Search Results (474)

Spirulina (Arthrospira spp.) and klamath (Aphanizomenon flos-aquae) are widely consumed cyanobacteria-based food supplements valued for their nutritional and health-promoting properties. However, these products are susceptible to contamination by cyanotoxins, which are potent toxins produced by co-occurring cyanobacteria that may pose health risks to consumers. In this study, we applied an integrated targeted and suspect screening approach to comprehensively assess the presence of cyanotoxins in commercial spirulina- and klamath-based food supplements. Targeted analysis was performed using UHPLC-QqQ under dynamic multiple reaction-monitoring conditions optimized for the determination of twelve cyclic peptide cyanotoxins. Suspect screening was conducted using high-resolution mass spectrometry (HRMS) with a Q-Orbitrap analyser, applying a specific workflow to detect additional related compounds lacking analytical standards. The method enabled the detection and identification of multiple cyanotoxins, including microcystins, nodularin, and anabaenopeptins. The combination of targeted and suspect workflows allowed for a broader coverage of potential related cyanotoxins. Several cyanotoxins were detected in a klamath-based supplement, with high concentrations of microcystin-RR, while additional variants were identified through suspect screening. These findings highlight the need for routine monitoring and stricter regulatory oversight of cyanobacteria-based supplements to ensure consumer safety. Full article

Cyanotoxins in agricultural waters pose a human and animal health risk. These toxins can be transported to nearby crops and soil during irrigation practices; they can remain in the soil for extended periods and be adsorbed by root systems. Additionally, in livestock watering ponds, cyanotoxins pose a direct ingestion risk. This work evaluated the performance of the random forest algorithm in estimating microcystin concentrations using eight in situ water quality measurements at one active livestock water pond and two working irrigation ponds in Georgia and Maryland, USA. Measurements of microcystin along with eight in situ-sensed water quality parameters were used to train and test the machine learning model. The models performed better at the Georgia ponds compared to the Maryland pond, and interior models performed better than nearshore or whole-pond models. The most important variables for microcystin prediction were water temperature and phytoplankton pigments. Overall, the random forest algorithm(RF), augmented with a ‘trainControl’ function to perform repeated cross validations, was able to explain 40% to 70% of the microcystin concentration variation in the three agricultural ponds. Water quality measurements showed potential to aid water monitoring/sampling design by predicting the microcystin concentrations in the studied ponds by using readily available and easy to collect in situ data. 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

Antipredator defenses of bloom-forming cyanobacteria species maximize their fitness but can reduce carbon and energy transfer efficiency to higher trophic levels, making them a key regulator of plankton communities in eutrophic waters. We investigated the grazing responses of the tropical cladoceran Moina micrura to different strains of the cyanobacteria Microcystis aeruginosa and Planktothrix isothrix, using a good food source (green algae Mono-raphidium capricornutum) as a control. Both Microcystis strains grow as unicellular and are microcystins producers; however, this cyanotoxin was not detected on the filamentous Planktothrix strains. M. micrura ingested all cyanobacteria at reduced rates compared to single diets with Monoraphidium. In mixed diets, food type had a significant effect on grazing responses, which differed interspecifically. Planktothrix was more grazed than Microcystis strains. Feeding selectivity on Monoraphidium was negatively affected by the increase of cyanobacteria in the diet. We observed varied responses across treatments, ranging from feeding inhibition to different degrees of tolerance toward cyanobacteria, particularly in non-microcystin-producing species. We also highlight the selectivity of small tropical cladocerans, a pattern that is not yet well documented. These findings emphasize that studies incorporating phyto- and zooplankton with a history of coexistence can provide more meaningful insights into natural ecosystem dynamics. Full article

