Marine macroalgae are foundation species of coastal ecosystems, maintaining close interactions with their microbiome for development and environmental adaptation. Although secure attachment to substrates is essential for both morphological development and survival, the potential causal link between microbial symbionts and this fundamental attachment process remains poorly understood. To address this gap, we integrated large-scale field sampling with functional validation to identify bacteria that influence the attachment of brown algae, specifically comparing attached and drifted individuals of Undaria pinnatifida and Ecklonia cava. Notably, Vibrio was consistently enriched in attached algae, whereas Marinomonas dominated drifted individuals. Translating these field observations into lab-scale validation, we isolated and evaluated their biofilm-formation capacity and impact on gametophyte settlement. A specific isolate belonging to the Vibrio aphrogenes clade exhibited superior biofilm formation and significantly enhanced algal abundance 2.57-fold in co-culture with U. pinnatifida gametophytes. These findings provide a scientific basis for developing bacterial inocula for seaweed seedling production and support broader macroalgae restoration strategies under changing environmental conditions.
This study evaluated the influence of algae-to-sludge inoculation ratio on biomass development and pollutant removal in an algal-bacterial symbiotic system (ABSS) treating shrimp farming wastewater. Batch reactors operated at ratios of 1:2-1:6, along with monoculture controls, were assessed for biomass characteristics, organic matter removal, and nitrogen transformation. The 1:3 ratio achieved the most balanced biomass growth (MLSS: +54.9%; MLVSS: +57.8%) and the highest removal efficiencies, reaching 60.5% ± 7.3%, 89.4% ± 2.9%, and 55.2% ± 15.2% for chemical oxygen demand (COD), ammonium (NH4 +-N), and total nitrogen (TN), respectively. Co-culture reactors consistently outperformed monocultures, suggesting the benefits of coupling algal photosynthesis with bacterial metabolism. The results indicate that biomass balance is a key operational factor governing system performance, likely through its influence on oxygen availability, substrate utilization, and internal mass transfer. Optimizing the algae-to-sludge ratio provides a simple and effective strategy to enhance ABSS performance without increasing aeration demand, offering practical implications for sustainable aquaculture wastewater treatment.
Guidelines for preparing and submitting proposals to modify or enhance Chapter F of the International Code of Nomenclature for algae, fungi, and plants are set out here. Such proposals will be considered by the Fungal Nomenclature Session of the XIII International Mycological Congress, to be held in Incheon, Korea in August 2027. A timetable is established for the submission of proposals, due by 31 December 2026, their publication in IMA Fungus, the release of the 'Synopsis of proposals' and the conduct of the pre-Congress guiding vote.
Auxin, primarily indole-3-acetic acid (IAA), is a central regulator of growth and development in land plants, but its physiological role in chlorophyte algae remains unclear. Here, we show that exogenous IAA modulates growth in Chlorella sorokiniana, Chlorella variabilis, and Chlamydomonas reinhardtii in a concentration-dependent manner. Low IAA concentrations promoted growth by accelerating the onset of cell division without affecting cell size, whereas higher concentrations inhibited proliferation. Radiotracer assays showed that all three species take up and release IAA across the plasma membrane through a combination of passive diffusion and energy-dependent, saturable processes. Competition by excess unlabeled natural and synthetic auxins further supported the presence of carrier-mediated transport with broad substrate recognition. Phylogenetic analyses identified potential PIN-like auxin exporters in chlorophytes and other non-plant eukaryotes, and structural modeling supported conservation of the overall PIN fold and predicted auxin-binding residues. However, functional assays in Xenopus laevis oocytes, tobacco BY-2 cultured cells, and Arabidopsis thaliana did not support a role for these proteins in directional auxin export. Instead, non-plant PIN homologs localized predominantly to the endoplasmic reticulum and showed limited or no transport activity in heterologous systems. Together, these findings indicate that auxin responsiveness and basic cellular auxin transport predate canonical PIN-mediated directional auxin export, which appears to be a later innovation of the streptophyte lineage.
