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Summary The origin story of land plants – the pivotal evolutionary event that paved the way for terrestrial ecosystems of today to flourish – lies within their closest living relatives: the streptophyte algae. Streptophyte cell wall composition has evolved such that profiles of cell wall polysaccharides can be used as taxonomic markers. Since xyloglucan is restricted to the streptophyte lineage, we hypothesized that fungal enzymes evolved in response to xyloglucan availability in streptophyte algal or land plant cell walls. The record of the origins of these enzymes is embedded in fungal genomes, and comparing genomes of fungi that share an ancient common ancestor can provide insights into fungal interactions with early plants. This Viewpoint contributes a review of evidence underlying current assumptions about the distribution of xyloglucan in plant and algal cell walls. We evaluate evolutionary scenarios that may have given rise to the observed distribution of putative xyloglucanases in fungi and discuss possible biological contexts in which these enzymes could have evolved. Our findings suggest that fungal xyloglucanase evolution was more likely driven by land plant diversification and biomass accumulation than by the first origins of xyloglucan in streptophyte algal cell walls. [ABSTRACT FROM AUTHOR]

Microalgae with increased amount of biomass and lipid yield are crucial for biodiesel production. Mixotrophic cultivation has prominence for increasing the micro‐algal cell concentration and hence the volumetric productivity owing to independent utilization of both the photo‐assimilation of CO2 and oxidative assimilation of organic carbon sources. In this study, Ankistrodesmus sp. IFRPD 1061 was examined under various concentrations of sodium acetate for concentration and productivity of biomass and lipid, lipid contents (LCs), and fatty acid profiles. The optimum condition was obtained at Day 21 with 10 mM sodium acetate, which gave 6.940 ± 0.057 g L−1 biomass concentration, 327.619 ± 2.020 mg L−1 day−1 biomass productivity, 2.795 ± 0.191 g L−1 lipid concentration, 131.955 ± 9.275 mg L−1 day−1 lipid productivity, and 40.286 % ± 3.079 % w/w LC. The optimum condition (10 mM sodium acetate) in an open pond cultivation attained maximum values at Day 14, that is, 0.575 ± 0.004 g L−1 biomass concentration, 38.161 ± 0.076 mg L−1 day−1 biomass productivity, 0.203 ± 0.002 g L−1 lipid concentration, 13.440 ± 0.197 mg L−1 day−1 lipid productivity, and 35.219 % ± 0.585 % w/w LC. The lipids recovered from mixotrophic micro‐algae were primarily unsaturated fatty acids, which are appropriate to produce biodiesel. The results revealed that a 10 mM sodium acetate concentration can enhance lipid accumulation within algal cells. [ABSTRACT FROM AUTHOR]

Caulerpa is a genus of green macroalgae that lives in tropical and subtropical coastal waters. It is an intriguing organism because, despite having plant-like structures, it is one giant cell – which, next to multiple nuclei, chloroplasts, and mitochondria, also contains endo- and epiphytic bacteria. The role of these bacteria is unknown, but they might impact the growth and development of the host, adaptation to environmental parameters, and, hence, the ecological success of these algae. We hypothesised that increased sulphide concentrations would trigger a significant shift in the microbial community composition associated with C. prolifera rhizoids, favouring sulphide-oxidizing bacteria. To test this hypothesis, we conducted a mesocosm experiment incubating C. prolifera in sediments with different sulphide concentrations and analysed the algal photosynthesis, growth, and microbiome composition. While photosynthesis was not affected, the Caulerpa weight-based growth rate decreased linearly with increasing sulphide concentration. To analyse the microbiome, we extracted DNA and RNA from the fronds, rhizoids, and the accompanying sediments and performed 16S amplicon sequencing. The microbiome of the fronds was unaffected in both the DNA and RNA samples. However, an increase in sulphide concentration coincided with a decrease in the relative abundance of sulphate-reducing bacteria associated with Caulerpa rhizoids, particularly from the family Desulfocapsaceae. In the RNA samples, potential sulphide oxidisers of the rhizoid-associated members of the Beggiatoaceae were detected. Our results suggest that the rhizobiome of Caulerpa plays a significant role in its adaptation to sulphide-rich environments, offering new insights into the complex interactions within marine holobionts. [ABSTRACT FROM AUTHOR]

The phenolic antioxidant 2,6-Di-tert-butyl-p-cresol (BHT) has been detected in various environments and is considered a potential threat to aquatic organisms. Algal-bacterial interactions are crucial for maintaining ecosystem balance and elemental cycling, but their response to BHT remains to be investigated. This study analyzed the physiological and biochemical responses of the microalga Isochrysis galbana and the changes of associated bacterial communities under different concentrations of BHT stress. Results showed that the biomass of I. galbana exhibited a decreasing trend with increasing BHT concentrations up to 40 mg/L. The reduction in chlorophyll, carotenoid, and soluble protein content of microalgal cells was also observed under BHT stress. The production of malondialdehyde and the activities of superoxide dismutase, peroxidase, and catalase were further determined. Scanning electron microscopy analysis revealed that BHT caused surface rupture of the algal cells and loss of intracellular nutrients. Proteomic analysis demonstrated the upregulation of photosynthesis and citric acid cycle pathways as a response to BHT stress. Additionally, BHT significantly increased the relative abundance of specific bacteria in the phycosphere, including Marivita, Halomonas, Marinobacter, and Alteromonas. Further experiments confirmed that these bacteria had the ability to utilize BHT as the sole carbon resource for growth, and genes related to the degradation of phenolic compounds were detected through pangenome analysis. [ABSTRACT FROM AUTHOR]

Exo‐β‐(1,3)‐glucanases are promising enzymes for use in the biofuel industry as they hydrolyse sugars such as laminarin, a major constituent of the algal cell wall. This study reports structural and biochemical characterizations of Aspergillus oryzae exo‐β‐(1,3)‐glucanase (AoBgl) belonging to the GH5 family. Purified AoBgl hydrolyses β‐(1,3)‐glycosidic linkages of the oligosaccharide laminaritriose and the polysaccharide laminarin effectively. We have determined three high‐resolution structures of AoBgl: (a) the apo form at 1.75 Å, (b) the complexed form with bound cellobiose at 1.73 Å and (c) the glucose‐bound form at 1.20 Å. The crystal structures, molecular dynamics simulation studies and site‐directed mutagenesis reveal the mode of substrate binding and interactions at the active site. The results also indicate that AoBgl effectively hydrolyses trisaccharides and higher oligosaccharides. The findings from our structural and biochemical studies would aid in rational engineering efforts to generate superior AoBgl variants and similar GH5 enzymes for their industrial use. [ABSTRACT FROM AUTHOR]

The marine Bacteroidota Zobellia galactanivorans has a polysaccharide utilization locus dedicated to the catabolism of the red algal cell wall galactan carrageenan and its unique and industrially important α‐3,6‐anhydro‐D‐galactose (ADG) monosaccharide. Here we present the first analysis of the specific molecular interactions that the exo‐(α‐1,3)‐3,6‐anhydro‐D‐galactosidase ZgGH129 uses to cope with the strict steric restrictions imposed by its bicyclic ADG substrate — which is ring flipped relative to D‐galactose. Crystallographic snapshots of key catalytic states obtained with the natural substrate and novel chemical tools designed to mimic species along the reaction coordinate, together with quantum mechanics/molecular mechanics (QM/MM) metadynamics methods and kinetic studies, demonstrate a retaining mechanism where the second step is rate limiting. The conformational landscape of the constrained 3,6‐anhydro‐D‐galactopyranose ring proceeds through enzyme glycosylation B1,4→[E4]≠→E4/1C4 and deglycosylation E4/1C4→[E4]≠→B1,4 itineraries limited to the Southern Hemisphere of the Cremer–Pople sphere. These results demonstrate the conformational changes throughout catalysis in a non‐standard, sterically restrained, bicyclic monosaccharide, and provide a molecular framework for mechanism‐based inhibitor design for anhydro‐type carbohydrate‐processing enzymes and for future applications involving carrageenan degradation. In addition, our study provides a rare example of distinct niche‐based conformational itineraries within the same carbohydrate‐active enzyme family. [ABSTRACT FROM AUTHOR]

