Search Results (333)

Extracellular vesicles (EVs), nanoscale membrane-enclosed particles, are natural carriers of proteins and nucleic acids. Microalgae are widely used as a source of bioactive substances in the food and cosmetic industries and definitely have a potential to be used as the producers of EVs for biomedical applications. In this study, the extracellular vesicles isolated from the culture medium of two unicellular microalgae, Chlamydomonas reinhardtii (Chlamy-EVs) and Parachlorella kessleri (Chlore-EVs), were characterized by atomic force microscopy (AFM), cryo-electronic microscopy (cryo-EM), and nanoparticle tracking analysis (NTA). The biocompatibility with human cells in vitro (HEK-293T, DF-2 and A172) and biodistribution in mouse organs and tissues in vivo were tested for both microalgal EVs. An exogenous therapeutic protein, human heat shock protein 70 (HSP70), was successfully loaded to Chlamy- and Chlore-EVs, and its efficient delivery to human glioma and colon carcinoma cell lines has been confirmed. Additionally, in order to search for potential therapeutic biomolecules within the EVs, their proteomes have been characterized. A total of 105 proteins were identified for Chlamy-EVs and 33 for Chlore-EVs. The presence of superoxide dismutase and catalase in the Chlamy-EV constituents allows for considering them as antioxidant agents. The effective delivery of exogenous cargo to human cells and the possibility of the particle yield optimization by varying the microalgae growth conditions make them favorable producers of EVs for biotechnology and biomedical application. Full article

The growing concern for environmental sustainability has led to an increased interest in biodegradable materials derived from renewable resources. This study explores the innovative use of residual biomass from the green photosynthetic microalga Chlamydomonas reinhardtii, left over after polysaccharide extraction, as a natural filler in the development of the compostable protein-based material SP-Milk^®. The microalgal biomass was characterized using Fourier transform infrared spectroscopy (FTIR) and UV-Visible Spectroscopy to assess its chemical and structural composition. Subsequently, it was incorporated into a biodegradable protein matrix, and the resulting biocomposites were evaluated for mechanical and thermal properties. The results demonstrate that the incorporation of algal filler improves the mechanical strength and elasticity of the material while reducing its glass transition temperature, highlighting its potential for use in sustainable applications as a possible substitute for conventional plastics. The biocomposite materials developed, based on the protein-based material SP-Milk^® and residual microalgal biomass, are environmentally friendly, contributing to the reduction in pollution and the risks associated with plastic accumulation. Thus, this study offers a simple, effective, and sustainable strategy for the valorization of microalgal biomass, enabling the production of biodegradable materials with enhanced mechanical performance, suitable for applications such as sustainable packaging within a circular economy framework. Full article

Ammonia is a critical compound for numerous industrial processes; however, the conventional methods for its production present substantial environmental challenges. Co-producing biofuels and ammonia from biomass through anaerobic digestion offers a promising alternative to address these concerns. This study presents a theoretical assessment of the co-production of biomethane and ammonia from microalgae and cyanobacteria, utilising water from abandoned mine and quarry pit-lakes—specifically focusing on the Alessandria district as a case study. The analysis is based on the average values reported in the literature for the anaerobic digestion of selected biomass types. The results highlight Arthrospira platensis, Chlamydomonas reinhardtii, Chlorella spp., and Chlorella pyrenoidosa as the most promising species due to their superior yields of both ammonia and biomethane. This work aims to promote new opportunities for repurposing disused mining pit-lakes, contributing to the development of sustainable pathways for the integrated production of biofuels and ammonia. In this context, exploring integrated biorefinery systems within a bio-based economy represents an auspicious direction for future research, potentially enhancing the process efficiency and reducing costs. Full article

The environment is undergoing a constant incorporation of new pollutants, which must be eliminated to avoid toxicity problems. Amoxicillin (AMX) is a widely used antibiotic today, and for this reason, it reaches natural media with the consequent environmental risk. Biosorption is an effective and environmentally friendly solution which can be used for the removal of AMX. In the present study, the properties of the living biomass of the microalga Chlamydomonas reinhardtii were studied to determine the capacity of this biomass to remove AMX. This biomass has demonstrated to have good qualities to remove AMX with a maximum capacity of 12.72 ± 0.57 mg g⁻¹. Light was an important factor in increasing the removal capacity of this living biomass by 35.2%. Although this antibiotic underwent spontaneous degradation (unaffected by light), the presence of the biomass increased the amount removed and the removal rate. The amount removed by this biomass in the presence of light was always higher than the amount lost by spontaneous degradation. The kinetics that best adjusted was pseudo-second order. Maximum removal was obtained at pH 6. A point of zero charge and Fourier transform infrared spectrometry were used to characterize the biomass and study the process. Full article

