Microcystin profiles in European noble crayfish Astacus astacus and water in Lake Steinsfjorden, Norway.

Lake Steinsfjorden, an important noble crayfish (Astacus astacus) habitat, is often affected by blooms of Planktothrix spp. that produce microcystins (MCs). A poor correlation between MCs by ELISA in the water and in crayfish tissue in a study in 2015 prompted further investigation by LC-HRMS. LC-HRMS analyses of filters from water samples and on selected crayfish tissue extracts from the 2015 study revealed the presence of known and previously unreported MCs. Crayfish samples from May and June 2015 were dominated by MCs from the Planktothrix bloom, whereas in September novel MCs that appeared to be metabolites of MC-LR were dominant, even though neither these nor MC-LR were detected in the water in 2015. A water sample from October 2016 also showed MCs typical of Planktothrix (i.e., [d-Asp3]- and [d-Asp3,Dhb7]MC-RR and -LR), but low levels of MC-RR and MC-LR were detected in the lake water for the first time. In late summer and autumn, the MC profiles of crayfish were dominated by the homonorvaline (Hnv) variant MC-LHnv, a putative metabolite of MC-LR. Taken together, ELISA, LC-HRMS and previous PCR analyses showed that although Planktothrix was part of the crayfish diet, it was not the sole source of MCs in the crayfish. Possibly, crayfish in Lake Steinsfjorden may be ingesting MCs from benthic cyanobacteria or from contaminated prey. Therefore, information on the cyanobacterial or MC content in the water column cannot safely be used to make predictions about MC concentrations in the crayfish in Lake Steinsfjorden. Interestingly, the results also show that targeted LC-MS analysis of the crayfish would at times have underestimated their MC content by nearly an order of magnitude, even if all previously reported MC variants had been included in the analysis.

Comprehensive strategies for microcystin degradation: A review of the physical, chemical, and biological methods and genetic engineering.

Addressing the threat of harmful cyanobacterial blooms (CyanoHABs) and their associated microcystins (MCs) is crucial for global drinking water safety. In this review, we comprehensively analyze and compares the physical, chemical, and biological methods and genetic engineering for MCs degradation in aquatic environments. Physical methods, such as UV treatments and photocatalytic reactions, have a high efficiency in breaking down MCs, with the potential for further enhancement in performance and reduction of hazardous byproducts. Chemical treatments using chlorine dioxide and potassium permanganate can reduce MC levels but require careful dosage management to avoid toxic by-products and protect aquatic ecosystems. Biological methods, including microbial degradation and phytoremediation techniques, show promise for the biodegradation of MCs, offering reduced environmental impact and increased sustainability. Genetic engineering, such as immobilization of microcystinase A (MlrA) in Escherichia coli and its expression in Synechocystis sp., has proven effective in decomposing MCs such as MC-LR. However, challenges related to specific environmental conditions such as temperature variations, pH levels, presence of other contaminants, nutrient availability, oxygen levels, and light exposure, as well as scalability of biological systems, necessitate further exploration. We provide a comprehensive evaluation of MCs degradation techniques, delving into their practicality, assessing the environmental impacts, and scrutinizing their efficiency to offer crucial insights into the multifaceted nature of these methods in various environmental contexts. The integration of various methodologies to enhance degradation efficiency is vital in the field of water safety, underscoring the need for ongoing innovation.

Cyanobacterial Harmful Algal Mats (CyanoHAMs) in tropical rivers of central Mexico and their potential risks through toxin production.

