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Between 2023 and 2024, a type of green alga was observed for the first time settling on Oil-tea Camellia leaves and branches in the eastern Oil-tea Camellia planting area of Hainan Island, forming a layer of gray-green moss with a rough surface that seriously interfered with the leaves' normal photosynthesis. To further research the issue, this study used the plant photosynthesis measurement system and the paraffin sectioning technique to compare and analyze the changes in photosynthetic characteristics and anatomical structure of healthy and green algal-covered Oil-tea Camellia leaves. At the same time, the algal strain was effectively separated and purified using the plate delineation method, and its species classification was determined by combining morphological observation and molecular identification based on SSU-ITS sequences. The results of the study demonstrated that the coating of green alga facilitated the lignification of the leaf's epidermal cell walls. After being covered by the green alga, the intercellular CO2 concentration (Ci) increased significantly by 21.5%, while the net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) all significantly decreased by 72.8%, 30.4%, and 24.9%, respectively. More specifically, the green alga that covers the leaves of Oil-tea Camellia was identified as Desmodesmus armatus of Chlorophyta. Notably, the green alga had a long growth cycle, did not undergo a decline phase within one month, had an optimal growth pH of 11.0, and could flourish in excessively alkaline conditions. In conclusion, this study not only reported for the first time the phenomena of D. armatus infesting Oil-tea Camellia leave, but also showed its unique physiological and ecological properties, providing a foundation for future research on relevant prevention and control approaches. [ABSTRACT FROM AUTHOR]

Environmental context: The increasing global demand for platinum and palladium for the development of new technologies will likely enhance their biogeochemical mobility. However, our understanding of the environmental risks of these metals remains incomplete. To help fill this knowledge gap, we determined the toxicity of various forms of platinum and palladium on a green alga. We found that palladium was more toxic than platinum and that platinum toxicity depended on the form tested. Rationale: Chemical equilibrium-based models such as the biotic ligand model (BLM) can be used to predict metal toxicity towards aquatic organisms. However, some metals such as platinum (Pt) and to a lesser extent palladium (Pd) are known to be kinetically hindered, i.e. reactions between these elements and ligands in solution might be slow relative to the biota exposure time. The BLM applicability may thus be limited for these metals and their ecological risk assessment may require consideration of their initial form of entry in aquatic ecosystems. Methodology: This study investigates the relationship between inorganic Pt and Pd initial speciation and their bioavailability and toxicity toward the unicellular green alga Raphidocelis subcapitata. Chloro- or amino-coordinated Pt and Pd complexes such as PtIICl42−, PtIVCl62−, PtII(NH3)42+, PdIICl42− and PdII(NH3)42+ were examined in 96-h algae exposure experiments to determine growth inhibition and metal accumulation. Investigation of the complex stability over time of the tested complexes was carried out using spectrophotometry measurements and kinetic calculations. Results: Similar accumulation and no toxicity (half maximal effective concentration, EC50 > 150 µg L−1) were observed for both in our tested conditions. Nevertheless, evidence of PtIICl42− dissociation was observed whereas PtII(NH3)42+ was stable. Exposure to PtIVCl62− showed stronger algal growth inhibition (EC50 = 142 µg L−1) than exposure to PtIICl42− but similar accumulation. This phenomenon might be partly explained by the generation of free chloride radicals through PtIV reduction in the presence of light. Similar accumulation and toxicity were observed for both PdIICl42− (EC50 = 4.69 µg L−1) and PdII(NH3)42+ (EC50 = 2.40 µg L−1). Discussion: These results were coherent with the relatively rapid speciation changes of the PtII complexes as observed and modelled. We therefore conclude that the initial speciation of the studied chloro- and amino-coordinated PtII and PdII complexes is not a determining parameter of their accumulation and toxicity towards R. subcapitata. Environmental context. The increasing global demand for platinum and palladium for the development of new technologies will likely enhance their biogeochemical mobility. However, our understanding of the environmental risks of these metals remains incomplete. To help fill this knowledge gap, we determined the toxicity of various forms of platinum and palladium on a green alga. We found that palladium was more toxic than platinum and that platinum toxicity depended on the form tested. (Image credit: J. Michaud-Valcourt.) [ABSTRACT FROM AUTHOR]

The main component of microfossils in the bottom sediments of Reindeer Lake from Spitsbergen, documenting the almost 8,000-year history of this water body, are algae representing colonies of a very rare species Pediastrum orientale (Skuja) Jankovská et Komárek 1995 with only a very small (lower than 1%) admixture of other green algae species. It has also been recorded in other lake sediments in Spitsbergen. The specimens belong to the morphotype “b” of the species, known previously from the Scandinavian lakes. Due to its unique nature and scarce information on ecological conditions, this study analysed the palaeoenvironmental factors favouring the occurrence of Pediastrum orientale together with an assessment of its bioindication value. The affinity of the species to oligotrophic lakes, where blooms of this alga are observed, was confirmed. The presence of numerous colonies of Pediastrum orientale in fossil lake sediments can provide a rationale for inferring palaeoecological conditions, including the trophic state of water bodies, thus expanding knowledge of their evolutionary directions and documenting key events in the geological history of the catchment. Further studies of lake gyttjas in Spitsbergen should pay more attention to the taxonomic composition of Pediastrum and other green algae, as well as to the determinants of sediment deposition in different lake catchment environments.

Today, using CO2 in microalgae cultures has been increasing for different purposes. Microalgae have the potential to produce high-value products along with CO2 fixation. Dunaliella is a two- flagellate green microalga. The relatively good quality protein and fatty acid, besides lacking an indigestible cell wall make this alga an exceptional food in aquaculture and poultry fostering. In addition, there are many indigenous strains of algae with the advantage of adaptation to the regional climate condition. The main objective of this study was to evaluate the CO2 effect on the growth pattern and biochemical composition of Dunaliella sp. ABRIINW-I1 is native to Urmia Lake. Results showed that using CO2 in the culture not only affects the biomass concentration (1.06 g/l AFDW vs 0.54 g/l in the control experiment) and growth period (reaching the stationary phase in 7 days rather than 14 days in the control experiment); but also influences the chemical composition. It seems that during the cultivation time, the lipid content increased in the cost of carbohydrates (33.1%DW). Fatty acid analysis revealed an optimal combination of saturated and unsaturated acids with the dominance of C16 and C18 fatty acids. It seems that CO2 injection had no significant effect on the type of FA. The nutritional values of the studied strain were validated in this study, particularly when treated with CO2. The results demonstrated that utilizing CO2 in an algal culture could lead to decreased cost and energy requirements. [ABSTRACT FROM AUTHOR]

The accumulation of information on the geographical distribution range, genetic structure, and host utilization of the symbiont is important for studying how the symbiont spreads its distribution. Pseudocladophora conchopheria is a green alga that grows on the shells of intertidal gastropods distributed in the Japanese Archipelago, the Ryukyu Archipelago, and the southern part of Korean Peninsula. However, we discovered algae similar to P. conchopheria on the shells of gastropods from Vietnam. Therefore, species identification of the algae and the host gastropods was performed based on morphological observations and molecular genetic methods. As a result, the morphological characteristics of the algae were consistent with those of P. conchopheria, and the morphological characteristics of the host gastropods were consistent with those of Lunella granulata. Molecular genetic methods further supported these results of morphological identification. Interestingly, their algae were more closely related to P. conchopheria attached to L. correensis from the Sea of Japan rather than those attached to L. granulata from the Ryukyu Archipelago. These results suggest that P. conchopheria has expanded its distribution by utilizing multiple hosts and are explained on a wider scale than previous findings. [ABSTRACT FROM AUTHOR]

