Analysis of cyanobacterial toxins by immunological methods

Cactus-Inspired Photonic Crystal Chip for Attomolar Fluorescence Multi-analysis

Automation and efficiency requirements of environmental monitoring are the pursuit of spontaneous sampling and ultrasensitivity for current sensory systems or detection apparatuses. In this work, inspired by cactus hierarchical structures, we develop a cactus-inspired photonic crystal chip to integrate spontaneous droplet sampling and fluorescence enhancement for sensitive multi-analyte detection. A conical hydrophilic pattern on hydrophobic surfaces can give rise to unidirectional Laplace pressure, which drives droplet transport to the assigned photonic crystal site. The nanostructure of photonic crystals has bigger capillarity to drive the droplet wetting uniformly into the photonic crystal matrix while performing prominent fluorescence enhancement by their photonic bandgap. A low to attomolar (2.24 × 10-19 M) fluorescence limit of detection (LOD) sensitivity can be achieved by the synergy of spontaneous droplet sampling and fluorescence enhancement. Focused on eutrophic water problems and algae pollution monitoring, a femtomolar (1.83 × 10-15 M) LOD and identification of various microcystins in urban environmental water can be achieved. The suitable integration of the unidirectional droplet transport by Laplace pressure and fluorescence enhancement by photonic crystals can achieve the spontaneous sampling and signal enhancement for ultratrace detections and sample survey of environmental monitoring and disease diagnosis.

As We Drink and Breathe: Adverse Health Effects of Microcystins and Other Harmful Algal Bloom Toxins in the Liver, Gut, Lungs and Beyond

Freshwater harmful algal blooms (HABs) are increasing in number and severity worldwide. These HABs are chiefly composed of one or more species of cyanobacteria, also known as blue-green algae, such as Microcystis and Anabaena. Numerous HAB cyanobacterial species produce toxins (e.g., microcystin and anatoxin—collectively referred to as HAB toxins) that disrupt ecosystems, impact water and air quality, and deter recreation because they are harmful to both human and animal health. Exposure to these toxins can occur through ingestion, inhalation, or skin contact. Acute health effects of HAB toxins have been well documented and include symptoms such as nausea, vomiting, abdominal pain and diarrhea, headache, fever, and skin rashes. While these adverse effects typically increase with amount, duration, and frequency of exposure, susceptibility to HAB toxins may also be increased by the presence of comorbidities. The emerging science on potential long-term or chronic effects of HAB toxins with a particular emphasis on microcystins, especially in vulnerable populations such as those with pre-existing liver or gastrointestinal disease, is summarized herein. This review suggests additional research is needed to define at-risk populations who may be helped by preventative measures. Furthermore, studies are required to develop a mechanistic understanding of chronic, low-dose exposure to HAB toxins so that appropriate preventative, diagnostic, and therapeutic strategies can be created in a targeted fashion.

Development and comparison of UPLC-ESI-MS and RP-HPLC-VWD methods for determining microcystin-LR

Microcystin-LR (MC-LR) generated by cyanobacteria is a kind of potent hepatotoxin, which poses a considerable threat to human health. In the research field of MC-LR removal, the quantitative analysis in a wide concentration range of samples is inevitable. In this paper, we presented the pseudo united use of an Ultra Performance Liquid Chromatography Mass Spectrometry (UPLC-MS) and High Performance Liquid Chromatography system with a Variable Wavelength Ultraviolet Detector (HPLC-VWD) approach to detect MC-LR. The UPLC-MS system was applied to determine MC-LR in trace concentration because of its high sensitivity. However, it is generally believed that the determination of high concentration samples by UPLC-MS will cause problems such as inaccurate quantification and contamination of ion sources. In consequence, the HPLC-VWD was employed to determine the high concentration of MC-LR. The sensitivity, precision and accuracy of the two methods were compared in detail. The linear ranges of UPLC-MS and HPLC-VWD methods were from 0.08 to 10 μg L⁻¹ and 1 to 5000 μg L⁻¹, respectively. The detection and quantification limits of UPLC-MS were 0.03–0.05 μg L⁻¹ and 0.08 μg L⁻¹, and the corresponding two values of HPLC-VWD were 0.6 and 1.0 μg L⁻¹. The recoveries of UPLC-MS and HPLC-VWD were 88.5–106.7% and 98.7–101.6%, with the relative standard deviations of 3.72–5.45% and 0.38–1.69%, respectively. The potential adsorption properties of MC-LR on filter membranes with diverse materials and pore sizes were evaluated and the negative results were obtained. The detection of MC-LR by UPLC-MS was free from matrix effects. The presented UPLC-MS and HPLC-VWD methods were used to analyze the water samples from Erhai Lake, which is located in Dali, Yunnan, China. The results of UPLC-MS analysis indicated that the MC-LR was only identified in water samples of Shuanglang Bay and Xier River, with concentrations of 0.120 and 0.303 μg L⁻¹, whereas MC-LR was not detected by HPLC-VWD.