Periphytic algae play essential roles in retaining heavy metals at the paddy soil-water interface. Climate warming imposes growing stress on paddy ecosystems, and straw biochar is widely used as an agricultural soil amendment. This study employed a combined experimental and modeling approach to investigate how straw biochar modulated Mn(II) and Cd(II) enrichment by the cyanobacterium Nostoc sp. under simulated warming (25-37 °C). Two-way ANOVA confirmed temperature, biochar dosage and their interaction significantly affected metal adsorption (p < 0.001), with biochar switching from mild metal stress alleviation at 25 °C to a synergistic stress amplifier under warming ≥ 34 °C. This shift caused algal biomass to drop by over 60% and metal enrichment capacity to decrease by 44.2-48.4%. Physicochemical characterization indicated that combined stress induced excessive extracellular polymeric substances (EPS) secretion, altered EPS composition, and impaired Mn(II) bio-oxidation. Under warming, straw biochar further caused oxidative damage and redirected algal gene expression from metal metabolism toward cellular defense and matrix production. Mn and Cd exhibited divergent adsorption kinetics, reflecting distinct uptake mechanisms. A random forest model (R2 = 0.77) identified temperature and biochar dose as key negative predictors of metal enrichment. These findings highlight that biochar's effects on algal metal retention depend strongly on temperature, guiding rational biochar application to reduce heavy metal risks in warming paddy soils.
Fucoidan shows promise for food and therapeutic applications; however, inadequate purification leads to inconsistent composition and over-claimed bioactivity. This study rigorously fractionated eight brown algae species from Hokkaido, Japan, using anion-exchange chromatography to generate three primary fractions (FN1, FN2, and FN3). While fractionation enriched sulfate content, it resulted in a >90% reduction in measured antioxidant activity. Multivariate analysis identified the interaction between sulfate and saccharide contents as the principal determinant of this residual activity. Makombu-derived FN3 was then enzymatically digested, treated with activated charcoal, and ultrafiltered to yield FN3 UF, which contained 48.9% sulfate and negligible glucuronic acid, as determined by high-performance anion-exchange chromatography with pulsed amperometric detection. Overall results suggest that the high activity typically reported is largely extrinsic, driven by co-extracted impurities, whereas the true intrinsic activity is trace (~1 μg/mg). Synchrotron small-angle X-ray scattering revealed that this refinement triggers an expansion of the Bragg distance from 12.6 nm (alginate-rich FN1) to 21.7 nm (sulfated FN3), providing the first direct physical evidence that sulfate-driven electrostatic repulsion governs fucoidan's nanostructural organization in solution. These findings establish a previously undocumented physical baseline, proving that rigorous chemical refinement is a mandatory prerequisite for reliable structure-function evaluations of fucoidan.
The genus Prototheca comprises achlorophyllous, obligately heterotrophic algae. To date, six species (P. blaschkeae, P. bovis, P. ciferrii, P. cutis, P. miyajii, and P. wickerhamii) have been recognized as pathogens of vertebrates, including humans, cattle, and companion animals. Protothecal infections are an emerging global concern, as reported cases continue to rise, especially in the veterinary sector. However, knowledge of the pathogenesis of the disease, including hostpathogen interactions remains rudimentary. Therefore, this study was conceived to investigate these interactions using an in vitro model, focusing on three clinically relevant species: P. bovis, P. ciferrii, P. wickerhamii, and, for the first time, the environmental species P. stagnora. Adhesion and internalization were assessed in murine keratinocytes (Kera 308) and macrophages (Raw 264.7) using co-culture assays and confocal microscopy. The findings were further corroborated by scanning and transmission electron microscopy. Bovine-associated species (P. bovis and P. ciferrii) efficiently adhered to macrophages (adhesion rate [AR], 29-83.8%) and were internalized at high levels (internalization rate [IR], 87.5-97.3%). The human-associated P. wickerhamii also interacted with macrophages, albeit to a somewhat lesser extent (AR, 22.6-35.8%; IR, 86.8-94.9%). Similar trends were observed in keratinocytes, although overall adhesion and internalization were less efficient (7.6-19.4% and 0-62%, respectively). In contrast, P. stagnora exhibited poor adhesion to both cell types (0.3-5.1%) with internalization occurring only in macrophages. Electron microscopy-assisted analyses revealed that pathogenic Prototheca species persist intracellularly, residing structurally intact within the macrophage cytoplasm. In summary, the results of this study provide evidence for the invasive potential of pathogenic Prototheca species toward host cells and point to cytosolic escape as a plausible mechanism of intracellular survival of the pathogen. Collectively, this study expands our understanding of Prototheca pathogenicity and highlights interspecies variation as a key determinant of virulence.
