Microcystin analysis in single filaments of Planktothrix spp. in laboratory cultures and environmental blooms

Single filaments of Planktothrix spp. were isolated from laboratory cultures of P. agardhii (NIES 595) and P. rubescens (SL 03) and from four freshwater lakes in England and Turkey. Filament lengths were measured and microcystins were extracted by freeze-thawing and boiling. Microcystin analysis of the isolated single filaments was performed by ELISA using antibodies raised against microcystin-LR with a minimum detection limit (MDL) of 11 pg filament(-1). In some cases a high percentage of the filaments from the environmental samples and laboratory cultures were below the MDL of the assay. Based on the filaments with detectable microcystin contents, P. agardhii from Bassenthwaite Lake (England) had the lowest mean microcystin concentration (0.7 fg microm(-3)), and the highest microcystin concentration (2.9 fg microm(-3)) was measured in P. rubescens from Iznik Lake (Turkey). We investigated the relationship for filaments with microcystin contents above MDL and their biovolume. Relationships varied widely although P. agardhii from Bassenthwaite showed a better (positive) relationship between filament biovolume and microcystin content than P. rubescens from environmental samples. Under culture conditions, P. rubescens showed a good relationship between filament biovolume and toxin content.

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.

Optimization of anabaenopeptin extraction from cyanobacteria and the effect of methanol on laboratory manipulation

Anabaenopeptins are commonly occurring bioactive peptides of cyanobacterial origin. Cyanobacteria (blue-green algae) are known to be capable of producing a large number of biologically active peptides, but the widespread occurrence of anabaenopeptins in particular, makes them ideal candidates for investigating the reasons that cyanobacteria produce such a complex spectrum of peptides and the wider implications of their natural function(s). Despite the identification of these peptides in cyanobacterial samples, little is known about the concentrations produced. For this reason, methods for the quantitative extraction of anabaenopeptins from lyophilized cyanobacterial cells were optimized. Higher yields of anabaenopeptins were obtained using aqueous methanol extraction than using water alone. However, repeat extractions using 50, 70 or 90% aqueous methanol did not result in significantly different total yields of the anabaenopeptin variants, ABPN-A and -B. Similarly, little difference was found in the quantification of purified ABPN-A and -B by high performance liquid chromatography with photodiode array detection (HPLC-PDA) when analyzed in methanol solutions of different concentrations. The effects of solvent concentration on the laboratory handling of ABPN-A and -B in glass and plastic containers were also investigated. Significantly lower concentrations of dissolved ABPN-A and -B were found when aqueous solutions came into contact with plastics, but not 50 or 100% methanol.

Immunogold localisation of microcystins in cryosectioned cells of Microcystis

Insights into the origins, function(s), and fates of cyanobacterial toxins may be obtained by an understanding of their location within cyanobacterial cells. Here, we have localised microcystins in laboratory cultures of Microcystis PCC 7806 and PCC 7820 by immunogold labelling. Cryosectioning was used for immunoelectron microscopy since microcystins were extracted during the ethanol-based dehydration steps routinely used for sample preparation. Microcystins were specifically localised in the nucleoplasm and were associated with all major inclusions of the microcystin-producing strains Microcystis PCC 7806 (MC(+)) and Microcystis PCC 7820, and labelling was preferentially associated with the thylakoids and around polyphosphate bodies. A mutant strain of Microcystis PCC 7806 (MC(-)) which does not produce microcystins was used as a control. Distribution of total gold label within each cell region or associated with inclusions indicated that most of the cells' microcystin pool was associated with the thylakoids (69%, PCC 7806 (MC(+)); 78%, PCC 7820), followed by the nucleoplasmic region (19%, PCC 7806 (MC(+)); 12%, PCC 7820). Cryosectioning is a useful technique since it reduces the extraction of microcystins during sample preparation for electron microscopy.

Return of the cycad hypothesis - does the amyotrophic lateral sclerosis/parkinsonism dementia complex (ALS/PDC) of Guam have new implications for global health?

