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The term cylindrospermopsins (CYNs) refers to a structurally related class of cyanobacterial metabolites comprised of a tricyclic guanidine group and a hydroxymethyluracil moiety. Most reports in environmental aquatic samples refer to cylindrospermopsin (CYN), and reports on other CYN alkaloids are scarce, due, in part, to a lack of versatile isolation protocols. Thus, using commercially available solid phase extraction (SPE) cartridges, we optimized an isolation protocol for the complete recovery of CYN, 7-deoxy-cylindrospermopsin (7D-CYN) and 7-deoxy-desulfo-cylindrospermopsin (7D-desulfo-CYN) from the same aliquot. The isolation protocol was adaptable depending on the nature of the sample (solid biomass, culture broth or environmental water sample) and tolerates up to 4 L of dense culture broth or 400 mg of lyophilized biomass. To quantitate the CYN alkaloids, we validated an LC-DAD-MS2 method, which takes advantage of the UV absorption of the uracil group (&lambda, 262 nm). Using electrospray ionization (ESI) in a positive ion mode, the high-resolution MS1 data confirms the presence of the protonated alkaloids, and the MS2 fragment assignment is reported as complementary proof of the molecular structure of the CYNs. We isolated three CYN alkaloids with different water solubility using the same lyophilized sample, with a purity that ranged from 95% to 99%. The biological activity of the purified CYNs, along with a synthetic degradation product of CYN (desulfo-cylindrospermopsin), was evaluated by assessing necrosis and apoptosis in vitro using flow cytometry. CYN&rsquo, s lethal potency in HepG2 cells was greater than the other analogs, due to the presence of all four functional groups: guanidine, uracil, C-7 hydroxyl and the sulfate residue.

In this study we tested the effects of a neurotoxic strain of the cyanobacterium Raphidiopsis raciborskii (CYRF-01) on the swimming activity and physiological parameters of Daphnia similis such as movements of the antennae, thoracic limbs, post-abdominal claw and heart rate. An acute assay was performed to test the effect on swimming activity, exposing newborns (b24 h) to different concentrations of live cells and observing the number of immobilized animals over a period of 48 h. For testing the effects on physiological parameters adult females (10–15 days) were exposed in a flow-through system and recorded with a digital camera. Results showed rapid effect of the strain CYRF on all parameters. Animals started to be immobilized in the first 30 min exposure and showed complete paralysis after 2 h in 500 μg L−1 and after 24 h in the other concentrations. Physiological parameters accompanied the same response pattern with effects starting after 30 min and some recovery at the end of 6 h exposure. Antennae stopped moving after 2–3 h at 250–500 μg L−1, explaining the paralysis of the swimming activity in Daphnia. Thoracic limbs movements were significantly inhibited after 30 min in all concentrations, staying at lower levels than control through the experiment. Post-abdominal claw movement were completely ceased after 30 min and remained stopped until the end of the trial. Heart rate showed a tendency to decrease abruptly in the first 30 min exposure in all concentrations, but showed significant lower values than control only at 500 μg L−1, between 3 and 4 h exposure, and a recovery at the end of 6 h. In conclusion, results show that neurotoxic cyanobacteria can impose severe constrains on the physiology of daphniids, which can have consequences to the oxygen uptake, swimming and feeding behavior and to the overall fitness of those organisms.

Predicting algal population dynamics using models informed by experimental data has been used as a strategy to inform the management and control of harmful cyanobacterial blooms. We selected toxic bloom-forming species Microcystis spp. and Raphidiopsis raciborskii (basionym Cylindrospermopsis raciborskii) for further examination as they dominate in 78 % and 17 %, respectively, of freshwater cyanobacterial blooms (cyanoHABs) reported globally over the past 30 years. Field measurements of cyanoHABs are typically based on biomass accumulation, but laboratory experiments typically measure growth rates, which are an important variable in cyanoHAB models. Our objective was to determine the usefulness of laboratory studies of these cyanoHAB growth rates for simulating the species dominance at a global scale. We synthesized growth responses of M. aeruginosa and R. raciborskii from 20 and 16 culture studies, respectively, to predict growth rates as a function of two environmental variables, light and temperature. Predicted growth rates of R. raciborskii exceeded those of M. aeruginosa at temperatures ≳ 25 °C and light intensities ≳ 150 μmol photons m−2 s-1. Field observations of biomass accumulation, however, show that M. aeruginosa dominates over R. raciborskii, irrespective of climatic zones. The mismatch between biomass accumulation measured in the field, and what is predicted from growth rate measured in the laboratory, hinders effective use of culture studies to predict formation of cyanoHABs in the natural environment. The usefulness of growth rates measured may therefore be limited, and field experiments should instead be designed to examine key physiological attributes such as colony formation, buoyancy regulation and photoadaptation. Improving prediction of cyanoHABs in a changing climate requires a more effective integration of field and laboratory approaches, and an explicit consideration of strain-level variability.