UPLC-MS and HPLC-VWD methods were used together for MC-LR determination in a wide concentration range. UPLC-MS can be applied in trace MC-LR determination, whereas HPLC-VWD is more suitable for high concentration range detection.

Biosensing of microcystins in water samples; recent advances

Safety and quality of water are significant matters for agriculture, animals and human health. Microcystins, as secondary metabolite of cyanobacteria (blue-green algae) and cyclic heptapeptide cyanotoxin, are one of the main marine toxins in continental aquatic ecosystems. More than 100 microcystins have been identified, of which MC-LR is the most important type due to its high toxicity and common detection in the environment. Climate change is an impressive factor with effects on cyanobacterial blooms as source of microcystins. The presence of this cyanotoxin in freshwater, drinking water, water reservoir supplies and food (vegetable, fish and shellfish) has created a common phenomenon in eutrophic freshwater ecosystems worldwide. International public health organizations have categorized microcystins as a kind of neurotoxin and carcinogen. There are several conventional methods for detection of microcystins. The limitations of traditional methods have encouraged the development of innovative methods for detection of microcystins. In recent years, the developed sensor techniques, with advantages, such as accuracy, reproducibility, portability and low cost, have attracted considerable attention. This review compares the well-known of biosensor types for detection of microcystins with a summary of their analytical performance.

An aptamer based fluorometric microcystin-LR assay using DNA strand-based competitive displacement

The high-affinity region of a truncated aptamer was applied to the development of a sensitive method for the determination of microcystin-LR (MC-LR) using competitive displacement and molecular beacons. In this assay, the fluorophore and quencher labelled complementary sequences of the aptamer are hybridized with the truncated aptamer to form a fluorophore-quencher pair. In the presence of MC-LR, the aptamer duplex dissociates, and the fluorophore-quencher pair is separated. This turn leads to an increase in the yellow fluorescence which is best measured at excitation/emission wavelengths of 555/580 nm. One of the truncated aptamers showed a 50-fold increase in the affinity (0.93 nM) compared to the wild type aptamer (50 nM). The truncated sequence shows considerable cross-reactivity with L congeners but none with other congeners. The assay works in 0.5 to 200 nM MC-LR concentration range. It was applied to spiked tap water samples and gave recoveries around 95 ± 5%. Graphical abstract Schematic representation of a method for determination of microcystin-LR via fluorescence that is induced by competitive displacement of complementary DNA strands in a truncated dsDNA aptamer.

A less saline Baltic Sea promotes cyanobacterial growth, hampers intracellular microcystin production, and leads to strain-specific differences in allelopathy

Salinity is one of the main factors that explain the distribution of species in the Baltic Sea. Increased precipitation and consequent increase in freshwater inflow is predicted to decrease salinity in some areas of the Baltic Sea. Clearly such changes may have profound effects on the organisms living there. Here we investigate the response of the commonly occurring cyanobacterium Dolichospermum spp. to three salinities, 0, 3 and 6. For the three strains tested we recorded growth, intracellular toxicity (microcystin) and allelopathic properties. We show that Dolichospermum can grow in all the three salinities tested with highest growth rates in the lowest salinity. All strains showed allelopathic potential and it differed significantly between strains and salinities, but was highest in the intermediate salinity and lowest in freshwater. Intracellular toxin concentration was highest in salinity 6. In addition, based on monitoring data from the northern Baltic Proper and the Gulf of Finland, we show that salinity has decreased, while Dolichospermum spp. biomass has increased between 1979 and 2013. Thus, based on our experimental findings it is evident that salinity plays a large role in Dolichospermum growth, allelopathic properties and toxicity. In combination with our long-term data analyses, we conclude that decreasing salinity is likely to result in a more favourable environment for Dolichospermum spp. in some areas of the Baltic Sea.