Marine algal lectins specific for high-mannose N-glycans have attracted attention because they strongly inhibit the entry of enveloped viruses, including influenza viruses and SARS-CoV-2, into host cells by binding to high-mannose-type N-glycans on viral surfaces. Here, we report a novel anti-influenza virus lectin (named HBL40), specific for complex-type N-glycans, which was isolated from a marine green alga, Halimeda borneensis. The hemagglutination activity of HBL40 was inhibited with both complex-type N-glycan and O-glycan-linked glycoproteins but not with high-mannose-type N-glycan-linked glycoproteins or any of the monosaccharides examined. In the oligosaccharide-binding experiment using 26 pyridylaminated oligosaccharides, HBL40 only bound to complex-type N-glycans with bi- and triantennary-branched sugar chains. The sialylation, core fucosylation, and the increased number of branched antennae of the N-glycans lowered the binding activity with HBL40. Interestingly, the lectin potently inhibited the infection of influenza virus (A/H3N2/Udorn/72) into NCI-H292 cells at IC50 of 8.02 nM by binding to glycosylated viral hemagglutinin (KD of 1.21 × 10−6 M). HBL40 consisted of two isolectins with slightly different molecular masses to each other that could be separated by reverse-phase HPLC. Both isolectins shared the same 16 N-terminal amino acid sequences. Thus, HBL40 could be useful as an antivirus lectin specific for complex-type N-glycans. [ABSTRACT FROM AUTHOR]

Caulerspiros A (1) and B (2), a new pair of α-tocopheroid isomers, with five known compounds (3-7) were isolated from the green alga Caulerpa racemosa var. turbinata. Their structures were elucidated by the method of comprehensive spectroscopy. The absolute configurations of 1 and 2 were established by the methods of ECD calculation and comparing with the previously reported literature. Compounds 1 and 2 represented the rare examples of α-tocopherol derivatives possessing a core unit of 1-oxaspiro[4.4]non 7-en-6-one. Additionally, the antibacterial activities of these seven compounds were also evaluated. However, none of them showed antibacterial activities with MIC values > 128 μg/ml. [ABSTRACT FROM AUTHOR]

Between 2023 and 2024, a type of green alga was observed for the first time settling on Oil-tea Camellia leaves and branches in the eastern Oil-tea Camellia planting area of Hainan Island, forming a layer of gray-green moss with a rough surface that seriously interfered with the leaves’ normal photosynthesis. To further research the issue, this study used the plant photosynthesis measurement system and the paraffin sectioning technique to compare and analyze the changes in photosynthetic characteristics and anatomical structure of healthy and green algal-covered Oil-tea Camellia leaves. At the same time, the algal strain was effectively separated and purified using the plate delineation method, and its species classification was determined by combining morphological observation and molecular identification based on SSU-ITS sequences. The results of the study demonstrated that the coating of green alga facilitated the lignification of the leaf’s epidermal cell walls. After being covered by the green alga, the intercellular CO2 concentration (Ci) increased significantly by 21.5%, while the net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) all significantly decreased by 72.8%, 30.4%, and 24.9%, respectively. More specifically, the green alga that covers the leaves of Oil-tea Camellia was identified as Desmodesmus armatus of Chlorophyta. Notably, the green alga had a long growth cycle, did not undergo a decline phase within one month, had an optimal growth pH of 11.0, and could flourish in excessively alkaline conditions. In conclusion, this study not only reported for the first time the phenomena of D. armatus infesting Oil-tea Camellia leave, but also showed its unique physiological and ecological properties, providing a foundation for future research on relevant prevention and control approaches.

The main component of microfossils in the bottom sediments of Reindeer Lake from Spitsbergen, documenting the almost 8,000-year history of this water body, are algae representing colonies of a very rare species Pediastrum orientale (Skuja) Jankovská et Komárek 1995 with only a very small (lower than 1%) admixture of other green algae species. It has also been recorded in other lake sediments in Spitsbergen. The specimens belong to the morphotype “b” of the species, known previously from the Scandinavian lakes. Due to its unique nature and scarce information on ecological conditions, this study analysed the palaeoenvironmental factors favouring the occurrence of Pediastrum orientale together with an assessment of its bioindication value. The affinity of the species to oligotrophic lakes, where blooms of this alga are observed, was confirmed. The presence of numerous colonies of Pediastrum orientale in fossil lake sediments can provide a rationale for inferring palaeoecological conditions, including the trophic state of water bodies, thus expanding knowledge of their evolutionary directions and documenting key events in the geological history of the catchment. Further studies of lake gyttjas in Spitsbergen should pay more attention to the taxonomic composition of Pediastrum and other green algae, as well as to the determinants of sediment deposition in different lake catchment environments. [ABSTRACT FROM AUTHOR]

In the current system, the disposal of plastic materials causes serious environmental pollution such as the generation of carbon dioxide and destruction of the ecosystem by micro-plastics. To solve this problem, bioplastics, biomass and biodegradable plastics have been developed. As part of our research, we have developed novel bioplastics called "cell-plastics", in which a unicellular green algal cell serves as a fundamental resource. The production of the cell-plastics would be expected to reduce environmental impact due to the usage of a natural product. Herein, to overcome the mechanical strength of cell-plastics, we used thermosetting epoxy and urethane resins containing Chlorella sp. as the green algae. We successfully fabricated thermosetting resins with a Chlorella sp. content of approximately 70 wt% or more. IR measurements revealed that the chemical structure of an epoxide or isocyanate monomer mixed with Chlorella sp. was modified, which suggests that the resins were hardened by the chemical reaction. In addition, we investigated the effect of thermosetting conditions such as temperature and compression for curing both resins. It was revealed that the Young's moduli and tensile strengths were controlled by thermosetting temperature and compression, whereas the elongation ratios of the resins were constant at low values regardless of the conditions. [ABSTRACT FROM AUTHOR]

The current study included shedding light on one genus of green alga Dunaliella salina spread from the saline brine ponds, Basrah Governorate, southern Iraq. Morphological results showed all algal samples from different brine ponds sites in Basrah governorate were belong to the species D. salina, and the measured enviro-nmental factors are commensurate with the growth of this species especially salinity, due to its increasing growth compatible increasing salinity with significantly P≤0.05 at concentrations 0-15% of sodium chloride salt, which equaled a salinity level more than 4 times the salinity of sea water, which amounted to 150 g/L. finding showed the concentration 5% of sodium chloride is considered it is a suitable concentration for the growth of all alga samples with no significant differences P≤0.05 between the generation time (G) and constant growth (K) for all cultures samples. Finding was proven that all isolates of the different sites showed the ability to produce total carotene in response to an increase or decrease in salinity, as is the case in the salinity-free control group as an effort that requires the alga to produce carotene, and this is an important characteristic for this species as well. From these results, it can be concluded that all isolates of algae from different sites belong to only one species diagnosed in the current study.