Paralytic shellfish poisoning toxins (PSPTs) are a class of neurotoxins most known for causing illness from consuming contaminated shellfish. These toxins are also present in freshwater systems with the concern that they contaminate drinking and recreational waters. This review provides (1) a complete list of the 84+ known PSPTs and important chemical features; (2) a complete list of all environmental freshwater PSPT detections; (3) an outline of the certified PSPT methods and their inherent weaknesses; and (4) a discussion of PSPT toxicology, the weaknesses in existing data, and existing freshwater regulatory limits. We show ample evidence of production of freshwater PSPTs by cyanobacteria worldwide, but data and method uncertainties limit a proper risk assessment. One impediment is the poor understanding of freshwater PSPT profiles and lack of commercially available standards needed to identify and quantify freshwater PSPTs. Further constraints are the limitations of toxicological data derived from human and animal model exposures. Unassessed mouse toxicity data from 1978 allowed us to calculate and propose toxicity equivalency factors (TEF) for 11-hydroxysaxitoxin (11-OH STX; M2) and 11-OH dcSTX (dcM2). TEFs for the 11-OH STX epimers were calculated to be 0.4 and 0.6 for 11α-OH STX (M2α) and 11β-OH STX (M2β), while we estimate that TEFs for 11α-OH dcSTX (dcM2α) and 11β-OH dcSTX (dcM2β) congeners would be 0.16 and 0.23, respectively. Future needs for freshwater PSPTs include increasing the number of reference materials for environmental detection and toxicity evaluation, developing a better understanding of PSPT profiles and important environmental drivers, incorporating safety factors into exposure guidelines, and evaluating the accuracy of the established no-observed-adverse-effect level. Full article

Biotechnology has increasingly focused on cyanobacteria as these microorganisms are a rich source of secondary metabolites with significant potential for various industries. Cyanobacterial metabolites have been described to have a wide range of biological activities, including cytotoxicity in cancer cells, inhibition of pathogenic bacteria and fungi, and inhibition of various enzymes, demonstrating a great diversity of bioactive compounds. The cyanobacterium Microcystis aeruginosa is well known for its toxicity and production of the cyanotoxin microcystin. However, another peptide produced by this cyanobacterium, microginins, has significant biotechnological potential. These linear pentapeptides were initially discovered for their angiotensin-converting enzyme (ACE) inhibitory activity. Subsequent studies have explored the full potential of this peptide, revealing its ability to inhibit other enzymes as well. This review aims to compile and systematize the microginins with biotechnological potential described in the literature, as well as outline their main structural characteristics and the predominant methodologies for their isolation and identification. Full article

Numerous remediation strategies exist for cyanobacterial harmful algal blooms (cyanoHABs); however, most are limited by challenges of scalability and adverse off-target effects on the surrounding ecosystem. Germicidal ultraviolet light (UV-C) has emerged as a promising method for suppressing cyanoHABs in a sustainable, chemical-free manner that is both scalable and results in limited off-target ecological effects in the surrounding area. In this study, the US Army Engineer Research and Development Center’s (ERDC)’s CyanoSTUN^TM (Cyanobacterial Suppression Through Ultraviolet-Light-C Neutralization) vessel was deployed to a cyanoHAB as part of a field trial to determine whether UV-C could effectively suppress cellular growth, degrade associated cyanotoxins, and inhibit harmful phytoplankton species more readily than beneficial species without the addition of chemicals. The cyanoHAB exhibited an average cyanobacteria abundance of 3.75 × 10⁵ cells/mL (n = 5, SD = 6.76 × 10⁴ cells/mL) and average total microcystin concentration of 3.5 µg/L (n = 5; SD = 0.24 µg/L). Pre- and post-treatment samples were collected and re-grown for 9 days in the laboratory to observe differences in microcystin, chlorophyll a, and phycocyanin concentrations, optical density, cell density, and community composition. The results of the field trial showed that the CyanoSTUN UV-C treatment effectively suppressed the growth of the cyanobacteria community for approximately two days at the three tested UV-C doses. The CyanoSTUN UV-C treatment also demonstrated a sustained, dose-dependent effect on microcystin concentration; the average reduction in microcystin concentration for 15, 30, and 45 mJ/cm² treatment doses was 31.6% (n = 10, SD = 20.1%; 1.3 µg/L reduced), 45.7% (n = 10, SD = 10.8%; 1.9 µg/L reduced), and 49.9% (n = 10, SD = 8.2%; 1.7 µg/L reduced), respectively, over the 9-day regrowth period. Non-cyanobacteria were too scarce in this CyanoHAB to conclude whether the CyanoSTUN UV-C inhibits harmful phytoplankton species more readily than beneficial species. Further field studies with the CyanoSTUN^TM are required to validate performance under more severe cyanoHAB conditions, however the results reported herein from the first field trial with the CyanoSTUN^TM suggest that this treatment method may offer water managers confronted with a CyanoHAB the ability to rapidly and safely pause a bloom for multiple days and reduce the risks posed by its associated cyanotoxins without adding chemicals. Full article

