Search Results (285)

Raceway ponds would allow the sustainable production of algal biomass because of their lower cost. However, for successful cultivation, the target organism needs to prevail despite unavoidable contamination by environmental strains. The development of efficient methods to control cyanobacterial proliferation is thus highly desirable. With the aim to identify new cyanobactericidal substances, a set of natural compounds was screened for the ability to inhibit the growth of a model cyanobacterial strain, Synechococcus elongatus PCC 6301. Three compounds, namely hydroquinone, juglone and plumbagin, were found to be active in the 10⁻⁶ to 10⁻⁴ M range. Activity was confirmed on a panel of 10 other cyanobacteria that showed different sensitivity, with concentrations causing 50% growth inhibition varying up to 2 orders of magnitude. Co-cultivation experiments showed that the growth of Microcystis aeruginosa PCC 7941 was almost completely suppressed at quinone concentrations at which that of Tolypothrix PCC 7601 was substantially unaffected. Juglone and plumbagin in the micromolar range also exerted toxic effects on eukaryotic microalgae, bacteria and yeast, whereas the growth of higher plants was affected only at higher concentrations. In the case of juglone, activity was lost with time after being dissolved, allowing water discharge/recycling. The results point at the aromatic 1.4-quinone/diol ring as a lead moiety for the development of chemicals to help maintaining monospecificity of microalgae cultures. Full article

An intracellular α-glucosidase was isolated and purified from a Pseudanabaena sp. cyanobacterial strain. Before the enzyme purification, the optimal cultural conditions were determined. Optimal culture conditions (15 g/L maltose, 2 g/L yeast extract, 23 ± 1 °C) yielded 3.3 g/L of biomass and 2186 U/L of α-glucosidase in a lab-scale bioreactor. The purified enzyme displayed a molecular mass of 52 kDa with optimum activity at 40 °C and pH 7.0, and maintained stability within an acidic and neutral range of pH 4.0 to 7.0. Enzyme activity was affected by both the concentration and interaction time of the metal ions and chelator. Kinetic constants of K_m, V_max, and k_cat for the hydrolysis of pNPG were determined as 2.0 Mm, 2.9 μmol min⁻¹, and 14.86 min⁻¹, respectively. The activation energy (E_a) was 24.2 kJ mol⁻¹ and the thermodynamic parameters of enthalpy (ΔH^*), entropy (ΔS^*) of activation, Gibbs free energy (ΔG^*), free energy of substrate binding (ΔG^*_E-S), and transition state formation (ΔG^*_Ε-Τ) were 21.6, −116, 57.8, −22.2, and −41.2 kJ mol⁻¹, respectively. Moreover, the thermodynamic parameters for thermal inactivation of the enzyme were ΔH^*= 131 kJ mol⁻¹, 105 ≤ ΔS^* ≤ 108 kJ mol⁻¹, and 96 ≤ ΔG^* ≤ 98 kJ mol⁻¹, while the thermal inactivation energy (E_(a)d) was determined to be 133 kJ mol⁻¹. This is the first detailed investigation concerning the characterization of α-glucosidase derived from cyanobacteria. The presented enzymatic characteristics provide a valuable predictive model for identifying suitable applications. Full article

Microcystis aeruginosa, a kind of cyanobacterium, can lead to water blooms under specific conditions and it is harmful to human and ecological security due to the toxins produced by certain strains. Artemisinin, which is derived from Artemisia annua Linn, has a strong allelopathic effect on algae. Artesunate is a water-soluble derivative of artemisinin. We investigated the effect of artesunate on M. aeruginosa, including growth and key photosynthetic parameters (Fv/Fm, φPSII). Our findings demonstrate that artesunate inhibits the growth of M. aeruginosa by damaging the photosynthetic center of photosystem II (PS II), and this inhibitory effect is enhanced with increasing concentration. At the concentration of 200 mol/L, the maximum inhibition rate was 41.62% for FACHB-315 and 43.19% for FACHB-927 after 96 h. After 24 h of exposure, the φPSII of the two strains decreased significantly (p < 0.01). These results could inform further studies on the use of artesunate to control cyanobacterial growth in water bodies and provide theoretical support for the application of artemisinin derivatives in treating water blooms. Full article