Cyanobacterial blue–green algal toxins are produced by harmful algal blooms (HABs). Most species of phytoplankton are not harmful, but excessive amounts of certain HAB taxa can cause harm to human and animal health, aquatic ecosystems and local economies. To investigate the prevalence of cylindrospermopsin (CYN) and anatoxin-a (ANA) in Singapore’s reservoirs, a hazard analysis was initiated to profile the CYN and ANA levels present. Water samples from 17 reservoirs were monitored monthly over a 12-month period (November 2012–October 2013). Analyses were conducted by liquid chromatography–tandem mass spectrometry (LC-MS/MS) using a triple-stage quadrupole mass spectrometer with a turbo-assisted ion spray source. CYN was more prevalent than ANA. Intracellular CYN concentrations exceeded 0.4μgL–1 in 6 of 17 man-made reservoirs surveyed, and slightly exceeded the provisional CYN drinking water guidelines of 1μgL–1 (National Health and Medical Research Council and National Resource Management Ministerial Council 2011) on one occasion (1.1μgL–1, July 2013) in one reservoir. The dominant cyanobacteria genera during that period were Cylindrospermopsis, Planktolyngbya, Pseudanabaena and Microcystis. For ANA, all 17 reservoirs had concentrations below 0.1μgL–1. Based on random forest analysis, the most important environmental factors affecting CYN concentrations were total nitrogen (most important), nitrate, total phosphorus and Cylindrospermopsis counts (least important). The findings of this study indicate that reducing total nitrogen concentrations may be useful in minimising CYN concentrations in tropical reservoirs.

Raphidiopsis raciborskii is a tropical toxic cyanobacterium that is rapidly expanding to diverse lake habitats in different climate zones by sophisticated adaptation mechanisms. This meta-analysis investigated correlations of R. raciborskii with water temperature and N:P (nitrogen to phosphorus)-ratios across four lakes with different climates and trophic states by means of long-term time series and the hybrid evolutionary algorithm HEA. The results have shown that in the lakes with temperate and Mediterranean climate, R. raciborskii is strongly correlated with water temperature since germination and growth rely on rising water temperatures in spring. In contrast, there was a weaker correlation with water temperature in subtropical and tropical lakes where pelagic populations of R. raciborskii are overwintering, and are present all year round. However, the highest abundances of R. raciborskii coincided with highest water temperature for the Mediterranean, subtropical and tropical lakes, whilst in the temperate Langer See the highest abundances of R. raciborskii occurred at 24.1 °C, even though temperatures of up to 27 °C were recorded in 2013 and 2014. The correlation of R. raciborskii with N:P-ratios proved to be strongest for the meso- to eutrophic Lake Kinneret (r2 = 0.8) and lowest for the eutrophic Lake Paranoa (r2 = 0.16). However, the assumption has been confirmed that R. raciborskii is growing fastest when waters are N-limited regardless of trophic states. In terms of phenology, the temperate and Mediterranean lakes displayed “fastest growth” in spring and early summer. In contrast, the growing season in subtropical and tropical lakes lasted from spring to autumn most likely because of overwintering populations, and growing importance of direct and indirect biotic regulating factors such as competition, grazing, remineralisation of nutrients along warming climate. In order to carry out a meta-analysis of time series across four different lakes, HEA served as powerful tool resulting in inferential models with predictive capacity for population dynamics of R. raciborskii just driven by water temperature or N:P-ratios, whilst coefficients of determination r2 served as criteria for hypotheses testing.

As yet European strains of Raphidiopsis raciborskii (previously Cylindrospermopsis raciborskii) have not been found to produce known cyanotoxins although their extracts have caused adverse effects in mammals, as shown using in vitro and in vivo experimental models. The present study investigated whether R. raciborskii isolated from Western Poland and Ukraine can affect fish cells using in vitro exposures of hepatocytes and red blood cells (RBC), and brain homogenates obtained from common carp (Cyprinus carpio) to 1.0% and 0.1% extracts of 7 strains. The studied extracts evoked different responses of catalase activity in hepatocytes with both increase and decrease observed under low and high concentrations. The cellular thiol pool was also altered with most extracts inducing a decrease in the activity of glutathione-S-transferase, and Ukrainian strains leading to an increase in glutathione level and a decrease in metallothionein content. All the studied extracts induced comparable reactive oxygen species formation, lipid peroxidation, protein carbonylation and DNA fragmentation in hepatocytes, and all but one increased the activity of caspase-3. Only one extract caused lysosomal membrane destabilization as measured by neutral red retention in RBC. In contrast to extracts of Ukrainian isolates, exposure of brain homogenates to extracts of Polish strains induced an increase in acetylcholinesterase activity suggesting the neurotoxic action of their exudates. The results indicate that both Polish and Ukrainian strains of R. raciborskii may pose a toxicological risk to freshwater fish, and further, that Polish strains may produce compound(s) evoking neurotoxic effects.