Microalgae interact with mineral particles in an aqueous environment, yet how clay minerals affect physiological processes in algal cells remains unexplored. In this study, we compared the effects of palygorskite (Pal) and montmorillonite (Mt), which respectively represent fibrous and layered clay minerals, on the physiological processes of Chlamydomonas reinhardtii. It was observed that C. reinhardtii responded differently to the treatments of Pal and Mt. The Pal particles bound tightly to and even inserted themselves into cells, resulting in a significant decrease in cell numbers from 27.35 to 21.02 × 10⁷ mL⁻¹. However, Mt was only loosely attached to the cell surface. The photosynthesis in the algal cells was greatly inhibited by Pal, with the rETR_max significantly reduced from 103.80 to 56.67 μmol electrons m⁻²s⁻¹ and the downregulation of IF2CP, psbH and OHP1, which are key genes involved in photosynthesis. In addition, Pal reduced the quantities of proteins and polysaccharides in extracellular polymeric substances (EPSs) and the P uptake by C. reinhardtii when the P level in the culture was 3.15 mg/L. However, no significant changes were found regarding the above EPS components or the amount of P in algal cells upon the addition of Mt. Together, the impacts of fibrous Pal on C. reinhardtii was more profound than those of layered Mt. Full article

Polyamines play a pivotal role in regulating the growth and metabolic adaptation of microalgae, yet their integrative regulatory roles remain underexplored. This review advances a comprehensive perspective of microalgae growth, integrating polyamine dynamics, amino acid metabolism, and redox balance. Polyamines (putrescine, spermidine, and spermine) biology in microalgae, particularly Chlamydomonas reinhardtii, is reviewed, exploring their critical function in modulating cell cycle progression, enzymatic activity, and stress responses through nucleic acid stabilization, protein synthesis regulation, and post-translational modifications. This review explores how the exogenous supplementation of polyamines modifies their intracellular dynamics, affecting growth phases and metabolic transitions, highlighting the complex regulation of internal pools of these molecules. Comparative analyses with Chlorella ohadii and Scenedesmus obliquus indicated species-specific responses to polyamine fluctuations, linking putrescine and spermine levels to important tunable metabolic shifts and fast growth phenotypes in phototrophic conditions. The integration of multi-omic approaches and computational modeling has already provided novel insights into polyamine-mediated growth regulation, highlighting their potential in optimizing microalgae biomass production for biotechnological applications. In addition, genomic-based modeling approaches have revealed target genes and cellular compartments as bottlenecks for the enhancement of microalgae growth, including mitochondria and transporters. System-based analyses have evidenced the overlap of the polyamines biosynthetic pathway with amino acids (especially arginine) metabolism and Nitric Oxide (NO) generation. Further association of the H₂O₂ production with polyamines metabolism reveals novel insights into microalgae growth, combining the role of the H₂O₂/NO rate regulation with the appropriate balance of the mitochondria and chloroplast functionality. System-level analysis of cell growth metabolism would, therefore, be beneficial to the understanding of the regulatory networks governing this phenotype, fostering metabolic engineering strategies to enhance growth, stress resilience, and lipid accumulation in microalgae. This review consolidates current knowledge and proposes future research directions to unravel the complex interplay of polyamines in microalgal physiology, opening new paths for the optimization of biomass production and biotechnological applications. Full article