Recently published work provides evidence in support of the cycad hypothesis for Lytico--Bodig, the Guamanian amyotrophic lateral sclerosis/parkinsonism dementia complex (ALS/PDC), based on a new understanding of Chamorro food practices, a cyanobacterial origin of beta-methylaminoalanine (BMAA) in cycad tissue, and a possible mechanism of biomagnification of this neurotoxic amino acid in the food chain. BMAA is one of two cycad chemicals with known neurotoxic properties (the other is cycasin, a proven developmental neurotoxin) among the many substances that exist in these highly poisonous plants, the seeds of which are used by Chamorros for food and medicine. The traditional diet includes the fruit bat, a species that feeds on cycad seed components and reportedly bioaccumulates BMAA. Plant and animal proteins provide a previously unrecognized reservoir for the slow release of this toxin. BMAA is reported in the brain tissue of Guam patients and early data suggest that some Northern American patients dying of Alzheimer's disease (AD) have detectable brain levels of BMAA. The possible role of cyanobacterial toxicity in sporadic neurodegenerative disease is therefore worthy of consideration. Recent neuropathology studies of ALS/PDC confirm understanding of this disorder as a 'tangle' disease, based on variable anatomical burden, and showing biochemical characteristics of 'AD-like' combined 3R and 4R tau species. This model mirrors the emerging view that other neurodegenerative disease spectra comprise clusters of related syndromes, owing to common molecular pathology, with variable anatomical distribution in the nervous system giving rise to different clinical phenotypes. Evidence for 'ubiquitin-only' inclusions in ALS/PDC is weak. Similarly, although there is evidence for alpha-synucleinopathy in ALS/PDC, the parkinsonian component of the disease is not caused by Lewy body disease. The spectrum of sporadic AD includes involvement of the substantia nigra and a high prevalence of 'incidental'alpha-synucleinopathy in sporadic AD is reported. Therefore the pathogenesis of Lytico-Bodig appears still to have most pertinence to the ongoing investigation of the pathogenesis of AD and other tauopathies.

Inhibition of several protein phosphatases by a non-covalently interacting microcystin and a novel cyanobacterial peptide, nostocyclin

Microcystins produced by cyanobacterial 'blooms' in reservoirs and lakes pose significant public health problems because they are highly toxic due to potent inhibition of protein serine/threonine phosphatases in the PPP family. A dehydrobutyrine (Dhb)-containing microcystin variant [Asp3, ADMAdda5, Dhb7]microcystin-HtyR isolated from Nostoc sp. was found to potently inhibit PP1, PP2A, PPP4 and PPP5 with IC50 values similar to those of microcystin-LR. However, in contrast to microcystin-LR, which forms a covalent bond with a cysteine residue in these protein phosphatases, Asp,ADMAdda,Dhb-microcystin-HtyR did not form any covalent interaction with PP2A. Since the LD50 for Asp,ADMAdda,Dhb-microcystin-HtyR was 100 microg kg(-1) compared to 50 microg kg(-1) for microcystin-LR, the data indicate that the non-covalent inhibition of protein phosphatases accounts for most of the harmful effects of microcystins in vivo. A 3-amino-6-hydroxy-2-piperidone containing cyclic peptide, nostocyclin, also isolated from Nostoc sp., was non-toxic and exhibited more than 500-fold less inhibitory potency towards PP1, PP2A, PPP4 and PPP5, consistent with the conclusion that potent inhibition of one or more these protein phosphatases underlies the toxicity of microcystins, both lacking and containing Dhb.

Occurrence of toxic blue-green algae in the Kucukcekmece lagoon (Istanbul, Turkey)

The concentration of microcystin (MC) in the Kucukcekmece Lagoon, Istanbul, Turkey, and the physicochemical and biological parameters of water quality were investigated from October 2000 to June 2003. Water samples were collected from surface waters at three sites. Most bloom samples were dominated by Microcystis aeruginosa. The major microcystin variants detected by HPLC-PDA were microcystin-YR and microcystin-LR. Microcystin concentration increased dramatically from early summer to early autumn and thereafter tended to decrease. The toxin concentration found in the filtered samples from surface waters varied between 0.06 and 24.2 microg L(-1) microcystin-LR equivalents. Each year extensive fish mortality was recorded between mid-June and early October, coinciding with heavy algal blooms. A comparison of the conditions associated with cyanotoxin episodes in 2000, 2001, and 2002 showed that the microcystin increase was related to temperature, high concentration of dissolved nutrients, high light intensity (PAR). The highest MC concentrations were recorded at temperatures between 24 degrees C and 28.5 degrees C. Field data showed that the highest MC concentration (>3 microg L(-1)) and the highest cyanobacterial biomass (>30 mg L(-1)) corresponded to a total nitrogen:total phosphorus ratio greater than 7:1. The highest concentrations of M. aeruginosa biomass (173 mg L(-1)) and MC (24.2 microg L(-1) MC-LR equiv.) and the highest salinity (8.8%) were measured concurrently in the lagoon. To our knowledge, this is the first evidence of cyanobacterial toxins in the Kucukcekmece Lagoon.