Cyanobacteria inhabiting lotic environments have been poorly studied and characterized in Mexico, despite their potential risks from cyanotoxin production. This article aims to fill this knowledge gap by assessing the importance of benthic cyanobacteria as potential cyanotoxin producers in central Mexican rivers through: (i) the taxonomic identification of cyanobacteria found in these rivers, (ii) the environmental characterization of their habitats, and (iii) testing for the presence of toxin producing genes in the encountered taxa. Additionally, we introduce and discuss the use of the term "CyanoHAMs" for lotic water environments. Populations of cyanobacteria were collected from ten mountain rivers and identified using molecular techniques. Subsequently, these taxa were evaluated for genes producing anatoxins and microcystins via PCR. Through RDA analyses, the collected cyanobacteria were grouped into one of three categories based on their environmental preferences for the following: (1) waters with high ionic concentrations, (2) cold-temperate waters, or (3) waters with high nutrient enrichment. Populations from six locations were identified to genus level: Ancylothrix sp., Cyanoplacoma sp., and Oxynema sp. The latter was found to contain the gene that produces anatoxins and microcystins in siliceous rivers, while Oxynema tested positive for the gene that produces microcystins in calcareous rivers. Our results suggest that eutrophic environments are not necessarily required for toxin-producing cyanobacteria. Our records of Compactonostoc, Oxynema, and Ancylothrix represent the first for Mexico. Four taxa were identified to species level: Wilmottia aff. murrayi, Nostoc tlalocii, Nostoc montejanii, and Dichothrix aff. willei, with only the first testing positive using PCR for anatoxin and microcystin-producing genes in siliceous rivers. Due to the differences between benthic growths with respect to planktonic ones, we propose the adoption of the term Cyanobacterial Harmful Algal Mats (CyanoHAMs) as a more precise descriptor for future studies.

Reconstitution and expression of mcy gene cluster in the model cyanobacterium Synechococcus 7942 reveals a role of MC-LR in cell division.

Cyanobacterial blooms pose a serious threat to public health due to the presence of cyanotoxins. Microcystin-LR (MC-LR) produced by Microcystis aeruginosa is the most common cyanotoxins. Due to the limitation of isolation, purification, and genetic manipulation techniques, it is difficult to study and verify in situ the biosynthetic pathways and molecular mechanisms of MC-LR. We reassembled the biosynthetic gene cluster (mcy cluster) of MC-LR in vitro by synthetic biology, designed and constructed the strong bidirectional promoter biPpsbA2 , transformed it into Synechococcus 7942, and successfully expressed MC-LR at a level of 0.006-0.018 fg cell-1 d-1 . We found the expression of MC-LR led to abnormal cell division and cellular filamentation, further using various methods proved that by irreversibly competing its GTP-binding site, MC-LR inhibits assembly of the cell division protein FtsZ. The study represents the first reconstitution and expression of the mcy cluster and the autotrophic production of MC-LR in model cyanobacterium, which lays the foundation for resolving the microcystins biosynthesis pathway. The discovered role of MC-LR in cell division reveals a mechanism of how blooming cyanobacteria gain a competitive edge over their nonblooming counterparts.

Climate change amplifies the risk of potentially toxigenic cyanobacteria.

Cyanobacterial blooms pose a significant threat to water security, with anthropogenic forcing being implicated as a key driver behind the recent upsurge and global expansion of cyanobacteria in modern times. The potential effects of land-use alterations and climate change can lead to complicated, less-predictable scenarios in cyanobacterial management, especially when forecasting cyanobacterial toxin risks. There is a growing need for further investigations into the specific stressors that stimulate cyanobacterial toxins, as well as resolving the uncertainty surrounding the historical or contemporary nature of cyanobacterial-associated risks. To address this gap, we employed a paleolimnological approach to reconstruct cyanobacterial abundance and microcystin-producing potential in temperate lakes situated along a human impact gradient. We identified breakpoints (i.e., points of abrupt change) in these time series and examined the impact of landscape and climatic properties on their occurrence. Our findings indicate that lakes subject to greater human influence exhibited an earlier onset of cyanobacterial biomass by 40 years compared to less-impacted lakes, with land-use change emerging as the dominant predictor. Moreover, microcystin-producing potential increased in both high- and low-impact lakes around the 1980s, with climate warming being the primary driver. Our findings chronicle the importance of climate change in increasing the risk of toxigenic cyanobacteria in freshwater resources.

Microcystins-Loaded Aged Nanoplastics Provoke a Metabolic Shift in Human Liver Cells.

Studies concerning the toxicity of pollutant-loaded nanoplastics (NPs) toward humans are still in their infancy. Here, we evaluated the adsorption of microcystins (MCs) by pristine and aged polystyrene nanoplastics (PSNPs), prepared MCs-loaded aged PSNPS (1, 5, 10, 15, and 19 µg/mg), and systematically mapped the key molecular changes induced by aged and MCs-loaded PSNPs to human hepatoblastoma (HepG2) cells. According to the results, MC-LR adsorption is increased 2.64-fold by aging, and PSNP accumulation is detected in HepG2 cells. The cytotoxicity of the MC-LR-loaded aged PSNPs showed a positive relationship with the MC-LR amount, as the cell viability in the 19 µg/mg loading treatment (aPS-MC19) was 10.84% lower than aged PSNPs; meanwhile, more severe oxidative damage was observed. Primary approaches involved stressing the endoplasmic reticulum and reducing protein synthesis that the aged PSNPs posed for HepG2 cells, while the aggravated cytotoxicity in aPS-MC19 treatment was a combined result of the metabolic energy disorder, oxidative damage, endoplasmic reticulum stress, and downregulation of the MC-LR target protein. Our results confirm that the aged PSNPs could bring more MC-LR into the HepG2 cells, significantly interfere with biological processes, and provide new insight into deciphering the risk of NPs to humans.