The formation of ordered dolomite under Earth's surface conditions remains a challenge, although many researchers have now shown that microbes can facilitate the precipitation of this common mineral. This study provides the first evidence of dolomite biomineralization by the green alga Spirogyra (Zygnematales, Chlorophyta), a globally dispersed lacustrine genus. Microbial mats formed by Spirogyra occur in the hyperalkaline and ephemeral lake Caballo Alba, located in Central Spain and characterized by water solutions with high Mg/Ca ratios. Microscopic, geochemical, mineralogical and cytochemical studies have shown that accumulations of carbonates occur within different cells and locations of the alga. Biominerals mostly consist of single crystals of magnesian calcite and dolomite with variable proportions of Ca2+ and Mg2+. High‐resolution transmission electron microscopy and selected area electron diffraction patterns of the carbonates confirm the pervasive presence of super‐lattice reflections typical of ordered dolomite in compositions with greater than 32 mol% MgCO3. The curved surfaces of some carbonate crystals and their attachment to the organic surfaces represent imprints of a confined growth in compartments that act as a template for crystal nucleation and shape the crystals. Dyes reveal chemical differences in these compartments which explain the polymineral biomineralization and suggest that the alga do not strictly control the precipitation process. Zygnematales algae related with Spirogyra date back possibly to the Early Palaeozoic, thus suggesting that dolomite biomineralization could have been a common process through the Phanerozoic. This discovery provides new insight into the biotic formation of orderly dolomite and aids in the reconstructions of past lacustrine environments of dolomite deposition. [ABSTRACT FROM AUTHOR]

Chlorococcum is a coccoid green algal genus, which contains almost 50 species. The genus is polyphyletic, but in a traditional sense, the cells are coccoid and non-motile with a cup-shape chloroplast in the vegetative stage, while the spores have chlamydomonad appearance. They are distributed worldwide mainly in terrestrial habitats, and the biotechnological potential of several strains has been reported. In this study, three new green algal strains from a shallow, temporary freshwater lake in Hungary are characterized using microscopic (light and transmission electron microscopy) and DNA-based methods (phylogenetic analysis of the ribosomal ITS region, the 18S ribosomal RNA and rbcL genes, and ITS secondary structure comparison). Based on the obtained results, one of the three new isolates is considered to represent a new species, which is described here as Chlorococcum szentendrense sp. nov. [ABSTRACT FROM AUTHOR]

The current study included shedding light on one genus of green alga Dunaliella salina spread from the saline brine ponds, Basrah Governorate, southern Iraq. Morphological results showed all algal samples from different brine ponds sites in Basrah governorate were belong to the species D. salina, and the measured enviro-nmental factors are commensurate with the growth of this species especially salinity, due to its increasing growth compatible increasing salinity with significantly P≤0.05 at concentrations 0-15% of sodium chloride salt, which equaled a salinity level more than 4 times the salinity of sea water, which amounted to 150 g/L. finding showed the concentration 5% of sodium chloride is considered it is a suitable concentration for the growth of all alga samples with no significant differences P≤0.05 between the generation time (G) and constant growth (K) for all cultures samples. Finding was proven that all isolates of the different sites showed the ability to produce total carotene in response to an increase or decrease in salinity, as is the case in the salinity-free control group as an effort that requires the alga to produce carotene, and this is an important characteristic for this species as well. From these results, it can be concluded that all isolates of algae from different sites belong to only one species diagnosed in the current study. [ABSTRACT FROM AUTHOR]

Oligosaccharides offer beneficial effects on immune system and gut health, such as immunomodulatory activity, anticancer activity, and complement activation. Functional oligosaccharides are widely found in plants, algae, bacteria, and higher fungi. The consumption of functional oligosaccharides can reduce the risk of lifestyle-related diseases, such as cardiovascular disease, cancer, obesity and type 2 diabetes. Marine macroalgae possess tremendous nutritional value and have been well-known to cure and prevent the chronic metabolic diseases. An increased interest in various bioactive natural products from marine macroalgae, as a potential source of effective agents, has been observed in recent years. Especially, green algae have attracted attentions for their important functional properties and potential biological applications. The effects of marine green algal oligosaccharides may delay the development of chronic metabolic diseases such as diabetes, and alter the metabolic abnormalities through various mechanisms of actions. Marine green algal oligosaccharides used to prevent and manage diabetes. The excellent performance was based on their chemical structures and glycosidic linkages. Our research is focus on structures, accessible sources, physiological and chemical characteristics, and potential health benefits of green algal functional oligosaccharides. Moreover, the project aims to to carry out research on new key gene mining and regulation mechanism of marine green algal functional oligosaccharides to dietary interventions for glucose metabolism. Our group engages in the nutritional evaluation research of functional components from marine algae and has achieved a series of original results: to firstly report the largest gram scale production of fucosylated oligosaccharide lacto-N-fucopentaose I, to firstly discovered the COL1A1 as one potential new biomarker and therapeutic target for type 2 diabetes, to reveal the new mode of regulation of algal oligosaccharides on glycometabolism network based on microRNAs, and to elucidate systematically molecular mechanisms of marine algal oligosaccharides to regulate glucose metabolism via mediating intestinal flora. These results make the important breakthrough in the theoretical basis of algal food nutrition and successfully realize them transformation and application. [ABSTRACT FROM AUTHOR]

We have previously created and expressed a chimeric polypeptide joining the PsaC subunit of Photosystem I (PSI) to the HydA2 hydrogenase of Chlamydomonas reinhardtii and demonstrated that it assembles into the PSI complex and feeds electrons directly to the hydrogenase domain, allowing for prolonged photobiological hydrogen production. Here we describe a new PSI-hydrogenase chimera using HydA1, the more abundant and physiologically active endogenous hydrogenase of this alga. When the PsaC-HydA1 polypeptide was expressed in a C. reinhardtii strain lacking endogenous hydrogenases, it was assembled into active PSI-HydA1 complexes that were accumulated at a level ∼75% that of PSI, which is ∼5 times higher than the PSI-HydA2 chimera. Hydrogen production by the chimera could be restored after complete inactivation by oxygen without requiring new synthesis of PSI or the PsaC-HydA1 polypeptide, demonstrating that the complex could be repaired in vivo. The PSI-HydA1 chimera reduces ferredoxin in vivo to such an extent that it can drive the Calvin-Benson-Bassham cycle, leading to high O 2 production rates, and eventually resulting in inactivation of the hydrogenase; use of media that drastically diminished CO 2 fixation and an O 2 -scavenging material allowed H 2 production for at least 4 days. • The PsaC-HydA1 fusion is expressed and assembles on photosystem I in vivo. • The chimeric PSI-HydA1 complex is accumulated at levels approaching wild-type PSI. • Light-dependent H 2 evolution switches to H 2 uptake upon CO 2 fixation. • PsaC-HydA1 can be reactivated in vivo after O 2 inactivation. [ABSTRACT FROM AUTHOR]