The current study focuses on the diversity, distribution and toxic potential of cyanobacteria in the waterbodies of Moscow, Russia. The research involves the sampling of natural and artificial water environments situated within the Moscow city agglomeration, including the waterbodies of recreational importance. A total of 20 strains of cyanobacteria, namely representatives of Anabaena, Aphanizomenon, Argonema, Dolichospermum, Microcystis and Woronichinia, are isolated from the collected samples. The morphology of the newly obtained strains is analyzed through light microscopy. The results of morphological identification are compared to the molecular data. The molecular phylogeny of the cyanobacterial strains is assessed on the basis of 16S rRNA sequencing. The detection of cyanotoxin-producing genes through PCR reveals two strains of Microcystis aeruginosa capable of microcystin synthesis. Further analysis using HPLC-HRMS demonstrates that microcystin production includes a high proportion (20–28%) of exceptionally toxic microcystin–leucine arginine compounds. Hereby, we discuss the morphology and phylogeny of the analyzed strains and provide comments on the toxic potential of cyanobacteria within the waterbodies of Moscow. Full article

HCBs (Harmful Cyanobacterial Blooms) are increasing in freshwaters across the globe, particularly at lower latitudes. In Southern Europe, a decrease in annual precipitation and an increase in drought periods have enhanced the occurrence of HCBs, impacting both freshwater ecosystems and human health. This review gathers information on isolated cyanobacterial strains with the potential to form cyanobacterial blooms or to be toxic that have been reported over the past half-century in Portugal. Strains of Microcystis aeruginosa are the most represented ones, many of them microcystin producers. Toxic M. aeruginosa strains have been isolated from lakes (Mira, Barrinha de Mira, and Blue), river sections (Tâmega and Guadiana), and reservoirs (Torrão, Vilar, Montargil, Patudos, Caia, Monte da Barca, Corgas, and Magos). Many other strains from potentially toxic species are listed, namely from Aphanizomenon gracile, Aphanizomenon flos-aquae, Sphaerospermopsis aphanizomenoides, Cuspidothrix issatschenkoi, Dolichospermum flos-aquae, Dolichospermum circinalis, Chrysosporum bergii, Raphidiopsis raciborskii or Planktothrix agardhii. Many of the isolated strains were able to produce cyanotoxins such as microcystins, saxitoxins, cylindrospermopsin, or anatoxin. Most isolates belong to the Portuguese culture collections ESSACC (Estela Sousa e Silva Algal Culture Collection); LEGE-CC (Blue Biotechnology and Ecotoxicology Culture Collection); and ACOI (Coimbra Collection of Algae). Despite many strains already having associated molecular data corroborating a correct identification, a large number of strains are still lacking DNA-based information for phylogenetic affiliation. The present checklist is intended to facilitate access to information regarding strains of potentially toxic cyanobacterial species from Portugal in order to contribute to a better understanding of species-specific HCBs at both regional and global scales. Full article

Our current knowledge of the cyanobacterial diversity in Egypt is still underestimated During our routine study on Egyptian cyanobacteria, two interesting and morphologically cryptic strains were isolated from streams of Bahr Yussef and Qarun Lake, one of the oldest lakes in the world, located at the Faiyum depression, Egypt. We applied the polyphasic approaches, combining the state-of-the-art morphotaxonomy, 16S rRNA gene phylogenies, and ecological preferences to precisely unravel the taxonomic positions of these two cyanobacterial strains. Based on a combination of their morphotaxonomic traits and 16S rRNA phylogenetic assessment, we identified them as Alkalinema pantanalense (Leptolyngbyaceae, Leptolyngbyales) and Roholtiella edaphica (Nostocaceae, Nostocales). Both species are considered new cyanobacterial records for Egypt and the African continent based on the available literature. From an ecological standpoint, both species are eutraphentic, where they could tolerate relatively elevated concentrations of NO₃⁻, NH₄⁺ (in particular for R. edaphica), and silicates, reflecting eutrophication signs in the ecosystems they colonize. This study adds to the limited molecular information available on the Egyptian cyanobacteria, and also highlights the need for re-investigation of Egyptian cyanobacteria, using polyphasic approaches, to better understand their taxonomy and ecology. Full article