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Marine seaweeds are recognized as a rich source of structurally diverse bioactive compounds, particularly sulfated polysaccharides with promising biomedical applications. In the present study, a sulfated polysaccharide Codium tomentosum fraction (PSCT) was extracted from the Moroccan green seaweed Codium tomentosum and subjected to comprehensive chemical, structural, and biological characterization. The extraction yield reached 22.01%, and the polysaccharide fraction was mainly composed of neutral sugars (66.84%), along with significant levels of sulfate groups (8.73%) and uronic acids (4.13%). Monosaccharide analysis revealed a predominance of galactose and arabinose, indicating a complex heteropolysaccharide structure. Spectroscopic and morphological analyses (FTIR, XRD, UV-Vis, and SEM-EDS) suggested predominantly amorphous characteristics and confirmed the sulfated profile of the extract. Biological evaluation demonstrated that PSCT exhibits multifunctional bioactivities. The extract showed notable antiviral activity against Herpes Simplex Virus 1 (HSV1), with an EC50 value of 12.22 ± 2.90 µg/mL and no detectable cytotoxicity (CC50 > 200.00 µg/mL). In addition, PSCT displayed strong antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans, with remarkably low MIC values ranging from 0.05 to 0.78 mg/mL. Furthermore, antioxidant assays revealed concentration-dependent activity, with up to 68% DPPH radical scavenging and an IC50 of 1.25 mg/mL, indicating a moderate antioxidant potential, along with notable reducing power in the FRAP assay. Overall, these findings highlight the potential of C. tomentosum-derived polysaccharides as multifunctional natural agents with antiviral, antimicrobial, and antioxidant properties, supporting their prospective application in pharmaceutical and biomedical fields.
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Carrageenans are versatile sulfated marine galactans that possess attractive modification-dependent bulk properties, making them prime candidates for various cosmetic, drug delivery, and food-related applications. The structural diversity and intrinsic complexity of carrageenans hamper access to homogeneous polysaccharides, limiting the development of many carrageenan-based applications. We devised a synthetic strategy for the acquisition of a panel of γ-carrageenan-derived oligosaccharides with varying sulfation profiles and chain length. To that end, we synthesized a set of specialized building blocks with an elaborate multilevel protecting group hierarchy, tailor-made to specifically accommodate the structural complexity of carrageenans. In doing so, we uncovered interdependent protecting group and reactivity constraints, which we resolved strategically to adapt the synthetic route across the panel of carrageenans and minimize trade-offs. Assembly of di-, tri-, and tetrasaccharides with precise control over monomer connectivity and regiodefined sulfation on a conjugation-ready linker showcased the first total synthesis of homogeneous carrageenan oligogalactans. We demonstrated that the application of the curated panel enabled elucidation of the effect of γ-carrageenan molecular features on IL-8 binding preferences via electrochemical sensing and surface analyses.
In the original publication [...].
DNA reactions on solid surfaces often suffer from low efficiency due to limited mass transfer and slow reaction kinetics, which greatly limits their biomedical applications. Here, we report a strategy to construct dynamic DNA biointerfaces based on moveable algal microrobots (AMs), whose autonomous motion-generated micro-hydrodynamics profoundly affects interfacial DNA reactions. After immobilizing DNA strands on the AMs, we uncover that the swimming speed of these microrobots is positively correlated with the kinetics of different DNA reactions from simple hybridization to complex enzymatic/nonenzymatic amplification reactions. This "motion-enhanced" effect mainly stems from the convection and mixing generated around the swimming cells, which greatly improve mass transfer velocity, thereby reducing hybridization times to minutes and enhance reaction efficiency. As a result, this feature is demonstrated to be useful in achieving ultrafast molecular recognition, ultrasensitive nucleic acid detection, and autonomous cell assembly in complex biological media. Our work provides a paradigm shift for overcoming the reaction efficiency bottleneck of DNA interface and paves a new avenue for designing intelligent bio-hybrid systems.