Immunoassays and biosensors for the detection of cyanobacterial toxins in water

Algal blooms are a frequent phenomenon in nearly all kinds of fresh water. Global warming and eutrophication by waste water, air pollution and fertilizers seem to lead to an increased frequency of occurrence. Many cyanobacteria produce hazardous and quite persistent toxins, which can contaminate the respective water bodies. This may limit the use of the raw water for many purposes. The purification of the contaminated water might be quite costly, which makes a continuous and large scale treatment economically unfeasible in many cases. Due to the obvious risks of algal toxins, an online or mobile detection method would be highly desirable. Several biosensor systems have been presented in the literature for this purpose. In this review, their mode of operation, performance and general suitability for the intended purpose will be described and critically discussed. Finally, an outlook on current developments and future prospects will be given.

Projected marine climate change: effects on copepod oxidative status and reproduction

Zooplankton are an important link between primary producers and fish. Therefore, it is crucial to address their responses when predicting effects of climate change on pelagic ecosystems. For realistic community-level predictions, several biotic and abiotic climate-related variables should be examined in combination. We studied the combined effects of ocean acidification and global warming predicted for year 2100 with toxic cyanobacteria on the calanoid copepod, Acartia bifilosa. Acidification together with higher temperature reduced copepod antioxidant capacity. Higher temperature also decreased egg viability, nauplii development, and oxidative status. Exposure to cyanobacteria and its toxin had a negative effect on egg production but, a positive effect on oxidative status and egg viability, giving no net effects on viable egg production. Additionally, nauplii development was enhanced by the presence of cyanobacteria, which partially alleviated the otherwise negative effects of increased temperature and decreased pH on the copepod recruitment. The interactive effects of temperature, acidification, and cyanobacteria on copepods highlight the importance of testing combined effects of climate-related factors when predicting biological responses.

Toxicological evaluation of microcystins in aquatic fish species: current knowledge and future directions

Microcystins (MCs) are algal toxins produced intracellularly within the algal cells, and are subsequently released into the aquatic systems. An increase in the frequency and intensity of occurrence of harmful algal blooms has directed the global attention towards the presence of MCs in aquatic systems. The effects of MCs on fish have been verified in a number of studies including histological, biochemical and behavioral effects. The toxicological effects of MCs on different organs of fish are related to the exposure route (intraperitoneal injection, feeding or immersion), the mode of uptake (passive or active transport) as well as biotransformation and bioaccumulation capabilities by different organs. This paper reviews the rapidly expanding literature on the toxicological evaluation of MCs in fish from both field studies and controlled laboratory experimental investigations, integrates the current knowledge available about the mechanisms involved in MC-induced effects on fish, and points out future research directions from a cross-disciplinary perspective. In addition, the need to carry out systematic fish toxicity studies to account for possible interactions between MCs and other environmental pollutants in aquatic systems is discussed.

Colloidal graphene as a transducer in homogeneous fluorescence-based immunosensor for rapid and sensitive analysis of microcystin-LR

