Further characterization of glycine-containing microcystins from the McMurdo dry Valleys of Antarctica

Toxicity of three microcystin variants on the histology, physiological and metabolism of hepatopancreas and intestinal microbiota of Litopenaeus vannamei

Microcystins (MCs) are prevalent harmful contaminants within shrimp aquaculture systems, exhibiting a diverse array of variants. Gut microbiota can engage in mutual interactions with the host through the gut-liver axis. In this study, the shrimp Litopenaeus vannamei were subjected to three different variants of MCs (LR, YR, RR) at a concentration of 1 μg/L each, and elucidated the alterations in both intestinal microbiota and hepatopancreas physiological homeostasis. The results showed that all three variants of MCs prompted histological alterations in the hepatopancreas, induced elevated levels of oxidative stress biomarkers (H2O2, T-SOD, and CAT), disturbed the transcription levels of immune-related genes (Crus, ALF, and Lys), along with an increase in apoptotic genes (Casp-3 and P53). Furthermore, the metabolic profiles of the hepatopancreas were perturbed, particularly in amino acid metabolism such as "lysine degradation" and "β-alanine metabolism"; the mTOR and FoxO signaling were also influenced, encompassing alterations in the transcription levels of related genes. Additionally, the alterations were observed in the intestinal microbiota's diversity and composition, particularly potential beneficial bacteria (Alloprevotella, Bacteroides, Collinsella, Faecalibacterium, and Prevotellaceae UCG-001), which exhibited a positive correlation with the metabolite berberine. These findings reveal that the three MCs variants can impact the health of the shrimp by interfering with the homeostasis of intestinal microbial and hepatopancreas physiology.

Toxic effects of three variants of microcystins on the intestinal histology, physiological and metabolic response of Litopenaeus vannamei

Microcystins (MCs) are harmful substances to the health of cultured shrimp, and there are many variants of MCs. Intestinal is the immune and metabolic center of the shrimp, and is also the target organ for MCs toxicity. In this study, the shrimp Litopenaeus vannamei juvenile were separately exposed to 1 μg/L of three MCs variants (LR, YR, RR) for 72 h respectively, and the changes of intestinal morphology, physiological response and metabolic function were analyzed. The results showed the three MCs variants stress caused intestinal mucosal damage and disordered the homeostasis of antimicrobial genes (ALF and Lys) expression. The mRNA expression levels of antioxidant genes (Nrf2 and GPx) and apoptosis factors (CytC and Casp-3) were increased, but that of detoxification gene (CYP450) was decreased. Furthermore, the intestinal metabolic pattern was also influenced by stresses, among which MC-LR induced more differential metabolites than that of MC-YR and MC-RR. The function of purine metabolism was highly influenced by the stress of three MCs variants, followed by amino acid metabolism, but there were differences in the types of amino acids. The metabolites citric acid, L-glutamine, L-tryptophan, spermine, UMP, and indole contributed to the metabolic pathway network. Nineteen stress-related metabolites were identified as candidates for subsequent screening of potential biomarkers. These results revealed the toxic effects of three MCs variants on the intestinal physiological and metabolic homeostasis of the shrimp.

Heterogeneous bacterial communities affected by phytoplankton community turnover and microcystins in plateau lakes of Southwestern China

Both phytoplankton and bacteria are fundamental organisms with key ecological functions in lake ecosystems. However, the mechanistic interactions through which phytoplankton community change and bacterial communities interact remain poorly understood. Here, the responses of bacterial communities to the community structure, resource-use efficiency (RUE), and community turnover of phytoplankton and microcystins (MCs) were investigated in Lake Dianchi, Lake Xingyun, and Lake Erhai of Southwestern China across two seasons (May and October 2020). Among phytoplankton, Cyanobacteria was the dominant species in all three lakes and attained greater dominance in October than in May due to variation in the RUE of nitrogen and phosphorus and environmental changes. The production of MCs, including MC_LR, MC_RR and MC_YR, was the result of the massive Cyanobacteria. Decreases in diversity and increases in heterogeneity were observed in the bacterial community structure. Nutrient levels, environmental factors and MCs (especially MC_YR) jointly affected the bacterial community in lakes, namely its diversity and community assembly. The cascading effects in lakes mediated by environmental conditions, phytoplankton community composition, RUE, community turnover, and MCs on bacterial communities were revealed in this study. These findings underscore the importance of relating phytoplankton community change and MCs to the bacterial community, which is fundamental for better understanding the lake ecosystem functioning and potential risks of MCs.

