Edible Seaweed Research Articles

Ethanol Extract of Sargassum siliquastrum Inhibits Lipopolysaccharide-Induced Nitric Oxide Generation by Downregulating the Nuclear Factor-Kappa B Signaling Pathway.

Sargassum siliquastrum (SS) is an edible brown seaweed widely consumed in Korea and considered a functional food source. Previous studies have reported various biological activities of SS extracts, including antioxidant and hepatoprotective properties. In the present study, we examined the anti-inflammatory effects of the SS extract and assessed the underlying mechanism of action. The SS extract significantly inhibited lipopolysaccharide (LPS)-induced nitric oxide (NO) production in a dose-dependent manner (% of NO production at 500 μg/mL: 60.1 ± 0.9%), with no obvious toxicity. Furthermore, the SS extract inhibited mRNA and protein expression levels of inducible NO synthase, as well as LPS-induced expression and production of proinflammatory cytokines such as IL-1β, IL-6, or TNF-α (IL-6 production (ng/mL) : LPS−: 0.7 ± 0.3; LPS+: 68.1 ± 2.8; LPS + SS extract: 51.9 ± 1.2; TNF-α production (ng/mL) : LPS−: 0.3 ± 0.1; LPS+: 23.0 ± 0.1; LPS + SS extract: 18.2 ± 10.8). Mechanistically, the SS extract attenuated LPS-induced activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (nuclear factor-kappa B, NF-κB) signaling pathway such as phosphorylation of NF-κB p65 and degradation of IκB-α, thereby blocking LPS-induced activation of NF-κB transcriptional activity. The SS extract also enhanced LPS-induced heme oxygenase-1 expression and attenuated LPS-induced cellular reactive oxygen species production (% of ROS production at 500 μg/mL: 52.2 ± 1.3%). Collectively, these findings suggest that the SS extract elicits anti-inflammatory effects in mouse macrophage cells.

Study on proximate composition of four seaweeds from Kilinochchi and Kalpitiya area of Sri Lanka

Some of the representatives from edible seaweeds (Gracilaria verrucosa, Gracilaria corticata, Turbinaria ornate, Sargassum polycystum) from Kilinochchi and Kalpitiya in Sri Lanka were investigated for proximate composition (moisture, protein, lipid and ash content). The proximate composition was significantly (p < 0.001) different across seaweed species. In this regard, moisture content (mean ± SD) varied from 76.33 ± 0.0% in T. ornata to 89.78 ± 0.6% in G. corticata. The S. polycystum presented the highest fat content (1.94 ± 0.5%); whereas, G. corticata showed the highest protein level (21.66 ± 1.1%). Fat content was low in T. ornata (0.37 ± 0.2%) and S. polycystum (1.94 ± 0.5%) while protein content was low in other three species. Also G. verrucosa and G. corticata had higher ash content (44.34 ± 3.8% and 44.34 ± 3.8% respectively) than other seaweed species. The variation in proximate composition was high among species and would be a healthy addition to normal diets.

Arsenic and Nutrient Composition Across Different Edible Seaweeds From Hawaii

ObjectivesSeaweed is used for various cultural, culinary, and medicinal purposes in Hawaii and has been consumed for generations around the world (i.e., the Pacific, Asia, and parts of Europe). In the US, seaweed is gaining popularity because of its reputation for being highly nutritional. However, some types of seaweed are known to accumulate heavy metals, including inorganic arsenic (iAs) species. While some seaweed species have been studied, there is still limited species-specific compositional data. The purpose of this study was to quantify arsenic and nutrient (i.e., macronutrient and mineral) levels in edible seaweeds.MethodsBrown algae (Sargassum aquifolium and Sargassum spp.), red algae (Gracilaria parvispora, Halymenia formosa, and Halymenia hawaiiana, and green algae (Ulva ohnoi) were analyzed using HPLC-ICP-MS for arsenic speciation. Proximate (protein, dietary fiber, ash, moisture, carbohydrate, crude fat, and crude protein) and mineral (P, K, Ca, Mg, Na, Fe, Mn, Zn, Cu, B) analyses were conducted. Values were expressed per freeze-dried weight (FDW) or fresh weight serving (FW) of seaweed.ResultsBrown algae had the highest concentration of total and iAs compared to all others. Statistical differences amongst macronutrients and minerals existed across seaweed species, with G. parvispora having higher Mn (∼510 µg/g FDW) and K (∼4.6 g/100g FDW) levels compared to all other samples (P < 0.05). Based on recommended nutritional daily values, G. parvispora (∼80 g FW) was high in Mn, H. formosa (∼100 g FW) was high in Fe, U. ohnoi (∼100 g FW) was high in Mg, and H. hawaiiana (∼100 g FW) was high in Mg, Fe, and Zn.ConclusionsOverall, these findings indicate significant differences in composition across seaweed species. As some seaweeds were excellent sources of essential nutrients while others were high in iAs, it is critical to continually expand compositional data to assess both nutritional adequacy and safety of diets.Funding SourcesUSDA-ARS, FDA.