Members of the genus Cylindrospermopsis represent an important environmental and health concern. Strains CS-508 and MVCC14 of C. raciborskii were isolated from freshwater reservoirs located in Australia and Uruguay, respectively. While CS-508 has been reported as non-toxic, MVCC14 is a saxitoxin (STX) producer. We annotated the draft genomes of these C. raciborskii strains using the assembly of reads obtained from Illumina MiSeq sequencing. The final assemblies resulted in genome sizes close to 3.6 Mbp for both strains and included 3202 ORFs for CS-508 (in 163 contigs) and 3560 ORFs for MVCC14 (in 99 contigs). Finally, both the average nucleotide identity (ANI) and the similarity of gene content indicate that these two genomes should be considered as strains of the C. raciborskii species. Electronic supplementary material The online version of this article (10.1186/s40793-018-0323-1) contains supplementary material, which is available to authorized users.

Cyanobacterial blooms are characterized by intense growth of one or few species that will dominate the phytoplankton community for periods of few months to an entire year or more. However, even during persistent blooms, important seasonal changes among dominant species can be observed. Pampulha reservoir is a tropical eutrophic reservoir presenting permanent blooms. To identify the main species in this environment, a closer analysis performed by microscopy and 16S-rRNA DGGE revealed Cylindrospermopsis raciborskii as highly dominant throughout the year. The second most abundant group comprised species belonging to the Microcystis genus. They followed a well-defined seasonal pattern described by interesting species-specific ecological trends. During thermal stratification in the rainy/warmer season, C. raciborskii dominated in the water column, while Microcystis spp. were abundant at the end of the dry season, a period characterized by higher total phosphorus concentrations. Phylogenetic analyses confirmed the two dominant taxa and their seasonal trends. The results showed that cyanobacteria major controlling factors were strongly species dependent, shifting from physical/climate related (stratification) to more chemical driven (nutrients/eutrophication). Identifying these drivers is therefore essential for the understanding of the bloom dynamics and the real risks associated with each species, and to eventually adopt the most appropriate and effective management strategies.

The cyanobacterium Raphidiopsis raciborskii is a nuisance in freshwater ecosystems. Strains vary in their physiological responses to environmental drivers, thus a greater understanding of the magnitude of strain variation is required to characterize the species. In this study, two strains of R. raciborskii isolated from a tropical Australian water reservoir were grown with and without phosphorus (P) to determine any relative response to P stress. The strains had the same growth rates and under P free conditions, cells grew at the same rate as P replete conditions until day 9 when cell growth ceased. There was no difference in the alkaline phosphatase activity per cell for the P replete and P free conditions, but the level of activity per cell was greater in CS-505 than CS-506. P acquisition genes were identified from the sequenced genomes; both strains contained the same genes, but with differences in copy number of phoA (7 and 6), phnK (3 and 1) and phnH (2 and 1) between CS-505 and CS-506 (respectively). The expression of P acquisition genes under P stress was measured throughout the experiment and shown to vary in magnitude and timing across strains, and in P replete versus P free cultures. In strain CS-505, upregulation of the pstS1 and phoA genes occurred late in the growth phase and into senescence. These genes are involved in phosphate uptake and use of various forms of organic P. For strain CS-506, there was upregulation of the phosphate uptake gene, pit, and organic P utilization genes, phoA, phoU, phnD and phnK, commencing late in the growth phase. Our study shows that despite the fact that these two strains were isolated from the same waterbody, they differed markedly in their gene expression response to P free conditions. This capacity of R. raciborskii to vary in strain responses to P conditions gives the organism flexibility in responding to environmental change, particularly P stress conditions.

Many species of cyanobacteria are capable of producing toxins and causing nuisance blooms, however response to environmental conditions is likely taxon-specific. Environmental factors influencing cyanobacterial composition and toxin production in lakes have been examined in many studies; yet are often confined to individual water bodies, or to a small number of systems within the same region. Here, data from the 2012 USEPA National Lakes Assessment are used to examine relationships between biovolume of common potentially-toxigenic cyanobacteria (Aphanizomenon spp., Cylindrospermopsis spp., Dolichospermum spp., Microcystis spp. and Planktothrix spp.) and environmental variables across the entire conterminous United States, and results are compared across nine distinct ecoregions. Total phosphorus and water clarity were identified as the most influential environmental factors correlated with phytoplankton community composition. The Northern, Southern and Temperate Plains ecoregions displayed the highest biovolumes of potentially toxigenic taxa on average, as well as highest mean concentrations of microcystin. In those three ecoregions, samples with microcystin concentrations greater than 1 ppb were primarily dominated by Planktothrix spp. while in all other ecoregions Dolichospermum spp. was the dominant genus. Canonical Correlation Analysis revealed a strong association between high microcystin concentrations and high nutrient concentrations (total nitrogen and total phosphorus), and between high microcystin concentrations and low percentage of watershed forest cover. Results from this study indicate that the likely occurrence of potentially toxigenic taxa in lakes and reservoirs is predictable on a biogeographical basis, depending on morphological and water quality characteristics. Data from this study may be useful to regional managers attempting to prevent or mitigate nuisance cyanobacterial blooms.