Herein, we reported the assembly of colloidal graphene (CG) and microcystin (MC)-LR-DNA bioconjugates to develop a homogeneous competitive fluorescence-based immunoassay for rapid and sensitive detection of MC-LR in water samples. Initially, the MC-LR-DNA probe was quickly adsorbed onto the CG surface through the strong noncovalent π-π stacking interactions and can be effectively quenched benefiting from the high quenching efficiency of CG. In contrast, the competitive binding of anti-MC-LR with MC-LR-DNA destroyed the graphene/MC-LR-DNA interaction, thus resulting in the restoration of fluorescence signal. This signal transduction mechanism made it possible for analysis of the target MC-LR. Taking advantage of the colloidal nature of the as-prepared graphene, the assay was carried out in homogeneous solution throughout, which avoided numerous immobilization, incubation, and washing steps that were necessary to traditional heterogeneous immunoassays, thereby reducing the whole assay time (within less than 35 min) and allowing a much better antigen-antibody interaction. Moreover, due to the direct competitive mode, the assay did not involve any antibody labeling or modification process, which would be beneficial to preserve the binding affinity of antigen-antibody. Under optimal conditions, the proposed immunosensor can be applied for quantitative analysis of MC-LR with a detection limit of 0.14 μg/L, which satisfied the World Health Organization (WHO) provisional guideline limit of 1 μg/L for MC-LR in drinking water, thus providing a powerful tool for rapid and sensitive monitoring of MC-LR in environmental samples.

Impact of sonication at 20 kHz on Microcystis aeruginosa, Anabaena circinalis and Chlorella sp

Blooms of toxic cyanobacteria such as Microcystis aeruginosa periodically occur within wastewater treatment lagoons in the warmer months, and may consequently cause contamination of downstream water and outages of the supply of recycled wastewater. Lab-scale sonication (20 kHz) was conducted on suspensions of M. aeruginosa isolated from a wastewater treatment lagoon, and two other algal strains, Anabaena circinalis and Chlorella sp., to investigate cell reduction, growth inhibition, release of microcystin and sonication efficiency in controlling the growth of the M. aeruginosa. For M. aeruginosa, for all sonication intensities and exposure times trialled, sonication led to an immediate reduction in the population, the highest reduction rate occurring within the initial 5 min. Sonication for 5 min at 0.32 W/mL, or for a longer exposure time (>10 min) at a lower power intensity (0.043 W/mL), led to an immediate increase in microcystin level in the treated suspensions. However, prolonged exposure (>10 min) to sonication at higher power intensities reduced the microcystin concentration significantly. Under the same sonication conditions, the order of decreasing growth inhibition of the three algal species was: A. circinalis > M. aeruginosa > Chlorella sp., demonstrating sonication has the potential to selectively remove/deactivate harmful cyanobacteria from the algal communities in wastewater treatment lagoons.

A peptidomic approach for monitoring and characterising peptide cyanotoxins produced in Italian lakes by matrix-assisted laser desorption/ionisation and quadrupole time-of-flight mass spectrometry

In recent years, the occurrence of cyanobacterial blooms in eutrophic freshwaters has been described all over the world, including most European countries. Blooms of cyanobacteria may produce mixtures of toxic secondary metabolites, called cyanotoxins. Among these, the most studied are microcystins, a group of cyclic heptapeptides, because of their potent hepatotoxicity and activity as tumour promoters. Other peptide cyanotoxins have been described whose structure and toxicity have not been thoroughly studied. Herein we present a peptidomic approach aimed to characterise and quantify the peptide cyanotoxins produced in two Italian lakes, Averno and Albano. The procedure was based on matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry mass spectrometry (MALDI-TOF-MS) analysis for rapid detection and profiling of the peptide mixture complexity, combined with liquid chromatography/electrospray ionisation quadrupole time-of- flight tandem mass spectrometry (LC/ESI-Q-TOF-MS/MS) which provided unambiguous structural identification of the main compounds, as well as accurate quantitative analysis of microcystins. In the case of Lake Averno, a novel variant of microcystin-RR and two novel anabaenopeptin variants (Anabaenopeptins B(1) and Anabaenopeptin F(1)), presenting homoarginine in place of the commonly found arginine, were detected and characterised. In Lake Albano, the peculiar peptide patterns in different years were compared, as an example of the potentiality of the peptidomic approach for fast screening analysis, prior to fine structural analysis and determination of cyanotoxins, which included six novel aeruginosin variants. This approach allows for wide range monitoring of cyanobacteria blooms, and to collect data for evaluating possible health risks to consumers, through the panel of the compounds produced along different years.