Mouse sperm-associated antigen 6-like (SPAG6L) evolved from SPAG6, the mammalian ortholog of Chlamydomonas PF16, which is localized in the central apparatus of the motile cilia and is essential for ciliary motility. Even though the amino acid sequences of the two SPAG6 proteins are highly similar, the two proteins have different biological expression patterns in vivo. No major phenotypes were discovered in the global Spag6 knockout mice. However, the global Spag6l knockout mice demonstrated multiple phenotypes in tissues with and without cilia. Since SPAG6L decorates microtubules and modulates cytoskeleton function, and Sertoli cells have a well-developed microtubule transport network, the potential function of SPAG6L in Sertoli cells was evaluated. The floxed Spag6l mice were crossed with Amh-Cre transgenic mice to inactivate the Spag6l gene specifically in Sertoli cells. Surprisingly, the fertility of the homozygous mutant males was not reduced. The testis size and sperm number and motility showed no significant difference to those of the control mice. Testicular histology also showed normal spermatogenesis. No significant changes were observed in the number of Sertoli cells and blood–testis barrier function. Our study showed that the inactivation of only Spag6l does not affect Sertoli cell function during the first 6 months of life. Full article

Molybdenum (Mo) is a vital micronutrient for nearly all living organisms, serving as a cofactor for molybdoenzymes that catalyze essential redox reactions in nitrogen metabolism. Among these enzymes, nitrate reductase plays a crucial role in nitrate assimilation. Maintaining Mo homeostasis—including uptake, storage, and utilization—is critical to avoid both deficiency and toxicity. Our research focuses on uncovering novel molecular components involved in Mo homeostasis, particularly in connection with nitrate assimilation, using Chlamydomonas reinhardtii, a model green microalga. To achieve this, we generated more than 5000 Chlamydomonas transformants through insertional mutagenesis using a paromomycin resistance cassette (AphVIII) and screened them for altered growth on nitrate and under different Mo concentrations. We identified four strains showing altered growth patterns when using nitrate as a nitrogen source or exhibiting increased sensitivity or resistance to Mo. The genomic alterations in these strains were identified. Notably, both a Mo-resistant and a Mo-sensitive transformant had disruptions in the genes that encoded ABC-type transport proteins, indicating a potential role for these proteins in Mo transport. Additionally, two strains were unable to grow on nitrate. One of them had a mutation in the CNX7, a gene involved in Mo cofactor biosynthesis, while the other had a mutation in BAT1, an amino acid transporter. The BAT1 mutant represents an interesting case study, as this gene has not previously been associated with nitrate metabolism. These findings enhance our understanding of Mo and nitrate homeostasis mechanisms and open new paths for engineering microalgae with improved nitrogen assimilation. Full article

Microalgae have evolved a diverse carotenoid profile, enabling efficient light harvesting and photoprotection. Previous studies have demonstrated the feasibility of genome editing in the green algal model species Chlamydomonas reinhardtii, leading to significant modifications in carotenoid accumulation. By overexpressing a fully redesigned β-carotene ketolase (bkt), the metabolic pathway of C. reinhardtii was successfully redirected toward astaxanthin biosynthesis, a high-value ketocarotenoid with exceptional antioxidant properties, naturally found in only a few microalgal species. In this study, a tailor-made double knockout targeting lycopene ε-cyclase (LCYE) and zeaxanthin epoxidase (ZEP) was introduced as a background for bkt expression to ensure higher substrate availability for bkt enzyme. The increased zeaxanthin availability resulted in a 2-fold increase in ketocarotenoid accumulation compared to the previously engineered bkt1 or bkt5 strain in the UVM4 background. Specifically, the best Δzl-bkt-expressing lines reached 2.84 mg/L under low light and 2.58 mg/L under high light, compared to 1.74 mg/L and 1.26 mg/L, respectively, in UVM4-bkt strains. These findings highlight the potential of rationally designed microalgal host strains, developed through genome editing, for biotechnological applications and high-value compound production. Full article