Mass production of microorganisms, algae among them, for new bioactive compounds and renewable innovative products is a current issue in biotechnology. The greatest challenge of basic research on this topic is to find the best solution for both physiology and scalability. In this study, the main goal was to highlight the contradictions of physiological and technological optimization in the same, relatively small, laboratory scale. The green alga Monoraphidium pusillum (Printz) Komárková-Legnorová was cultured in a conventional Erlenmeyer flask (as air bubbled in a tank-type photobioreactor) and in a hybrid (fermenter type + helical tubular type) photobioreactor of the same volume (2.8 L). Higher cell numbers from 1.7–2.3-fold, 2–2.8-fold higher dry masses, and 1.9–2.6-fold higher total lipid contents (mg·L−1) were measured in the tank reactor than in the hybrid reactor. Cultures in the conventional tank reactor were characterized with better nutrient utilization (42.8–77.7% higher phosphate uptake) and more diverse lipid composition than in the hybrid reactor. The study highlights that well-scalable arrangements and settings could be not optimal (or unsuitable in some cases) from a physiological point of view. The results suggest certain developmental directions for complex, well-scalable devices and highlight the importance of testing the gained physiological optima on these systems. [ABSTRACT FROM AUTHOR]

Indonesia has marine biological natural resources consisting of fish, seaweed, crabs and shrimp which are very potential. The purpose of this study was to determine the composition of pigments in Ulva sp (Chlorophyta), Padina australis (Paeophyta) and Hypnea sp (Rhodophyta) obtained from Tablolong waters. The method used in this research is descriptive qualitative and quantitative. Proof of pigment in samples using thin layer chromatography (TLC). The results of pigment analysis of Ulva sp obtained twelve color spots with identified pigment types consisting of chlorophyll a, chlorophyll b, xanthophyll, b-carotene and feofitin. The pigment content identified in Padina australis samples are chlorophyll b, feoforbid, xanthophyll, chlorophyll a, carotene and feofitin a. The types of pigments identified in Ulva sp include pigment chlorophyll a, chlorophyll b, carotene and feofitin from the total color spots formed. Based on the results of this study concluded that non-cultivated seaweed obtained from Tablolong waters contains carotenoid and chlorophyll pigments. Suggestions from this study are expected to do an analysis of pigment content analysis in the dry season time period and continued with antioxidant testing. Indonesia memiliki Sumber Daya Alam hayati laut yang terdiri dari ikan, rumput laut, kepiting dan udang yang sangat potensial. Tujuan penelitian ini adalah untuk mengetahui komposisi pigmen pada Ulva sp (Chlorophyta), Padina australis (Paeophyta) dan Hypnea sp (Rhodophyta) yang diperoleh dari perairan Tablolong. Metode yang digunakan dalam penelitian ini adalah deskriptif kualitatif dan kuantitatif. Pembuktian pigmen pada sampel menggunakan Kromatografi lapis tipis (KLT). Hasil analisis pigmen dari Ulva sp diperoleh dua belas spot warna dengan jenis pigmen yang teridentifikasi terdiri dari klorofil a, klorofil b, xantofil, b-karoten dan feofitin. Kandungan pigmen yang teridentifikasi pada sampel Padina australis adalah klorofil b, feoforbid, xantofil, klorofil a, karoten dan feofitin a. Jenis pigmen yang teridentifikasi pada Ulva sp meliputi pigmen klorofil a, klorofil b, karoten dan feofitin dari total spot warna yang terbentuk. Berdasarkan hasil penelitian dapat disimpulkan bahwa rumput laut non budidaya yang diperoleh dari perairan Tablolong memiliki kandungan pigmen karotenoid dan klorofil. Saran dari penelitian ini diharapkan dilakukan peneltian analisis kandungan pigmen pada periode waktu musim kemarau serta dilanjutkan dengan uji antioksidan.

Abstract Treatment for tumors depends on host immune system. The antitumor and immunoregulatory activities of Ulva lactuca polysaccharide (ULP) were evaluated in H22 tumor‐bearing mice and cyclophosphamide‐induced immunosuppressed mice, respectively. The structural properties of ULP were identified through multi‐angle laser light scattering, high‐performance liquid chromatography, Fourier‐transformed infrared, and nuclear magnetic resonance. It was composed of α‐D‐Manp‐(1→, →2,4)‐β‐L‐Rhap‐(1→, β‐D‐GlcpA‐(1→, β‐GalpA‐(1→, →2,4)‐α‐D‐Glcp‐(1→, and →6)‐β‐D‐Galp‐(1→ with the molecular weight of 1.46 × 105 Da. Its antioxidant, anti‐inflammatory, and antitumor effects were determined. Liver and tumor tissues were collected for histopathological, immunohistochemical, and western blotting analysis. ULP showed the great tumor growth inhibition of 74.41% compared with cyclophosphamide, which has side effects on immune system. ULP enhanced the expression of p53 to inhibit tumorigenesis, promoted the activation of IKKα, and inhibited the activation of p65 within the NF‐κB pathway. ULP inhibited the tumor growth through downregulating the expressions of PI3K/Akt and mTOR, and promoting BAX/Bcl‐2 ratio. The inhibition of TRAF2/TNF‐α and CD31/VEGF achieved a direct killing effect on tumor cells and inhibited tumor proliferation by inhibiting angiogenesis, respectively. Moreover, ULP increased the levels of immunoglobulin M and total superoxide dismutase, decreased the level of methane dicarboxylic aldehyde, and inhibited the activation of PI3K/AKT/mTOR/p70S6k pathways. The results showed that ULP exhibited pronounced antitumor activity and immunoregulatory effect.

SUMMARY: Although the green seaweed Ulva is one of the most common seaweeds in the coastal regions with well‐studied ecological characteristics, few reverse genetic technologies have been developed for it. The clustered regularly interspaced short palindromic repeats (CRISPR)‐Cas9 system is a simple genome‐editing technology based on a ribonucleoprotein (RNP) complex composed of an endonuclease and programmable RNA to target particular DNA sequences. Genome editing makes it possible to generate mutations on a target gene in non‐model organisms without established transgenic technologies. In this study, we applied the CRISPR‐Cas9 RNP genome‐editing system to the green seaweed Ulva prolifera, using polyethylene glycol (PEG)‐mediated transfection. Our experimental system disrupts a single gene (UpAPT) encoding adenine phosphoribosyl transferase (APT) and generates a resistant phenotype for gametophytes cultured in a medium with toxic compound 2‐fluoroadenine. The PEG‐mediated transfection used for gametes resulted in 2‐fluoroadenine‐resistant strains containing short indels or substitutions on UpAPT. Our results showed that the CRISPR‐Cas9 system with PEG‐mediated transfection was efficient for genome editing in Ulva. [ABSTRACT FROM AUTHOR]