Herein, we report on the synthesis of Ni and Zn clusters on the surface of TiO₂ as well as their bimetallic NiZn analogs. The materials were prepared by incipient wet impregnation of colloidal TiO₂ followed by microwave (MW) irradiation to graft the clusters to TiO₂ surface. The materials were further immobilized onto glass slides and exhibited high surface area, high mechanical stability, and porosity with accessible pores. The main species responsible for visible light degradation of microcystin LR via the interface charge transfer (IFCT) of excited e⁻ to surface metal clusters were found to be O₂^•− and h⁺. The optimal nominal grafting concentration was 0.5 wt.% for Ni and 1.0 wt.% for Zn, while for the bimetal modification (NiZn), the optimal nominal concentration was 0.5 wt.%. Compared to monometallic, bimetallic grafting showed a lower kinetic constant, albeit still improved compared to bare TiO₂. Bimetal-modified titania showed a lower photocurrent compared to single metal-grafted TiO₂ and poorer interfacial charge transport, namely, more recombination sites—possibly at the interface between the Ni and Zn domains. This work highlights the efficiency of using MW irradiation for grafting sub-nano-sized metallic species to TiO₂ in a homogeneous way. However, further strategies using MW irradiation for the structural design of bimetallic cocatalysts can be implemented in the future. Full article

Cylindrospermopsin is an emerging cyanotoxin that can lead to phytotoxicity through different mechanisms. The presence of CYN in irrigation waters is of concern due to potential accumulation in plants, increasing the risk of human exposure by the consumption of vegetables. In this case, it is proposed to evaluate the effects of CYN on a crop considered staple food in Colombia, such as Solanum tuberosum, group Phureja var Criolla Colombia, known as “yellow potato”. This work evaluates for the first time the effects of CYN in potato plants exposed to this toxin using two different irrigation systems, surface and sprinkler irrigation. The parameters evaluated were CYN bioaccumulation and biotransformation in different parts of the potato plants irrigated with water containing CYN at environmentally relevant concentrations (84.65, 33.80, 3.05 and 3.05 µg/L after first, second, and third to fourth applications, respectively) and changes in nutritional mineral content in tubers. For this purpose, the concentrations of CYN and its potential metabolites in leaves, stem, roots, and tubbers of the plants exposed to the toxin were determined by Ultra-high Performance Liquid Chromatography–MS/MS (UHPLC-MS/MS). Mineral content was determined by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). CYN bioaccumulation was detected only in aerial parts of plants with sprinkler irrigation. A total of 57 CYN metabolites were found, and the main differences obtained in CYN biotransformation are linked to tissues and exposure conditions. There are significant differences in levels of Ca, K, Mg, Na, P, Cu, Fe, Mn, and Zn in tubers depending on CYN treatment, with higher contents after surface irrigation, and lower content with sprinkler application. These results demonstrate that the exposure conditions are an important factor for the potential presence and effects of CYN in potato plants. Full article