The cyanobacterium Raphidiopsis raciborskii is of environmental and social concern in view of its toxicity, bloom-forming characteristics and increasingly widespread occurrence. However, while availability of macronutrients and micronutrients such as N and Fe are critically important for the growth and metabolism of this organism, the physiological response of toxic and non-toxic strains of R. raciborskii to varying Fe and N availabilities remains unclear. By determining physiological parameters as a function of Fe and N availability, we demonstrate that R. raciborskii growth and N

The community structures of phytoplankton are important factors and indicators of lake water quality. Harmful algal blooms severely impact water supply, recreational activities and wildlife habitat. This study aimed to examine the phytoplankton composition and variations using microscopy, and identify harmful Cyanobacteria in weekly samples taken from four sites at Harsha Lake in southwest Ohio. Over the course of the summer in 2015, the phytoplankton of Harsha Lake consisted mainly of 13 taxa belonging to Bacillariophyta, Chlorophyta, Cryptophyta, Cyanobacteria, Dinophyta and Euglenophyta. Their significant successions started with Bacillariophyta and/or Chlorophyta, then bloomed with Cyanobacteria and ended with Chlorophyta and/or Dinophyta. Cyanobacteria members: Microcystis, Planktothrix, Dolichospermum, Aphanizomenon, Cylindrospermopsis, and Oscillatoria from the Cyanophyceae were identified to be dominant genera. These organisms varied spatially and temporally in similar patterns along with the variations of nutrients and formed the summer bloom with the total biomasses ranging from 0.01 to 114.89 mg L−1 with mean of 22.88 mg L−1. M. aeruginosa and P. rubescens were revealed as the microcystin producers, while A. circinalis and Aphanizomenon sp. were identified as a saxitoxin producer through cloning and sequencing PCR products of mcyA, mcyE and sxtA genes. The biomasses of phytoplankton, Cyanobacteria and Microcystis were positively correlated to nutrients, especially to total nitrogen. The total ELISA measurement for microcystin positively correlated with Cyanobacteria (R2 = 0.66, P < 0.0001), Microcystis (R2 = 0.64, P < 0.0001) and phytoplankton (R2 = 0.59, P < 0.0001). The basic information on the occurrence and biomasses of Cyanobacteria and total phytoplankton, and the analysis for toxic species, which were the first report for the inland water in Ohio, USA, will document the succession patterns of phytoplankton and toxin production over a season and provide data to predict risk occurrence to both human and ecological factors.

Cylindrospermopsin (CYN) is a cyanotoxin that is of particular concern for its potential toxicity to human and animal health and ecological consequences due to contamination of drinking water. The increasing emergence of CYN around the world has led to urgent development of rapid and high-throughput methods for its detection in water. In this study, a highly sensitive monoclonal antibody N8 was produced and characterized for CYN detection through the development of a direct competitive time-resolved fluorescence immunoassay (TRFIA). The newly developed TRFIA exhibited a typical sigmoidal response for CYN at concentrations of 0.01&ndash, 100 ng mL&minus, 1, with a wide quantitative range between 0.1 and 50 ng mL&minus, 1. The detection limit of the method was calculated to be 0.02 ng mL&minus, 1, which is well below the guideline value of 1 &mu, g L&minus, 1 and is sensitive enough to provide an early warning of the occurrence of CYN-producing cyanobacterial blooms. The newly developed TRFIA also displayed good precision and accuracy, as evidenced by low coefficients of variation (4.1&ndash, 6.5%). Recoveries ranging from 92.6% to 108.8% were observed upon the analysis of CYN-spiked water samples. Moreover, comparison of the TRIFA with an ELISA kit through testing 76 water samples and 15 Cylindrospermopsis cultures yielded a correlation r2 value of 0.963, implying that the novel immunoassay was reliable for the detection of CYN in water and algal samples.

