples were harvested during a spring phytoplankton bloom period in the North Sea for about three months. Polysaccharides from all HMWDOM and POM samples were extracted and analysed by carbohydrate microarray analysis. Additionally, glycans in the HMWDOM samples were also studied by monosaccharide analysis

Carbohydrates and carbohydrate degradation gene abundance and transcription in Atlantic waters of the Arctic

Carbohydrates are chemically and structurally diverse, represent a substantial fraction of marine organic matter and are key substrates for heterotrophic microbes. Studies on carbohydrate utilisation by marine microbes have been centred on phytoplankton blooms in temperate regions, while far less is known from high-latitude waters and during later seasonal stages. Here, we combine glycan microarrays and analytical chromatography with metagenomics and metatranscriptomics to show the spatial heterogeneity in glycan distribution and potential carbohydrate utilisation by microbes in Atlantic waters of the Arctic. The composition and abundance of monomers and glycan structures in POM varied with location and depth. Complex fucose-containing sulfated polysaccharides, known to accumulate in the ocean, were consistently detected, while the more labile beta-1,3-glucan exhibited a patchy distribution. Through 'omics analysis, we identify variations in the abundance and transcription of carbohydrate degradation-related genes across samples at the community and population level. The populations contributing the most to transcription were taxonomically related to those known as primary responders and key carbohydrate degraders in temperate ecosystems, such as NS4 Marine Group and Formosa. The unique transcription profiles for these populations suggest distinct substrate utilisation potentials, with predicted glycan targets corresponding to those structurally identified in POM from the same sampling sites. By combining cutting-edge technologies and protocols, we provide insights into the carbohydrate component of the carbon cycle in the Arctic during late summer and present a high-quality dataset that will be of great value for future comparative analyses.ISSN:2730-615

Structures and functions of algal glycans shape their capacity to sequester carbon in the ocean

Algae synthesise structurally complex glycans to build a protective barrier, the extracellular matrix. One function of matrix glycans is to slow down microorganisms that try to enzymatically enter living algae and degrade and convert their organic carbon back to carbon dioxide. We propose that matrix glycans lock up carbon in the ocean by controlling degradation of organic carbon by bacteria and other microbes not only while algae are alive, but also after death. Data revised in this review shows accumulation of algal glycans in the ocean underscoring the challenge bacteria and other microbes face to breach the glycan barrier with carbohydrate active enzymes. Briefly we also update on methods required to certify the uncertain magnitude and unknown molecular causes of glycan-controlled carbon sequestration in a changing ocean

Automated synthesis of fucoidan enables molecular investigations in marine glycobiology

Fucoidan, a sulfated polysaccharide found in algae, occupies a central yet enigmatic role in marine carbon sequestration and exhibits a wide array of bioactivities. However, the inherent molecular diversity and structural complexity of fucoidan hinders precise structure-function studies. To address this, we present a rapid and reproducible automated synthesis method for generating well-defined linear and branched α-fucan oligosaccharides. Our syntheses include oligosaccharides with up to 20 cis-glycosidic linkages, diverse branching patterns, and 11 sulfate monoesters. In this study, we showcase the utility of these glycans by (i) characterizing two endo-acting fucoidan glycoside hydrolases (GH107), (ii) serving as standards for NMR experiments to confirm suggested structures of algal fucoidans, and (iii) developing a fucoidan microarray. This microarray enabled precise screening of the molecular specificity of four monoclonal antibodies targeting fucoidan. Utilizing the antibody BAM2, identified here for its specificity to α-(1→3)-fucoidans featuring 4-O-sulfate esters, we provide evidence that such a fucoidan motif is present in a globally abundant marine diatom, Thalassiosira weissflogii. Automated glycan assembly provides a robust platform for accelerating research in marine glycobiology, offering access to fucoidan oligosaccharides with distinct structures, thereby facilitating advancements in our collective understanding of how fucoidan\u27s structure influences its function