Applying synchrotron radiation-based attenuated total reflection-fourier transform infrared to chemically characterise organic functional groups in terrestrial soils of King George Island, Antarctica

Anthropogenic activities, especially associated with fossil fuel combustion, are raising concerns worldwide, but remote areas with extreme climate conditions, such as Antarctica, are isolated from the adverse influence of human civilisation. Antarctica is considered as the most untouched place on Earth. Such pristine areas, which have extremely low chemical pollutant concentrations owing to restricted anthropogenic impacts, exemplify plausible model environments to test the reliability and sensitivity of advanced analytical techniques employed to chemically characterise and evaluate the spatial distribution of chemical pollutants. Here, synchrotron radiation-based attenuated total reflection-Fourier transform infrared (SR-ATR-FTIR) spectroscopy was employed to evaluate the variations in the organic functional groups (OFGs) of terrestrial soils of King George Island, Antarctica. Second-derivative SR-ATR-FTIR spectroscopy coupled with several multivariate statistical techniques highlighted the influence of anthropogenic activities on the alterations of OFGs in terrestrial soils collected near airports. Moreover, the daily activities of penguins could also have caused fluctuations in some OFGs of the samples the close to the Tombolo area and Ardley Island. The findings proved the effectiveness of SR-ATR-FTIR in evaluating the potential sources of variations in the chemical constituents, especially OFGs, in Antarctic terrestrial soils.

Microcystin production by oscillatorialean cyanobacteria isolated from cryopreserved Antarctic mats

Twenty cyanobacterial strains of eight morphospecies isolated from deep-frozen (-15 °C) mat samples originally collected on Ross Island, in Victoria Land, and on the McMurdo Ice Shelf were screened for the presence of genes encoding for production of anatoxins, cylindrospermopsin, microcystin/nodularin and saxitoxin. One strain of each of Microcoleus autumnalis and Phormidesmis priestleyi and two strains of Wilmottia murrayi were found to produce microcystin. No toxin production was detected in the other 16 strains representing five species. The four toxin-producing strains were characterised using both morphological and molecular approaches. Phylogenetic analyses using partial 16S rRNA sequences were consistent with the morphological identification of all four strains. They were all found to contain a fragment of the mcyE gene, which is involved in microcystin biosynthesis. ELISA analysis of extracts from cultures of these strains confirmed the presence of low concentrations of microcystin: 0.35 μg/L in M. autumnalis, <0.15 μg/L in P. priestleyi, 1.60 μg/L in W. murrayi strain 1 and 0.9 μg/L in W. murrayi strain 2. This study includes the first report of microcystin synthesis by W. murrayi.

LC-MS/MS Validation and Quantification of Cyanotoxins in Algal Food Supplements from the Belgium Market and Their Molecular Origins

Food supplements are gaining popularity worldwide. However, harmful natural compounds can contaminate these products. In the case of algae-based products, the presence of toxin-producing cyanobacteria may cause health risks. However, data about the prevalence of algal food supplements on the Belgian market and possible contaminations with cyanotoxins are scarce. Therefore, we optimized and validated a method based on Ultra High Performance Liquid Chromatography-Tandem Mass Spectrometry to quantify eight microcystin congeners and nodularin in algal food supplements. Our analytical method was successfully validated and applied on 35 food supplement samples. Nine out of these samples contained microcystin congeners, of which three exceeded 1 µg g−1, a previously proposed guideline value. Additionally, the mcyE gene was amplified and sequenced in ten products to identify the taxon responsible for the toxin production. For seven out of these ten samples, the mcyE gene could be amplified and associated to Microcystis sp. EFSA and posology consumption data for algal-based food supplements were both combined with our toxin prevalence data to establish different toxin exposure scenarios to assess health risks and propose new guideline values.