Will "Air Eutrophication" Increase the Risk of Ecological Threat to Public Health?

Aquatic eutrophication, often with anthropogenic causes, facilitates blooms of cyanobacteria including cyanotoxin producing species, which profoundly impact aquatic ecosystems and human health. An emerging concern is that aquatic eutrophication may interact with other environmental changes and thereby lead to unexpected cascading effects on terrestrial systems. Here, we synthesize recent evidence showing the possibility that accelerating eutrophication will spill over from aquatic ecosystems to the atmosphere via "air eutrophication", a novel concept that refers to a process promoting the growth of airborne algae, some of them with the capacity to produce toxic compounds for humans and other organisms. Being catalyzed by various anthropogenic forcings─including aquatic eutrophication, climate warming, air contamination, and artificial light at night─accelerated air eutrophication may be expected in the future, posing a potentially increasing risk of threat to public health and the environment. So far knowledge of this topic is sparse, and we therefore consider air eutrophication a potentially important research field and propose an agenda of cross-discipline research. As a contribution, we have calculated a tolerable daily intake of 17 ng m-3 day-1 for the nasal intake of microcystins by humans.

Nature-Based Solution to Eliminate Cyanotoxins in Water Using Biologically Enhanced Biochar.

Climate change and high eutrophication levels of freshwater sources are increasing the occurrence and intensity of toxic cyanobacterial blooms in drinking water supplies. Conventional water treatment struggles to eliminate cyanobacteria/cyanotoxins, and expensive tertiary treatments are needed. To address this, we have designed a sustainable, nature-based solution using biochar derived from waste coconut shells. This biochar provides a low-cost porous support for immobilizing microbial communities, forming biologically enhanced biochar (BEB). Highly toxic microcystin-LR (MC-LR) was used to influence microbial colonization of the biochar by the natural lake-water microbiome. Over 11 months, BEBs were exposed to microcystins, cyanobacterial extracts, and live cyanobacterial cells, always resulting in rapid elimination of toxins and even a 1.6-1.9 log reduction in cyanobacterial cell numbers. After 48 h of incubation with our BEBs, the MC-LR concentrations dropped below the detection limit of 0.1 ng/mL. The accelerated degradation of cyanotoxins was attributed to enhanced species diversity and microcystin-degrading microbes colonizing the biochar. To ensure scalability, we evaluated BEBs produced through batch-scale and continuous-scale pyrolysis, while also guaranteeing safety by maintaining toxic impurities in biochar within acceptable limits and monitoring degradation byproducts. This study serves as a proof-of-concept for a sustainable, scalable, and safe nature-based solution for combating toxic algal blooms.

Integrating regular and transcriptomic analyses reveal resistance mechanisms in Corbicula fluminea (Müller, 1774) in response to toxic Microcystis aeruginosa exposure.

The frequent occurrence of cyanobacterial blooms (CYBs) caused by toxic Microcystis aeruginosa poses a great threat to aquatic organisms. Although freshwater benthic bivalves have proven to be capable of uptake high levels of microcystins (MCs) due to their filter-feeding habits, there is a paucity of information concerning their systemic resistance mechanisms to MCs. In this study, the resistance mechanisms in Corbicula fluminea (O. F. Müller, 1774) in response to the exposure of toxic M. aeruginosa were explored through transcriptional analysis combined with histopathological and biochemical phenotypic analysis. Toxic M. aeruginosa exposure caused dose-dependent histological damage in the hepatopancreas. The conjugation reaction catalyzed by glutathione S-transferases was vulnerable to being activated by high concentrations of M. aeruginosa (10 ×105 cells mL-1). Additionally, reactive oxygen species scavenging processes mediated by superoxide dismutase and catalase were active in the initial stage of toxic M. aeruginosa exposure. The results of the integrated biomarker response index suggested that the biotransformation and antioxidant defense system in C. fluminea could be continuously activated after acute exposure to the high concentration of toxic M. aeruginosa. The eggNOG and GO analysis of the differentially expressed genes (DEGs) indicated that DEGs were significantly enriched in transporter activity, oxidant detoxification and response to oxidative stress categories, which were consistent with the alterations of biochemical indices. Besides, DEGs were significantly annotated in a few KEGG pathways involved in biotransformation (oxidation, cooxidation and conjugation) and immunoreaction (lysosome and phagosome responses), which could be responsible for the tolerance of C. fluminea to toxic M. aeruginosa. These findings improve our understanding of potential resistance mechanisms of freshwater bivalves to MCs.