Cyanobacteria are a natural source of bioactive compounds increasingly recognized for their anti-inflammatory properties. In the Euganean Thermal District (Italy), thermal muds, used to cure arthro-rheumatic diseases, are prepared using natural clay and thermal water, resulting in a mature mud characterized by a complex microbial biofilm dominated by Cyanobacteria. Among these, Phormidium sp. ETS-05 has been shown to contribute to the therapeutic properties of the mud, mainly through the production of bioactive compounds such as exopolysaccharides (EPSs) and glycoglycerolipids (GLs). In contrast, the role of biomolecules from Thermospirulina andreolii ETS-09 and Kovacikia euganea ETS-13, also abundant in mature muds but at higher maturation temperatures, has not been investigated. This study focuses on the lipid profiles of these cyanobacteria, cultivated under temperature conditions that mimic their natural environment and that are different for the three species. Lipid extracts were analyzed for GLs classes and fatty acid composition, and their anti-inflammatory potential was assessed in vivo using a zebrafish inflammation model. All extracts showed anti-inflammatory activity with Phormidium sp. ETS-05 displaying the highest lipid content and the most rapid and potent beneficial effect, likely due to the specific composition of its GLs, presenting the greatest abundance of polyunsaturated fatty acids. These findings provide new insights into the biological basis of the therapeutic effects of Euganean muds and emphasize the importance of maturation conditions for cyanobacterial growth and bioactive lipid production. Full article

Sequencing cyanobacteria from xenic cultures is often challenging when their DNA extracts are confounded by DNA from their heterotrophic microbiome. Using an iterative DNA lysis protocol can fractionate between DNA from the cyanobacterium and the heterotrophic strains. To further demonstrate the utility of this protocol, it was used to sequence another xenic culture of cyanobacteria. This effort led to the assembly of a megabase-length cyanobacterial chromosome; however, repeated ribosomal regions created assembly issues even after adding data from another sequencing run to improve coverage. A separate DNA preparation from a single cell lysis step was also run for comparison but yielded a markedly lower proportion of cyanobacterial reads (<2%). Instead, the circular cyanobacterial chromosome was closed with targeted amplicon sequencing. Phylogenetic analysis assigned this strain to the genus Pseudanabaena. Within the metagenomic assembly were the genomes of six heterotrophic strains, preliminarily assigned as belonging to the genera Acidovorax, Hydrogenophaga, Lysobacter, Novosphingobium, Sediminicoccus, and Tabrizicola. Lysobacter sp. BL-A-41-H3’s chromosome was also assembled as a closed circular contig. This study demonstrates that iterative lysis enriches for cyanobacterial DNA and enables concurrent genome assembly of cohabitating heterotrophs alongside the host cyanobacterium. Full article

In the process of the work of a coal power station is formed ash and slag, which, along with process water, are deposited in the dumps. Coal ash waste dumps significantly degrade the surrounding environment due to their unprotected surfaces, which are highly susceptible to wind and water erosion. This results in the dispersion of contaminants into adjacent ecosystems. Pollutants migrate into terrestrial and aquatic systems, compromising soil quality and water resources, and posing documented risks to the environment and human health. Primary succession on the coal ash dumps of the Apatity thermal power plant (Murmansk Region, NW Russia) was initiated by cyanobacterial colonization. We studied cyanobacterial communities inhabiting three spoil sites that varied in time since decommissioning. These sites are characterized by exceptionally high concentrations of calcium and magnesium oxides—levels approximately double those found in the region’s natural soils. A total of 18 cyanobacterial taxa were identified in disposal sites. Morphological analysis of visible surface crusts revealed 16 distinct species. Furthermore, 24 cyanobacterial strains representing 11 species were successfully isolated into unialgal culture and tested with a molecular genetic approach to confirm their identification from 16S rRNA. Three species were determined with molecular evidence. Cyanobacterial colonization of coal fly ash disposal sites begins immediately after deposition. Primary communities initially exhibit low species diversity (four taxa) and do not form a continuous ground cover in the early years. However, as succession progresses—illustrated by observations from a 30-year-old deposit—spontaneous surface revegetation occurs, accompanied by a marked increase in cyanobacterial diversity, reaching 12 species. Full article