The high-altitude pre-Andean region of the Atacama Desert is characterized by its stark volcanic rock formations and unique hydrothermal gypsum outcrops (gypcrete) that it hosts. This study delves into the biomolecular composition of the endolithic phototrophic microbes that thrive within these gypcretes. Using advanced Raman spectroscopy techniques, including Raman imaging (complemented by microscopic and 3D microscopic observations), herein we unveil new insights into the adaptive strategies of these gypsum-inhabiting algae. Our Raman imaging results provide a detailed chemical map of carotenoids associated with microbial colonization. This map reveals a significant gradient in pigment content, highlighting a critical survival mechanism for algae and cyanobacteria in this polyextreme environment. Intriguingly, we detected signals for carotenoids not only in the algae-colonized layer, but also deeper within the gypsum matrix - indicating pigment migration following cell disruption. In addition, we conducted an in-depth analysis of individual algal cells from the Trebouxiaceae family, noting their color variations from green to orange, plus describing the spectral differences in detail. This investigation identified in-vivo pigments (carotenoids, chlorophyll) and lipids at the cellular level, offering a comprehensive view of the molecular adaptations enabling life in one of the Earth's most extreme habitats. [ABSTRACT FROM AUTHOR]

Achieving food sustainability is one of the biggest challenges in the new millennium. Plant factory cultivation systems provide an alternative for food sustainability, while they often suffer from algal blooms. The overuse of conventional algaecides has caused significant environmental pollution and concerns about food security. Here, we design a nanoenabled metal‐organic algaecide that is self‐assembled from natural polyphenols and two functional metal ions for providing shading effects and delivering active ingredients synergistically to suppress algal blooms. Black wattle tannin (BWT) and Fe3+ ions are utilized to develop self‐assembled FeBWT nanoalgaecides with significant shading effects for decreasing light transmission (up to 97 %) and effectively inhibiting algal photosynthesis. Further, the FeBWT is functionalized with Cu2+ ions (bimetallic Cu/FeBWT) to target the algal cells and release Cu2+ ions via phenolic‐mediated cell surface interactions, thus enhancing the inhibition efficiency. Importantly, the biosafety of Cu/FeBWT is demonstrated through toxicity tests on zebrafish and NIH3T3 cells. In our real‐world field test, the Cu/FeBWT demonstrates high algal inhibition performance (>95 %, over 30 days), and enhances the accumulation of food nutrients in model plant lettuces. Collectively, the supramolecular metal‐organic nanoalgaecide provides a promise for nanoagrochemical application and promotes food sustainability and security. [ABSTRACT FROM AUTHOR]

This study investigated the changes in sea ice temperature, microalgae species distribution, shape changes, and photosynthetic activity observed in the first‐year ice that forms in winter in Saroma‐ko Lagoon, Hokkaido, Japan. Temperatures at the bottom of the ice remained constant at −1.7°C, near the freezing point, while they varied between −6 and −1°C with diel fluctuations at the surface layer. Carefully collected algal samples showed high photosynthetic quantum yield and acclimation to the light intensities of individual ice layers; this indicates that the algal photosynthetic activity responds to dynamic changes in the ice environment, such as variations in temperature, salinity, and brine space. The algal communities consisted of more than 95% diatoms. Smaller algal cells were distributed in the upper layer of the sea ice compared to the lower layers. Chaetoceros sp., the dominant small‐cell species, was evenly distributed throughout the layers. In contrast, Detonula confervacea, the dominant large‐cell species, was unevenly distributed in the lower layer, with smaller colony size and cell volume in the upper layer. The shape differences observed in this species were thought to be a response to the changing environment within the first‐year sea ice. [ABSTRACT FROM AUTHOR]

The term 'sphaerocrystals' (also sphaerites) in classic plant morphology was usually applied to spherical bodies visible in polarized light with a characteristic 'Maltese cross' and consisting of both inorganic and organic compounds. Initially sphaerocrystals were found in algal cells but were later also discovered in various organs of vascular plants (including seeds). Several authors noticed spherical particles on the seed surface and in testa cells of some Euphorbia species but a comprehensive study of this character in the genus (including the morphological origin of such particles) has not been carried out. We studied 72 species belonging to all 21 sections of Euphorbia subgenus Esula for presence of spherical particles on seed surface and in the testa using scanning, transmission, confocal laser electron microscopy, and light microscopy; histochemical and element analyses were also involved. We found that these particles have the same morphological features (including the demonstration of 'Maltese cross' in polarized light) as the 'classic' sphaerocrystals. We have recorded sphaerocrystals in 53 sampled species belonging to 20 sections of Euphorbia subgenus Esula ; they are localized mostly in mesotesta cells and in some species are exuded onto the seed surface where they are often aggregated into clusters. Sphaerocrystals were absent in the sampled species (with one exception) of one of the major clades of the subgenus, formed by E. sect. Helioscopia and E. sect. Holophyllum. The absence of sphaerocrystals in this early divergent lineage of E. subgen. Esula may be related with adaptation of species of this lineage to more mesic habitats. [ABSTRACT FROM AUTHOR]

Phytoplankton are an important part of aquatic ecosystems and substantially contribute to primary productivity. Under certain conditions, phytoplankton can grow or cluster in large numbers, resulting in enormous economic losses and serious threats to human life and health. In this study, complex causative species of algal blooms were examined and regulatory factors were determined in a reservoir formed by harbor construction. The reservoir is isolated from the harbor by sluice gates, forming a separate water region. Twelve species of phytoplankton, including normally and abnormally blooming species, were identified to be causing blooms in this continuous water. Different from the areas where simple algae caused blooms, multiple bloom-causative species, which were completely different, occurred at several stations. In this study area, whereas the abundance of algal cells was above 10 million cells/L, the total phosphorus concentration was higher than 0.2 mg/L. When the total phosphorus concentration was lower than 0.2 mg/L, there was no algal bloom. In waters with total algal cell abundance over 10 million, the N/P ratios were all <8. This study indicates that the occurrence of algal blooms in this water was influenced by the concentrations of total nitrogen and phosphorus, and total phosphorus plays a more important role. [ABSTRACT FROM AUTHOR]

The main focus of this study was on a biorefinery approach using the microalga Haematococcus pluvialis for the production of the valuable bioproduct astaxanthin. In addition, the study aimed to explore the use of residual algal biomass for biodiesel production. Accordingly, the impact of two light intensities (16 and 66 µmol photons m−2 s−1) during short (20 days) and prolonged (50 days) photoperiods was examined on the growth parameters, chlorophylls, astaxanthin, and biochemical compounds along with fatty acid (FA) profile of H. pluvialis. Moreover, the physical and chemical properties of H. pluvialis derived biodiesel were evalutaed. Results revealed that higher light exposure (66 µmol photons m−2 s−1) increased the algal biomass (g L−1) and biomass productivity (mg L−1 d−1) of H. pluvialis during both short and prolonged photoperiods. Additionally, the highest chlorophyll (a + b) (mg g−1) content was found in cultures exposed to low light (16 µmol photons m−2 s−1) during 20 and 50 days of the experiment. Whilst the cultures under higher light conditions exhibited the highest astaxanthin content (mg g−1) over the induction period. Furthermore, the biochemical composition of cells changed under different light intensities in this study. The algal cultures under higher light conditions remarkably increased in lipid content along with a significant decrease in protein and carbohydrate contents. Besides, all the FA components in algal biomass under low and higher light conditions were acceptable to produce biodiesel. The highest theoretical methane potential was obtained in algal cells cultivated under higher light conditions with a short photoperiod. The results of this study hold the potential to contribute significantly towards the development of an integrated, cost-effective biorefinery strategy aimed at the simultaneous production of astaxanthin and biodiesel. [ABSTRACT FROM AUTHOR]