Immunoassay technology: Research progress in microcystin-LR detection in water samples

Increasing global warming and eutrophication have led to frequent outbreaks of cyanobacteria blooms in freshwater. Cyanobacteria blooms cause the death of aquatic and terrestrial organisms and have attracted considerable attention since the 19th century. Microcystin-LR (MC-LR) is one of the most typical cyanobacterial toxins. Therefore, the fast, sensitive, and accurate determination of MC-LR plays an important role in the health of humans and animals. Immunoassay refers to a method that uses the principle of immunology to determine the content of the tested substance in a sample using the tested substance as an antigen or antibody. In analytical applications, the immunoassay technology could use the specific recognition of antibodies for MC-LR detection. In this review, we firstly highlight the immunoassay detection of MC-LR over the past two decades, including classical enzyme-link immunosorbent assay (ELISA), modern immunoassay with optical signal, and modern immunoassay with electrical signal. Among these detection methods, the water environment was used as the main detection system. The advantages and disadvantages of the different detection methods were compared and analyzed, and the principles and applications of immunoassays in water samples were elaborated. Furthermore, the current challenges and developmental trends in immunoassay were systematically introduced to enhance MC-LR detection performance, and some critical points were given to deal with current challenges. This review provides novel insight into MC-LR detection based on immunoassay method.

Detection of Microcystin-LR in the Cells and Natural Lake Water Samples by A Unique Fluorescence-Based Method

Microcystin-LR (MC-LR) is widely distributed in natural lakes and could strongly inhibit protein phosphatase activity; it is also a potent liver tumor promoter. Over the last two decades, tremendous efforts have been devoted to enhance the detection of MC-LR in water samples. However, the traditional method is complex and costly, and achieving the fast, sensitive, and accurate determination of MC-LR in the cells and natural lakes by using fluorescence signal changes is fairly difficult. Our work explores novel fluorescent probes that are capable of concurrently analyzing and detecting MC-LR in the cells and water. In this study, we introduce, for the first time, 5-AF and 6-AF as small-molecule fluorescent probes suitable for MC-LR detection in the cells and water samples based on fluorescence signal changes. We titrated 5-AF and 6-AF with MC-LR in pure water, scanned the fluorescence of the sample, and then obtained the equation the fluorescence intensity versus MC-LR concentration curve. MC-LR in lake water samples was crudely purified, and then 5-AF was added to measure its fluorescence peak. The fluorescence intensity of 5-AF is significantly enhanced with increasing MC-LR concentration. This enhancement trend is stable and could be mathematically modeled. We also comprehensively analyzed the mechanism and recognition principle of the probe response to MC-LR in natural lake water. Moreover, we believe that 5-AF may be capable of detecting exogenous MC-LR in cells. The results of this study reveal that these unique fluorescent probes may be applied to construct near-infrared fluorescent probes that could detect MC-LR levels in vivo.

Microcystis Sp. Co-Producing Microcystin and Saxitoxin from Songkhla Lake Basin, Thailand

The Songkhla Lake Basin (SLB) located in Southern Thailand, has been increasingly polluted by urban and industrial wastewater, while the lake water has been intensively used. Here, we aimed to investigate cyanobacteria and cyanotoxins in the SLB. Ten cyanobacteria isolates were identified as Microcystis genus based on16S rDNA analysis. All isolates harbored microcystin genes, while five of them carried saxitoxin genes. On day 15 of culturing, the specific growth rate and Chl-a content were 0.2-0.3 per day and 4 µg/mL. The total extracellular polymeric substances (EPS) content was 0.37-0.49 µg/mL. The concentration of soluble EPS (sEPS) was 2 times higher than that of bound EPS (bEPS). The protein proportion in both sEPS and bEPS was higher than the carbohydrate proportion. The average of intracellular microcystins (IMCs) was 0.47 pg/cell on day 15 of culturing, while extracellular microcystins (EMCs) were undetectable. The IMCs were dramatically produced at the exponential phase, followed by EMCs release at the late exponential phase. On day 30, the total microcystins (MCs) production reached 2.67 pg/cell. Based on liquid chromatograph-quadrupole time-of-flight mass spectrometry, three new MCs variants were proposed. This study is the first report of both decarbamoylsaxitoxin (dcSTX) and new MCs congeners synthesized by Microcystis.