LOCALIZATION OF MICROCYSTIN SYNTHETASE GENES IN COLONIES OF THE CYANOBACTERIUM MICROCYSTIS USING FLUORESCENCE IN SITU HYBRIDIZATION(1)

To better understand the production of microcystins (MCs) in Microcystis colonies, fluorescence in situ hybridization (FISH) methods were developed to detect DNA involved in the synthesis of these cyanobacterial hepatotoxins. Using colonies of Microcystis aeruginosa (Kütz.) Kütz. isolated from environmental blooms of cyanobacteria and from a colony-forming, MC-producing laboratory strain of Microcystis, amplified PCR products were observed, coincident with positive controls. The total MC content of individual colonies of Microcystis, determined by ELISA, showed a positive correlation with colony cross-sectional area. FISH analysis of Microcystis colonies gave high fluorescence in comparison to negative controls, indicating the presence of MC synthetase DNA (mcyA) in situ. FISH analysis for MC synthetase genes has the potential to be developed into an effective early warning tool for drinking and recreational water management.

Analysis of dissolved microcystins in surface water samples from Kovada Lake, Turkey

Dissolved (extracellular) microcystin (MC) concentrations were determined at 3 sampling stations on Lake Kovada, Turkey. The dominant species of cyanobacteria found in August and September of 2006 were Microcystis aeruginosa, Synechococcus sp., Phormidium limosum, Phormidium formosa and Planktothrix limnetica. MC concentrations in water were measured by ELISA and MC variants were examined by HPLC-PDA. Quantitative analysis by HPLC indicated that five MC variants (MC-LR, -RR, -LA, -LW, -LF) were identified in water samples from Kovada Lake. The maximum concentration of dissolved MC-LW was 98.9 microg l(-1) in October. MC-LR was only detected in May at a concentration of 0.5 microg l(-1). The cross reactivity of the antibody (MC10E7) to variants such as MC-LA MC-LW & MC-LF was low. Hence the results determined by ELISA were lower than those determined by HPLC in September and October samples due to differences in the specificity of the antibody to MC variants. Total extracellular MCs was quantified by ELISA and ranged from 0.73 to 48.5 microg MC-LR equivalents l(-1), which in some cases exceeded the WHO provisional Guideline Value for MC-LR in drinking water. This study confirms that the lakes of Turkey should be monitored for toxic cyanobacteria and for MCs to avoid or reduce the potential exposure of people to these health hazards.

Liquid chromatography coupled to quadruple time-of-flight tandem mass spectrometry for microcystin analysis in freshwaters: method performances and characterisation of a novel variant of microcystin-RR

Cyanobacteria, also called blue-green algae, occur worldwide within water blooms in eutrophic lakes and drinking water reservoirs, producing several biotoxins (cyanotoxins). Among these, microcystins (MCs) are a group of cyclic heptapeptides showing potent hepatotoxicity and activity as tumour promoters. So far, at least 89 MCs from different cyanobacteria genera have been characterised. Herein, ion trap, matrix-assisted laser desorption/ionisation time-of-flight (MALDI-ToF) and quadruple time-of-flight (Q-ToF) mass spectrometry (MS)-based methods were tested and compared for analysing MCs in freshwaters. Method performances in terms of limit of detection, limit of quantification, mean recoveries, repeatability, and specificity were evaluated. In particular, a liquid chromatography/electrospray ionisation (LC/ESI)-Q-ToF-MS/MS method was firstly described to analyse MCs in freshwaters; this technique is highly selective and sensitive, and allowed us to characterise the molecular structure of an unknown compound. Indeed, the full structural characterisation of a novel microcystin variant from a bloom of Planktothrix rubescens in the Lake Averno, near Naples, was attained by the study of the fragmentation pattern. The new cyanotoxin was identified as the 9-acetyl-Adda variant of microcystin-RR.