In this paper, cultivable actinobacteria were isolated, cultured, and identified from the heavily algal-bloomed waters of Taihu Lake using 16S rRNA gene sequencing. Among the isolates, a single strain exhibiting vigorous cyanocidal activity against Microcystis aeruginosa FACHB-905 was selected for further investigation. The cyanocidal efficacy and underlying mechanisms of this strain, designated TH05, were assessed through using chlorophyll content, cyanobacterial inhibition rate, and cyanobacterial cell morphology measurements. In addition, oxidative stress responses, expression of key functional genes in FACHB-905, and variations in microcystin concentrations were comprehensively evaluated. Cyanobacterial blooms caused by Microcystis aeruginosa pose serious ecological and public health threats due to the release of microcystins (MCs). In this study, we evaluated the cyanocidal activity and mechanism of a novel actinomycete strain, Streptomyces sp. TH05. Optimization experiments revealed that a light–dark cycle of 12 h/12 h, temperature of 25 °C, and pH 7 significantly enhanced cyanocidal efficacy. Under these conditions, TH05 achieved an 84.31% inhibition rate after seven days of co-cultivation with M. aeruginosa. Scanning electron microscopy revealed two distinct cyanocidal modes: direct physical attachment of TH05 mycelia to cyanobacterial cells, causing cell wall disruption, and indirect membrane damage via extracellular bioactive compounds. Biochemical analyses showed increased levels of malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) during the first five days, peaking at 2.47-, 2.12-, and 1.91-fold higher than control levels, respectively, indicating elevated oxidative stress. Gene expression analysis using elf-p as a reference showed that TH05 modulated key genes associated with photosynthesis (PsaB, PstD1, PstD2, RbcL), DNA repair and stress response (RecA, FtsH), and microcystin biosynthesis (McyA, McyD). All genes were upregulated except for RbcL, which was downregulated. In parallel, microcystin content peaked at 32.25 ng/L on day 1 and decreased to 16.16 ng/L by day 9, which was significantly lower than that of the control group on day 9 (29.03 ng/L). These findings suggest that strain TH05 exhibits potent and multifaceted cyanocidal activity, underscoring its potential for application in the biological control of cyanobacterial blooms. Full article

Microcystins (MCs) are the most toxic and abundant cyanotoxins found in natural waters during harmful cyanobacterial blooms. These toxins pose a significant threat to plant, animal, and human health due to their toxicity. Degradation of MCs by MC-degrading bacteria is a promising method for controlling these toxins, demonstrating safety, high efficiency, and cost-effectiveness. In this study, we isolated potential MC-degrading bacteria (strains TA13, TA14, and TA19) from Lake Kasumigaura in Japan and found that they possess a high capacity for MC degradation. Based on 16S rRNA gene sequencing, all three isolated strains were identified as belonging to the Klebsiella species. These bacteria effectively degraded MC-RR, MC-YR, and MC-LR under various temperature and pH conditions within 10 h, with the highest degrading activity and degradation rate observed at 40 °C. Furthermore, the isolated strains efficiently degraded MCs not only under neutral pH conditions, but also in alkaline environments. Additionally, we detected the MC-degrading gene (mlrA) in all three isolated strains, marking the first report of the mlrA gene in Klebsiella species. The copy number of the mlrA gene in the strains increased after exposure to MCs. These findings indicate that strains TA13, TA14, and TA19 significantly contribute of MC bioremediation in Lake Kasumigaura during cyanobacterial blooms. Full article

This study aimed to investigate phytoplankton dynamics and water quality at three drinking water intakes (Duchang, Hukou, and Xingzi) in Poyang Lake through monthly monitoring from May 2023 to April 2024. The results showed that a total of 168 species of phytoplankton were identified in nine phyla, and there were significant spatial and temporal differences in the abundance of phytoplankton at the three waterworks intakes, with a spatial trend of annual mean values of Duchang > Xingzi > Hukou and a seasonal trend of summer and autumn > spring and winter. The dominant species of phytoplankton in the waterworks intakes of the three waterworks also showed obvious spatial and temporal differences. Cyanobacteria (particularly Pseudanabaena sp. and Microcystis sp.) dominated the phytoplankton communities during summer and autumn, demonstrating significant water degradation potential. In contrast, Cyclotella sp. prevailed in winter and spring assemblages. Based on water quality assessments at the three intake sites, the Duchang County intake exhibited year-round mild eutrophication with persistent mild cyanobacterial blooms (June–October), while the other two sites maintained no obvious bloom conditions. Further analyzing the toxic/odor-producing algal strains, the numbers of dominant species of Pseudanabaena sp. and Microcystis sp. in June–October in Duchang County both exceeded 1.0 × 10⁷ cells·L⁻¹. It is necessary to focus on their release of ATX-a (ichthyotoxin-a), 2MIB (2-Methylisoborneol), MCs (microcystins), etc., to ensure the safety of the water supply at the intake. Building upon these findings, we propose a generalized algal monitoring framework, encompassing three operational pillars: (1) key monitoring area identification, (2) high-risk period determination, and (3) harmful algal warnings. Each of these is substantiated by our empirical observations in Poyang Lake. Full article