Algal Toxic Compounds and Their Aeroterrestrial, Airborne and other Extremophilic Producers with Attention to Soil and Plant Contamination: A Review

The review summarizes the available knowledge on toxins and their producers from rather disparate algal assemblages of aeroterrestrial, airborne and other versatile extreme environments (hot springs, deserts, ice, snow, caves, etc.) and on phycotoxins as contaminants of emergent concern in soil and plants. There is a growing body of evidence that algal toxins and their producers occur in all general types of extreme habitats, and cyanobacteria/cyanoprokaryotes dominate in most of them. Altogether, 55 toxigenic algal genera (47 cyanoprokaryotes) were enlisted, and our analysis showed that besides the “standard” toxins, routinely known from different waterbodies (microcystins, nodularins, anatoxins, saxitoxins, cylindrospermopsins, BMAA, etc.), they can produce some specific toxic compounds. Whether the toxic biomolecules are related with the harsh conditions on which algae have to thrive and what is their functional role may be answered by future studies. Therefore, we outline the gaps in knowledge and provide ideas for further research, considering, from one side, the health risk from phycotoxins on the background of the global warming and eutrophication and, from the other side, the current surge of interest which phycotoxins provoke due to their potential as novel compounds in medicine, pharmacy, cosmetics, bioremediation, agriculture and all aspects of biotechnological implications in human life.

A Mini-Review on Detection Methods of Microcystins

Cyanobacterial harmful algal blooms (CyanoHABs) produce microcystins (MCs) which are associated with animal and human hepatotoxicity. Over 270 variants of MC exist. MCs have been continually studied due of their toxic consequences. Monitoring water quality to assess the presence of MCs is of utmost importance although it is often difficult because CyanoHABs may generate multiple MC variants, and their low concentration in water. To effectively manage and control these toxins and prevent their health risks, sensitive, fast, and reliable methods capable of detecting MCs are required. This paper aims to review the three main analytical methods used to detect MCs ranging from biological (mouse bioassay), biochemical (protein phosphatase inhibition assay and enzyme linked immunosorbent assay), and chemical (high performance liquid chromatography, liquid chromatography-mass spectrometry, high performance capillary electrophoresis, and gas chromatography), as well as the newly emerging biosensor methods. In addition, the current state of these methods regarding their novel development and usage, as well as merits and limitations are presented. Finally, this paper also provides recommendations and future research directions towards method application and improvement.

Toxic benthic freshwater cyanobacterial proliferations: Challenges and solutions for enhancing knowledge and improving monitoring and mitigation

1. This review summarises knowledge on the ecology, toxin production, and impacts of toxic freshwater benthic cyanobacterial proliferations. It documents monitoring, management, and sampling strategies, and explores mitigation options. 2. Toxic proliferations of freshwater benthic cyanobacteria (taxa that grow attached to substrates) occur in streams, rivers, lakes, and thermal and meltwater ponds, and have been reported in 19 countries. Anatoxin- and microcystin-containing mats are most commonly reported (eight and 10 countries, respectively). 3. Studies exploring factors that promote toxic benthic cyanobacterial proliferations are limited to a few species and habitats. There is a hierarchy of importance in environmental and biological factors that regulate proliferations with variables such as flow (rivers), fine sediment deposition, nutrients, associated microbes, and grazing identified as key drivers. Regulating factors differ among colonisation, expansion, and dispersal phases. 4. New -omics-based approaches are providing novel insights into the physiological attributes of benthic cyanobacteria and the role of associated microorganisms in facilitating their proliferation. 5. Proliferations are commonly comprised of both toxic and non-toxic strains, and the relative proportion of these is the key factor contributing to the overall toxin content of each mat. 6. While these events are becoming more commonly reported globally, we currently lack standardised approaches to detect, monitor, and manage this emerging health issue. To solve these critical gaps, global collaborations are needed to facilitate the rapid transfer of knowledge and promote the development of standardised techniques that can be applied to diverse habitats and species, and ultimately lead to improved management.