Lakes are important sources of greenhouse gases, yet bloom-driven emissions are often assessed from total algal biomass, ignoring algal functional composition. This study examined how cyanobacteria (Microcystis aeruginosa), green algae (Chlorella vulgaris), diatoms (Cyclotella meneghiniana), and dominance-based mixtures regulate DOM transformation and CO2/N2O production under eutrophic conditions. It integrated to pure-culture experiments, water-sediment microcosms, sterilization controls, DOM fluorescence spectroscopy, gas monitoring, and metagenomics to resolve an algae-DOM-microbe-gas cascade. Cyanobacteria produced protein-like DOM and stimulated carbon mineralization, with CO2 exceeding 20 mmol L-1 by day 36; cyanobacteria-dominant mixtures followed a similar high-CO2 trajectory. Green algae generated tyrosine-like DOM and caused the strongest NO2- accumulation, reaching 5.21 mg L-1 by day 21, corresponding to the highest N2O production; this pattern also occurred in green-algae-dominant mixtures. Diatom-only and diatom-dominant treatments favored humic-like DOM, organic carbon retention, and the weakest short-term CO2/N2O accumulation. Sterilization reduced inorganic carbon and greenhouse gas production, supporting microbial control. Background summer metagenomics provided functional context, showing algal-DOM turnover potential through carbon metabolism, glycolysis/gluconeogenesis, pyruvate metabolism, and the TCA cycle, while nirK and other nitrogen genes indicated capacity for substrate-driven incomplete nitrogen reduction. Functional differentiation among Candidatus_Planktophila, Limnohabitans, Rhodoferax, and Cyanobium linked DOM processing with potential gas-production pathways. These results show algal community composition, rather than biomass alone, regulates greenhouse gas production by shaping DOM quality, nutrient intermediates, and microbial C-N pathways. Incorporating algae composition into greenhouse gas assessment, this novel algae-DOM-microbe-gas framework provides mechanistic support for improving eutrophication management and lake-emission mitigation.
Algae have shown an effective defense system that enables their survival in environments exposed to radiation stress, especially from ultraviolet (UV) light and ionizing radiation. Their protective system comprises specific photoprotective chemicals along with a multilayered antioxidant strategy that encompasses both non-enzymatic and enzymatic approaches. In this defence system, scytonemin and mycosporin-like amino acids play a crucial role in photoprotection by functioning as natural sunscreen with high photostability and strong UV-absorbing capacity. These chemical compounds also possess antioxidant properties that help minimize indirect damage produced by reactive oxygen species formed after radiation exposure. Scytonemin becomes significant due to its capability to block 90% of UV-radiation, effectively absorbing all types of UV (A, B and C) wavelengths. In the process of quenching photosensitization products and scavenging free radicals, carotenoids act as a stress reliever by preventing oxidative damage and lipid peroxidation. The internally generated ROS gets neutralized by algae, which utilize an enzymatic antioxidant system. In the enzymatic defence system of algae, ascorbate peroxidase, catalase, superoxide dismutase and glutathione reductase play important roles in ROS elimination. Additionally, α-tocopherol and ascorbic acid which are non-enzymatic antioxidants, complement the enzymatic reaction described above. The biochemical properties of these photoprotective and antioxidant compounds have significant biotechnological implications, applications in pharmaceuticals, cosmetics, anticancer treatments, nutraceuticals and antimicrobials. Interestingly, exposure to low-dose radiation has been shown to enhance algae growth, stimulate the production of valuable metabolites for biofuels and biomaterials and strengthen the resilience of cultivated strains against stressors.
Developea is a poorly studied group of flagellated protists, with only seven species known to date. It is closely related to parasitic oomycetes, hyphochytriomycetes, Pirsoniales, and photosynthetic ochrophytes (e.g., diatoms and brown algae), altogether forming the large clade Gyrista within supergroup Stramenopiles. Due to their deep phylogenetic position and phagotrophic feeding mode, developeans might have preserved ancestral characteristics shared with related large and important sister groups. Despite their cosmopolitan distribution, only few environmental 18S rRNA gene sequences related to Developea are known. Here we describe 12 new strains which represent eight new species and two new genera, as well as the previously described species Developayella elegans. We provide feeding experiments on diverse eukaryotic prey, including red algae, diatoms, and heterotrophic flagellates. The ability of the new developean species to successfully consume red algae represents missing piece of the previously postulated developean-like phagoheterotrophic model for the symbiotic ancestor of photosynthetic stramenopiles. Three species, including D. elegans, are omnivorous, i.e. able to survive on either eukaryotic or prokaryotic prey. Finally, we observe new and rare morphological features for Developea, such as facultative multiflagellated life stages, cysts and self-aggregation. These features might have been present in the ancestor of Stramenopiles.