The possible regulatory effects of C2H2 zinc finger proteins, which are important transcription factors, on intertidal seaweed responses to abiotic stress are unclear. This study was conducted to comprehensively analyze the C2H2 gene family of a representative intertidal seaweed species (Pyropia haitanensis) and clarify its genomic characteristics and biological functions. A total of 107 PhC2H2 zinc finger protein-encoding genes distributed on five P. haitanensis chromosomes were identified and divided into three subgroups. The expression levels of 85, 61, 58, 45, and 41 PhC2H2 genes responded in the maturation of filaments, high-temperature, salt, low-irradiance, and dehydration stress, respectively. The PhC2H2 gene family was conserved during Porphyra evolution, with no indications of large-scale genome-wide replication events. On average, PhC2H2 genes had more transposable element (TE) insertions than Pyropia yezoensis and Porphyra umbilicalisC2H2 genes, suggesting that TE insertions may have been the main driver of PhC2H2 gene family expansion. A key gene (PhC2H2.94) screened following a quantitative trait locus analysis was significantly responsive to high-temperature stress and was associated with photosynthesis, peroxisomes, the ubiquitin proteasome pathway, and the endoplasmic reticulum-related protein processing pathway, which contribute to the stress tolerance of P. haitanensis. Additionally, PhC2H2.94 transgenic Chlamydomonas reinhardtii exhibited increased tolerance to heat stress. This study provides new insights and genetic resources for characterizing the molecular mechanism underlying intertidal seaweed responses to abiotic stresses and breeding stress-resistant macroalgae. Full article

The increasing use of nanostructured silver-containing inorganic materials raises concerns about their impact on aquatic organisms. This study assessed the toxicity of silver-modified bentonite composites on Chlamydomonas sp. Two materials were tested: silver-exchanged bentonite (Ben-Ag) and its reduced form (Ben-Ag (H₂)).Microalgae were exposed to 0.5 IC₅₀, 1.5 IC₅₀, and 2 IC₅₀. Ben-Ag showed higher toxicity than Ben-Ag (H₂), which even promoted algal growth at low doses. Fluorescence microscopy revealed morphological shrinkage in treated cells. Increased phenol content, elevated malondialdehyde (MDA) levels, and altered antioxidant enzyme activities further confirmed Ben-Ag toxicity, along with reduced growth and photosynthetic pigments. Transcriptomic analysis revealed significant changes in gene expression under Ben-Ag exposure. Genes involved in photosynthesis (petB, psbL), caspase activity (casp), and carotenoid metabolism (Q2CHY) were down-regulated, indicating stress-induced damage. In contrast, genes encoding stress response enzymes (SOD, peroxidase), carbon metabolism enzymes (rbcL, PGQ1), and β-carotene biosynthesis (Q2BKT) were up-regulated, reflecting cellular defense mechanisms. Overall, the study highlights the high toxicity of Ben-Ag to Chlamydomonas sp., emphasizing the importance of evaluating environmental risks before using such materials in aquatic environments. Full article

Cyanobacteria negatively affect zooplankton through several mechanisms including mechanical interference, toxicity, and poor food quality due to a shortage of essential lipids. To understand the nature of each of these mechanisms, they should be examined independently. The goal of our study was to assess the influence of cyanobacteria food quality on the competitive outcomes between the small-bodied Daphnia longispina and the large-bodied Daphnia magna. We conducted life-table experiments to assess R* (population threshold food concentration), competition experiments to determine the outcome of competition, and computer simulation experiments at high levels of food supply, which are difficult to realize in laboratory conditions. We used two types of food: the high-quality green algae Chlamydomonas klinobasis (GREEN) and the cyanobacterium Synechococcus elongatus (CYANO), which contains low levels of essential lipids, but is non-toxic and unicellular. We found that the small-bodied D. longispina was a superior competitor in GREEN, while the large-bodied D. magna was more abundant in CYANO. We established that the species ratio in GREEN was dependent on competitive interaction, while abundances of daphnids in CYANO were controlled by poor food quality. Since cyanobacteria act as a powerful force for structuring cladoceran communities, the role of competition for food between these two Daphnia species greatly declined under their effects. Full article

The contamination of water by heavy metals is among the main ecological challenges of society due to industrialization and urbanization. To overcome this issue, various treatment processes have been developed. Phycoremediation is considered a promising strategy offering advantages in terms of cost-effectiveness. The present work aims to investigate the cellular responses of an isolated green microalga strain (Chlamydomonas sp.) to chromium (Cr) and copper (Cu) exposure in single and bimetallic systems. At ½ IC₅₀ concentration, the metal removal efficiencies were reported: up to 58.11 ± 0.979% for Cu and 41.4 ± 0.870% for Cr in single systems. When both metals were combined, Cr removal efficiency improved to 57.71 ± 0.832%, whereas Cu removal efficiency showed minimal variation, reaching 58.43 ± 1.059%. Furthermore, Cu and Cr appeared to have a negative effect on cell growth and photosynthetic pigment accumulation. An enhancement in lipid content for microalgae cells after Cu and/or Cr exposure, particularly C14:0, C16:0, C20:0, C18:0, C16:1, C18:1, and C20:1, as well as polysaccharides, was detected, whereas the protein content decreased. FTIR analysis showed that several functional groups could be involved in the phycoremediation process. Full article