The records of blooms and cyanotoxins in the Brazilian Legal Amazon are scarce and do not represent the reality observed in recent years when there was an increase in notifications and studies carried out in this region. In this article, we carefully analyzed 48 studies to identify the locations where the blooms occurred, the most frequent species, and the tests performed to detect cyanotoxins within the territory of the Brazilian Legal Amazon. The analyzed studies identified approximately 145 taxa of cyanobacteria, and the most frequent species belong to the genera Microcystis and Planktothrix. The most frequently detected cyanotoxin was microcystin, and, in some locations, even with a low cell density, there was the production of toxins. In most cases, Microcystis and Dolichospermum were the major genera associated with blooms and toxin production. The state of Pará had the highest number of records of toxin-producing cyanobacteria, including records of seasonal events, while Acre had no records. This work contributes to our knowledge of the geographic distribution and occurrence of cyanobacteria and cyanotoxins in the Brazilian Amazon and proposes new strategies for improving the monitoring of cyanotoxins in the Amazon region. Full article

Algal blooms produced by cyanobacteria liberate microcystins and other toxins that create a public health hazard. During the 2018 bloom of Microcystis aeruginosa in Florida, USA, residential and recreational exposures were associated with an increased risk of self-reporting respiratory, gastrointestinal, or ocular symptoms for 125 participants. Subsequently, 207 persons were interviewed between 2019 and 2024 in the absence of large-scale algal blooms and were considered non-exposed. Analyses of cyanotoxins and brevetoxins in water and air showed only intermittent, background levels of toxins during the non-bloom period. The purpose of this report was to compare symptom reporting between active bloom and non-bloom periods. The assessment of information bias from self-reported symptoms is an important issue in epidemiologic studies of harmful algal blooms. During the non-bloom period, no statistically significant associations with residential, recreational, or occupational exposures were found for any symptom group. Estimated risks for respiratory, gastrointestinal, and ocular symptoms, headache, and skin rash were significantly higher for persons sampled during the bloom than the non-bloom period with odds ratios (ORs) of 2.3 to 8.3. ORs for specific respiratory symptoms were also significantly elevated. After adjustment for confounders and multiple exposures in multivariable analyses, the differences in symptom reporting between bloom and non-bloom periods remained statistically significant. In summary, the use of self-reported symptoms in this epidemiologic study of exposure to a cyanobacterial algal bloom did not appear to introduce substantial information bias. Full article

Toxic cyanobacterial blooms are prevalent in surface waters. Depending on several conditions, these blooms produce cyanotoxins. Human exposure to these toxins can occur through multiple routes, including contaminated crops through irrigation with contaminated water. Analytical methods have been developed for cyanotoxin quantification to investigate these exposures. Yet, proper comparisons between different labs via proficiency tests or interlaboratory comparison tests, as well as method quality assurance, are impossible. Developing reference materials for cyanotoxins in plants would help resolve these problems. Therefore, a novel liquid hydroculture setup was optimized to grow and contaminate strawberries. During fruit ripening, these plants were exposed to growth medium contaminated with pure microcystin-LR or freeze-dried cyanobacterial biomass containing different microcystin congeners. Afterwards, fruits, greens, and roots were harvested. Validated UHPLC-MS/MS methods were used to quantify the microcystin congeners in the growth medium and the plants. Furthermore, both contamination conditions resulted in the accumulation of toxin(s) in the roots and the greens. Yet in the contamination models, no toxin(s) accumulated in the fruits. Therefore, this contamination approach, combined with strawberries as a berry plant model, is only suitable for reference material production for limited matrices. Our cultivation model to produce reference material could be evaluated for other berry producers. Full article

In non-ribosomal peptide synthesis of cyanobacteria, promiscuous adenylation domains allow the incorporation of clickable non-natural amino acids into peptide products—namely into microcystins (MCs) or into anabaenopeptins (APs): 4-azidophenylalanine (Phe-Az), N-propargyloxy-carbonyl-L-lysine (Prop-Lys), or O-propargyl-L-tyrosine (Prop-Tyr). Subsequently, chemo-selective labeling is used to visualize the clickable cyanopeptides using Alexa Fluor 488 (A488). In this study, the time-lapse build up or decline of azide- or alkyne-modified MCs or APs was visualized during maximum growth, specifically MC biosynthesis in Microcystis aeruginosa and AP biosynthesis in Planktothrix agardhii. Throughout the time-lapse build up or decline, the A488 signal occurred with heterogeneous intracellular distribution. There was a fast increase or decrease in the A488 signal for either Prop-Tyr or Prop-Lys, while a delayed or unobservable A488 signal for Phe-Az was related to increased cell size as well as a reduction in growth and autofluorescence. The proportion of clickable MC/AP in peptide extracts as recorded by a chemical–analytical technique correlated positively with A488 labeling intensity quantified via laser-scanning confocal microscopy for individual cells or via flow cytometry at the population level. It is concluded that chemical modification of MC/AP can be used to track intracellular dynamics in biosynthesis using both analytical chemistry and high-resolution imaging. Full article