Trace element bioaccumulation in edible red seaweeds (Rhodophyta): A risk assessment for consumers

As a precursor to risk assessment and risk management through consuming contaminated seafood, food safety needs to be quantified and assured. Seaweed is an increasing dietary component, especially in developing countries, but there are few studies assessing uptake rates of contaminants from this route. As such, the present study determined likely human uptake due to the trace elemental (Fe, Mn, Ni, Cu, Zn, Se, Hg, and As) concentrations in the edible red seaweeds (Rhodophyta) Gelidium pusillum and Hypnea musciformis, growing in the industrialised Cox's Bazar coastal area of Bangladesh. Metal and metalloid concentrations in G. pusillum were in the order (mg/kg): Fe (797 ± 67) > Mn (69 ± 4) > Ni (12 ± 5) > Zn (9 ± 4) > Cu (9 ± 4) >Se (0.1 ± 0.1) > Hg (0.1 ± 0.01), and in H. musciformis: Fe (668 ± 58) > Mn (28 ± 5) > Ni (14 ± 2) > Zn (11 ± 5) > Cu (6 ± 4) >Se (0.2 ± 0.03) > Hg (0.04 ± 0.01). Despite the industrial activities in the area, and based on 10 g. day−1 seaweed consumption, it is concluded that these concentrations pose no risk to human health as part of a normal diet according to the targeted hazard quotient and hazard index (THQ and HI) (values < 1). In addition, and as a novel aspect for seaweeds, Selenium Health Benefit Values (Se-HBV) were determined and found to have positive values. Seaweed can be used as an absorber of inorganic metals for removing contamination in coastal waters. The results are a precursor to further research regarding the efficiency and rate at which seaweeds can sequester metal contamination in water. In addition, management techniques need to be developed thereby to control the contaminant inputs.

Characteristics of Nori-Like Product Prepared from Seaweeds Growing in Indonesia

ABSTRACT Nori is a dried edible seaweed product used in Japanese cuisine made originally from seaweed from the genus Porphyra. Porphyra usually grows in sub-tropic coastal waters and is rarely found in tropical zones like Indonesia. For this reason, it is important to find local raw materials to substitute Porphyra to produce nori-like products in Indonesia. The present work aimed to study the physicochemical characteristics, fatty acid profiles, color components, and mineral contents of nori-like products formulated from seaweeds growing in Indonesia. The seaweeds used were Gracilaria verrucosa, Ulva lactuca, and Caulerpa racemosa. The proportion of each seaweed for nori-like product formulation was 100:0:0; 75:25:0; 75:0:25; 50:50:0; 50:0:50, and 50:25:25, respectively. Based on color, dietary fiber, and minerals (Mg and Ca), the formula of nori-like product processed from Gracilaria and Ulva with the proportion of 50:50 had a better than the commercial nori.