Understanding triacylglycerol (TAG) metabolism is crucial for developing algae as a source of biodiesel. TAGs are the main reservoir of energy in most eukaryotes. The final, rate-limiting step in the formation of TAGs is catalyzed by 1,2-diacylglycerol acyltransferases (DGATs). In the green alga Chlamydomonas reinhardtii, DGAT3 is phylogenetically related to plant DGAT3 but unrelated to other DGATs from eukaryotes, such as DGAT1 and DGAT2. In this study, we described the conformational preferences and the lipid-binding features of the DGAT3 from C. reinhardtii. To characterize its conformational stability and structural features, we used several biophysical probes, namely, fluorescence, circular dichroism (CD), and differential scanning calorimetry (DSC). Our results showed that the protein was mainly disordered, containing a small population of folded conformations in a narrow pH range (pH 8 to 10). The conformational stability of the folded structure of DGAT3 was very low, as shown by urea or guanidinium denaturations. Thermal denaturation, followed by fluorescence or CD, as well as calorimetric denaturation, followed by DSC, did not yield any transition in the pH range where DGAT3 acquired a “native-like” conformation. Furthermore, we used two approaches to demonstrate the interaction of DGAT3 with lipid membranes at the pH at which it had acquired a “native-like” conformation. The first involved the measurement of anisotropy and fluorescence quenching of the protein. The second approach focused on examining possible modifications of the biophysical properties of lipids due to their interaction with DGAT3, through anisotropy measurements and leakage assays. Both methods produced consistent results, suggesting that DGAT3 preferentially interacted with negatively charged membranes. These results will allow the design of a more efficient and stable DGAT3, as well as an in-depth understanding of how the metabolism of TAGs is accomplished in C. reinhardtii. Full article

During our research on the diversity of diatoms and green microalgae from Egypt, four new-to-science, newly recorded, and poorly known species were retrieved from different Egyptian habitats. The new benthic diatom species Halamphora shaabanii A.A. Saber, El-Sheekh, Levkov, H. Saber et Cantonati sp. nov., which could not be identified using the currently available literature, was described from the high-conductivity, oasis lake Abu Nuss in the El-Farafra Oasis, located in the Western Desert of Egypt, employing both light (LM) and scanning electron (SEM) microscopy observations. A detailed comparison of the biometrically distinctive traits, and ecological preferences, of this new diatom species revealed sufficient differentiations from its morphologically most closely related species: H. atacamana, H. caribaea, H. ectorii, H. gasseae, H. halophila, H. mosensis, H. poianensis, and H. vantushpaensis. Ecologically, Halamphora shaabanii can tolerate relatively high nutrients (N and P) and prefers saline inland environments with NaCl water types. The araphid diatom Pseudostaurosiropsis geocollegarum was observed in the epilithic diatom assemblages of the River Nile Damietta Branch and identified on the basis of LM and SEM. From an ecological standpoint, P. geocollegarum seems to prefer elevated nutrient concentrations (meso-eutraphentic species), reflecting different human influences on the freshwater River Nile Damietta Branch. Based on the available literature, this is the first documentation of this freshwater diatom species for Egypt, and the second record for the African continent. Two green motile microalgae, Chlamydomonas proboscigera and Gonium pectorale, were isolated and identified from the terrestrial biomes of the arid habitat “Wadi El-Atshan” in the Eastern Desert of Egypt. C. proboscigera is reported herein for the first time in the Egyptian algal flora, while G. pectorale is poorly documented in the available literature. In light of our findings, the Egyptian habitats, particularly the isolated desert ecosystems, are interesting biodiversity hotspots and have a richer algal microflora than earlier anticipated. Furthermore, more in-depth taxonomic studies, using a combined polyphasic approach, are needed not only to foster our knowledge of the Egyptian and African algal and cyanobacterial diversity and biogeography, but also to be further used in applied environmental sciences. Full article