Freshwater cyanobacterial harmful algal blooms (FCHABs) alter zooplankton communities, often adversely, through the production of cyanotoxins. While Daphnia magna is frequently used to evaluate the impact of toxicants, it is not commonly found in tropical waters; cladocerans from tropical and subtropical waterbodies should be used in bioassays. Here, we evaluated the impact of crude cyanobacteria extracts on three common, native species (Daphnia laevis, Ceriodaphnia dubia, and Simocephalus vetulus) based on acute and chronic bioassays. We analyzed the toxicity of cyanobacterial consortium collected from Lake Zumpango, Mexico. The FCHAB was dominated by Planktothrix agardhii (1.16 × 10⁶ ind mL⁻¹). A series of freeze/thaw/sonification cycles at 20 kHz was used to extract the toxic metabolites and the concentration of dissolved microcystin-LR equivalents was measured using an ELISA immunological kit. S. vetulus was the most sensitive species, with a median lethal concentration of 0.43 compared to 1.19 µg L⁻¹ of D. magna at 48 h. S. vetulus was also the most sensitive in chronic evaluations, showing a negative rate of population increase (−0.10 d⁻¹) in experiments with 20% crude extract. Full article

Although algae possess a high capacity for carbon sequestration, the recalcitrant multilayered cell wall structure and residual microcystin toxicity associated with Microcystis aeruginosa significantly hinder the efficient recovery of algal biomass resources. This study developed a synergistic ozone-ultrasonication (O₃-US) pretreatment strategy, systematically comparing its cell-disruption efficacy with standalone O₃ or US, using harvested algal biomass from natural aquatic systems dominated by Microcystis aeruginosa. The synergistic effects revealed were: (1) O₃-mediated oxidation of extracellular polymeric substances and cell wall matrices, (2) the release of ultrasound-induced cavitation-enhancing intracellular components, and (3) an improvement in the O₃ mass transfer by hydrodynamic shear forces. Through response surface methodology optimization, the O₃-US process achieved maximal performance at 0.14 gO₃/gTSS, with a 4 W/mL ultrasonic intensity, and a 20 min duration. Remarkably, the released protein was 289.2 mg/gTSS, which was 4.3-fold and 1.9-fold, respectively, more than that released in O₃ pretreatment and US pretreatment, while the polysaccharide was 87.5 mg/gTSS, increased by 2.4-fold and 3.1-fold respectively, compared to O₃ alone and US alone. The released solubilized chemical oxygen demand (SCOD) was 1037.1 mg/gTSS, increased by 43.3% and 216.1%, respectively, relative to O₃ alone and US alone. DNA quantification further validated the synergistic cell disruption caused by O₃-US. Fluorescence excitation-emission matrix (EEM) spectroscopy identified biodegradable aromatic proteins (Regions I-II) and soluble microbial byproducts (Region IV) as dominant organic fractions, demonstrating enhanced bioavailability. The hybrid process reduced energy consumption by 33.3% in ultrasonic intensity and 60% in duration versus US alone, while achieving 94.5% microcystin-LR (MC-LR) degradation, which showed a 96.6% risk reduction compared to ultrasonic treatment. This work establishes an efficient, low-energy, and safe pretreatment technology for algal resource recovery, synergistically enhancing intracellular resource release while mitigating cyanotoxin hazards in algal biomass valorization. Full article