Several theories for aging are constantly put forth to explain the underlying mechanisms. Oxidative stress, DNA dysfunction, inflammation, and mitochondrial dysfunction, along with the release of cytochrome c are some of these theories. Diseases such as type 2 diabetes mellitus, intestinal dysfunction, cardiovascular diseases, hepatic injury, and even cancer develop with age and eventually cause death. Ulva polysaccharides, owing to their special structures and various functions, have emerged as desirable materials for keeping healthy. These polysaccharide structures are found to be closely related to the extraction methods, seaweed strains, and culture conditions. Ulvan is a promising bioactive substance, a potential functional food, which can regulate immune cells to augment inflammation, control the activity of aging-related genes, promote tumor senescence, enhance mitochondrial function, maintain liver balance, and protect the gut microbiome from inflammatory attacks. Given the desirable physiochemical and gelling properties of ulvan, it would serve to improve the quality and shelf-life of food. • The theories of aging were discussed and summarized following in time. • The unhealthy aging of the body can be a huge damage to human beings. • The structural characteristics and healthy aging effects of ulvan were described. • More attentions and technics were necessary to investigate the healthy aging of ulvan. [ABSTRACT FROM AUTHOR]

This study describing the morphology of the green algae Geminella protogenita (Kützing) West, which is a rare species found in the territories of Southern Brazil. Although this taxon is widely distributed worldwide, it is known to rarely occur in the regions where it has been registered previously, which is because little attention is given to its taxonomic characteristics based on the morphology. Photomicrographs and cell morphometric data were obtained to conduct the taxonomic characterization. Here, we also provide data on its global distribution and the type of environments to better contribute in the understanding of the biology of this species. [ABSTRACT FROM AUTHOR]

Ulva is a green seaweed that is widely distributed in coastal areas around the world, and genomic information has been reported for several species. However, research on reverse genetics methods is still in its early stages. Although our group has recently achieved efficient knockout of Ulva by introducing Cas9 ribonucleoprotein (RNP) through the PEG method, a precise knock-in transformation method is needed to understand gene and protein functions. Here, we report the development of a targeted insertional mutagenesis method by transfection of Cas9 RNP, donor dsDNA, and single-stranded DNAs homologous to the DSB site created by Cas9 and donor dsDNA. The target gene was RbcS , a well-known high-expression gene, and we attempted to knock in the EGFP or 2A peptide- EGFP sequence at the C-terminus region. This method was also applied to the adenine phosphoribosyltransferase (APT) gene, enabling selection by the toxic compound 2-fluoroadenine. A longer DNA fragment (2.6 kb) expressing EGFP under the RbcS promoter was inserted at the DSB site on the APT locus. As a result, EGFP knock-in transformants were obtained, and the transformant progeny exhibited high EGFP expression levels for several generations. Our method greatly advances the genetic engineering and functional analysis of target genes in Ulva. • Genetic transformation in seaweed remains a challenge. • Cas9 RNP, donor dsDNA, and single-stranded DNAs enable a targeted insertional mutagenesis in Ulva. • Knock-in mutants maintain EGFP expression for several generations. • This methodology marks a significant advancement in biotechnological research for seaweeds. [ABSTRACT FROM AUTHOR]

Microalgae have the potential to recycle CO2 as starch and triacylglycerol (TAG), which provide alternative source of biofuel and high added-value chemicals. Starch accumulates in the chloroplast, whereas TAG accumulates in the cytoplasmic lipid droplets (LD). Preferential accumulation of starch or TAG may be achieved by switching intracellular metabolic carbon flow, but our knowledge on this control remains limited. Are these two products mutually exclusive? Or, does starch act as a precursor to TAG synthesis, or vice versa? To answer these questions, we analyzed carbon flow in starch and lipids using a stable isotope 13C in Chlamydomonas debaryana NIES-2212, which accumulates, without nutrient limitation, starch in the exponential growth phase and TAG in the stationary phase. Pulse labeling experiments as well as pulse labeling and chase experiments were conducted, and then, gas chromatography-mass spectrometry (GC-MS) analysis was performed on starch-derived glucose and lipid-bound fatty acids. We exploited the previously developed method of isotopomer analysis to estimate the proportion of various pools with different isotopic abundance. Starch turned over rapidly to provide carbon for the synthesis of fatty acids in the exponential phase cells. Most fatty acids showed rapid and slow components of metabolism, whereas oleic acid decayed according to a single exponential curve. Highly labeled population of fatty acids that accumulated during the initial labeling decreased rapidly, and replaced by low abundance population during the chase time, indicating that highly labeled fatty acids were degraded and the resulting carbons were re-used in the re-synthesis with about 9-fold unlabeled, newly fixed carbons. Elongation of C16–C18 acids in vivo was indicated by partially labeled C18 acids. The accumulation of TAG in the stationary growth phase was accounted for by both de novo synthesis and remodeling of membrane lipids. These results suggest that de novo synthesis of starch and TAG was rapid and transient, and also almost independent to each other, but there is a pool of starch quickly turning over for the synthesis of fatty acids. Fatty acids were also subject to re-synthesis. Evidence was also provided for remodeling of lipids, namely, re-use of acyl groups in polar lipids for TAG synthesis.

There is little information available regarding genomic differences between sexes in ulvophycean green algae. The detection of these differences will enable the development of sex‐discriminating molecular markers, which are useful for algae showing little apparent difference between sexes. In this study, we identified male‐ and female‐specific DNA sequences in the ulvophycean marine green alga Monostroma angicava, which has a dioicous heteromorphic haplo‐diplontic life cycle, via next‐generation sequencing. Fluorescence in situ hybridization (FISH) showed that signals for the sex‐specific sequences exist only in the nuclei of the corresponding sex, confirming the specificity of the sequences. Sex‐specific molecular markers that targeted these sequences successfully distinguished the sex of gametophytes even in geographically distant populations, indicating that the sex‐specific sequences are universal. These results consistently suggest that male and female gametophytes of M. angicava are genetically different, implying that sex may be determined genetically in this alga. [ABSTRACT FROM AUTHOR]

Microalgae have the potential to recycle CO2 as starch and triacylglycerol (TAG), which provide alternative source of biofuel and high added-value chemicals. Starch accumulates in the chloroplast, whereas TAG accumulates in the cytoplasmic lipid droplets (LD). Preferential accumulation of starch or TAG may be achieved by switching intracellular metabolic carbon flow, but our knowledge on this control remains limited. Are these two products mutually exclusive? Or, does starch act as a precursor to TAG synthesis, or vice versa? To answer these questions, we analyzed carbon flow in starch and lipids using a stable isotope 13C in Chlamydomonas debaryana NIES-2212, which accumulates, without nutrient limitation, starch in the exponential growth phase and TAG in the stationary phase. Pulse labeling experiments as well as pulse labeling and chase experiments were conducted, and then, gas chromatography-mass spectrometry (GC-MS) analysis was performed on starch-derived glucose and lipid-bound fatty acids. We exploited the previously developed method of isotopomer analysis to estimate the proportion of various pools with different isotopic abundance. Starch turned over rapidly to provide carbon for the synthesis of fatty acids in the exponential phase cells. Most fatty acids showed rapid and slow components of metabolism, whereas oleic acid decayed according to a single exponential curve. Highly labeled population of fatty acids that accumulated during the initial labeling decreased rapidly, and replaced by low abundance population during the chase time, indicating that highly labeled fatty acids were degraded and the resulting carbons were re-used in the re-synthesis with about 9-fold unlabeled, newly fixed carbons. Elongation of C16–C18 acids in vivo was indicated by partially labeled C18 acids. The accumulation of TAG in the stationary growth phase was accounted for by both de novo synthesis and remodeling of membrane lipids. These results suggest that de novo synthesis of starch and TAG was rapid and transient, and also almost independent to each other, but there is a pool of starch quickly turning over for the synthesis of fatty acids. Fatty acids were also subject to re-synthesis. Evidence was also provided for remodeling of lipids, namely, re-use of acyl groups in polar lipids for TAG synthesis. [ABSTRACT FROM AUTHOR]