Microcystins: Biogenesis, Toxicity, Analysis, and Control

Microcystins are cyclic peptide toxins formed by cyanobacteria. These toxins are recognized for their association with algal blooms, posing a significant threat to ecosystems and drinking water quality. Due to the growing environmental concerns they raise, a comprehensive review on microcystins' genesis, toxicity, and analytical methods for their quantitative determination is outlined. Genes, including the mcyABC cluster, regulate microcystin biogenesis. Bioanalytical experiments have identified key environmental factors, such as temperature and nitrogen availability, that promote microcystin production. Microcystin toxicity is explored based on its modulatory effects on protein phosphatases 1 and 2A in specific tissues and organs. Additionally, biochemical mechanisms of chelation, transportation, resultant oxidative stress, and tumor promotion abilities of microcystins are also discussed. Various analytical methods to separate, detect, and quantify microcystins, including the quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay, nuclear magnetic resonance spectroscopy, and chromatographic platforms-linked tandem mass spectrometry (LC-MS) for unequivocal structural identification, are also reviewed. Since control of microcystins in water is of great necessity, both water treatment and mechanisms of abiotic transformation and microbial degradation are also discussed.

Chronic effects of microcystin-LR at environmental relevant concentrations on photosynthesis of Typha angustifolia Linn

Understanding the growth and development of aquatic plants in eutrophic water is of great significance for the selection of potential candidate plant for use in the phytoremediation of eutrophic aquatic ecosystems. The present study aimed to investigate the chronic effects of microcystin-LR (MC-LR) on photosynthesis in the leaves of Typha angustifolia Linn. Photosynthetic activity was stimulated in the leaves following exposure to 4.6 μg L^-1 MC-LR for six weeks based on the enhancement of Ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) activity and net photosynthetic rate (P_N). However, P_N decreased significantly after exposure to 49.1 or 98.3 μg L^-1 MC-LR, via non-stomatal limitation by reducing the chlorophyll a and b contents and Rubisco activity. In addition, glycolate oxidase (GO) and serine:glyoxylate aminotransferase (SGAT) activities decreased significantly, indicating that the photorespiration pathway was affected adversely. The intercellular carbon dioxide (C_i) concentration decreased significantly following exposure to 98.3 μg L^-1 MC-LR, accompanied with decreases in P_N and stomatal conductivity (g_s), indicating that stomatal limitation on the photosynthesis system in T. angustifolia L. was observed after exposure to 98.3 μg L^-1 MC-LR. Under long-term exposure to MC-LR (49.1-98.3 μg L^-1), oxidation stress was severe in the aquatic plant, and non-stomatal limitation or stomatal limitation effects on the photosynthesis system were obvious, resulting in decreases in photosynthesis rates.

Limited Microcystin, Anatoxin and Cylindrospermopsin Production by Cyanobacteria from Microbial Mats in Cold Deserts

Toxic metabolites are produced by many cyanobacterial species. There are limited data on toxigenic benthic, mat-forming cyanobacteria, and information on toxic cyanobacteria from Central Asia is even more scarce. In the present study, we examined cyanobacterial diversity and community structure, the presence of genes involved in toxin production and the occurrence of cyanotoxins in cyanobacterial mats from small water bodies in a cold high-mountain desert of Eastern Pamir. Diversity was explored using amplicon-based sequencing targeting the V3-V4 region of the 16S rRNA gene, toxin potential using PCR-based methods (mcy, nda, ana, sxt), and toxins by enzyme-linked immunosorbent assays (ELISAs) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Molecular identification of cyanobacteria showed a high similarity of abundant taxa to Nostoc PCC-73102, Nostoc PCC-7524, Nodularia PCC-935 and Leptolyngbya CYN68. The PCRs revealed the presence of mcyE and/or ndaF genes in 11 samples and mcyD in six. The partial sequences of the mcyE gene showed high sequence similarity to Nostoc, Planktothrix and uncultured cyanobacteria. LC-MS/MS analysis identified six microcystin congeners in two samples and unknown peptides in one. These results suggest that, in this extreme environment, cyanobacteria do not commonly produce microcystins, anatoxins and cylindrospermopsins, despite the high diversity and widespread occurrence of potentially toxic taxa.