Toxins of cyanobacteria

Blue-green algae are found in lakes, ponds, rivers and brackish waters throughout the world. In case of excessive growth such as bloom formation, these bacteria can produce inherent toxins in quantities causing toxicity in mammals, including humans. These cyanotoxins include cyclic peptides and alkaloids. Among the cyclic peptides are the microcystins and the nodularins. The alkaloids include anatoxin-a, anatoxin-a(S), cylindrospermopsin, saxitoxins (STXs), aplysiatoxins and lyngbyatoxin. Both biological and chemical methods are used to determine cyanotoxins. Bioassays and biochemical assays are nonspecific, so they can only be used as screening methods. HPLC has some good prospects. For the subsequent detection of these toxins different detectors may be used, ranging from simple UV-spectrometry via fluorescence detection to various types of MS. The main problem in the determination of cyanobacterial toxins is the lack of reference materials of all relevant toxins. In general, toxicity data on cyanotoxins are rather scarce. A majority of toxicity data are known to be of microcystin-LR. For nodularins, data from a few animal studies are available. For the alkaloids, limited toxicity data exist for anatoxin-a, cylindrospermopsin and STX. Risk assessment for acute exposure could be relevant for some types of exposure. Nevertheless, no acute reference doses have formally been derived thus far. For STX(s), many countries have established tolerance levels in bivalves, but these limits were set in view of STX(s) as biotoxins, accumulating in marine shellfish. Official regulations for other cyanotoxins have not been established, although some (provisional) guideline values have been derived for microcystins in drinking water by WHO and several countries.

Sampling and analysis of microcystins: Implications for the development of standardized methods

Microcystins (MC), a group of cyanotoxins, have been found in lakes and rivers worldwide. One goal of MC research is to develop models which predict MC concentrations, but these efforts have been hampered by a lack of standardized methods necessary for comparing data across studies. Here, we investigate the effect of chemical analysis (HPLC-PDA and ELISA), sample collection (whole water, plankton tow and surface scum), and choice of normalizing parameter (volume, dry weight, and chlorophyll a) on reported MC concentrations. Samples were collected over three years from a temperate mesotrophic, shallow lake with episodic blooms of cyanobacteria. We found that microcystins were up to four times higher in lake samples when analyzed by ELISA relative to HPLC-PDA and that MC concentration measured by HPLC explained less than half of the variation in MC concentrations measured by ELISA. Also, samples collected by plankton tow gave consistently higher concentrations than whole water samples. An additional HPLC analysis of two chlorophyte cultures revealed the presence of compounds with a similar UV absorbance spectrum to MC-LR, suggesting that identifying MC based solely on UV absorbance is not valid. Our results document the discrepancy in MC concentrations that can arise by using different methods throughout all stages of sampling, analysis, and reporting of MC concentrations.

Accumulation of nodularin in sediments, mussels, and fish from the Gulf of Gdańsk, southern Baltic Sea

In the Gulf of Gdańsk, as in other parts of the Baltic Sea, toxic blooms of Nodularia spumigena are an annual phenomenon. In the present work, the accumulation of nodularin (NOD), a cyanobacterial pentapeptide hepatotoxin, in sediments, blue mussels, and flounders from the Gulf of Gdańsk was studied by enzyme-linked immunosorbent assay (ELISA). In the surface layers of the sediments NOD concentration ranged from 2.3 ng/g dry weight (dw) several months after cyanobacterial bloom to 75 ng/g dw during the bloom. The highest toxin content in mussels was 139 ng/g dw. In two sampling stations situated in the coastal waters of the Gulf of Gdańsk the concentrations of NOD in sediments and mussels were significantly lower than those measured in the Gulf of Finland. In sediments and mussels collected in the Gulf of Gdańsk, the toxin was also detected in March when N. spumigena did not occur. In flounder, NOD accumulated in the liver (489 ng/g dw), guts (21 ng/g dw), and gonads (21 ng/g dw). Hybride quadrupole-time-of-flight liquid chromatography/mass spectrometry/mass spectrometry (TOF-LC/MS/MS) confirmed the presence of NOD in sediment, mussel, and fish samples. Additionally, other NOD analogues, ([DMAdda(3)]NOD and [dhb(5)]NOD), were detected in sediments and mussel tissue. No NOD conjugates with reduced glutathione or cysteine were found in fish and mussels.