It is established that green algae and land plants progressively colonized freshwater and terrestrial habitats throughout the Paleozoic Era, but little is known about the ecology of Paleozoic saline lakes. Here, we report lipid biomarker and petrographic evidence for the occurrence of a green alga as a major primary producer in a late Paleozoic alkaline lake (Fengcheng Formation; 309–292 Ma). A persistently saline and alkaline lacustrine setting is supported by mineralogical and lipid biomarker evidence alongside extremely enriched δ15Nbulk values (+16 to +24‰) for the lake depocenter. The prominence of C28 and C29 steroids, co‐occurring with abundant carotene‐derived accessory pigment markers in these ancient rocks, is suggestive of prolific primary production and elevated source inputs from haloalkaliphilic green algae. The high C28/C29‐sterane ratios (0.78–1.29) are significantly higher than the typical marine value reported for late Paleozoic rocks (<0.5) and thus are associated with certain groups of chlorophytes. Adaptation to such extreme lacustrine environments, aided by enhanced biosynthesis of certain cell membrane lipids, likely played an important role in the evolution and physiological development of ancient green algae. [ABSTRACT FROM AUTHOR]

A novel photoreceptor dualchrome 1 (DUC1), containing a fused structure of cryptochrome and phytochrome, was discovered in the marine green alga Pycnococcus provasolli. The DUC1 phytochrome region (PpDUC1-N) binds to the bilin (linear tetrapyrrole) chromophores, phytochromobilin (PΦB) or phycocyanobilin (PCB), and reversibly photoconverts between the orange-absorbing dark-adapted state and the far-red-absorbing photoproduct state. This contrasts with typical phytochromes, which photoconvert between the red-absorbing dark-adapted and far-red-absorbing photoproduct states. In this study, we examined the molecular mechanism of PpDUC1-N to sense orange light by identifying the chromophore species synthesized by P. provasolli and the amino acid residues within the PpDUC1-N responsible for sensing orange light in the dark-adapted state. We focused on the PcyA homolog of P. provasolli (PpPcyA). Coexpression with the photoreceptors followed by an enzymatic assay revealed that PpPcyA synthesized PCB. Next, we focused on the PpDUC1-N GAF domain responsible for chromophore binding and light sensing. Ten amino acid residues were selected as the mutagenesis target near the chromophore. Replacement of these residues with those conserved in typical phytochromes revealed that three mutations (F290Y/M304S/L353M) resulted in a 23-nm red-shift in the dark-adapted state. Finally, we combined these constructs to obtain the PΦB-binding F290Y/M304S/L353M mutant and a 38-nm red-shift was observed compared with the PCB-binding wild-type PpDUC1. The binding chromophore species and the key residues near the chromophore contribute to blue-shifted orange light sensing in the dark-adapted state of the PpDUC1-N., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists.)

Trace metal contaminations in natural waters, wetlands, and wastewaters pose serious threats to aquatic ecosystems—mainly via targeting microalgae. In this work, we investigated the effects of toxic amounts of chromium and cadmium ions on the structure and function of the photosynthetic machinery of Chlorella variabilis cells. To halt the propagation of cells, we used high concentrations of Cd and Cr, 50–50 mg L−1, in the forms of CdCl2 x 2.5 H2O and K2Cr2O7, respectively. Both treatments led to similar, about 50% gradual diminishment of the chlorophyll contents of the cells in 48 h, which was, however, accompanied by a small (~10%) but statistically significant enrichment (Cd) and loss (Cr) of ß-carotene. Both Cd and Cr inhibited the activity of photosystem II (PSII)—but with more severe inhibitions with Cr. On the contrary, the PsbA (D1) protein of PSII and the PsbO protein of the oxygen-evolving complex were retained more in Cr-treated cells than in the presence of Cd. These data and the higher susceptibility of P700 redox transients in Cr-treated cells suggest that, unlike with Cd, PSII is not the main target in the photochemical apparatus. These differences at the level of photochemistry also brought about dissimilarities at higher levels of the structural complexity of the photosynthetic apparatus. Circular dichroism (CD) spectroscopy measurements revealed moderate perturbations in the macro-organization of the protein complexes—with more pronounced decline in Cd-treated cells than in the cells with Cr. Also, as reflected by transmission electron microscopy and small-angle neutron scattering, the thylakoid membranes suffered shrinking and were largely fragmented in Cd-treated cells, whereas no changes could be discerned with Cr. The preservation of integrity of membranes in Cr-treated cells was most probably aided by high proportion of the de-epoxidized xanthophylls, which were absent with Cd. It can thus be concluded that beside strong similarities of the toxic effects of Cr and Cd, the response of the photosynthetic machinery of C. variabilis to these two trace metal ions substantially differ from each other—strongly suggesting different inhibitory and protective mechanisms following the primary toxic events.

Mass production of microorganisms, algae among them, for new bioactive compounds and renewable innovative products is a current issue in biotechnology. The greatest challenge of basic research on this topic is to find the best solution for both physiology and scalability. In this study, the main goal was to highlight the contradictions of physiological and technological optimization in the same, relatively small, laboratory scale. The green alga Monoraphidium pusillum (Printz) Komárková-Legnorová was cultured in a conventional Erlenmeyer flask (as air bubbled in a tank-type photobioreactor) and in a hybrid (fermenter type + helical tubular type) photobioreactor of the same volume (2.8 L). Higher cell numbers from 1.7–2.3-fold, 2–2.8-fold higher dry masses, and 1.9–2.6-fold higher total lipid contents (mg·L−1) were measured in the tank reactor than in the hybrid reactor. Cultures in the conventional tank reactor were characterized with better nutrient utilization (42.8–77.7% higher phosphate uptake) and more diverse lipid composition than in the hybrid reactor. The study highlights that well-scalable arrangements and settings could be not optimal (or unsuitable in some cases) from a physiological point of view. The results suggest certain developmental directions for complex, well-scalable devices and highlight the importance of testing the gained physiological optima on these systems.