Diverse taxa of cyanobacteria produce beta-N-methylamino-L-alanine, a neurotoxic amino acid

Cyanobacteria can generate molecules hazardous to human health, but production of the known cyanotoxins is taxonomically sporadic. For example, members of a few genera produce hepatotoxic microcystins, whereas production of hepatotoxic nodularins appears to be limited to a single genus. Production of known neurotoxins has also been considered phylogenetically unpredictable. We report here that a single neurotoxin, beta-N-methylamino-L-alanine, may be produced by all known groups of cyanobacteria, including cyanobacterial symbionts and free-living cyanobacteria. The ubiquity of cyanobacteria in terrestrial, as well as freshwater, brackish, and marine environments, suggests a potential for wide-spread human exposure.

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.

Leucine aminopeptidase M inhibitors, cyanostatin A and B, isolated from cyanobacterial water blooms in Scotland

Two leucine aminopeptidase M inhibitors, cyanostatin A and B, were isolated from cyanobacterial water blooms at Loch Rescobie in Scotland, and specifically from a Microcystis species. Both inhibitors were lipopeptides containing 3-amino-2-hydroxydecanoic acid and weak inhibitors of protein phosphatase (PP2A). Both strongly inhibited the activity of leucine aminopeptidase M with IC50 values of 40 and 12 ng/ml, respectively.

Interlaboratory comparison trial on cylindrospermopsin measurement

The hepatotoxin cylindrospermopsin (CYN) is a potent inhibitor of protein synthesis in mammalian cells. It is produced by freshwater cyanobacterial blooms in countries such as Australia, the United States, Israel, Thailand, and Brazil. An interlaboratory comparison was organized as a first step to evaluate the measurement of CYN in lyophilized cyanobacterial cells. Six laboratories from Europe, Israel, and Australia participated in the trial. All of the methods used for extraction of the toxin and the high-performance liquid chromatography (HPLC) analysis were satisfactory on the basis of statistical evaluation, according to ISO standards 5725-1 and -2. Further comparison of all the extraction methods by the organizer indicated that the most effective extraction procedure used 5% formic acid to prevent interference in chromatograms by contaminant compounds when analyzed using HPLC employing isocratic conditions of 5% (v/v) aqueous methanol plus 0.1% (v/v) trifluoroacetic acid as the mobile phase.

Inhibition of plant protein synthesis by the cyanobacterial hepatotoxin, cylindrospermopsin

Cylindrospermopsin, a cyanobacterial guanidine alkaloid hepatotoxin and protein synthesis-inhibitor, was assayed for its effects on the germination of pollen from tobacco (Nicotiana tabacum cv Samsun NN). Pollen germination, measured by Alcian Blue dye-binding, was inhibited by cylindrospermopsin between 5 and 1000 microg ml(-1). As a protein synthesis-inhibitor, cylindrospermopsin did not inhibit pollen germination to the same extent as cycloheximide on a gravimetric basis, but significantly reduced the amount of (14)C-(U)-l-leucine labelling in pollen tubes. The inhibition of tobacco pollen germination may be amenable for development as a bioassay for cylindrospermopsin, although this would require a pre-concentration step for the monitoring of environmental samples. Implications of these observations for current spray-irrigation practices are discussed.

Accumulation and depuration of the cyanobacterial toxin cylindrospermopsin in the freshwater mussel Anodonta cygnea

Cylindrospermopsin (CYN) is a toxic alkaloid produced by several genera of freshwater cyanobacteria. This compound has been implicated in outbreaks of human sickness and the death of domestic and wild animals. Given that several of the cyanobacterial genera known to produce CYN are common components of the phytoplankton of freshwaters including aquaculture facilities, we studied the accumulation of CYN in the freshwater mussel (swan mussel) Anodonta cygnea. Anodonta were exposed to CYN-producing cultures of the cyanobacterium Cylindrospermopsis raciborskii for 16 days and were found to accumulate the toxin to concentrations up to 2.52 microg g tissue dry weight(-1). There was considerable variation in the concentrations of CYN detected in different parts of the body. At the end of a 2-week accumulation period the distribution of CYN in the body of Anodonta was as follows: haemolymph (68.1%), viscera (23.3%), foot and gonad (7.7%) and mantle (0.9%). No CYN was detected in the gills or adductor muscle of any animals. Following a 2-week depuration period, approximately 50% of the toxin remained in the tissues. Based on the recently derived guideline value for CYN in human drinking water (1 microg l(-1)) and the concentrations of this compound in animal tissues reported here, there is a clear need for the increased monitoring of this compound in organisms grown for human and animal consumption.