Dual characteristics of Bellamya aeruginosa encountering Microcystis aeruginosa: Algal control and toxin depuration.

The benthic gastropods Bellamya aeruginosa (B. aeruginosa) is ubiquitous in freshwater in China and neighboring countries with great edible value. It has been recognized as a potential manipulator to control harmful algal blooms due to its filtration on algal cells. In this study, the control effect of B. aeruginosa on toxic and non-toxic Microcystis aeruginosa (M. aeruginosa), and the accumulation and depuration of microcystins (MCs) in the snail were systematically explored. Results indicated that although toxic M. aeruginosa could protect itself via producing MCs, the introduction of B. aeruginosa could still effectively inhibit the algae with cell density below 1 × 106 cells/mL. Hepatopancreas was the primary target of MCs in all tissues of B. aeruginosa, presenting a maximum of 3089.60 ng/g DW when exposed to toxic M. aeruginosa of 1.0 × 107 cells/mL. The enrichment of MCs in other tissues following the order of digestive tract > gonad > mantle > muscle. Interestingly, snail could again excrete previously enriched MCs when transferred to non-toxic M. aeruginosa, giving rise to over 80% reduction of MCs in the body. After depuration, the estimated daily intake (EDI) of free MCs in intact individuals and the edible parts of B. aeruginosa were both lower than the tolerable daily intake (TDI). These results implicated that B. aeruginosa could control low density of M. aeruginosa in spring. Particularly, the snail could be perfectly safe to consume by purifying for a while after using as manipulator.

Different environmental factors drive the concentrations of microcystin in particulates, dissolved water, and sediments peaked at different times in a large shallow lake.

Global distribution and health threats of microcystins (MCs) have received much more attention, but there are still significant knowledge gaps in the peak periods and driving factors of MC in different phases of freshwater ecosystems. Thus, we systematically analyzed the annual variation of different MC congeners (-LR, -RR, and -YR, where L, R, and Y respectively represent leucine, arginine, and tyrosine) in particulates, dissolved water, and sediments in three eutrophic bays of Lake Taihu, China. The results indicated that particulate MCs concentration was the highest, followed by dissolved and sediment MC, with the mean concentration of 7.58 µg/L, 1.48 µg/L, and 0.15 µg/g (DW), respectively. Except for particulate MC, the concentrations of the other two types of MC showed significant differences among the three bays. The dominant congeners of the three types of MCs were different, with the highest proportion of MC-LR being observed in sediment MCs and the lowest in particulate MCs. The peak period of the three types of MC was also different, with particulate MCs reaching their peak in July and October, dissolved MCs in May to July and October, and sediment MCs reaching their peak in September. Consistent with our hypothesis, the dynamics of different types of MCs were driven by different environmental factors. Particulate MCs were primarily related to biological parameters, followed by TP and dissolved carbon. By contrast, dissolved MCs strongly correlated with water temperature and dissolved oxygen. While sediment MCs were primarily driven by properties of sediments, followed by different forms of nitrogen in the water column. Our results suggested that particulate and dissolved MCs in northern Lake Taihu pose high health threats, especially in the peak period. Moreover, a more detailed and targeted risk management strategy should be designed to prevent the possible hazards posed by different types of MC.