The influence of microalgae on the formation of associated prokaryotic assemblages in halophilic microbial communities is currently underestimated. The aim of this study was to characterize shifts in prokaryotic assemblages of halophilic microalgae upon their transition to laboratory cultivation. Monoalgal cultures belonging to the classes Chlorodendrophyceae, Bacillariophyceae, Trebouxiophyceae, and Chlorophyceae were isolated from habitats with intermediate salinity, about 100 g/L, nearby Elton Lake (Russia). Significant changes were revealed in the structure of algae-associated prokaryotic assemblages, indicating that microalgae supported sufficiently diverse and even communities of prokaryotes. Despite some similarities in their prokaryotic assemblages, taxon-specific complexes of dominant genera were identified for each microalga species. These complexes were most different among Alphaproteobacteria, likely due to their close association with microalgae. Other taxon-specific bacteria included members of phylum Verrucomicrobiota (Coraliomargarita in assemblages of Navicula sp.) and class Gammaproteobacteria (Salinispirillum in microbiomes of A. gracilis). After numerous washings of algal cells, only alphaproteobacteria Marivibrio remained in all assemblages of T. indica, likely due to a firm attachment to the microalgae cells. Our results may be useful for further efforts to develop technologies applied for industrial cultivation of halophilic microalgae and for developing approaches to obtain new prokaryotes with a microalgae-associated lifestyle. [ABSTRACT FROM AUTHOR]

This study focuses on determining the optimum external operating parameters of algal cell lysis for extraction of bio-oil from Chlorella biomass. Response surface methodology has been applied to a regression analysis model for optimizing solvent ratios, i.e., ethyl acetate to ethanol (E.A.:E) ratio for maximum extraction of bio-oil and aqueous deep eutectic solvent to biomass (aDES:biomass) ratio for algal pretreatment for the enhanced yield of bio-oil. Optimized process conditions were 15 min of homogenization combined with ultrasonication (hybrid method). The aDES:biomass ratio of 8.25 caused the highest cell disruption efficiency to liberate bio-oil from encapsulated cells. The solvent ethyl acetate to ethanol ratio (E.A.:E) was optimum at 0.8 for maximum extraction of bio-oil, and studies indicated a maximum bio-oil yield of 94.0% using this hybrid pretreatment process combined with ultrasonication and homogenization. The GC–MS characterization technique was used to analyze the bio-oil, which showed it consisted of 67.93% Di-ethyl phthalate (DEP) and 32.07% esters compounds (C12–C40 hydrocarbons range). The produced DEP from Chlorella biomass using this sustainable green approach is very promising. The estimated cost was around Rs 49 per gm (equivalent to Rs 664.56 for 13.58 gm), which indicates the potential for a cost-effective method to produce pure DEP from Chlorella biomass. [ABSTRACT FROM AUTHOR]

Microalgae and seaweed have been consumed as food for several decades to combat starvation and food shortages worldwide. The most famous edible microalgae species are Nostoc, Spirulina, and Aphanizomenon, in addition to seaweeds, which are used in traditional medicine and food, such as Nori, which is one of the most popular foods containing Pyropia alga as a major ingredient. Recently, many applications use algae-derived polysaccharides such as agar, alginate, carrageenan, cellulose, fucoidan, mannan, laminarin, ulvan, and xylan as gelling agents in food, pharmaceuticals, and cosmetics industries. Moreover, pigments (carotenoids particularly astaxanthins, chlorophylls, and phycobilins), minerals, vitamins, polyunsaturated fatty acids, peptides, proteins, polyphenols, and diterpenes compounds are accumulated under specific cultivation and stress conditions in the algal cells to be harvested and their biomass used as a feedstock for the relevant industries and applications. No less critical is the use of algae in bioremediation, thus contributing significantly to environmental sustainability. This review will explore and discuss the various applications of microalgae and seaweeds, emphasising their role in bioremediation, recent products with algal added-value compounds that are now on the market, and novel under-developing applications such as bioplastics and nanoparticle production. Nonetheless, special attention is also drawn towards the limitations of these applications and the technologies applied, and how they may be overcome. [ABSTRACT FROM AUTHOR]

Dissolved organic matter and nutrients released from leaf litter are important cross‐ecosystem resources supporting freshwater food webs. Dissolved organic matter supports heterotrophic organisms in freshwater communities. However, the role of nutrients released from leaf litter in the autochthonous production in aquatic ecosystems is not well understood. Therefore, we investigated how dissolved nutrients released from leaf litter affect algal growth, biomass production, and cellular elemental ratios. Specifically, we experimentally examined the response of green algae to nitrogen (N) and phosphorus (P) released from leaf litter of 11 temperate tree species and the degree of deficiency of nutrient elements other than N and P relative to algal demand in these litter leachates by supplementing these elements. We found that algal growth did not significantly increase with dissolved N or P in the leaf leachates. In contrast, algal biomass production increased with dissolved N concentration, regardless of amendment. Algal growth and production limitation by deficiency of elements other than N and P was found only in the leachate of Japanese hemlock, indicating that the concentrations or release efficiencies of these elements in this leaf litter were lower than those of N and P relative to algal requirements. More importantly, leaf litter leachates from different tree species altered algal cell quotas and C:N:P ratios, which would affect secondary production. These results suggest that variations in leaf litter leachate stoichiometry caused by vegetation change would affect the abundance and chemical composition of phytoplankton, and thus the trophic transfer efficiency between phytoplankton and herbivorous zooplankton. [ABSTRACT FROM AUTHOR]

This study aimed to assess the impact of microalgal concentrations in diets on the settlement and metamorphosis stages of pediveliger larvae and spat of Crassostrea gigas oysters. Diets containing microalgal concentrations of 8, 12, and 16×104 cells mL-1 were administered for seven days during the larval settlement phase of pediveliger larvae. In the metamorphosis and postlarval cultivation phases, diets with microalgal concentrations of 8, 16, 24, and 32×104 cells mL-1 and a control group without food were tested for 14 and 21 days, respectively. Growth, yield, and survival were assessed every seven days. The diet comprised 30% Isochrysis galbana and 70% Chaetoceros muelleri microalgae. In the metamorphosis phase, the results revealed no significant differences in larval metamorphosis rate and survival across the tested diets. The concentrations exhibited similar survival in the spat with an initial average shell height of 0.657 ± 0.05 mm, with a significant difference only in growth. In the spat with an initial average shell height of 0.830 ± 0.12 mm, no differences in survival were observed among the tested concentrations. We concluded that diets of 12 and 16×104 cells mL-1 provide high rates of larval metamorphosis and spat yield during the larval settlement and metamorphosis phases. During the spat cultivation phases, diets of 32 and 24×104 cells mL-1 could optimize the cultivation time and yield of C. gigas spat in the laboratory. However, when considering survival alone, no advantage was found in providing a diet with a microalgal concentration above 8×104 cells mL-1 across all C. gigas oyster cultivation phases. [ABSTRACT FROM AUTHOR]

In this study, the regulation of abscisic acid (ABA) on cell growth and lipid biosynthesis was investigated under salt-induced stress in Chlorella pyrenoidosa. It is found that as suffering from only salt stress, although the lipid content of single cell was improved, the inhibitory effects of stress on cell proliferation was visible. When the algal cells were exposed to salt stress and ABA conditions, lipid productivity was increased (45.35 mg L-1 d-1) by 1.17-fold compared to that of control cells (20.91 mg L-1 d-1), and the inhibition to cell growth was relieved. Transcriptomic analysis revealed that after adding ABA, these genes involved in antioxidant activity, jasmonic acid (JA) biosynthesis, and lipid biosynthesis were upregulated. Subsequently, we observed that the levels of glutathione, total antioxidant capacity, trehalose, and JA were elevated and the levels of reactive oxygen species were reduced. This study presents an effective approach to improve lipid production in algal cells, a new mechanism on that ABA alleviates intracellular oxidative stress through JA signaling pathway was elaborated. [ABSTRACT FROM AUTHOR]

Light quality has significant effects on the growth and metabolite accumulation of algal cells. However, the related mechanism has not been fully elucidated. This study reveals that both red and blue light can promote the growth and biomass accumulation of Chlorella pyrenoidosa, with the enhancing effect of blue light being more pronounced. Cultivation under blue light reduced the content of total carbohydrate in Chlorella pyrenoidosa, while increasing the content of protein and lipid. Conversely, red light decreased the content of protein and increased the content of carbohydrate and lipid. Blue light induces a shift in carbon flux from carbohydrate to protein, while red light transfers carbon flux from protein to lipid. Transcriptomic and metabolomic analysis indicated that both red and blue light positively regulate lipid synthesis in Chlorella pyrenoidosa, but they exhibited distinct impacts on the fatty acid compositions. These findings suggest that manipulating light qualities can modulate carbon metabolic pathways, potentially converting protein into lipid in Chlorella pyrenoidosa. [ABSTRACT FROM AUTHOR]