Effects of Microcystis cells, cell extracts and lipopolysaccharide on drinking and liver function in rainbow trout Oncorhynchus mykiss Walbaum

Liver mass (hepatosomatic index, HSI) increased by approximately 18% and water content in the gut by approximately 13 ml kg(-1) in freshwater rainbow trout exposed for 24 h to intact cells of a microcystin-producing cyanobacterium (Microcystis PCC 7813) together with administration of heterotrophic bacterial LPS. Exposure to broken (ultrasonicated) cyanobacterial cells together with administration of bacterial LPS increased HSI by approximately 50% and water content in the gut by almost 30 ml kg(-1). Exposure to broken or unbroken Microcystis cells without administration of bacterial LPS resulted in increased water content of the gut (by approximately 13 ml kg(-1)) with insignificant changes in HIS. Drinking rate increased with increasing dosage of bacterial LPS alone. The increased volume of water in the gut potentially increases the opportunity for uptake of waterborne toxins, including microcystins, and increased liver mass is a symptom consistent with the toxic effects of microcystins. It is concluded that exposure of fish to the cell contents of cyanobacteria (e.g. Microcystis PCC 7813) promotes osmoregulatory imbalance resulting from stimulation of the drinking response, increased volume of fluid in the gut and inability to remove excess water.

Laboratory studies of dissolved radiolabelled microcystin-LR in lake water

The fate of dissolved microcystin-LR was studied in laboratory experiments using surface water taken from a eutrophic lake. Based on initial range finding, a concentration of 50 microg l(-1) dissolved 14C-microcystin-LR was selected for subsequent time-course experiments. The first was performed in May before the cyanobacterial bloom season and low increases in the radioactivity of particulate fractions occurred with an approx. halving of the cyano-toxin during 4 days. The radioactivity of the dissolved fraction remained stable and there was no significant formation of radiolabelled inorganic carbon. A second time-course experiment was performed in September during the cyanobacterial bloom season. At the end of the four-day incubation period, the microcystin-LR concentration had decreased to an undetectable level and 24% of the added radiolabelled substance was found in different particulate fractions. The study demonstrated that biodegradation of dissolved microcystin-LR occurred in water collected at a lake surface with carbon dioxide as a major end-product.

Effects of light on the microcystin content of Microcystis strain PCC 7806

Many cyanobacteria produce microcystins, hepatotoxic cyclic heptapeptides that can affect animals and humans. The effects of photosynthetically active radiation (PAR) on microcystin production by Microcystis strain PCC 7806 were studied in continuous cultures. Microcystis strain PCC 7806 was grown under PAR intensities between 10 and 403 micro mol of photons m(-2) s(-1) on a light-dark rhythm of 12 h -12 h. The microcystin concentration per cell, per unit biovolume and protein, was estimated under steady-state and transient-state conditions and on a diurnal timescale. The cellular microcystin content varied between 34.5 and 81.4 fg cell(-1) and was significantly positively correlated with growth rate under PAR-limited growth but not under PAR-saturated growth. Microcystin production and PAR showed a significant positive correlation under PAR-limited growth and a significant negative correlation under PAR-saturated growth. The microcystin concentration, as a ratio with respect to biovolume and protein, correlated neither with growth rate nor with PAR. Adaptation of microcystin production to a higher irradiance during transient states lasted for 5 days. During the period of illumination at a PAR of 10 and 40 micro mol of photons m(-2) s(-1), the intracellular microcystin content increased to values 10 to 20% higher than those at the end of the dark period. Extracellular (dissolved) microcystin concentrations were 20 times higher at 40 micro mol of photons m(-2) s(-1) than at 10 micro mol of photons m(-2) s(-1) and did not change significantly during the light-dark cycles at both irradiances. In summary, our results showed a positive effect of PAR on microcystin production and content of Microcystis strain PCC 7806 up to the point where the maximum growth rate is reached, while at higher irradiances the microcystin production is inhibited.