Traditional Knowledge and Modern Motivations for Consuming Seaweed (Limu) in Samoa

Seaweeds are a traditional food throughout the Pacific. In Samoa, the edible seaweeds limu fuafua (sea grapes, Caulerpa racemosa and C. chemnitzia) and limu a’au (red seaweed, Halymenia durvillei and Halymenia sp.) are hand-harvested and consumed fresh or cooked, respectively. However, there is limited scientific or traditional documentation of these commodities. Here, we assess the traditional use and cultural value of edible seaweeds and explore modern consumer preferences and perceived nutritional benefits. Structured enumerator-administered questionnaires were used to examine the relationship between consumption and demographics and subsequently to assess the key motivators for consumption, including perceived nutritional benefits. A total of 320 participants were surveyed across 20 village communities, with 95% reporting consumption of Caulerpa and 40% of Halymenia. Consumption was primarily on a weekly to monthly basis, and even once a day. Motivators and barriers for consumption were then assessed in 320 village participants with an additional 203 intercept interviews at fish markets. A content analysis of the open-ended questions revealed the key motivators for eating limu were health and taste (positive), whereas the key barriers were taste (negative) and availability. We identify opportunities to develop a nutrient evidence base for Samoan seaweeds to aid in marketing, especially for youth.

Ultrasonication followed by enzymatic hydrolysis as a sample pre-treatment for the determination of Ag nanoparticles in edible seaweed by SP-ICP-MS

Seaweed can bioaccumulate nanomaterials that would be transferred to the trophic chain. This work describes the optimization of a method for the separation of silver nanoparticles (AgNPs) from seaweed using an ultrasound-assisted enzymatic hydrolysis method and ulterior determination by single particle inductively coupled plasma mass spectrometry (SP-ICP-MS).The following parameters affecting the isolation of AgNPs were optimized using a Palmaria palmata (red seaweed) sample previously exposed to AgNPs: type of sonication (bath vs. ultrasonic probe), ultrasound amplitude, sonication time, sonication mode (pulsed vs. continuous sonication), concentration of the enzymes mixture (Macerozyme R-10®), and enzymatic hydrolysis time. The stability of AgNPs during extraction was tested by transmission electron microscopy (TEM) and using a standard of 15 nm of polyvinylpyrrolidone (PVP)-coated AgNPs analyzed by SP-ICP-MS. The analytical performance was evaluated with good results. For total Ag determination, the limits of detection and quantification were 2.2 and 7.7 ng g−1, respectively; and for AgNPs determination, the limits of detection in size and number were 14 nm and 4.34 × 107 part g−1, respectively. Besides, the matrix effect, the repeatability and the analytical recovery were also studied. Finally, the method was applied to the analysis of several red (Palmaria palmata) and green (Ulva sp.) seaweed samples.

Antibacterial Gelidium amansii polysaccharide-based edible films containing cyclic adenosine monophosphate for bioactive packaging

A homogeneous polysaccharide (GAP), with a molecular weight of 51.8 kDa, was isolated from edible red seaweed Gelidium amansii. Composition analysis suggested GAP contained 5.31% sulfate and 17.33% 3,6-anhydro-galactose and was mainly composed of galactose. Furthermore, GAP, as a biopolymer matrix, was used to form the composite films with the small biological molecules cytidine-5′-monophosphate (CMP), adenosine-5′-monophosphate (AMP), and cyclic adenosine monophosphate (cAMP). Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectrum, and X-ray diffraction (XRD) results showed that CMP, AMP, and cAMP interacted with the film substrates and might made films more complex. Notably, the addition of CMP, AMP, and cAMP promoted the light, water vapor, and oxygen barrier ability, surface wettability, mechanical strength, and antimicrobial activity against Gram-negative and –positive bacteria. Finally, GAP-based films composited with cAMP (cAMPF) exhibited the best characteristics were applied to fish packaging and preservation at 4 °C and extended the fish shelf life. All these data suggested the potential value of cAMPF as a functional edible polysaccharide film applied in food industries.

Inhibitory Effects of Polyphenols-Rich Components From Three Edible Seaweeds on Inflammation and Colon Cancer in vitro.