Mitsoamide: A cytotoxic linear lipopeptide from the Madagascar marine cyanobacterium Geitlerinema sp

A new cytotoxic and linear peptide (IC50 460 nM to NCI-H460 human lung tumor cells) was isolated from the marine cyanobacterium Geitlerinema sp. The planar structure of mitsoamide was deduced by 1D and 2D NMR experiments in combination with MS analyses. The structure of mitsoamide contains an unusual polyketide unit (3,7-dimethoxy-5-methyl-nonanedioic acid, DMNA), incorporates a homolysine (HomoLys) residue and possesses a highly unusual piperidine aminal moiety. The configurations of the relatively common amino acids present in mitsoamide (Ala, Ile, N-Me-Ile, Phe, Val) were determined by chiral HPLC analysis of the acid hydrolysate.

Biotechnological significance of toxic marine dinoflagellates

Dinoflagellates are microalgae that are associated with the production of many marine toxins. These toxins poison fish, other wildlife and humans. Dinoflagellate-associated human poisonings include paralytic shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning, and ciguatera fish poisoning. Dinoflagellate toxins and bioactives are of increasing interest because of their commercial impact, influence on safety of seafood, and potential medical and other applications. This review discusses biotechnological methods of identifying toxic dinoflagellates and detecting their toxins. Potential applications of the toxins are discussed. A lack of sufficient quantities of toxins for investigational purposes remains a significant limitation. Producing quantities of dinoflagellate bioactives requires an ability to mass culture them. Considerations relating to bioreactor culture of generally fragile and slow-growing dinoflagellates are discussed. Production and processing of dinoflagellates to extract bioactives, require attention to biosafety considerations as outlined in this review.

Asymmetric multicomponent reactions (AMCRs): the new frontier

Asymmetric multicomponent reactions involve the preparation of chiral compounds by the reaction of three or more reagents added simultaneously. This kind of addition and reaction has some advantages over classic divergent reaction strategies, such as lower costs, time, and energy, as well as environmentally friendlier aspects. All these advantages, together with the high level of stereoselectivity attained in some of these reactions, will force chemists in industry as in academia to adopt this new strategy of synthesis, or at least to consider it as a viable option. The positive aspects as well as the drawbacks of this strategy are discussed in this Review.

Legal and security requirements for the air transportation of cyanotoxins and toxigenic cyanobacterial cells for legitimate research and analytical purposes

Cyanotoxins are now recognised by international and national health and environment agencies as significant health hazards. These toxins, and the cells which produce them, are also vulnerable to exploitation for illegitimate purposes. Cyanotoxins are increasingly being subjected to national and international guidelines and regulations governing their production, storage, packaging and transportation. In all of these respects, cyanotoxins are coming under the types of controls imposed on a wide range of chemicals and other biotoxins of microbial, plant and animal origin. These controls apply whether cyanotoxins are supplied on a commercial basis, or stored and transported in non-commercial research collaborations and programmes. Included are requirements concerning the transportation of these toxins as documented by the United Nations, the International Air Transport Association (IATA) and national government regulations. The transportation regulations for "dangerous goods", which by definition include cyanotoxins, cover air mail, air freight, and goods checked in and carried on flights. Substances include those of determined toxicity and others of suspected or undetermined toxicity, covering purified cyanotoxins, cyanotoxin-producing laboratory strains and environmental samples of cyanobacteria. Implications of the regulations for the packaging and air-transport of dangerous goods, as they apply to cyanotoxins and toxigenic cyanobacteria, are discussed.

Variation between strains of the cyanobacterium Microcystis aeruginosa isolated from a Portuguese river

AIMS

The aim of this study was to investigate toxicological differences between strains of the cyanobacterium Microcystis aeruginosa isolated from a potable water supply in the north of Portugal over a 2-month period.

METHODS AND RESULTS

Twenty-six strains of M. aeruginosa were isolated, grown in pure culture, and tested using a range of techniques including matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), ELISA and a PCR procedure targeting the genes implicated in the production of toxic microcystins. There was considerable variation with respect to the amounts of microcystin produced by each of the strains as measured by ELISA, with values ranging from 0.02 to 0.53% dry weight. The results of the MALDI-TOF MS analysis demonstrated the presence of several chemically distinct forms of microcystin as well as aeruginosins, anabaenopeptins and several other unidentified peptide-like compounds.