Structural Diversity, Characterization and Toxicology of Microcystins

Hepatotoxic microcystins (MCs) are the most widespread class of cyanotoxins and the one that has most often been implicated in cyanobacterial toxicosis. One of the main challenges in studying and monitoring MCs is the great structural diversity within the class. The full chemical structure of the first MC was elucidated in the early 1980s and since then, the number of reported structural analogues has grown steadily and continues to do so, thanks largely to advances in analytical methodology. The structures of some of these analogues have been definitively elucidated after chemical isolation using a combination of techniques including nuclear magnetic resonance, amino acid analysis, and tandem mass spectrometry (MS/MS). Others have only been tentatively identified using liquid chromatography-MS/MS without chemical isolation. An understanding of the structural diversity of MCs, the genetic and environmental controls for this diversity and the impact of structure on toxicity are all essential to the ongoing study of MCs across several scientific disciplines. However, because of the diversity of MCs and the range of approaches that have been taken for characterizing them, comprehensive information on the state of knowledge in each of these areas can be challenging to gather. We have conducted an in-depth review of the literature surrounding the identification and toxicity of known MCs and present here a concise review of these topics. At present, at least 279 MCs have been reported and are tabulated here. Among these, about 20% (55 of 279) appear to be the result of chemical or biochemical transformations of MCs that can occur in the environment or during sample handling and extraction of cyanobacteria, including oxidation products, methyl esters, or post-biosynthetic metabolites. The toxicity of many MCs has also been studied using a range of different approaches and a great deal of variability can be observed between reported toxicities, even for the same congener. This review will help clarify the current state of knowledge on the structural diversity of MCs as a class and the impacts of structure on toxicity, as well as to identify gaps in knowledge that should be addressed in future research.

Sublethal effects of microcystin-LR in the exposure and depuration time in a neotropical fish: Multibiomarker approach

Eutrophication is an ecological process that results in cyanobacterial blooms. Microcystin-LR is the most toxic variant of microcystins and may cause toxic effects in the organisms, mainly in hepatic tissues. The aims of this study were to use multiple biomarkers in order to evaluate the sublethal effects of a low concentration of MC-LR (1 μg/L) in fish Geophagus brasiliensis by waterborne exposure; and evaluate the depuration of this toxin during 15 days. A group of 30 fish was exposed to 1 μg/L of MC-LR solution for 96 h in a static bioassay. After this time, blood, brain, muscle, liver, gonad and gills were collected from half of the exposed fish group in order to evaluate chemical, biochemical, histological and genotoxic biomarkers. The rest of the fish group was submitted to the depuration experiment with free MC-LR water for 15 days. After this time the same tissues were collected and evaluated using biomarkers analysis. Toxic effects were found mostly in the fish liver from depuration time as alterations on the antioxidant system and histopathologies. The results showed that even low concentrations can cause sublethal effects to aquatic organisms, and cyanotoxins monitoring and regulation tools are required.

The Diversity of Cyanobacterial Toxins on Structural Characterization, Distribution and Identification: A Systematic Review

The widespread distribution of cyanobacteria in the aquatic environment is increasing the risk of water pollution caused by cyanotoxins, which poses a serious threat to human health. However, the structural characterization, distribution and identification techniques of cyanotoxins have not been comprehensively reviewed in previous studies. This paper aims to elaborate the existing information systematically on the diversity of cyanotoxins to identify valuable research avenues. According to the chemical structure, cyanotoxins are mainly classified into cyclic peptides, alkaloids, lipopeptides, nonprotein amino acids and lipoglycans. In terms of global distribution, the amount of cyanotoxins are unbalanced in different areas. The diversity of cyanotoxins is more obviously found in many developed countries than that in undeveloped countries. Moreover, the threat of cyanotoxins has promoted the development of identification and detection technology. Many emerging methods have been developed to detect cyanotoxins in the environment. This communication provides a comprehensive review of the diversity of cyanotoxins, and the detection and identification technology was discussed. This detailed information will be a valuable resource for identifying the various types of cyanotoxins which threaten the environment of different areas. The ability to accurately identify specific cyanotoxins is an obvious and essential aspect of cyanobacterial research.