Polyphenols from edible seaweeds display various health benefits which have not been adequately studied. This study aimed to characterize the composition of extractable polyphenol-rich components (EPCs) and non-extractable polyphenol-rich components (NEPCs) from three edible seaweeds (i.e., Laminaria japonica, Ulva lactuca, and Porphyra tenera) and evaluate their anti-inflammatory capacities in activated macrophages and anticancer properties in colon cancer cells. Both EPCs and NEPCs from three edible seaweeds against lipopolysaccharides (LPS) stimulated nitric oxide in activated macrophages. Immunoblotting and qRT-PCR indicated that EPCs and NEPCs regulated the expression levels of proinflammatory enzymes, proinflammatory cytokines, and antioxidant enzymes in macrophages. Furthermore, EPCs and NEPCs lowered the viability of colon cancer cells, while normal colon cells were not affected. Additionally, EPCs and NEPCs induced cellular apoptosis and led to G0/G1 cell cycle arrest in HCT116 cells. Overall, these results provide a rationale for future animal and human studies designed to examine the anti-inflammatory and chemopreventive capacities of polyphenols-rich components from L. japonica, U. lactuca, and P. tenera.

Gaps in knowledge about distribution, utilization, and management of Sargassaceae (Fucales, Phaeophyta) in Okinawa Island, southern Japan

Communities based on Sargassaceae have various ecosystem functions. However, the resource status of Sargassaceae beds in subtropical seas and their value as conservation targets remain unclear. The purpose of this study was to evaluate changes in the distribution of Sargassaceae species and the commercial value of Sargassaceae, and to determine whether there are gaps in knowledge about the distribution, use, management, and conservation of Sargassaceae species on Okinawa Island. For this purpose, we examined the occurrence records of Sargassaceae to determine the distributional changes from the past and inferred future changes of Sargassaceae bed using future water temperature projection datasets. In addition, through a literature review and interviews, we clarified how Sargassaceae is used, managed, and conserved in the island. Comparing the records of occurrence prior to 2000 with those of recent years, it is clear that the number of sites where occurrence was confirmed on the west coast of the island has decreased significantly. Sargassaceae is recognized for its role as a sea vegetable and nursery for sea urchins but monitoring and conservation activities of the Sargassaceae community are very limited. In addition, there are several points that were not in accordance with the actual situation, such as the listing of widely distributed species in the Red List. Based on the literature data, the tolerance of Sargassaceae species to high water temperature in Okinawa Island was summarized, and it was suggested that a monthly-mean water temperature increase of about 2 °C compared to the current level would not have a significant impact on their growth. Although it is assumed that Sargassaceae beds will be maintained, present monitoring and conservation systems are not sufficient. Therefore, it is important to strengthen the management system and to properly recognize and utilize the value of the Sargassaceae community sustainably.

Potent Bioactive Compounds From Seaweed Waste to Combat Cancer Through Bioinformatics Investigation.

The seaweed industries generate considerable amounts of waste that must be appropriately managed. This biomass from marine waste is a rich source of high-value bioactive compounds. Thus, this waste can be adequately utilized by recovering the compounds for therapeutic purposes. Histone deacetylases (HDACs) are key epigenetic regulators established as one of the most promising targets for cancer chemotherapy. In the present study, our objective is to find the HDAC 2 inhibitor. We performed top-down in silico methodologies to identify potential HDAC 2 inhibitors by screening compounds from edible seaweed waste. One hundred ninety-three (n = 193) compounds from edible seaweeds were initially screened and filtered with drug-likeness properties using SwissADME. After that, the filtered compounds were followed to further evaluate their binding potential with HDAC 2 protein by using Glide high throughput virtual screening (HTVS), standard precision (SP), extra precision (XP), and quantum polarized ligand docking (QPLD). One compound with higher negative binding energy was selected, and to validate the binding mode and stability of the complex, molecular dynamics (MD) simulations using Desmond were performed. The complex-binding free energy calculation was performed using molecular mechanics-generalized born surface area (MM-GBSA) calculation. Post-MD simulation analyses such as PCA, DCCM, and free energy landscape were also evaluated. The quantum mechanical and electronic properties of the potential bioactive compounds were assessed using the density functional theory (DFT) study. These findings support the use of marine resources like edible seaweed waste for cancer drug development by using its bioactive compounds. The obtained results encourage further in vitro and in vivo research. Our in silico findings show that the compound has a high binding affinity for the catalytic site of the HDAC 2 protein and has drug-likeness properties, and can be utilized in drug development against cancer.