Abstract Background Hydrogen photoproduction from green microalgae is regarded as a promising alternative solution for energy problems. However, the simultaneous oxygen evolution from microalgae can prevent continuous hydrogen production due to the hypersensitivity of hydrogenases to oxygen. Sulfur deprivation can extend the duration of algal hydrogen production, but it is uneconomical to alternately culture algal cells in sulfur-sufficient and sulfur-deprived media. Results In this study, we developed a novel way to simulate sulfur-deprivation treatment while constantly maintaining microalgal cells in sulfur-sufficient culture medium by overexpressing an endogenous microRNA (miR1166.1). Based on our previous RNA-seq analysis in the model green alga Chlamydomonas reinhardtii, three endogenous miRNAs responsive to sulfur deprivation (cre-miR1166.1, cre-miR1150.3, and cre-miR1158) were selected. Heat-inducible expression vectors containing the selected miRNAs were constructed and transformed into C. reinhardtii. Comparison of H2 production following heat induction in the three transgenic strains and untransformed control group identified miR1166.1 as the best candidate for H2 production regulation. Moreover, enhanced photobio-H2 production was observed with repeated induction of miR1166.1 expression. Conclusions This study is the first to identify a physiological function of endogenous miR1166.1 and to show that a natural miRNA can regulate hydrogen photoproduction in the unicellular model organism C. reinhardtii.

Phytohormones play key roles in many aspects of plant growth and development, as well as in resistance to abiotic stresses. The presence of heavy metal limits phytohormone endogenous level; however, the application of brassinosteroids (BRs) restores phytohormone homeostasis and reduces unfavorable consequences of heavy metal on plant growth. Therefore, the aim of this study was to (1) broaden previously published analyses/findings to study the effect of 24-epibrassinolide (EBL) and/or lead (Pb) on Acutodesmus obliquus phytohormone level after 5 days of cultivation using LC-QToF-MS quantification technique and (2) extend the total amount of quantified phytohormones in A. obliquus. The study confirmed that exogenous EBL increased the contents of gibberellin A3 (GA3), auxins (AXs) (indole-3-acetic acid, phenylacetic acid), BRs brassinolide, 24-epibrassinolide (EBL), 28-homobrassinolide, castasterone, 24-epicastasterone, typhasterol, cathasterone, 6-deoxotyphasterol, as well as different types of cytokinins (CKs): free bases, ribosides, and conjugates (N- and O-glucosides). On the other hand, treatment with Pb had an opposite effect on BRs, GA3, AXs, and free bases, as well as ribosides of CKs. The abscisic acid (ABA) level decreased under EBL treatment but increased in response to Pb stress. The level of N-glucosides, as well as O-glucosides of CKs, also significantly increased in response to Pb alone. Interestingly, the co-application of EBL and Pb led to an increase in BRs, GA3, AXs, and CKs content in the algae. Principal component analysis revealed that based on treatments, increase of GA3, BRs, and AXs was found to be in the following order: 1 μM EBL > 0.01 μM Pb + 1 μM EBL > 500 μM Pb + 1 μM EBL > control > 0.01 μM Pb > 500 μM Pb. Moreover, very strong significant linear relations between almost all studied AXs and BRs were noted. Summarizing, this research did not only allow to detect the occurrence of ABA, GA3, AXs, BRs, and CKs in A. obliquus for the first time but also to study the combined action of EBL and Pb, as well as compare it with treatment alone. [ABSTRACT FROM AUTHOR]

Trace metal contaminations in natural waters, wetlands, and wastewaters pose serious threats to aquatic ecosystems—mainly via targeting microalgae. In this work, we investigated the effects of toxic amounts of chromium and cadmium ions on the structure and function of the photosynthetic machinery of Chlorella variabilis cells. To halt the propagation of cells, we used high concentrations of Cd and Cr, 50–50 mg L−1, in the forms of CdCl2 x 2.5 H2O and K2Cr2O7, respectively. Both treatments led to similar, about 50% gradual diminishment of the chlorophyll contents of the cells in 48 h, which was, however, accompanied by a small (~10%) but statistically significant enrichment (Cd) and loss (Cr) of ß-carotene. Both Cd and Cr inhibited the activity of photosystem II (PSII)—but with more severe inhibitions with Cr. On the contrary, the PsbA (D1) protein of PSII and the PsbO protein of the oxygen-evolving complex were retained more in Cr-treated cells than in the presence of Cd. These data and the higher susceptibility of P700 redox transients in Cr-treated cells suggest that, unlike with Cd, PSII is not the main target in the photochemical apparatus. These differences at the level of photochemistry also brought about dissimilarities at higher levels of the structural complexity of the photosynthetic apparatus. Circular dichroism (CD) spectroscopy measurements revealed moderate perturbations in the macro-organization of the protein complexes—with more pronounced decline in Cd-treated cells than in the cells with Cr. Also, as reflected by transmission electron microscopy and small-angle neutron scattering, the thylakoid membranes suffered shrinking and were largely fragmented in Cd-treated cells, whereas no changes could be discerned with Cr. The preservation of integrity of membranes in Cr-treated cells was most probably aided by high proportion of the deepoxidized xanthophylls, which were absent with Cd. It can thus be concluded that beside strong similarities of the toxic effects of Cr and Cd, the response of the photosynthetic machinery of C. variabilis to these two trace metal ions substantially differ from each other—strongly suggesting different inhibitory and protective mechanisms following the primary toxic events. [ABSTRACT FROM AUTHOR]

Oxygenic photosynthesis converts light energy into chemical energy via electron transport and assimilates CO2 in the Calvin–Benson cycle with the chemical energy. Thus, high light and low CO2 conditions induce the accumulation of electrons in the photosynthetic electron transport system, resulting in the formation of reactive oxygen species. To prevent the accumulation of electrons, oxygenic photosynthetic organisms have developed photoprotection mechanisms, including non-photochemical quenching (NPQ) and alternative electron flow (AEF). There are diverse molecular mechanisms underlying NPQ and AEF, and the corresponding molecular actors have been identified and characterized using a model green alga Chlamydomonas reinhardtii. In contrast, detailed information about the photoprotection mechanisms is lacking for other green algal species. In the current study, we examined the photoprotection mechanisms responsive to CO2 in the green alga Chlorella variabilis by combining the analyses of pulse-amplitude-modulated fluorescence, O2 evolution, and the steady-state and time-resolved fluorescence spectra. Under the CO2-limited condition, ΔpH-dependent NPQ occurred in photosystems I and II. Moreover, O2-dependent AEF was also induced. Under the CO2-limited condition with carbon supplementation, NPQ was relaxed and light-harvesting chlorophyll-protein complex II was isolated from both photosystems. In C. variabilis, the O2-dependent AEF and the mechanisms that instantly convert the light-harvesting functions of both photosystems may be important for maintaining efficient photosynthetic activities under various CO2 conditions. [ABSTRACT FROM AUTHOR]

A facile, convenient and green method has been employed for the synthesis of silver nanoparticles (AgNPs) using dried biomass of a green alga, Chlorella ellipsoidea. The phytochemicals from the alga, as a mild and non‐toxic source, are believed to serve as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of a surface plasmon resonance band at 436 nm and energy dispersive X‐ray spectroscopy. The transmission electron microscopy images showed the nanoparticles to be nearly spherical in shape with different sizes. A dynamic light scattering study revealed the average particle size to be 220.8 ± 31.3 nm. Fourier transform infrared spectroscopy revealed the occurrence of alga‐derived phytochemicals attached to the outer surface of biogenically accessed silver nanoparticles. The powder X‐ray diffraction study revealed the face‐centred cubic crystalline structure of the nanoparticles. The as‐synthesized biomatrix‐loaded AgNPs exhibited a high photocatalytic activity for the degradation of the hazardous pollutant dyes methylene blue and methyl orange. The catalytic efficiency was sustained even after three reduction cycles. A kinetic study indicated the degradation rates to be pseudo‐first order with the degradation rate being 4.72 × 10−2 min−1 for methylene blue and 3.24 × 10−2 min−1 for methyl orange. The AgNPs also exhibited significant antibacterial activity against four selected pathogenic bacterial strains. [ABSTRACT FROM AUTHOR]