Kelp, brown macroalgae in the order Laminariales, provide ecosystem services vital to ocean biodiversity. However, kelp forests worldwide are declining due to abiotic stressors such as ocean warming. In this study, we present results from high-resolution confocal microscopy and in vivo imaging system imaging using protocols developed to visualize kelp gametophyte cells exposed to heat-stress treatments. Imaging revealed chloroplast mislocalization, fragmentation, and subsequent loss of chloroplasts in heat-stressed gametophyte cells. Additionally, nuclei exhibited fragmentation and a progressive loss of fluorescent signal, and the associated microbiome proliferated under various heat-stress treatments. Notably, because brown algae possess a continuous outer membrane that connects the nuclear envelope and the chloroplast envelope, these observations suggest a cellular vulnerability underlying thermal sensitivity in brown macroalgae. Finally, by comparing heat-stress tolerant and heat-stress sensitive genotypes, we found that genotypes with higher heat tolerance exhibited substantially fewer abnormalities compared to sensitive ones.
Gamma-aminobutyric acid (GABA) is a four-carbon non-proteinogenic amino acid that is primarily known for its role as an inhibitory neurotransmitter in mammals. It is synthesized from glutamate by the enzyme L-glutamic acid decarboxylase and metabolized via the GABA shunt pathways. GABA is known to influence various metabolic processes, and recent studies have shown its influence on lipid metabolism. This review explores the distinct relationship between GABA and lipid metabolism by highlighting their role in physiological processes in animals, plants, and microalgae. In animals, GABA acts as a metabolic regulator, particularly in the liver, where it mitigates diseases associated with fat accumulation, such as obesity, hyperlipidemia, and type 2 diabetes mellitus, by modulating adipogenesis and lipogenesis (fat synthesis and accumulation), lipolysis (fat breakdown), and thermogenesis and oxidation (energy expenditure). Conversely, in plants and algae, it plays a vital role in stress responses and developmental processes by suppressing lipid membrane degradation and by promoting lipid accumulation. We also delve into the metabolic pathways through which GABA interacts with lipid metabolism, including its connection to the tricarboxylic acid cycle and its involvement in the GABA shunt. This review underscores the multifaceted nature of GABA, revealing its critical contribution to lipid homeostasis, highlighting its relevance in metabolic disorders in animals, and stress responses in both plants and algae. Despite being a relatively underexplored area, the GABA-lipid relationship holds substantial significance due to its involvement in varied physiological processes, suggesting promising avenues for future therapeutic research and biotechnological applications.
Phytoplankton serve as a source of nutrients for bacteria in the marine environment. The interactions between algae and bacteria are known to include mutualism, commensalism, competition, or antagonism. This occurs in the microenvironment surrounding phytoplankton cells, the phycosphere, an interface rich in nutrients and organic molecules exuded by the cells. Here, based on in situ observations and on an in vitro interaction study, we report on a novel form of starvation-induced hunting that the cells of selected Vibrio species exert on dinoflagellates. The results showed that Vibrio atlanticus was capable of attacking and killing the dinoflagellate Alexandrium pacificum ACT03. Briefly, the observed mechanism of algal-killing consists of first, the 'immobilization stage' involving the secretion of algicidal metabolites that disrupt the flagella of the algae. In the 'attack stage', Vibrios simultaneously surround algal cells at high density for a brief period without invading them. Finally, the 'killing stage' in which the lysis and consumption of the dinoflagellates occur. By using a combination of biochemical, proteomic, molecular, and fluorescence microscopy approaches, we showed that this relationship is not related to the decomposition of algal organic matter, Vibrio quorum-sensing pathways, toxicity of the algae, or pathogenicity of the bacterium but is conditioned by nutrient stress, iron availability, and linked to the iron-vibrioferrin transport system of V. atlanticus. This is the first evidence of a new mechanism that could be involved in regulating Alexandrium spp. blooms and giving Vibrio a competitive advantage in obtaining nutrients from the environment. The interaction model we propose here suggests that Vibrio could play a role in regulating the proliferation of Alexandrium spp., giving it a competitive advantage in obtaining nutrients from the environment.