Increasing demand for rare earth elements (REEs) has stimulated research on novel recovery methods from sources like industrial effluents. Our recent study demonstrated that algal biofilms are good candidates for the adsorption of REEs and that the extracellular polymeric substances (EPS) within the biofilm were a key accumulator of REEs. In this work, we measured the desorption kinetics, extents, and selectivity of REEs from the algae Euglena mutabilis in suspensions and biofilms using aqueous solutions of HCl at pH between 1.5 and 4, and Na2EDTA at pH 5. We examined the potential for reusing suspended and biofilm biomass for repeated adsorption–desorption cycles. The desorption kinetics were similar for suspensions and biofilms, with equilibrium being reached within 20 min. The extent of desorption was higher in biofilms with 86% and 95% desorption, compared to suspensions which had 72% and 74% desorption using HCl and Na2EDTA, respectively. We postulate that the difference between suspensions and biofilms is attributed to the binding sites in the EPS matrix of the biofilm being more readily protonated than those at the algal cell wall surface. Heavy REEs were found to preferentially desorb at pH 4 over lighter REEs. After 3 repeated adsorption–desorption cycles, the adsorption capacity of biofilms increased by 280% and 80% using HCl and Na2EDTA, respectively, compared to an 80% decrease in biosorption capacity for the suspension. The increase in biofilm biosorption capacity was attributed to the simultaneous desorption of divalent cations alongside REEs from the EPS increasing the number of available binding sites. [ABSTRACT FROM AUTHOR]

As two significant pollutants, the increased concentrations of copper ions and microplastics in coastal waters pose a substantial threat to the health of marine ecosystems. This study explored the individual and combined toxic effects of copper ions and microplastics on the marine diatom Skeletonema costatum. The results indicated that copper ions at a concentration of 0.05 mg/L exerted a negative impact on the growth of S. costatum; however, the influence of microplastics on algal cell growth was more complex: there was no significant inhibition of algal cell growth observed within the first 72 h of cultivation, but a pronounced negative effect on cell growth was noted between 72 and 96 h, with high concentrations (10.00 mg/L) of microplastics even causing a premature stagnation phase in algal cell growth. When both pollutants were present simultaneously, their impact on cell growth was similar to that of the microplastic pollution group, yet the growth condition was better than that of the copper ion pollution group. Through investigation of adsorption rates and toxicity mitigation rates, it was found that the adsorption of copper ions by microplastics was a significant reason for the improved growth condition of algal cells in the mixed pollution group compared to the copper ion pollution group. However, in the later stages of cultivation, the inhibitory effect of microspheres on algal cell growth counteracted their mitigating effect on copper ion toxicity. This study provides a reference for evaluating the impact of microplastics and heavy metals on coastal ecosystem health and for revealing the interactions between different pollutants. [ABSTRACT FROM AUTHOR]

Increasing the marine carbon dioxide (CO 2) absorption capacity by adding alkaline minerals into the world's oceans is a promising marine carbon dioxide removal (mCDR) approach to increase the ocean's CO 2 storage potential and mitigate ocean acidification. Still, the biological impacts of dispersion of alkaline minerals need to be evaluated prior to its field deployment, especially the impacts of the initial discharge causing local and temporary extreme alkalinity/pH changes. In this study, the toxicity effect on marine microalgae of two commonly used alkaline minerals, calcium hydroxide (Ca(OH) 2) and magnesium hydroxide (Mg(OH) 2), was determined by adding the same equivalent molar concentration of hydroxyl ions. Cultures of marine green microalgae Tetraselmis suecica were exposed to Ca(OH) 2 or Mg(OH) 2 , in concentrations mimicking the initial high concentrations following a dispersion scenario from a ship. A short-term exposure with high-alkaline mineral concentration called "dispersion phase" was followed by a dilution step and a "regrowth" phase over 6 d. There was no detectable effect of Mg(OH) 2 treatment on algae growth either after the dispersion phase or during the regrowth phase, compared to control treatments. The Ca(OH) 2 treatment resulted in very few living algal cells after the dispersion phase, but a similar growth rate was observed during the regrowth phase as was for the Mg(OH) 2 and control treatments. Standardized whole effluent toxicity (WET) tests were carried out with a range of Mg(OH) 2 concentrations using a sensitive marine diatom, Skeletonema costatum, which confirmed the relatively low toxicity effect of Mg(OH) 2. Similar biological effects were observed on natural microalgae assemblages from a local seawater source when applying the same Mg(OH) 2 concentration range and exposure time used in the WET tests. The results suggest that Mg(OH) 2 is relatively safe compared to Ca(OH) 2 with respect to marine microalgae. [ABSTRACT FROM AUTHOR]

Bacterial membrane vesicles (BMVs) are crucial biological vehicles for facilitating interspecies and interkingdom interactions. However, the extent and mechanisms of BMV involvement in bacterial-algal communication remain elusive. This study provides evidence of BMVs delivering cargos to targeted microalgae. Membrane vesicles (MVs) from Chitinimonas prasina LY03 demonstrated an algicidal profile similar to strain LY03. Further investigation revealed Tambjamine LY2, an effective algicidal compound, selectively packaged into LY03-MVs. Microscopic imaging demonstrated efficient delivery of Tambjamine LY2 to microalgae Heterosigma akashiwo and Thalassiosira pseudonana through membrane fusion. In addition, the study demonstrated the versatile cargo delivery capabilities of BMVs to algae, including the transfer of MV-carried nucleic acids into algal cells and the revival of growth in iron-depleted microalgae by MVs. Collectively, our findings reveal a previously unknown mechanism by which algicidal bacteria store hydrophobic algicidal compounds in MVs to trigger target microalgae death and highlight BMV potency in understanding and engineering bacterial-algae cross-talk. [ABSTRACT FROM AUTHOR]

The vampire amoebae (Vampyrellida, Rhizaria) inhabit freshwater, marine, and terrestrial ecosystems and consume a wide range of eukaryotic prey. This includes diverse microalgae, fungi, and microscopic animals. One of the most captivating aspects of the vampyrellids is their ability to extract the cell contents of other eukaryotes after local dissolution of the prey cell wall, a feeding strategy that occurs in several vampyrellid families, but is best studied in Vampyrella species that attack zygnematophyte green algae. Here, we report two new vampyrellid strains from temperate moorlands in Germany with a yet‐undescribed feeding strategy: internal protoplast extraction and cell wall regurgitation. This feeding strategy involves the phagocytosis of whole desmid cells (genus Closterium, Zygnematophyceae), internal cleavage of the algal cell wall, extraction of the cell contents, and subsequent exocytosis of bundled empty cell walls. The large primary food vacuole formed during the process has exceptional functions, as it forms internal feeding pseudopodia, packages algal cell contents into smaller secondary vacuoles, and transforms into a "waste vacuole" with cell wall remnants. The new feeding strategy, which – in the widest sense – is reminiscent of the pellet casting of owls, reveals a stunningly sophisticated behavior of single protist cells. Based on morphological, phylogenetic, and autecological data, both vampyrellid strains are nearly identical and here assigned to a new and quite unique vampyrellid taxon, Strigomyxa ruptor gen. et sp. nov. (Leptophryidae, Vampyrellida). [ABSTRACT FROM AUTHOR]

Microbialites provide geological evidence into Earth's early ecosystems, recording long‐standing interactions between co‐evolving life and the environment. Yet, after more than 100 years of research, the complex interplay between environmental and biological forces involved in microbialite growth is still debated. Laguna de Los Cisnes, located in Chilean Tierra del Fuego, Patagonia, provides a unique opportunity to study these interactions. This lake, which became ice‐free around 10 000 years ago, features carbonate microbialites developed by algal–microbial communities. Macroscopically, the organo‐sedimentary deposits exhibit a consistent primary crater‐like architecture, showcasing macrostructural variations such as dish‐shaped, hemispherical, columnar and lenticular morphologies. This study explores the environmental and biological factors shaping microbialite macrostructure by analysing the distribution of dominant morphotypes across the basin. Concurrently, it examines the internal mesostructure and microstructure of microbialites in association with prevailing algal–microbial communities. The incremental development of these communities contributes to the distinct crater‐like morphology observed in microbialites from Laguna de Los Cisnes. The mineral encrustation of the green alga Percursaria percursa emerges as a primary driver of lithification, evidenced by the preservation of microfossils within the microstructure of the microbialites. Simultaneously, physical environmental factors, including waves, Langmuir cells and accommodation space influence the location of the algal–microbial carbonate factory, determining the spatial distribution and temporal succession of different crater architecture variants. Laguna de Los Cisnes, hosting well‐preserved subfossil outcrops and living microbialites, serves as a remarkable living laboratory for understanding microbialite morphogenesis. This study contributes to a novel model that captures the fundamental role of algal–microbial communities in determining the primary macrostructural architecture of microbialites before environmental factors come into play, merely reshaping this architecture into different morphotypes. [ABSTRACT FROM AUTHOR]