The microalga Dunaliella salina has been broadly studied for different purposes such as beta-carotene production, toxicity assessment and salinity tolerance, yet research on the habitat suitability of this alga has rarely been reported. The present research aims to apply a suitable monitoring and modelling methods (two critical steps in ecological researches) to predict the abundance of D. salina. The abundance of D. salina was predicted by decision tree model (J48 algorithm) in 10 different monitoring sites during 1-year study period (2016–2017) in the Meighan wetland, one of the valuable hypersaline wetlands in Iran. The abundance of alga (as output of model) together with various water quality and physical-habitat wetland characteristics (as inputs of model) were monthly and repeatedly monitored in two different depths (one from the surface layer and another one from the depth of maximum 50 cm) which in total resulted in 240 instances (120 instances for each depth). Based on trial and error, a sevenfold cross-validation resulted in the highest predictive performances of the model (CCI > 75% and Cohen's Kappa > 0.65). According to the model's prediction, the number of sunny hours might be one of the most important driving parameters to meet the habitat requirements of alga in the hypersaline wetland. Model also predicted that an increase in dissolved oxygen and sodium concentrations might increase the abundance of D. salina in the salt wetland. In contrast, an increase in total suspended solids concentration and monthly precipitation might lead to a decrease in the abundance of alga. Chi-square test of independence showed a significant difference between the abundance of the D. salina and spatio-temporal patterns in the wetland (Pearson chi-square statistic = 221.7, p = 0.001) so warm seasons (spring and summer) had more contribution to the sampling of the species than cold seasons (autumn and winter). The difference in the abundance of the species in different sampling sites can be attributed due to the various anthropogenic activities. [ABSTRACT FROM AUTHOR]

Aquatic organisms are exposed to many stressors, e.g., heavy metals. Brassinosteroids, a plant hormone group, can effectively stimulate plants to defend against the negative impact of a heavy metal. The present study was conducted with an aim to find out the influence of 24-epibrassinolide (EBL) on Acutodesmus obliquus treated with 0.01 and 500 μM of lead (Pb) ions during 7 days of cultivation. Pb has a toxic effect on algal cultures because it limits both the growth and development and induces oxidative stress. Simultaneously, 1 μM EBL was involved in protecting algal cells against the toxic effect of Pb. Despite the presence of Pb, EBL significantly increased the number of algal cells and their metabolite content (e.g., proteins, monosaccharides, chlorophylls, carotenes, and xanthophylls). Cultures treated concurrently with EBL and Pb were characterized by a reduction in their content of endogenous Pb, H2O2, and malondialdehyde. Also, EBL increased the activity of catalase, ascorbate peroxidase, superoxide dismutase, glutathione reductase, and the content of ascorbate and glutathione. EBL increased the phytochelatin synthase activity, thereby enhancing the production of phytochelatins accountable for both binding and detoxification of Pb. These results indicate the influence of EBL on the inhibitory effect of Pb in A. obliquus. These findings help to clarify the role of BRs in the algal adaptation to the prevailing stressful conditions. [ABSTRACT FROM AUTHOR]

Carnosine, a dipeptide composed of β-alanine and histidine, is predominantly found in animals such as mammals, birds, and fish, with no known presence in plants, microalgae, and other organisms. It can undergo methylation to produce anserine, β-alanyl- N -methyl-L-histidine. These imidazole peptides are known for their antioxidative properties and fatigue recovery effects. The synthesis of carnosine is catalyzed by carnosine synthase, encoded by the ATPGD1 or CARNS1 gene. Recently, homologous proteins to carnosine synthase have been reported from several microalgal genomes, although their biological functions remain unknown. In this study, we investigated the role of carnosine synthase-like protein in the green alga Monoraphidium braunii SAG 48.87. Initially, we examined the accumulation of carnosine and anserine in M. braunii cells cultivated under various conditions. Interestingly, salt stress induced the accumulation of anserine. The cells treated with 420 mM NaCl accumulated 38.3 μg g−1 dry weight (DW) of anserine. Expression of ATPGD1a , putatively annotated as a carnosine synthase gene, was induced under salt stress conditions, while expression of ATPGD1b was downregulated. The Escherichia coli cells expressing the recombinant ATPGD1a primarily accumulated anserine (269.9 μg g−1 DW) and a small amount of carnosine, although we could not confirm any carnosine or anserine synthesis by the purified recombinant protein. These findings suggest that the carnosine synthase homolog in microalgae may play a role in synthesizing imidazole dipeptides, and anserine could serve as a salt protective agent and help stabilize cellular functions, particularly under salt conditions. This is the first observation of the synthesis of the imidazole dipeptide from any organism except animals and anserine protecting from salt stress. • We found anserine in the cells of a green alga Monoraphidium braunii. • Salt stress induced the accumulation of anserine in M. braunii. • Applying anserine or carnosine relieved from the salt stress. • A gene for carnosine synthase-like protein, ATPGD1a , induced under salt. • Expression of ATPGD1a in Escherichia coli produced anserine. [ABSTRACT FROM AUTHOR]

Genome sequence of an ulvan-degrading bacterium, Vibrio sp. strain 10N, is presented. The genome is 5,358,550 bp with a G + C content of 46.5%. A total of 4,712 coding sequences, including two novel ulvan lyase genes encoding a BNR4 and a glycoside hydrolase (GH88) motif, are known to be involved in the degradation of green algae., Competing Interests: The authors declare no conflict of interest.

Glutaredoxins (GRXs) are thioredoxin superfamily members exhibiting thiol-disulfide oxidoreductase activity and/or iron-sulfur (Fe-S) cluster binding capacities. These properties are determined by specific structural factors. In this study, we examined the capacity of the class I Chlamydomonas reinhardtii GRX2 recombinant protein to catalyze both protein glutathionylation and deglutathionylation reactions using a redox sensitive fluorescent protein as a model protein substrate. We observed that the catalytic cysteine of the CPYC active site motif of GRX2 was sufficient for catalyzing both reactions in the presence of glutathione. Unexpectedly, spectroscopic characterization of the protein purified under anaerobiosis showed the presence of a [2Fe-2S] cluster despite having a presumably inadequate active site signature, based on past mutational analyses. The spectroscopic characterization of cysteine mutated variants together with modeling of the Fe–S cluster-bound GRX homodimer from the structure of an apo-GRX2 indicate the existence of an atypical Fe–S cluster environment and ligation mode. Overall, the results further delineate the biochemical and structural properties of conventional GRXs, pointing to the existence of multiple factors more complex than anticipated, sustaining the capacity of these proteins to bind Fe–S clusters.