Importance of bacterial biodegradation and detoxification processes of microcystins for environmental health

Microcystins (MC) the most frequently reported cyanobacterial harmful algal bloom toxins primarily found in some species of freshwater genera pose a serious threat to human and animal health. To reduce health risks associated with MC exposure it is important to remove these toxins found in drinking and recreational waterbodies. Since the physical and chemical water treatment methods are inefficient in completely degrading MC, alternative approaches to effectively detoxify MC have become the focus of global research. The aim of this review was to provide the current approach to cost-effective biological treatment methods which utilize bacteria to degrade MC without generation of harmful by-products. In addition, the catabolic pathways involved in MC-degradation involving proteins encoded mlr gene cluster, intermediate products and efficiencies of bacteria strain/bacteria community are presented and compared.

New Method for Simultaneous Determination of Microcystins and Cylindrospermopsin in Vegetable Matrices by SPE-UPLC-MS/MS

Cyanotoxins are a large group of noxious metabolites with different chemical structure and mechanisms of action, with a worldwide distribution, producing effects in animals, humans, and crop plants. When cyanotoxin-contaminated waters are used for the irrigation of edible vegetables, humans can be in contact with these toxins through the food chain. In this work, a method for the simultaneous detection of Microcystin-LR (MC-LR), Microcystin-RR (MC-RR), Microcystin-YR (MC-YR), and Cylindrospermopsin (CYN) in lettuce has been optimized and validated, using a dual solid phase extraction (SPE) system for toxin extraction and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for analysis. Results showed linear ranges (5⁻50 ng g-1 f.w.), low values for limit of detection (LOD) (0.06⁻0.42 ng g-1 f.w.), and limit of quantification (LOQ) (0.16⁻0.91 ng g-1 f.w.), acceptable recoveries (41⁻93%), and %RSDIP values for the four toxins. The method proved to be robust for the three variables tested. Finally, it was successfully applied to detect these cyanotoxins in edible vegetables exposed to cyanobacterial extracts under laboratory conditions, and it could be useful for monitoring these toxins in edible vegetables for better exposure estimation in terms of risk assessment.

Exposure routes and health effects of microcystins on animals and humans: A mini-review

Microcystins (MCs) pollution has quickly risen in infamy and has become a major problem to public health worldwide. MCs are a group of monocyclic hepatotoxic peptides, which are produced by some bloom-forming cyanobacteria in water. More than 100 different MCs variants posing a great threat to animals and humans due to their potential carcinogenicity have been reported. To reduce MCs risks, the World Health Organization has set a provisional guideline of 1 μg/L MCs in human's drinking water. This paper provides an overview of exposure routes of MCs into the human system and health effects on different organs after MCs exposure including the liver, intestine, brain, kidney, lung, heart and reproductive system. In addition, some evidences on human poisoning and deaths associated with MCs exposure are presented. Finally, in order to protect human life against the health threats posed by MCs, this paper also suggests some directions for future research that can advance MCs control and minimize human exposure to MCs.

Toxic Cyanobacteria in Svalbard: Chemical Diversity of Microcystins Detected Using a Liquid Chromatography Mass Spectrometry Precursor Ion Screening Method

Cyanobacteria synthesize a large variety of secondary metabolites including toxins. Microcystins (MCs) with hepato- and neurotoxic potential are well studied in bloom-forming planktonic species of temperate and tropical regions. Cyanobacterial biofilms thriving in the polar regions have recently emerged as a rich source for cyanobacterial secondary metabolites including previously undescribed congeners of microcystin. However, detection and detailed identification of these compounds is difficult due to unusual sample matrices and structural congeners produced. We here report a time-efficient liquid chromatography-mass spectrometry (LC-MS) precursor ion screening method that facilitates microcystin detection and identification. We applied this method to detect six different MC congeners in 8 out of 26 microbial mat samples of the Svalbard Archipelago in the Arctic. The congeners, of which [Asp³, ADMAdda⁵, Dhb⁷] MC-LR was most abundant, were similar to those reported in other polar habitats. Microcystins were also determined using an Adda-specific enzyme-linked immunosorbent assay (Adda-ELISA). Nostoc sp. was identified as a putative toxin producer using molecular methods that targeted 16S rRNA genes and genes involved in microcystin production. The mcy genes detected showed highest similarities to other Arctic or Antarctic sequences. The LC-MS precursor ion screening method could be useful for microcystin detection in unusual matrices such as benthic biofilms or lichen.