CONCLUSIONS

The growth of individual strains that comprise bloom populations, with unique 'chemotypes' can potentially be an important factor affecting the toxicity of bloom populations. Molecular probes, targeting the genes responsible for microcystin production were shown to be useful for distinguishing between toxic and nontoxic strains and showed good agreement with the results obtained from the other analyses.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results of this study show that the analysis of cyanobacterial bloom populations at the subspecies (strain) level can potentially provide important information regarding the toxin-producing potential of a cyanobacterial bloom and could be used as an 'early warning' for toxic bloom development.

Detection of microcystin synthetase genes in health food supplements containing the freshwater cyanobacterium Aphanizomenon flos-aquae

In this study we investigated the presence of toxin-producing cyanobacterial contaminants in food supplements manufactured from blooms of the non-toxic freshwater cyanobacterium Aphanizomenon flos-aquae. Previous reports investigating the contamination of health food supplements with toxin-producing cyanobacteria have used chemical and or biochemical methods such as HPLC, ELISA and protein phosphatase assays. Whilst these studies have drawn attention to the presence of hepatotoxic microcystins in some commercially available food supplements, the methods used do not provide any information on the source of the contaminant. Such information would be useful for the quality control of food supplements produced for human consumption. In this study we applied a molecular technique, involving the amplification of the 16s rRNA gene, the phycocyanin operon, and two genes of the microcystin synthetase gene cluster to show that all 12 food supplement samples, sourced from various internet distributors and containing non-toxic A. flos-aquae, also contained toxigenic cyanobacteria. Sequencing of the microcystin synthetase genes detected in all of the food supplements showed that M. aeruginosa was the organism responsible for the production of microcystins in the samples. The presence of microcystins in the food supplements was confirmed by ELISA, with concentrations within the range of 0.1--4.72 microgg(-1) (microcystin-LR equivalents). Given that the molecular methods applied here are highly sensitive, and show good agreement with the results obtained from ELISA, we believe that they could potentially be used as a quality control technique for food products that contain cyanobacteria.

Risk of human exposure to paralytic toxins of algal origin

The most significant neurotoxins produced by harmful algal blooms (HABs) are paralytic shellfish toxins (PSTs) found in shellfish and freshwater. Human exposure to neurotoxins through the food consumption represents a severe hazard to human health and the exposure through contaminated water represents an added risk often difficult to recognize. Furthermore, there is an insufficient knowledge of toxicokinetics of these complex toxins produced by HABs. If human acute exposure occurs, the diagnosis of intoxication is typically based upon symptomatology and analysis of shellfish tissue by mouse bioassay, HPLC-FLD analysis and mouse neuroblastoma assay. However, the health risks due to chronic exposure should also be considered and its prevention could be reached with a better understanding of sub-lethal doses of these toxins. In this context, information required for development of a diagnostic protocol should include knowledge about toxicokinetics and toxicodynamics of these neurotoxins. We emphasise the importance of research on biomarkers to prevent, predict and diagnose acute and chronic human exposure to PST.

Cyanobacterial toxins: risk management for health protection

This paper reviews the occurrence and properties of cyanobacterial toxins, with reference to the recognition and management of the human health risks which they may present. Mass populations of toxin-producing cyanobacteria in natural and controlled waterbodies include blooms and scums of planktonic species, and mats and biofilms of benthic species. Toxic cyanobacterial populations have been reported in freshwaters in over 45 countries, and in numerous brackish, coastal, and marine environments. The principal toxigenic genera are listed. Known sources of the families of cyanobacterial toxins (hepato-, neuro-, and cytotoxins, irritants, and gastrointestinal toxins) are briefly discussed. Key procedures in the risk management of cyanobacterial toxins and cells are reviewed, including derivations (where sufficient data are available) of tolerable daily intakes (TDIs) and guideline values (GVs) with reference to the toxins in drinking water, and guideline levels for toxigenic cyanobacteria in bathing waters. Uncertainties and some gaps in knowledge are also discussed, including the importance of exposure media (animal and plant foods), in addition to potable and recreational waters. Finally, we present an outline of steps to develop and implement risk management strategies for cyanobacterial cells and toxins in waterbodies, with recent applications and the integration of Hazard Assessment Critical Control Point (HACCP) principles.