Nowadays Cylindrospermopsis raciborskii (C. raciborskii) and the metabolites produced, such as cylindrospermopsin (CYN), pose a serious threat to the ecosystem. Advanced oxidation technologies have been verified as constituting a very promising means to eliminate the risk from harmful algae. But so far little research has focused on the visible-light photocatalytic destruction of C. raciborskii cells and the degradation of their metabolites. In our study, N-doped TiO

Unlike microcystin, cylindrospermospin (CYN) concentrations in fishpond water and their accumulation in fish tissues have been largely unexplored. This study determined CYN levels in water and tilapia fish organs from three tropical fishponds in southern Egypt. Water and fish samples were collected monthly from fishponds for 12 months (Oct 2012 to Sep 2013). The results revealed that six CYN-producing species of cyanobacteria dominated phytoplankton populations and formed blooms in these fishponds during warm months. Among these species, Anabaena affinis, Planktothrix agardhii, Cylindrospermopsis catemaco, and C. philippinensis were assigned as CYN producers for the first time in the present study. The highest cell densities of CYN-producing species in fishponds were recorded in August and September 2013, correlating with high temperature, pH and nutrient concentrations. Dissolved CYN was found in fishpond waters at levels (0.3–2.76 μg L−1) very close to those of particulate CYN (0.4–2.37 μg L−1). CYN was also estimated in tilapia fish organs at levels up to 417 ng g−1 in the intestines, 1500 ng g−1 in the livers, and 280 ng g−1in edible muscles. Compared to the recommended guideline (0.03 μg kg−1 day−1), the estimated daily intake (EDI) of CYN in our samples of edible muscles exceeded this limit by a factor of 1.3–14 during summer and autumn. This might represent a risk to human health upon consumption of such contaminated fish muscles. Therefore, fishponds worldwide should be monitored for the presence toxic cyanobacteria to protect humans from their potent toxins.

Cyanobacteria are microscopic, prokaryotic organisms capable of mass development in aquatic ecosystems. Cyanobacterial blooms, observed often in various fresh and brackish waters, are growing global problem due to the eutrophication process and climate changes. Different cyanobacterial species may produce wide range of various biologically active secondary metabolites, which may be harmful to aquatic organisms, animals and humans. Microcystins (MCs) are the most known and frequently studied cyanobacterial compounds classified to cyanotoxins. But cyanobacteria are producers of several hundred of other toxins (e.g. nodularins, cylindrospermopsins, anatoxins, saxitoxins), and potentially harmful substances (e.g. oligopeptides other than MCs). In this paper, the present knowledge about cyanobacterial blooms, toxins and other metabolites is shown concisely with references to the latest review reports broadly describing the issues discussed. Human health risks caused by cyanobacteria is also presented

Cyanobacteria tend to become the dominant phytoplankton component in eutrophic freshwater environments during warmer seasons. However, general observations of cyanobacterial adaptive advantages in these circumstances are insufficient to explain the prevalence of one species over another in a bloom period, which may be related to particular strategies and interactions with other components of the plankton community. In this study, we present an integrative view of a mixed cyanobacterial bloom occurring during a warm, rainy period in a tropical hydropower reservoir. We used high-throughput sequencing to follow temporal shifts in the dominance of cyanobacterial genera and shifts in the associated heterotrophic bacteria community. The bloom occurred during late spring-summer and included two distinct periods. The first period corresponded to Microcystis aeruginosa complex (MAC) dominance with a contribution from Dolichospermum circinale; this pattern coincided with high water retention time and low transparency. The second period corresponded to Cylindrospermopsis raciborskii and Synechococcus spp. dominance, and the reservoir presented lower water retention time and higher water transparency. The major bacterial phyla were primarily Cyanobacteria and Proteobacteria, followed by Actinobacteria, Bacteroidetes, Verrucomicrobia, and Planctomycetes. Temporal shifts in the dominance of cyanobacterial genera were associated with physical features of the water (retention time and transparency) and with shifts in the associated heterotrophic bacteria. The MAC bloom was associated with a high abundance of Bacteroidetes, particularly Cytophagales. In the second bloom period, Planctomycetes increased in relative abundance, five Planctomycetes OTUs were positively correlated with Synechococcus or C. raciborskii OTUs. Our results suggest specific interactions of the main cyanobacterial genera with certain groups of the heterotrophic bacterial community; the results suggest that considering biotic interactions may lead to a better understanding of the shifts in cyanobacterial dominance.

International audience; Phylogenetic relationships among heterocytous genera (the Nostocales order) have been profoundly modified since the use of polyphasic approaches that include molecular data. There is nonetheless still ample scope for improving phylogenetic delineations of genera with broad ecological distributions, particularly by integrating specimens from specific or up-to-now poorly sampled habitats. In this context, we studied 36 new isolates belonging to Chrysosporum, Dolichospermum, Anabaena, Anabaenopsis, and Cylindrospermopsis from freshwater ecosystems of Burkina-Faso, Senegal, and Mayotte Island. Studying strains from these habitats is of particular interest as we suspected different range of salt variations during underwent periods of drought in small ponds and lakes. Such salt variation may cause different adaptation to salinity. We then undertook a polyphasic approach, combining molecular phylogenies, morphological analyses, and physiological measurements of tolerance to salinity. Molecular phylogenies of 117 Nostocales sequences showed that the 36 studied strains were distributed in seven lineages: Dolichospermum, Chrysosporum, Cylindrospermopsis Raphidiopsis, Anabaenopsis, Anabaena sphaerica var tenuis/Sphaerospermopsis, and two independent Anabaena sphaerica lineages. Physiological data were congruent with molecular results supporting the separation into seven lineages. In an evolutionary context, salinity tolerance can be used as an integrative marker to reinforce the delineation of some cyanobacterial lineages. The history of this physiological trait contributes to a better understanding of processes leading to the divergence of cyanobacteria. In this study, most of the cyanobacterial strains isolated from freshwater environments were salt-tolerant, thus suggesting this trait constituted an ancestral trait of the heterocytous cyanobacteria and that it was probably lost two times secondarily and independently in the ancestor of Dolichospermum and of Cylindrospermopsis. (C) 2018 Elsevier B.V. All rights reserved.