Simultaneous Analysis of Cyanotoxins ß-N-methylamino-L-alanine (BMAA) and Microcystins-RR, -LR, and -YR Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

ß-N-methylamino-L-alanine (BMAA) and its isomers, 2,4-diaminobutyric acid (2,4-DAB) and N-(2-aminoethyl)-glycine (AEG), along with microcystins (MCs)-RR, -LR, and -YR (the major MC congeners), are cyanotoxins that can cause detrimental health and environmental impacts during toxic blooms. Currently, there are no reverse-phase (RP) LC-MS/MS methods for the simultaneous detection and quantification of BMAA, its isomers, and the major MCs in a single analysis; therefore, multiple analyses are required to assess the toxic load of a sample. Here, we present a newly developed and validated method for the detection and quantification of BMAA, 2,4-DAB, AEG, MC-LR, MC-RR, and MC-YR using RP LC-MS/MS. Method validation was performed, assessing linearity (r2 > 0.996), accuracy (>90% recovery for spiked samples), precision (7% relative standard deviation), and limits of detection (LODs) and quantification (LOQs) (ranging from 0.13 to 1.38 ng mL-1). The application of this combined cyanotoxin analysis on a culture of Microcystis aeruginosa resulted in the simultaneous detection of 2,4-DAB (0.249 ng mg-1 dry weight (DW)) and MC-YR (4828 ng mg-1 DW). This study provides a unified method for the quantitative analysis of BMAA, its isomers, and three MC congeners in natural environmental samples.

Cyanotoxins in African waterbodies: occurrence, adverse effects, and potential risk to animal and human health.

Public concerns about cyanotoxins production in water and its detrimental impacts on human and animal health are growing primarily due to the widespread eutrophication observed in aquatic ecosystems. A review of relevant literature was done to determine the degree of cyanotoxin occurrence and its harmful effects in African waterbodies. Data were extracted from 64 published studies from 1990 to 2022 that quantified the concentration of cyanotoxins in African aquatic ecosystems. Cyanotoxins have been reported in 95 waterbodies (29 lakes, 41 reservoirs, 10 ponds, 9 rivers, 5 coastal waters, and 1 irrigation canal) from 15 African countries. Cyanotoxins were documented in all the regions of Africa except the central region. Microcystins have been reported in nearly all waterbodies (98.9%), but anatoxin-a (5.3%), cylindrospermopsin (2.1%), nodularins (2.1%), homoanatoxin-a (1.1%), and ß-N-methylamino-L-alanine (1.1%) were encountered in a small number of water ecosystems, homoanatoxin-a and ß-N-methylamino-L-alanine each occurred in one waterbody. The largest concentrations of microcystins and nodularins were reported in South African Lakes Nhlanganzwani (49,410 µg L-1) and Zeekoevlei (347,000 µg g-1). Microcystin concentrations exceeding the WHO guideline for lifetime drinking water (1 µg L-1) were reported in 63% of the aquatic ecosystems surveyed. The most frequently reported toxin-producing cyanobacteria genus is Microcystis spp. (73.7%), followed by Oscillatoria spp. (35.8%) and Dolichospermum spp. (33.7%). Cyanotoxin-related animal mortality and human illness were reported in the continent. Consequently, it is necessary to regularly monitor the level of nutrients, cyanobacteria, and cyanotoxins in African waterbodies in an integrated manner to devise a sustainable water resources management.

Cyanotoxins, biosynthetic gene clusters, and factors modulating cyanotoxin biosynthesis.

Cyanobacterial harmful algal blooms (CHABs) are a global environmental concern that encompasses public health issues, water availability, and water quality owing to the production of various secondary metabolites (SMs), including cyanotoxins in freshwater, brackish water, and marine ecosystems. The frequency, extent, magnitude, and duration of CHABs are increasing globally. Cyanobacterial species traits and changing environmental conditions, including anthropogenic pressure, eutrophication, and global climate change, together allow cyanobacteria to thrive. The cyanotoxins include a diverse range of low molecular weight compounds with varying biochemical properties and modes of action. With the application of modern molecular biology techniques, many important aspects of cyanobacteria are being elucidated, including aspects of their diversity, gene-environment interactions, and genes that express cyanotoxins. The toxicological, environmental, and economic impacts of CHABs strongly advocate the need for continuing, extensive efforts to monitor cyanobacterial growth and to understand the mechanisms regulating species composition and cyanotoxin biosynthesis. In this review, we critically examined the genomic organization of some cyanobacterial species that lead to the production of cyanotoxins and their characteristic properties discovered to date.

Risk assessment and identification of factors influencing the historical concentrations of microcystin in Lake Taihu, China.