With increasing demand of fossil fuels and water pollution and their environmental impacts, marine green microalgae have gained special attention in both scientific and industrial fields. This is due to their fast growth in non-arable lands with high photosynthetic activity, their metabolic plasticity, as well as their high CO2 capture capacity. Tetraselmis species, green and eukaryotic microalgae, are not only considered as a valuable source of biomolecules including pigments, lipids, and starch but also widely used in biotechnological applications. Tetraselmis cultivation for high-value biomolecules and industrial use was demonstrated to be a non-cost-effective strategy because of its low demand in nutrients, such as phosphorus and nitrogen. Recently, phycoremediation of wastewater rich in nutrients, chemicals, and heavy metals has become an efficient and economic-alternative that allows the detoxification of waters and induces mechanisms in algal cells for biomolecules rich-energy synthesis to regulate their metabolic pathways. This review aims to shed light on Tetraselmis species for their different culture conditions and metabolites bioaccumulation, as well as their human health and environmental applications. Additionally, phycoremediation of contaminants associated to biofuel production in Tetraselmis cells and their different intracellular and extracellular mechanisms have also been investigated. [ABSTRACT FROM AUTHOR]

To achieve long-term and efficient photobiological hydrogen production by green algal aggregates remains a challenge. Herein, we demonstrated that mixotrophic cultivation of green algal aggregates can greatly increase the hydrogen production of Chlorella pyrenoidosa by 37 times, and the period of the hydrogen production was up to 21 days with a hydrogen yield of 14.97 mmol L−1. We found that glucose enabled the green algal culture flocculated by cationic etherified starch anaerobic overall, while the algal cells remained highly active. Therefore, long-term effective hydrogen production by green algae was realized. The simplicity and low cost of the method, which requires only cationic etherified starch and glucose, gives it a good potential for scale-up applications and a positive impact on the energy and environment fields. [Display omitted] • A new strategy of mixotrophic cultivation increased the H 2 production by 37 times. • H 2 production was prolonged to 21 days by supplementation with 50 mM glucose. • Large green algal aggregates up to 1000 μm were formed. • Algal aggregates were wholly anaerobic while maintaining high cellular activity. [ABSTRACT FROM AUTHOR]

SUMMARY: Green feather algae (Bryopsidales) undergo a unique life cycle in which a single cell repeatedly executes nuclear division without cytokinesis, resulting in the development of a thallus (>100 mm) with characteristic morphology called coenocyte. Bryopsis is a representative coenocytic alga that has exceptionally high regeneration ability: extruded cytoplasm aggregates rapidly in seawater, leading to the formation of protoplasts. However, the genetic basis of the unique cell biology of Bryopsis remains poorly understood. Here, we present a high‐quality assembly and annotation of the nuclear genome of Bryopsis sp. (90.7 Mbp, 27 contigs, N50 = 6.7 Mbp, 14 034 protein‐coding genes). Comparative genomic analyses indicate that the genes encoding BPL‐1/Bryohealin, the aggregation‐promoting lectin, are heavily duplicated in Bryopsis, whereas homologous genes are absent in other ulvophyceans, suggesting the basis of regeneration capability of Bryopsis. Bryopsis sp. possesses >30 kinesins but only a single myosin, which differs from other green algae that have multiple types of myosin genes. Consistent with this biased motor toolkit, we observed that the bidirectional motility of chloroplasts in the cytoplasm was dependent on microtubules but not actin in Bryopsis sp. Most genes required for cytokinesis in plants are present in Bryopsis, including those in the SNARE or kinesin superfamily. Nevertheless, a kinesin crucial for cytokinesis initiation in plants (NACK/Kinesin‐7II) is hardly expressed in the coenocytic part of the thallus, possibly underlying the lack of cytokinesis in this portion. The present genome sequence lays the foundation for experimental biology in coenocytic macroalgae. Significance Statement: The exceptionally coenocytic body and remarkable regeneration ability of Bryopsis have attracted biologists for years. However, molecular biological tools remain underdeveloped, partly due to the lack of genome information. Here, we report high‐quality assembly and annotation of the genome, providing a crucial resource for experimental biology and genomics studies of Bryopsis. Furthermore, comparative genomic analysis reveals a unique gene repertoire that possibly underlies the highly regenerative coenocytic body. [ABSTRACT FROM AUTHOR]

Eukaryotic phytoplankton, also known as algae, form the basis of marine food webs and drive marine carbon sequestration. Algae must regulate their motility and gravitational sinking to balance access to light at the surface and nutrients in deeper layers. However, the regulation of gravitational sinking remains largely unknown, especially in motile species. Here, we quantify gravitational sinking velocities according to Stokes' law in diverse clades of unicellular marine microalgae to reveal the cell size, density, and nutrient dependency of sinking velocities. We identify a motile algal species, Tetraselmis sp., that sinks faster when starved due to a photosynthesis-driven accumulation of carbohydrates and a loss of intracellular water, both of which increase cell density. Moreover, the regulation of cell sinking velocities is connected to proliferation and can respond to multiple nutrients. Overall, our work elucidates how cell size and density respond to environmental conditions to drive the vertical migration of motile algae. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic required great efforts to develop efficient vaccines in a short period of time. However, innovative vaccines against SARS-CoV-2 virus are needed to achieve broad immune protection against variants of concern. Polymeric-based particles can lead to innovative vaccines, serving as stable, safe and immunostimulatory antigen delivery systems. In this work, polymeric-based particles called thiolated PAA/Schizo were developed. Poly (acrylic acid) (PAA) was thiolated with cysteine ethyl ester and crosslinked with a Schizochytrium sp. cell wall fraction under an inverse emulsion approach. Particles showed a hydrodynamic diameter of 313 ± 38 nm and negative Zeta potential. FT-IR spectra indicated the presence of coconut oil in thiolated PAA/Schizo particles, which, along with the microalgae, could contribute to their biocompatibility and bioactive properties. TGA analysis suggested strong interactions between the thiolated PAA/Schizo components. In vitro assessment revealed that thiolated particles have a higher mucoadhesiveness when compared with non-thiolated particles. Cell-based assays revealed that thiolated particles are not cytotoxic and, importantly, increase TNF-α secretion in murine dendritic cells. Moreover, immunization assays revealed that thiolated PAA/Schizo particles induced a humoral response with a more balanced IgG2a/IgG1 ratio. Therefore, thiolated PAA/Schizo particles are deemed a promising delivery system whose evaluation in vaccine prototypes is guaranteed. [ABSTRACT FROM AUTHOR]

An understanding of thermal limits and variation across geographic regions is central to predicting how any population may respond to global change. Latitudinal clines, in particular, have been used to demonstrate that populations can be locally adapted to their own thermal environment and, as a result, not all populations will be equally impacted by an increase in temperature. But how robust are these signals of thermal adaptation to the other ecological challenges that animals commonly face in the wild? Seasonal changes in population density, food availability, or photoperiod are common ecological challenges that could disrupt patterns of thermal tolerance along a cline if each population differentially used these signals to anticipate future temperatures and adjust their thermal tolerances accordingly. In this study, we aimed to test the robustness of a cline in thermal tolerance to simulated signals of seasonal heterogeneity. Experimental animals were derived from clones of the Australian water flea, Daphnia carinata, sampled from nine distinct populations along a latitudinal transect in Eastern Australia. We then factorially combined summer (18 h light, 6 h dark) and winter (6 h light, 18 h dark) photoperiods with high (5 million algal cells individual−1 day−1) and low (1 million algal cells individual−1 day−1) food availabilities, before performing static heat shock assays to measure thermal tolerance. We found that the thermal tolerances of the clonal populations were sensitive to both measures of seasonal change. In general, higher food availability led to an increase in thermal tolerances, with the magnitude of the increase varying by clone. In contrast, a switch in photoperiod led to rank‐order changes in thermal tolerances, with heat resistance increasing for some clones, and decreasing for others. Heat resistance, however, still declined with increasing latitude, irrespective of the manipulation of seasonal signals, with clones from northern populations always showing greater thermal resistance, most likely driven by adaptation to winter thermal conditions. While photoperiod and food availability can clearly shape thermal tolerances for specific populations, they are unlikely to overwhelm overarching signals of thermal adaptation, and thus, observed clines in heat resistance will likely have remained robust to these forms of seasonal heterogeneity. [ABSTRACT FROM AUTHOR]