Like many complex natural products, the intricate architecture of saxitoxin (STX) has hindered full exploration of this scaffold’s utility as a tool for studying voltage-gated sodium ion channels and as a pharmaceutical agent. Established chemical strategies can provide access to the natural product; however, a chemoenzymatic route to saxitoxin that could provide expedited access to related compounds has not been devised. The first step toward realizing a chemoenzymatic approach toward this class of molecules is the elucidation of the saxitoxin biosynthetic pathway. To date, a biochemical link between STX and its putative biosynthetic enzymes has not been demonstrated. Herein, we report the first biochemical characterization of any enzyme involved in STX biosynthesis. Specifically, the chemical functions of a polyketide-like synthase, SxtA, from the cyanobacteria Cylindrospermopsis raciborskii T3 are elucidated. This unique megasynthase is comprised of four domains: methyltransferase (MT), GCN5-related N-acetyl-transferase (GNAT), acyl carrier protein (ACP), and the first example of an 8-amino-7-oxononanoate synthase (AONS) associated with a multi-domain synthase. We have established that this single polypeptide carries out the formation of two carbon-carbon bonds, two decarboxylation events and a stereospecific protonation to afford the linear biosynthetic precursor to STX (4). The synthetic utility of the SxtA AONS is demonstrated by the synthesis of a suite of α-amino ketones from the corresponding α-amino acid in a single step.

Geosmin (trans-1, 10-dimethyl-trans-9-decalol) is a key compound which causes taste and odour (T&O) issues in water. Despite no recorded health hazards, water consumers reject the water with geosmin due to its unpleasant earthy T&O. Cyanobacteria are prokaryotes, grow in light habitats preferring neutral or alkaline conditions and recorded to produce geosmin. The aim of this study was to screen any correlation between geosmin and cyanobacteria. Geosmin contamination level in 12 raw water bodies used to drinking and treatment purposes in Sri Lanka covering 5 districts (Anuradhapura, Pollonnaruwa, Ampara, Batticcaloe and Trincomalee) were analyzed using Gas Chromatography-Mass Spectrometry coupled with Solid-phase micro extraction. Enumeration and identification of cyanobacteria was carried out using standard APHA method. Prominent cyanobacteria identified were Anabaena sp., Microcystis sp., Oscillatoria sp. and Cylindrospermopsis sp. Geosmin levels ranged from 7.8 to 10.9 ppt where the highest level was recorded in Nuwara tank (10.9 ppt) and the lowest was detected in Nallachchiya tank (7.8 ppt). Jayanthi tank, Sagama tank, Kondavatuwana tank, Unnichchi tank and Kantale tank hadgeosmin levels below 1.5 ppt (Minimum detection level 1.5 ppt) during the sampling time. 68% of the sampling locations exceeded the human threshold level (5 ppt). According to a questionnaire survey, more than 95% end water consumers rejected drinking water contaminated with geosmin (N=200). Total Cyanobacteria cell Density (T.C.D) was positively correlated with geosmin and total phosphorous (p 17). Nuwara tank had a N: P ratio of 16.2 which signifies either nitrogen or phosphorous can be limited (N: P=10-17). Based on total nitrogen and total phosphorous values, Jayanthi tank, Sagama tank, Kondawatuwanana tank and Unnachchi tank classified to be Oligotrophic and Nachchadoowa tank, Kala tank, Nallachchiya tank, Thuruwila tank, Tissa tank and Nuwara tank to be Eutrophic status. Thus, the results of the study indicate there is a direct positive variation between geosmin, cyanobacteria and total phosphorous. Keywords: Geosmin, Cyanobacteria, N:P ratio, Solid-phase micro extraction, Gas Chromatography-Mass Spectrometry