Understanding the history of microcystins (MCs) pollution in large lakes can help inform future lake management. We collected sediment cores from Lake Taihu to: investigate the long-term record of MCs (MC-LR, MC-YR, and MC-RR), explore the main environmental drivers of MCs, and assess their public health and ecological risks. Results showed that MCs content in all cores increased over time. The core from north Taihu had the highest MC concentrations, with an average total MCs (sum of MC-LR, MC-YR, and MC-RR = TMCs) content of (74.31±328.55) ng/g. The core from eastern Taihu showed the lowest average TMCs content of (2.91±3.95) ng/g. PCA showed that sediment MCs at the three sites were positively correlated with sediment chlorophyll-a. MC-LR and MC-YR in northern and western Taihu negatively correlated with both the sediment total organic carbon/sediment total nitrogen ratio (STOC/STN) and water nitrate (NO3--N) concentration, but three MC congeners at eastern Taihu showed positive correlations with water orthophosphate (PO43--P), NO3--N, and STOC/STN. Generalized additive model analysis at each site revealed that NO3--N was the main TMCs driver in northern and western Taihu where phytoplankton dominated, whereas PO43--P was the main TMCs driver in eastern Taihu where macrophytes dominated. At the whole lake scale, total phosphorus (TP) and PO43--P were the most important environmental drivers influencing MCs; TP explained 47.4%, 44.2%, and 47.6% while orthophosphate explained 34.8%, 31.2%, and 34.7% of the deviance on TMCs, MC-LR, and MC-YR, respectively. NO3--N also showed a strong effect on MCs variation, especially on MC-YR. Risk assessment showed that both ecological and public health risk has increased in recent years. We conclude that while control of phosphorus and nitrogen input should be a major focus for future lake management, lake zone-specific management strategies may also be important.

Identification of Novel Microcystins Using High-Resolution MS and MSn with Python Code.

Cyanotoxins called microcystins (MCs) are highly toxic and can be present in drinking water sources. Determining the structure of MCs is paramount because of its effect on toxicity. Though over 300 MC congeners have been discovered, many remain unidentified. Herein, a method is described for the putative identification of MCs using liquid chromatography (LC) coupled with high-resolution (HR) Orbitrap mass spectrometry (MS) and a new bottom-up sequencing strategy. Maumee River water samples were collected during a harmful algal bloom and analyzed by LC-MS with simultaneous HRMS and MS/MS. Unidentified ions with characteristic MC fragments (135 and 213 m/z) were recognized as possible novel MC congeners. An innovative workflow was developed for the putative identification of these ions. Python code was written to generate the potential structures of unidentified MCs and to assign ions after the fragmentation for structural confirmation. The workflow enabled the putative identification of eight previously reported MCs for which standards are not available and two newly discovered congeners, MC-HarR and MC-E(OMe)R.

Improving the Quantification of Cyanotoxins Using a Mass Balance-Based Effective Concentration-Equivalent Concentration Approach.

Two commonly used methods for cyanotoxin analysis are enzyme-linked immunosorbent assay (ELISA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Each method has its advantages and disadvantages, and discrepancies are commonly observed between the two methods due to various factors including the ELISA antibody cross-reacting to different cyanotoxin congeners. However, reliable cyanotoxin monitoring methods and accurate interpretation of results are needed for water utilities to guide recreational water planning and drinking water treatment operations. In this study, we explored an innovative "effective concentration-equivalent concentration" (EC-EQ) approach to improve the interpretation of ELISA results and the comparison to LC-MS/MS results. The precision of ELISA results was first improved by reporting the sample ECs and EQs derived from their ELISA dose curves. Concentrations of each cyanotoxin as measured by LC-MS/MS were then combined with their respective ELISA cross-reactivities to calculate their theoretical ELISA responses. Finally, instead of comparing the results from the two methods directly, the equivalent concentration based on one single reference cyanotoxin was used for reporting and comparison. This integrated mass balance-based approach provides a more reliable interpretation of results by considering the reactivity differences between toxins as well as their mixture effects. This approach has been successfully applied to microcystin (one main group of cyanotoxins) standard mixtures and cyanobacterial bloom samples to interpret and compare their ELISA and LC-MS/MS detection results. The study provides guidance to utilities on how to obtain more accurate cyanotoxin monitoring results and better understand the discrepancy between the two methods.

A review and assessment of cyanobacterial toxins as cardiovascular health hazards.