Chaetoceros Ehrenberg is one of the most diverse genera of planktonic diatoms. The species in section Chaetoceros are characterized by cells and setae having numerous chloroplasts and being widely distributed. However, the delimitations of some species are problematic because of limited morphological information in the classical descriptions. Monoclonal strains of the section Chaetoceros were established, morphological features were studied using light and electron microscopy, and the hypervariable D1–D3 region of the nuclear ribosomal large subunit gene was sequenced to address phylogenetic relationships. Fifteen species belonging to the section Chaetoceros were recorded, including two new species, C. hainanensis sp. nov. and C. tridiscus sp. nov. Chaetoceros hainanensis was characterized by straight chains, narrowly lanceolate to hexagonal apertures, sibling setae diverging in nearly right angles, stipule-shaped spines on terminal setae and arrowhead-shaped spines on intercalary setae. C. tridiscus had short straight chains, narrowly lanceolate apertures, arrowhead-shaped spines and circular poroids arranged in a grid pattern on terminal and intercalary setae. The phylogenetic analyses revealed six groups formed by 19 species within the section Chaetoceros, which was found to be monophyletic. The subdivision of the section is still not well understood. The morphological characters within each group varied considerably and molecular information on more species are needed to enrich the phylogenetic profiling. [ABSTRACT FROM AUTHOR]

In the monitoring the discharge of ballast water, the count of living algal cells is of utmost significant. Variable fluorescence, denoted as Fv, stands as an optimal parameter for photosynthetic fluorescence, efficiently charactering the living algal cells count, unaffected by the ballast waters' complex background fluorescence environment. This study deeply investigates the quantitative relationship between Fv and the count of living algal cells. Observations indicate that single cell fluorescence yield (abbreviated as SCF) varies significantly across different algae species, leading to considerable errors in quantifying living algal cell count in ballast water with unknown components using the calibration relationship between Fv and the cell count. Thus, correcting SCF prior to calibration becomes necessary. The paper proposes an innovative SCF correction method based on cell cross-sectional area and an eμ factor (where μ is the expected value of the functional absorption cross-section of PSII) This method mitigates the influence of cell size and species differences on quantifying the living algal cell count. Correction operation trials revealed that dividing the SCF measurement by cell cross-sectional area and multiplying by eμ enhanced the correction effect. Comparative experiments demonstrated marked improvement: Relative errors (REs) for Chlorella pyrenoidosa and Chlorella marine, both belonging to the Chlorophyta group, fell from 92.1% and 90.6% to 37.2% and 9.5% respectively post-correction. Similarly, REs for Thalassiosira weissflogii and Nitzschia closterium minutissima, from the Bacillariophyta group, decreased from 74.7% and 68.1% to 14.3% and 19.1% respectively. The RE of Peridinium from the Pyrrophyta group dropped from 28.4% to 12.1%. The results underscore the effectiveness of cell cross-sectional area and eμ in correcting SCF, thus offering a novel correction method for swift and precise measurement of living algal cell count in ballast water, based on variable fluorescence. [ABSTRACT FROM AUTHOR]

The capacity of living algal cells to efficiently eliminate metals from water is well known and achieved through the mechanisms of biosorption and bioaccumulation. These investigations highlight the potential of indigenous microalgae for the elimination of toxic elements such as cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni), and lead (Pb) from aqueous solutions. To identify algal strains that are effective in removing heavy metals, samples of soil and water were collected from areas contaminated with industrial and municipal effluents. Among the 11 isolates obtained from various sites contaminated with heavy metals, three isolates (designated as A, I and K) were able to tolerate both the threshold and double threshold levels of the tested heavy metals. Subsequent liquid assays confirmed the efficiency of the three selected algal isolates in removing heavy metals, with isolates A and I demonstrating effectiveness in removing all tested heavy metals, exhibiting removal rates of cadmium ranging from 40% to 80%, cobalt ranging from 20% to 60%, chromium up to 90%, nickel ranging from 40% to 90%, and lead ranging from 50% to 70%. Isolate K displayed the highest efficiency in only removing lead, specifically 86.23% at 21 DAI (Days After Inoculation), and therefore was not chosen for further characterization. Through morphological and molecular characterization, isolates A and I were identified as Coelastrella thermophila AAU BR A and Chlorella sp. AAU BR I, respectively. In conclusion, the results demonstrate that the native algal isolates have the potential to serve as eco-friendly agents for remediating heavy metal-contaminated water. [ABSTRACT FROM AUTHOR]

Environmental context: Plastic pollution is widespread and continues to be a major concern, both for the environment and human health. Identifying nanoplastics is challenging but is important to understand how they behave once in the environment. It is shown that a combination of single particle (SP) and single cell (SC) inductively coupled plasma mass spectrometry (ICP-MS) can be used to quantify nanoplastics on a per cell basis after exposure to algal cells. The effects of plastic pollution on human health and the environment are not well known but there are significant concerns. Although research has increased in recent years, there remain many obstacles to the quantification of nanoplastics. This rapid communication demonstrates that combined single particle (SP)– and single cell (SC)–inductively coupled plasma–mass spectrometry (ICP-MS) provide a novel means to quantify pre-formed core–shell metal–plastic composite nanoparticles when exposed to two freshwater algal cells, Cryptomonas ovata (C. ovata) and Cryptomonas ozolini (C. ozolini). It is shown that individual palladium plastic nanoparticles (Pd NPPs) exposed to algal cells form agglomerates in the cell suspension respectively consisting of 165 and 157 (±3.8) individual Pd NPPs for C. ozolini and C. ovata cells, and that the agglomerates are also cell-associated with 1.75–1.85 agglomerates per cell. Environmental context. Plastic pollution is widespread and continues to be a major concern, both for the environment and human health. Identifying nanoplastics is challenging but it is important to understand how they behave once in the environment. It is shown that a combination of single particle (SP)– and single cell (SC)–inductively coupled plasma–mass spectrometry (ICP-MS) can be used to quantify nanoplastics on a per cell basis after exposure to algal cells. (Image credit: E. C. Bair.) [ABSTRACT FROM AUTHOR]

In the presented study, the effectiveness of a siloxane polyether (HOL7) coating on glass against microbiological colonization was assessed using microalgae as a key component of widespread aerial biofilms. The siloxane polyether was successfully synthesized by a hydrosilylation reaction in the presence of Karstedt's catalyst. The product structure was confirmed by NMR spectroscopy and GPC analysis. In addition, the thermal stability of HOL7 was studied by thermogravimetric measurement. Subsequently, the surfaces of glass plates were modified with the obtained organosilicon derivative. In the next step, a microalgal experiment was conducted. A mixture of four strains of algal taxa isolated from building materials was used for the experiment—Chlorodium saccharophilum PNK010, Klebsormidium flaccidum PNK013, Pseudostichococcus monallantoides PNK037, and Trebouxia aggregata PNK080. The choice of these algae followed from their wide occurrence in terrestrial environments. Application of an organofunctional siloxane compound on the glass reduced, more or less effectively, the photosynthetic activity of algal cells, depending on the concentration of the compound. Since the structure of the compound was not based on biocide-active agents, its effectiveness was associated with a reduction in water content in the cells. [ABSTRACT FROM AUTHOR]