Raphidiopsis and Cylindrospermopsis are planktic, freshwater bloom-forming cyanobacteria of great concern to human health due to the production of potent cyanotoxins. The presence (in Cylindrospermopsis) or absence (in Raphidiopsis) of heterocytes is the traditional character used to distinguish them. This has led to misidentifications and to questions about the validity of the genus Raphidiopsis. We studied two strains of R. mediterranea isolated from Argentinean shallow lakes using a polyphasic approach that included the morphological description of the natural populations and their ultrastructural, physiological and molecular characterisation. Heterocyte differentiation was not observed in the field or in cultures of R. mediterranea submitted to nitrogen deprivation. These results support the occurrence of stable native populations of R. mediterranea without heterocytes, which would not be a part of the Cylindrospermopsis complex life cycle. Based on 16S rRNA, 16S–23S ITS, and cpcBA-IGS sequences, these two genera are virtually identical. Thus, strains of Raphidiopsis and Cylindrospermopsis make up a monophyletic lineage in all phylogenetic reconstructions. Furthermore, the 16S–23S ITS secondary structure provided further evidence that these two genera cannot be separated. The intermixed position in the trees points to several losses of heterocytes during the evolution of these cyanobacteria. We conclude that these two genera should not be regarded as separate and distinct generic units and propose their unification under the name Raphidiopsis, respecting the principle of priority. Accordingly, we revisited and emended the description of Raphidiopsis. Fil: Aguilera, Anabella. Fundación para Investigaciones Biológicas Aplicadas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; Argentina Fil: Berrendero Gómez, Esther. University of South Bohemia; República Checa Fil: Kaštovský, Jan. University of South Bohemia; República Checa Fil: Echenique, Ricardo Omar. Facultad de Ciencias Naturales y Museo, Universidad Nacional de la Plata; Argentina Fil: Salerno, Graciela Lidia. Fundación para Investigaciones Biológicas Aplicadas; Argentina

Harmful cyanobacterial blooms have become increasingly common in freshwater ecosystems in recent decades, mainly due to eutrophication and climate change. Water becomes unreliable for human consumption. Here, we report a comprehensive study carried out to investigate the water quality of several Campina Grande reservoirs. Our approach included metagenomics, microbial abundance quantification, ELISA test for three cyanotoxins (microcystin, nodularins, and cylindrospermopsin), and in vivo ecotoxicological tests with zebrafish embryos. Cytometry analysis showed high cyanobacterial abundance, while metagenomics identified an average of 10.6% of cyanobacterial sequences, and demonstrated the presence of Microcystis, Cylindrospermopsis, and toxin coding genes in all ponds. Zebrafish embryos reared with pond water had high mortality and diverse malformations. Among the ponds analyzed, Araçagi showed the highest lethality (an average of 62.9 ± 0.8%), followed by Boqueirão (lethality average of 62.5 ± 0.8%). Here, we demonstrate that water from ponds undergoing extremely drought conditions have an abundance of potentially harmful cyanobacteria and their toxins. Our findings are consistent with a scenario in which polluted drinking water poses a great risk to human health.

Bisphenol A has attracted worldwide attention due to its harmful effects on humans, animals and plants. In this study, the toxicological effects of BPA on Cylindrospermopsis raciborskii were assessed based on chlorophyll a fluorescence and transcriptome analyses. The results showed that the growth of C. raciborskii was significantly inhibited when BPA exceeded 0.1 mg L−1. A marked rise of phase J was observed at a concentration greater than 0.1 mg L−1, while a K phase appeared at 20 mg L−1. The chlorophyll a fluorescence parameters of RC/CS0, F0, φP0, φE0, and ψ0, underwent a significant decline under all treatments of BPA, whereas a significant increase in both VJ and M0 occurred under all concentrations of BPA. Additionally, ABS/RC and DIo/RC markedly increased at 10 mg L−1 and 20 mg L−1. The transcriptome analysis revealed that the genes of photosynthesis, including psbA, psbB, psbC, psbD, apcA, apcB, cpcA, and cpcB, as well as those of chlorophyll and carotenoid biosynthesis, namely hemN, acsF, chlL, chlN, chlP, crtB, pds, were all down-regulated. Moreover, BPA also inhibited the oxidative phosphorylation, glycolysis/gluconeogenesis, citrate cycle (TCA cycle), and fatty acid metabolism in C. raciborskii. Taken together, these results suggest BPA can negatively affect the expression of multiple genes and the vital energy metabolism process to arrest the growth and photosynthesis of C. raciborskii.

The microbial community structures of drinking water treatment sludge (DWTS) generated for raw water (RW) from different locations and with different source types - including river water, lake water and reservoir water -were investigated using high-throughput sequencing. Because the unit operations in the six DWTPs were similar, community composition in fresh sludge may be determined by microbial community in the corresponding RW. Although Proteobacteria, Cyanobacteria, Bacteroidetes, Firmicutes, Verrucomicrobia, and Planctomycetes were the dominant phyla among the six DWTS samples, no single phylum exhibited similar abundance across all the samples, owing to differences in total phosphorus, chemical oxygen demand, Al, Fe, and chloride in RW. Three genera of potentially toxic cyanobacteria (Planktothrix, Microcystis and Cylindrospermopsis), and four potential pathogens (Escherichia coli, Bacteroides ovatus, Prevotella copri and Rickettsia) were found in sludge samples. Because proliferation of potentially toxic cyanobacteria and Rickettsia in RW was mainly affected by nutrients, while growth of Escherichia coli, Bacteroides ovatus and Prevotella copri in RW may be influenced by Fe, control of nutrients and Fe in RW is essential to decrease toxic cyanobacteria and pathogens in DWTS.