‘Edible seaweeds’ as an alternative to animal-based proteins in the UK: Identifying product beliefs and consumer traits as drivers of consumer acceptability for macroalgae

Edible macroalgae (i.e., ‘seaweeds’) are a nutritious and sustainable alternative to animal-based proteins. However, consumption of seaweeds in Western countries remains low, and little is known about individual drivers of acceptance. The aim of this study was to further explore the consumer acceptability of seaweed-based food products in the UK. In an online study (N = 476), participants were presented with a general description of edible seaweeds, and descriptions of seaweed-based food products (e.g., ‘seaweed burger’). Participants were asked to rate beliefs about product attributes, and reported acceptance in terms of liking, willingness to try, willingness to buy, and readiness to adopt as a meat alternative. It was predicted that positive beliefs about seaweed-based products would be significantly associated with greater acceptance, and that seaweed-based products would be more favourable than a general description of seaweeds. Supporting study hypotheses, structural equation modelling showed that positive beliefs about taste/ edibility and familiarity significantly predicted acceptance (p <.01). Taste/ edibility was higher for seaweed-based products compared to a general description of seaweeds (p <.001), and perceiving foods to be tasty and familiar mediated the negative effect of food neophobia on consumer acceptance (p <.05). Other product beliefs – including cost, healthiness, and sustainability – were relatively poor predictors of acceptance (p >.05). These results support the consumer acceptance of seaweeds, and identify scope for utilising specific attributes of seaweeds (as drivers of acceptance) in future product development.

Traditional Cooking Methods Affect Color, Texture and Bioactive Nutrients of Undaria pinnatifida.

Undaria pinnatifida (U. pinnatifida) is an edible brown seaweed with high health value. The objective of this study was to evaluate the effect of traditional cooking methods (i.e., blanching, steaming, boiling and baking) on the color, texture and bioactive nutrients of U. pinnatifida, so as to screen out the traditional cooking methods more suitable for U. pinnatifida. In this study, methods of blanching and boiling resulted in better reduction in total color difference (0.91 ± 0.58 and 0.79 ± 0.34, respectively) and retention of chlorophyll A (62.99 ± 1.27 µg/g FW and 51.35 ± 1.69 µg/g FW), along with better elevation of fucoxanthin content (increased by 11.05% and 18.32%, respectively). Baking method got the best retention of total phenol content (1.62 ± 0.11 mg GAE/g DW), followed by methods of boiling and blanching (1.51 ± 0.07 mg GAE/g DW and 1.43 ± 0.05 mg GAE/g DW). Among these cooking methods, blanching and boiling seemed to be the more suitable for U. pinnatifida compared to other methods. These results could help to determine the better cooking methods for U. pinnatifida products and provide a scientific and theoretical basis for improving human dietary health.

Application of ED-XRF spectra for determination of macroelements in edible seaweeds

The application of an increased number of edible seaweeds in gastronomy requires accurate, rapid, and non-destructive mineral evaluation. In this work, energy dispersive X-ray fluorescence (ED-XRF) spectra were used to determine Ca, K, and P in edible green, red, and brown seaweeds from the Portuguese coasts. ED-XRF raw spectra of seaweed samples were correlated against results of conventional inductively coupled plasma-optical emission spectrometry (ICP-OES), by the full cross-validation partial least-square (CVPLS) regression method, with nonlinear iterative partial least squares (NIPALS) algorithm. The standard reference material (Thallus laminariae) was used for the validation of CVPLS. Statistical parameters, correlation coefficients (R2), root mean square errors (RMSE), and bias, were used for the assessment of the CVPLS method. For selected minerals, R2 was high (0.88–0.95), while RMSE values (< 1.02) and bias (0) were low, thus indicating a viable potential for their routine analysis by ED-XRF. These findings highlighted the quality of ED-XRF spectral data, which can be used for an efficient non-destructive determination of macroelements in edible seaweeds on a large food industrial scale.

Optimization of High-Pressure-Assisted Extraction of Cadmium and Lead from Kelp (Laminaria japonica) Using Response Surface Methodology.