Microalgae are promising production platforms for the cost-effective production of recombinant proteins. We have recently established that the red alga Porphyridium purpureum provides superior transgene expression properties, due to the episomal maintenance of transformation vectors as multicopy plasmids in the nucleus. Here, we have explored the potential of Porphyridium to synthesize complex pharmaceutical proteins to high levels. Testing expression constructs for a candidate subunit vaccine against the hepatitis C virus (HCV), we show that the soluble HCV E2 glycoprotein can be produced in transgenic algal cultures to high levels. The antigen undergoes faithful posttranslational modification by N-glycosylation and is recognized by conformationally selective antibodies, suggesting that it adopts a proper antigenic conformation in the endoplasmic reticulum of red algal cells. We also report the experimental determination of the structure of the N-glycan moiety that is attached to glycosylated proteins in Porphyridium. Finally, we demonstrate the immunogenicity of the HCV antigen produced in red algae when administered by injection as pure protein or by feeding of algal biomass. [ABSTRACT FROM AUTHOR]

This study introduces an evaluation methodology tailored for bioreactors, with the aim of assessing the stress experienced by algae due to harmful contaminants released from antifouling (AF) paints. We present an online monitoring system equipped with an ultra-sensitive sensor that conducts non-invasive measurements of algal culture's optical density and physiological stage through chlorophyll fluorescence signals. By coupling the ultra-sensitive sensor with flash-induced chlorophyll fluorescence, we examined the dynamic fluorescence changes in the green microalga Chlamydomonas reinhardtii when exposed to biocides. Over a 24-h observation period, increasing concentrations of biocides led to a decrease in photosynthetic activity. Notably, a substantial reduction in the maximum quantum yield of primary photochemistry (FV/FM) was observed within the first hour of exposure. Subsequently, we detected a partial recovery in FV/FM; however, this recovery remained 50% lower than that of the controls. Integrating the advanced submersible sensor with fluorescence decay kinetics offered a comprehensive perspective on the dynamic alterations in algal cells under the exposure to biocides released from antifouling coatings. The analysis of fluorescence relaxation kinetics revealed a significant shortening of the fast and middle phases, along with an increase in the duration of the slow phase, for the coating with the highest levels of biocides. Combining automated culturing and measuring methods, this approach has demonstrated its effectiveness as an ultrasensitive and non-invasive tool for monitoring the physiology of photosynthetic cultures. This is particularly valuable in the context of studying microalgae and their early responses to various environmental conditions, as well as the potential to develop an AF system with minimal harm to the environment. [ABSTRACT FROM AUTHOR]

Chemical compounds, such as the CS gas employed in military operations, have a number of characteristics that impact the ecosystem by upsetting its natural balance. In this work, the toxicity limit and microorganism's reaction to the oxidative stress induced by O-chlorobenzylidenemalonitrile, a chemical found in CS gas, were assessed in relation to the green algae Chlorella pyrenoidosa. A number of parameters, including the cell growth curve, the percent inhibition in yield, the dry cell weight, the percentage viability and productivity of algal biomass flocculation activity, and the change in oxygen production, were analyzed in order to comprehend the toxicological mechanisms of O-chlorobenzylidenemalonitrile on algal culture. Using fluorescence and Fourier transform infrared spectroscopy (FTIR), the content of chlorophyll pigments was determined. The values obtained for pH during the adaptation period of the C. pyrenoidosa culture were between 6.0 and 6.8, O2 had values between 6.5 and 7.0 mg/L, and the conductivity was 165–210 µS/cm. For the 20 µg/mL O-chlorobenzylidenemalonitrile concentration, the cell viability percentage was over 97.4%, and for the 150 µg/mL O-chlorobenzylidenemalonitrile concentration was 74%. The ECb50 value for C. pyrenoidosa was determined from the slope of the calibration curve; it was estimated by extrapolation to the value of 298.24 µg/mL. With the help of this study, basic information on the toxicity of O-chlorobenzylidenemalonitrile to aquatic creatures will be available, which will serve as a foundation for evaluating the possible effects on aquatic ecosystems. The management of the decontamination of the impacted areas could take the results into consideration. [ABSTRACT FROM AUTHOR]

Jet pump cavitation reactors (JPCRs) have significant potential to be used in water treatment applications. During their operation, the hydroxyl radicals generated by cavitation collapse produce a strong oxidation capacity, which is one of the key mechanisms in disrupting algal cells. In this paper, we investigate the hydroxyl radicals produced by single cavitation bubble in a JPCR. The numerical method includes a bubble dynamic model, molecular diffusion model, energy balance equation, and chemical reaction model for predicting the hydroxyl radical production. Additionally, the pressure distribution within a JPCR is tested and used to analyze the single-bubble performance. The effects of the JPCR operating conditions and structure parameters on hydroxyl radical production are further discussed. Our results indicate that, when the flow rate ratio is positive, the number of hydroxyl radicals is closely related to the development and collapse of the cavitation bubble and reaches a peak value under the critical condition. When the flow rate ratio is negative, the maximum production of hydroxyl radicals appears under backflow stagnation condition. In general, increasing the throat length–diameter ratio and diffuser angle encourages the production of hydroxyl radicals, whereas increasing the area ratio inhibits their generation. [ABSTRACT FROM AUTHOR]

In order to elucidate the effects of nitrification inhibitor dicyandiamide (DCD) on physiological and biochemical characteristics of paddy diazotrophic cyanobacteria and provide a theoretical basis for reasonable application of DCD and diazotrophic cyanobacteria in paddy fields, the variations of growth, photosynthesis, nitrogenase activity, activities of antioxidative enzymes, and oxidative damage characteristics of a paddy diazotrophic cyanobacterium Aliinostoc sp. YYLX235 under DCD stress were investigated. The results showed that the growth of Aliinostoc sp. YYLX235 was inhibited by DCD at concentrations of 100 ~ 300 mg⋅L-1. The activities of cellular vitality and N2-fixation significantly decreased at a DCD concentration of 50 mg⋅L-1. The photosystem II of Aliinostoc sp. YYLX235 exhibited hormetic effects under DCD stress, with characteristics of increasing cellular pigment contents and improvement of electron transfer efficiency. The activities of superoxide dismutase (SOD) and catalase (CAT) in cells of Aliinostoc sp. YYLX235 were positively correlated with DCD concentration in the medium. The oxidative-antioxidative system in cells of Aliinostoc sp. YYLX235 lost balance when DCD concentration ranged from 200 mg⋅L-1 to 300 mg⋅L-1, resulting in oxidative damage to algal cells. The results of this study indicate that DCD has strong negative effects on growth, cellular vitality, and N2-fixation activity of paddy diazotrophic cyanobacteria. Thus, the application of diazotrophic cyanobacteria-based bio-fertilizer and DCD should be staggered. [ABSTRACT FROM AUTHOR]

In September 2023, several hatcheries in Latin America experienced significant mortality rates, up to 90%, in zoea stage 2 of Penaeus vannamei. Observations of fresh mounts revealed structures resembling lipid droplets, similar to those seen in a condition known as "las bolitas syndrome". Routine histopathological examinations identified detached cells and tissues in the digestive tracts of affected zoea, contrasting with the typical algal cell contents seen in healthy zoea. Polymerase chain reaction (PCR) testing for over 20 known shrimp pathogens indicated minimal differences between diseased and healthy batches. Both groups tested negative for acute hepatopancreatic necrosis disease (AHPND) but positive for Vibrio species and Rickettsia-like bacteria in the diseased samples. Histological analyses of the affected zoea revealed characteristic tissue degeneration in the hepatopancreas, forming spheres that eventually migrated into the upper gut, midgut, and midgut caeca, a pathology identified as bolitas syndrome (BS). Microbiological assessments revealed Vibrio species at concentrations of 106 CFU zoea/g in affected zoea, approximately two orders of magnitude higher than in healthy zoea. Bacterial isolation from both healthy and BS-affected zoea on thiosulphate–citrate–bile salts–sucrose (TCBS) agar and CHROMagar™ (Paris, France), followed by identification using API 20E, identified six strains of Vibrio alginolyticus. Despite similarities to "las bolitas syndrome" in fresh mounts, distinct histopathological differences were noted, particularly the presence of sloughed cells in the intestines and variations in hepatopancreatic lobes. This study highlights the critical need for further research to fully understand the etiology and pathology of bolitas syndrome in zoea stage 2 of P. vannamei to develop effective mitigation strategies for hatchery operations. [ABSTRACT FROM AUTHOR]