Eutrophicated waters frequently support bloom-forming cyanobacteria, many of which produce potent cyanobacterial toxins (cyanotoxins). Cyanotoxins can cause adverse health effects in a wide range of organisms where the toxins may target the liver, other internal organs, mucous surfaces and the skin and nervous system. This review surveyed more than 100 studies concerning the cardiovascular toxicity of cyanotoxins and related topics. Over 60 studies have described various negative effects on the cardiovascular system by seven major types of cyanotoxins, i.e. the microcystin (MC), nodularin (NOD), cylindrospermopsin (CYN), anatoxin (ATX), guanitoxin (GNTX), saxitoxin (STX) and lyngbyatoxin (LTX) groups. Much of the research was done on rodents and fish using high, acutely toxin concentrations and unnatural exposure routes (such as intraperitoneal injection), and it is thus concluded that the emphasis in future studies should be on oral, chronic exposure of mammalian species at environmentally relevant concentrations. It is also suggested that future in vivo studies are conducted in parallel with studies on cells and tissues. In the light of the presented evidence, it is likely that cyanotoxins do not constitute a major risk to cardiovascular health under ordinary conditions met in everyday life. The risk of illnesses in other organs, in particular the liver, is higher under the same exposure conditions. However, adverse cardiovascular effects can be expected due to indirect effects arising from damage in other organs. In addition to risks related to extraordinary concentrations of the cyanotoxins and atypical exposure routes, chronic exposure together with co-existing diseases could make some of the cyanotoxins more dangerous to cardiovascular health.

The detoxification activities and mechanisms of microcystinase towards MC-LR.

Microcystins (MCs) are the most common and toxic cyanotoxins that are hazardous to human health and ecosystems. Microcystinase is the enzyme in charge of the initial step in the biodegradation of MCs. The characterization, application conditions, and detoxification mechanisms of microcystinase from an indigenous bacterium Sphingopyxis sp. YF1 towards MC-LR were investigated in the current study. The microcystinase gene of strain YF1 was most similar to Sphingomonas sp. USTB-05 and contained a CAAX-family conversed abortive Infection (ABI) domain. The microcystinase was successful obtained and purified by overexpression in Escherichia coli. The highest degradation rate of MC-LR was 1.0 µg/mL/min under the optimal condition of 30 â„ƒ, pH 7, 20 µg/mL MC-LR, and 400 µg/mL microcystinase. The MC-degrading product was identified as linearized MC-LR, which possessed a much lower inhibitory activity against protein phosphatase 2A than MC-LR. Microcystinase interacted with MC-LR via amino acid residues involved in through the formation of conventional Hydrogen Bond, Pi-Pi T-shapes, Van der Waals force, and so on. The optimal MC-degrading condition of pure microcystinase and its detoxification mechanisms against MC-LR were revealed. The toxicity of purified linearized MC-LR was explored for the first time. These findings suggest that pure microcystinase may efficiently detoxify MCs and it is promising in the bioremediation of MC-polluted environments.

Detection and Characterization of Nodularin by Using Label-Free Surface-Enhanced Spectroscopic Techniques.

Nodularin (NOD) is a potent toxin produced by Nodularia spumigena cyanobacteria. Usually, NOD co-exists with other microcystins in environmental waters, a class of cyanotoxins secreted by certain cyanobacteria species, which makes identification difficult in the case of mixed toxins. Herein we report a complete theoretical DFT-vibrational Raman characterization of NOD along with the experimental drop-coating deposition Raman (DCDR) technique. In addition, we used the vibrational characterization to probe SERS analysis of NOD using colloidal silver nanoparticles (AgNPs), commercial nanopatterned substrates with periodic inverted pyramids (KlariteTM substrate), hydrophobic Tienta® SpecTrimTM slides, and in-house fabricated periodic nanotrenches by nanoimprint lithography (NIL). The 532 nm excitation source provided more well-defined bands even at LOD levels, as well as the best performance in terms of SERS intensity. This was reflected by the results obtained with the KlariteTM substrate and the silver-based colloidal system, which were the most promising detection approaches, providing the lowest limits of detection. A detection limit of 8.4 × 10-8 M was achieved for NOD in solution by using AgNPs. Theoretical computation of the complex vibrational modes of NOD was used for the first time to unambiguously assign all the specific vibrational Raman bands.