Kelp (Laminaria japonica) is a popular and nutritious sea vegetable, but it has a strong biosorption capacity for heavy metals. The high content of cadmium (Cd) and lead (Pb) is a threat to the quality of kelp. The objective of this study was to investigate the effects of high-pressure-assisted extraction (HPAE) conditions on Cd and Pb removal efficiency from kelp. Pressure intensity (0.1–200 MPa), the number of HPAE cycles (one to five) and acetic acid concentration (0–10%) were optimized using response surface methodology. The pressure intensity had the most significant positive effects on Cd and Pb removal efficiency, while the correlation between acetic acid concentration and removal efficiency was positive for Cd and negative for Pb. The optimum conditions for the removal of Cd and Pb were attained at 188 MPa, with four cycles and with an acetic acid concentration of 0%. At optimum conditions, the experimental values of removal efficiency were 61.14% (Cd) and 70.97% (Pb), and this was consistent with the predicted value, confirming the validity of the predictive model.

Comprehensive Lipidomic Analysis of Three Edible Brown Seaweeds Based on Reversed-Phase Liquid Chromatography Coupled with Quadrupole Time-of-Flight Mass Spectrometry.

A comprehensive lipidomic analysis was performed onto three edible brown seaweeds, namely Laminaria japonica, Undaria pinnatifida, and Scagassum natans, using reversed-phase liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (RPLC-Q-TOF-MS/MS). In total, 675 lipid molecules, including glycolipids (GLs), phospholipids, sphingolipids (SLs), betaine lipids, and glycerolipids, were identified and semiquantified. With the exception of the high content of diacylglycerols found in L. japonica (54.6% of total lipids), GLs were the dominant component in the three brown seaweeds (27.7-56.7% of total lipids), containing a high proportion of eicosapentaenoic acid. Interestingly, SLs represented by ceramide and hexosylceramide containing phytosphingosine and α-hydroxy fatty acid structures were detected in the three brown seaweeds. A large number of acylated GLs were identified and reported for the first time in these seaweeds, including acylated monogalactosyldiacylglycerol and acylated digalactosyldiacylglycerol containing nonoxidized fatty acids. The bioactive lipids identified herein could be considered potential biomarkers for identifying these seaweeds, evaluating their nutritional value and further promoting their utilization.

Vortex-assisted matrix solid-phase dispersion: An eco-friendly alternative for the determination of halogens in edible seaweed

Edible seaweed has been widely consumed around the world through oriental cuisine and it is important to monitor the levels of some elements, especially halogens. This study proposes, for the first time, the development of an analytical method using the vortex-assisted matrix solid-phase dispersion (VA-MSPD) combined with alkaline extraction of halogens (F, Cl, Br, and I) in edible seaweed for further determination by ion chromatography. The proposed method was evaluated using edible seaweed of the Nori (Porphyra spp.) type and applied to samples of the Wakame (Undaria pinnatifida), Kombu (Laminaria ochroleuca), and Hijiki (Hizikia fusiformis) types. Important VA-MSPD parameters were investigated and using 0.1 g sample, 1 g sea sand as solid support, 50 mmol L−1 (NH4)2CO3 as extraction solution, and 5 min of maceration, higher extraction efficiencies were obtained. The method was linear within the evaluated range (R2 > 0.99) for all elements and no matrix effect was observed. The detection limits of the method were 27, 26, 19, and 28 μg g−1 for F, Cl, Br, and I, respectively. The accuracy was evaluated by a recovery test (ranging from 92 to 108%) and analysis of certified reference materials for apple leaves (NIST 1515) and peach leaves (NIST 1547), which had a good agreement (ranging from 97 to 101%) with the certified values. Comparing the results with those obtained by inductively coupled plasma-mass spectrometry after microwave-induced combustion, no significant difference was found between the results, and the relative standard deviations were lower than 12%. The proposed method proved to be efficient for the determination of halogens in different algae species, showing advantages such as simplicity and low cost, combined to the use of a material from renewable sources (sea sand) as a solid support, contributing to the principles of Green Analytical Chemistry.

Comparative Gene Expression and Physiological Analyses Reveal Molecular Mechanisms in Wound-Induced Spore Formation in the Edible Seaweed Nori.