With the wide application of nanomaterials, the concentration of nanomaterials in natural water continues to increase, which poses a severe threat to the water environment. However, the influence of organic matter and nanomaterials rich in natural water on the toxic effect of algae growth is still unclear. In this study, the effects of humic acid (HA) and nano-cerium oxide (nCeO2) on the physiology and transcriptome of Chlorella sp. were analyzed, and the mechanism of the toxic effect of HA on Chlorella sp. under nCeO2 stress was revealed. Under 20–200 mg/L nCeO2 stress, the growth of Chlorella cells was inhibited and the highest inhibition rate reached 52% within 200 mg/L nCeO2. The Fv/Fm and ETRmax values of Chlorella sp. decreased from 0.490 and 24.45 (20 mg/L nCeO2) to 0.488 and 23.4 (100 mg/L nCeO2), respectively. Under the stimulation of nCeO2, the level of reactive oxygen species in algal cells was increased, accompanied by lipid peroxidation and membrane damage. However, the addition of HA at concentrations of 5–10 mg/L effectively alleviated the toxic effect of nCeO2 on Chlorella sp. Transcriptome analysis showed that 10 mg/L HA could alleviate the cellular stress at 100 mg/L nCeO2 on Chlorella sp. by regulating genes related to photosynthesis and metabolism pathways. Moreover, the downregulation of genes (e.g., Lhca1, Lhcb1, AOC3, and AOC2) indicated that HA reduced the level of oxidative stress in Chlorella sp. These findings offer novel insights of evaluating the ecotoxicity nCeO2 and HA in natural water environment and their impact on Chlorella sp. [ABSTRACT FROM AUTHOR]

The composition of species and the physiological status of microalgal cells serve as significant indicators for monitoring marine environments. Symbiotic with corals, Symbiodiniaceae are more sensitive to the environmental response. However, current methods for evaluating microalgae tend to be population-based indicators that cannot be focused on single-cell level, ignoring potentially heterogeneous cells as well as cell state transitions. In this study, we proposed a microalgal cell detection method based on computer vision and microfluidics, which combined microscopic image processing, microfluidic chip and convolutional neural network to achieve label-free, sheathless, automated and high-throughput microalgae identification and cell state assessment. By optimizing the data import, training process and model architecture, we solved the problem of identifying tiny objects at the micron scale, and the optimized model was able to perform the tasks of cell multi-classification and physiological state assessment with more than 95% mean average precision. We discovered a novel transition state and explored the thermal sensitivity of three clades of Symbiodiniaceae, and discovered the phenomenon of cellular heat shock at high temperatures. The evolution of the physiological state of Symbiodiniaceae cells is very important for directional cell evolution and early warning of coral ecosystem health. [ABSTRACT FROM AUTHOR]

Microalgae have rigid, complex cell walls hindering direct lipid extraction. Cell disruption techniques are used to rupture these cellular structures to increase lipid extraction. Researchers investigating the downstreamprocessing of microalgae do not always have access to microalgal cultivation systems to generate large amounts of fresh microalgal biomass. Using resuspended freeze-dried microalgal biomass as a model laboratory system for concentrated fresh biomass during cell disruption experiments offers greater flexibility in experimental planning and omits investment costs of microalgal cultivation equipment. So far, it however remains unclear whether freeze-dried resuspended biomass can be used as a model laboratory system to represent concentrated fresh biomass during cell disruption and lipid extraction experiments. This paper thus evaluated the suitability of resuspended freeze-dried Nannochloropsis as a model laboratory system for concentrated fresh Nannochloropsis during cell disruption. Ultrasound assisted cell disruption was used as example cell disruption technique and lipid extraction efficiency and free fatty acid content were investigated. Tap water and 3% sodium chloride are both suitable resuspension media for the resuspension of freeze-dried Nannochloropsis. Resuspension duration should be limited (< 120 min) to prevent the formation of free fatty acids. The condition of the biomass (concentrated fresh, or resuspended freeze-dried) prior to ultrasound assisted cell disruption did not influence the resulting lipid extraction efficiency. Resuspended freeze-dried Nannochloropsis biomass in tap water or 3% sodium chloride can thus be used as a model laboratory system for fresh microalgal biomass during research on ultrasound assisted lipid extraction. The generalization of the results to other cultivation conditions, cell disruption techniques, components of interest or microalgal species should be carefully assessed. [ABSTRACT FROM AUTHOR]

Algal blooms are caused by excessive levels of nitrogen, phosphorus, and other plant nutrients in water. Algae and algal organic matter (AOM) pose a great threat to the quality of drinking water. This manuscript offers a systematic review of algal removal by ferrate (Fe(VI)) oxidation, including the conditions for the removal of different algae by Fe(VI) and the factors affecting the removal efficiency. On this basis, the oxidation and coagulation mechanisms of algae removal by Fe(VI) are discussed. Then, the review introduces the process combining Fe(VI) pre-oxidation with aluminum sulfate action. The addition of aluminum sulfate can further enhance the coagulation effect and reduce the formation of disinfection byproducts (DBPs) in the subsequent chlorination process by effectively removing AOM, which is recognized as a precursor of DBPs. In addition, recent studies on the combined application of Fe(VI) and Fe(II) are also reviewed. In a reasonable dose range, the synergistic effect of Fe(VI) and Fe(II) can significantly improve the removal of algae and algal toxins. Finally, this review provides a comprehensive evaluation of the applicability of Fe(VI) in removing algal material, offers guidance for the harmless treatment of algae with Fe(VI), and identifies future research questions. [ABSTRACT FROM AUTHOR]

Coral growth depends on the partnership between the animal hosts and their intracellular, photosynthetic dinoflagellate symbionts. In this study, we used the sea anemone Aiptasia, a laboratory model for coral biology, to investigate the poorly understood mechanisms that mediate symbiosis establishment and maintenance. We found that initial colonization of both adult polyps and larvae by a compatible algal strain was more effective when the algae were able to photosynthesize and that the long-term maintenance of the symbiosis also depended on photosynthesis. In the dark, algal cells were taken up into host gastrodermal cells and not rapidly expelled, but they seemed unable to reproduce and thus were gradually lost. When we used confocal microscopy to examine the interaction of larvae with two algal strains that cannot establish stable symbioses with Aiptasia, it appeared that both pre- and post-phagocytosis mechanisms were involved. With one strain, algae entered the gastric cavity but appeared to be completely excluded from the gastrodermal cells. With the other strain, small numbers of algae entered the gastrodermal cells but appeared unable to proliferate there and were slowly lost upon further incubation. We also asked if the exclusion of either incompatible strain could result simply from their cells' being too large for the host cells to accommodate. However, the size distributions of the compatible and incompatible strains overlapped extensively. Moreover, examination of macerates confirmed earlier reports that individual gastrodermal cells could expand to accommodate multiple algal cells. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'. [ABSTRACT FROM AUTHOR]

Aims This study explored the effects of slightly acidic electrolyzed water (SAEW) on algae to exploit technologies that effectively suppress algal growth in hydroponic systems and improve crop yield. Methods and Results The effects of SAEW on algal growth and the response mechanisms of algae to SAEW were investigated. Moreover, we studied whether the application of SAEW adversely affected tomato seedling growth. The results showed that SAEW significantly inhibited algal growth and destroyed the integrity of the algal cells. In addition, the intracellular oxidation−reduction system of algae was greatly influenced by SAEW. The H2O2, O2−, malondialdehyde (MDA), and reactive oxygen species (ROS) fluorescence signals were significantly induced by SAEW, and superoxide dismutase (SOD), peroxidase (POD), and glutathione reductase (GR) activities were greatly enhanced by a low SAEW concentration but significantly inhibited by SAEW with a high available chlorine concentration, which may contribute to heavy oxidative stress on algal growth and cell structure break down, eventually causing the death of algae and cell number decrease. We also found that regardless of the concentration of SAEW (from 10 to 40 mg L−1), there was no significant change in the germination index, length, or fresh weight of the hydroponic tomato seedlings. Conclusions Our findings demonstrate that SAEW can be used in hydroponic systems to restrain algae with no negative impact on tomato plants. [ABSTRACT FROM AUTHOR]