Crocadepsins-Depsipeptides from the Myxobacterium Chondromyces crocatus Found by a Genome Mining Approach

Analysis of the genome sequence of the myxobacterium Chondromyces crocatus Cm c5 revealed the presence of numerous cryptic megasynthetase gene clusters, one of which we here assign to two previously unknown chlorinated metabolites by a comparative gene inactivation and secondary metabolomics approach. Structure elucidation of these compounds revealed a unique cyclic depsipeptide skeleton featuring β- and δ-amide bonds of aspartic acid and 3-methyl ornithine moieties, respectively. Insights into their biosynthesis were obtained by targeted gene inactivation and feeding experiments employing isotope-labeled precursors. The compounds were produced ubiquitously by the species Chondromyces crocatus and were found to inhibit the carbon storage regulator-RNA interaction.

Toxicity at the Edge of Life: A Review on Cyanobacterial Toxins from Extreme Environments

Cyanotoxins are secondary metabolites produced by cyanobacteria, of varied chemical nature and toxic effects. Although cyanobacteria thrive in all kinds of ecosystems on Earth even under very harsh conditions, current knowledge on cyanotoxin distribution is almost restricted to freshwaters from temperate latitudes. In this review, we bring to the forefront the presence of cyanotoxins in extreme environments. Cyanotoxins have been reported especially in polar deserts (both from the Arctic and Antarctica) and alkaline lakes, but also in hot deserts, hypersaline environments, and hot springs. Cyanotoxins detected in these ecosystems include neurotoxins-anatoxin-a, anatoxin-a (S), paralytic shellfish toxins, β-methylaminopropionic acid, N-(2-aminoethyl) glycine and 2,4-diaminobutyric acid- and hepatotoxins -cylindrospermopsins, microcystins and nodularins-with microcystins being the most frequently reported. Toxin production there has been linked to at least eleven cyanobacterial genera yet only three of these (Arthrospira, Synechococcus and Oscillatoria) have been confirmed as producers in culture. Beyond a comprehensive analysis of cyanotoxin presence in each of the extreme environments, this review also identifies the main knowledge gaps to overcome (e.g., scarcity of isolates and -omics data, among others) toward an initial assessment of ecological and human health risks in these amazing ecosystems developing at the very edge of life.

High diversity of microcystins in a Microcystis bloom from an Algerian lake

Microcystins (MCs) are cyanobacterial heptapeptides, produced by several genera and species of cyanobacteria, which have been involved in poisoning of animals throughout the world and have also been implicated in human health problems. They are regarded as the most frequently occurring and widespread of the cyanotoxins, with more than 100 MC variants reported to date including the present study. The lake des Oiseaux is a shallow permanent freshwater lake located in north-eastern Algeria. It is an important natural reserve playing a major role for the migratory birds after the crossing of the Mediterranean Sea and from the Sahara desert. In recent years, possibly related to increased eutrophication of the lake, massive blooms of cyanobacteria identified as Microcystis spp. have been observed. A bloom sample collected in September 2013 was analyzed by the serine/threonine phosphatase PP2A inhibition assay and liquid chromatography-mass spectrometry to determine respectively, the total concentration of MCs and the different variants of these toxins present. The results revealed that the Microcystis spp. bloom sample contained microcystins of which 21 putatively congeners were detected. Among these, 12 known microcystins (MC-RR, MC-LR, MC-FR, MC-WR, MC-YR, MC-LA, MC-(H4)YR, MC-HilR, [Asp(3)]MC-RAba, and [Glu(OCH3)(6)]MC-LR) and two new congeners ([Asp(3)]MC-HarAba and [Glu(OCH3)(6)]MC-FR) were characterized, considering their molecular mass and the fragment ions produced by collision-induced dissociation of the [M+H](+) ions. MC-RR was the major (43.4%) in the bloom sample.