Genetic reprogramming of differentiated cells is studied broadly in multicellular Viridiplantae as an adaptation to herbivory or damage; however, mechanisms underlying cell development and redifferentiation are largely unknown in red algae, their nearest multicellular relatives. Here we investgate cell reprogramming in the widely cultivated, edible seaweed Neopyropia yezoesis (“nori”), where vegetative cells in wounded blades differentiate and release as large numbers of asexual spores. Based upon physiological changes and transcriptomic dynamics after wound stress in N. yezoensis and its congener Neoporphyra haitanensis, another cultivar that does not differentiate spores after wounding, we propose a three-phase model of wound-induced spore development in N. yezoensis. In Phase I, propagation of ROS by RBOH and SOD elicites systematic transduction of the wound signal, while Ca2+ dependent signaling induces cell reprogramming. In Phase II, a TOR signaling pathway and regulation of cyclin and CDK genes result in cell divisions that spread inward from the wound edge. Once sporangia form, Phase III involves expression of proteins required for spore maturation and cell wall softening. Our analyses not only provide the first model for core molecular processes controlling cellular reprogramming in rhodophytes, but also have practical implications for achieving greater control over seeding in commercial nori farming.

Metabolism of a hybrid algal galactan by members of the human gut microbiome.

Native porphyran is a hybrid of porphryan and agarose. As a common element of edible seaweed, this algal galactan is a frequent component of the human diet. Bacterial members of the human gut microbiota have acquired polysaccharide utilization loci (PULs) that enable the metabolism of porphyran or agarose. However, the molecular mechanisms that underlie the deconstruction and use of native porphyran remains incompletely defined. Here, we have studied two human gut bacteria, porphyranolytic Bacteroides plebeius and agarolytic Bacteroides uniformis, that target native porphyran. This reveals an exo-based cycle of porphyran depolymerization that incorporates a keystone sulfatase. In both PULs this cycle also works together with a PUL-encoded agarose depolymerizing machinery to synergistically reduce native porphyran to monosaccharides. This provides a framework for understanding the deconstruction of a hybrid algal galactan, and insight into the competitive and/or syntrophic relationship of gut microbiota members that target rare nutrients.

Modeling the life cycle of four types of phytoplankton and their bloom mechanisms in a benthic-pelagic coupled ecosystem

Harmful diatom (Coscinodiscus waillesi and Eucampia zodiacus) blooms frequently occur in the western coastal area of Japan from late autumn to early spring, causing discoloration of edible seaweed nori (Pyropia yezoensis). One of the causes of the discoloration is thought to be nutrient depletion (oligotrophication) due to nutrient uptake by diatoms. The goal of our study was to elucidate the mechanisms underlying phytoplankton blooms and the effects of such blooms on comprehensive nutrient cycles in the benthic-pelagic ecosystem. We developed a new ecosystem model, EMAGIN-L.P., simultaneously representing phytoplankton life cycle and the benthic-pelagic ecosystem. The life cycles of four types of phytoplankton—dinoflagellates (DFL), small diatoms (SDA), Coscinodiscus wailesii (CDW), and Eucampia zodiacus (EZ)—were numerically modeled and incorporated into an existing ecosystem model, ECOHYM (Sohma et al., 2008a), representing the food web among the benthic and pelagic systems and carbon-nitrogen-phosphorus-oxygen-coupled cycles driven by biogeochemical and physical processes. The model was applied to the Harima-Nada Sea where the discoloration of nori frequently occurs. The model reproduced the differences in timing and scale of the four phytoplankton blooms, and each bloom could be explained by a combination of temperature suitability, light availability, nutrient limitation, and vertical mixing within the water column. Furthermore, through a sensitivity analysis, competition for nutrient uptake among different types of phytoplankton was observed in the model. That is, from June to October, when DFL and SDA blooms occur, the SDA nutrient uptake rate is high and SDA suppresses the DFL bloom, while from November to March, when CDW and EZ blooms occur, the nutrient uptake rate of EZ is high and the CDW bloom is slightly suppressed. The developed model representing the phytoplankton bloom mechanisms in the whole benthic-pelagic coupled ecosystem will be a useful tool for revealing the mechanisms underlying the nutrient cycle and the contribution of harmful diatom blooms to the discoloration of nori. The modeling approach presented in this paper (i.e., categorizing different types of major phytoplankton and incorporating their life cycle into the entire benthic-pelagic coupling ecosystem) can be an effective method to understand, predict, and manage the problems caused by harmful diatom blooms across different damage types, harmful diatom species, and ocean areas.