Copper (Cu) is an essential micronutrient for cyanobacteria, where it functions as a cofactor in key proteins involved in photosynthesis and antioxidant defense. However, at elevated concentrations, Cu becomes toxic, exhibiting algicidal effects by disrupting metal homeostasis and competing for metal-binding sites on critical cellular proteins. Due to the considerable morphological and physiological diversity within the phylum Cyanobacteria, the thresholds for Cu deficiency or toxicity vary considerably among strains. Maintaining Cu homeostasis in cyanobacterial cells is a complex process involving multiple layers of regulation. It begins at the extracellular polysaccharide layer, involves specialized membrane-bound proteins (in the outer, plasma, and thylakoid membranes), and results in transcriptional regulation in response to intracellular Cu status. This review summarizes the current understanding of Cu uptake and efflux pathways in cyanobacteria and explores how these mechanisms contribute to maintaining cellular Cu balance. The knowledge gained may contribute to the application of cyanobacteria in bioremediation strategies and/or the targeted use of Cu in the control of harmful cyanobacterial blooms. Full article

Soil degradation has been accelerating globally due to climate change, which threatens food production, biodiversity, and ecosystem balance. Traditional soil restoration strategies are often expensive, slow, or unsustainable in the long term. In this context, cyanobacteria have emerged as promising biotechnological alternatives, being the only prokaryotes capable of performing oxygenic photosynthesis. Moreover, they can capture atmospheric carbon and nitrogen, release exopolysaccharides (EPSs) that stabilize the soil, and facilitate the development of biological soil crusts (biocrusts). In recent years, the convergence of multi-omics tools, such as metagenomics, metatranscriptomics, and metabolomics, has advanced our understanding of cyanobacterial dynamics, their metabolic potential, and symbiotic interactions with microbial consortia, as exemplified by the cyanosphere of Microcoleus vaginatus. In addition, recent advances in bioinformatics have enabled high-resolution taxonomic and functional profiling of environmental samples, facilitating the identification and prediction of resilient microorganisms suited to challenging degraded soils. These tools also allow for the prediction of biosynthetic gene clusters and the detection of prophages or cyanophages within microbiomes, offering a novel approach to enhance carbon sequestration in dry and nutrient-poor soils. This review synthesizes the latest findings and proposes a roadmap for the translation of molecular-level knowledge into scalable biotechnological strategies for soil restoration. We discuss approaches ranging from the use of native biocrust strains to the exploration of cyanophages with the potential to enhance cyanobacterial photosynthetic activity. By bridging ecological functions with cutting-edge omics technologies, this study highlights the critical role of cyanobacteria as a nature-based solution for climate-smart soil management in degraded and arid ecosystems. Full article

Cyanobacterial blooms are becoming increasingly frequent and intense worldwide, often dominated by Microcystis aeruginosa, a species capable of producing a wide array of bioactive metabolites beyond microcystins. This study evaluates the ecotoxicological potential of a non-microcystin-producing strain, M. aeruginosa CCIBt3106, using acute immobilization assays with three microcrustacean species: Daphnia similis, Artemia salina, and Parhyale hawaiensis. Biomass was extracted using solvents of varying polarity, and selected extracts (aqueous and 50% methanol) were further fractionated and analyzed via high-resolution liquid chromatography–tandem mass spectrometry (HR-LC-MS/MS). Significant toxicity was observed in D. similis and P. hawaiensis, with EC₅₀ values ranging from 660 to 940 µg mL⁻¹. Metabolomic profiling revealed the presence of chemically diverse metabolite classes, including peptides, polyketides, and fatty acyls, with putative annotations linked to known bioactivities. These findings demonstrate that cyanobacterial strains lacking microcystins can still produce complex metabolite mixtures capable of inducing species-specific toxic effects under environmentally relevant exposure levels. Overall, the results highlight the need to expand ecotoxicological assessments and monitoring frameworks to include non-microcystin cyanobacterial metabolites and strains in water quality management. Full article