Cyanobacteria inhabit hypersaline, marine and freshwater environments. Some toxic and non-toxic species can form harmful blooms. The aim of this study was to identify potentially harmful cyanobacterial species in the oyster banks of Términos Lagoon, the southeastern Gulf of Mexico. Six sample sites (up to 2-m depth) were monitored monthly from August 2012 to September 2013. Water temperature, salinity, pH, dissolved oxygen saturation (% DO), inorganic nutrients and abundance of cyanobacteria were determined. Temperature and salinity were characterized by marked seasonal differences (26.8 to 30.6 °C and 6.1 to 19.5, respectively). The pH values (ranging from 7.1 to 8.4) and the % DO (88.4 to 118.2 %) suggest a predominance of photosynthetic activity in the windy season (October-February). Elevated nutrient contents are associated with the period of increased river discharge, determined by water circulation and biogeochemical processes. Fourteen taxa were identified, of which Anabaena sp., Merismopedia sp., Oscillatoria sp. and Cylindrospermopsis cuspis produced blooms. Cyanobacterial abundances were on the order of magnitude of 106 cells L-1 in October 2012 at stations S1-S6, with an average value of 3.2x105 cells L-1 and a range of 2000 to 3.1x106 cells L-1 throughout the study period; however, they showed a remarkable absence during the windy season (October to January). Anabaena sp. and C. cuspis reached abundances of 1.9x106 and 1.3x106 cells L-1, respectively. The latter caused the temporary closure of oyster Crassostrea virginica harvesting for 15 days in October 2012. Las cianobacterias habitan en ambientes hipersalinos, marinos y de agua dulce. Algunas especies tóxicas y no tóxicas pueden formar florecimientos nocivos. El objetivo de este estudio fue identificar las especies de cianobacterias potencialmente nocivas en los bancos ostrícolas de laguna de Términos, sureste del Golfo de México. Seis sitios de muestreo (hasta 2 m de profundidad) fueron monitoreados mensualmente de agosto de 2012 a septiembre de 2013. Se midió la temperatura del agua, salinidad, pH, saturación de oxígeno, nutrientes inorgánicos y abundancia de cianobacterias. La temperatura y la salinidad se caracterizaron por marcadas diferencias estacionales (26,8 a 30,6 °C y 6,1 a 19,5, respectivamente). Los valores de pH (de 7,1 a 8,4) y la saturación de oxígeno disuelto (de 88,4 a 118,2 %) sugieren un predominio de la actividad fotosintética en la temporada de nortes (octubre-enero). Las concentraciones elevadas de los nutrientes están asociados al periodo de mayor descarga de los ríos, determinados por la circulación y los procesos biogeoquímicos. Se identificaron 14 taxa, de los cuales Anabaena sp., Merismopedia sp., Oscillatoria sp. y Cylindrospermopsis cuspis formaron florecimientos. Las abundancias de cianobacterias fueron del orden de magnitud de 106 células L-1 en octubre de 2012 en las estaciones S1-S6, con un valor promedio de 3.2x105 células L-1 y un rango de 2000 a 3.1x106 células L-1 a lo largo del periodo de estudio. Sin embargo, mostraron una ausencia notable durante la temporada de nortes (octubre a enero). Anabaena sp. y C. cuspis alcanzaron abundancias de 1.9x106 y 1.3x106 células L-1, respectivamente. Este último causó el cierre temporal de la colecta del ostión Crassostrea virginica durante 15 días en octubre de 2012.

In tropical and subtropical lakes, eutrophication often leads to nuisance blooms of Cylindrospermopsis raciborskii. In laboratory experiments, we tested the combined effects of flocculant polyaluminum chloride (PAC) and lanthanum-modified bentonite (LMB) on the sinking and growth rates of three C. raciborskii strains. We tested the hypothesis that the combination of PAC and LMB would (1) effectively sink C. raciborskii in a test tube experiment and (2) impair C. raciborskii growth, irrespective of the biomass of the inoculum (bloom) and the strain in the growth experiment. We tested the recommended (LMB1) and a three-times higher dose of LMB (LMB3). The combined addition of PAC and LMB enhanced the sedimentation of all C. raciborskii strains. Moreover, both the PAC and LMB doses decreased the phosphate concentration. PAC and LMB1 decreased the growth rate of all strains, but the efficacy depended on the biomass and strain. The combined addition of PAC and LMB3 inhibited the growth of all strains independently of the biomass and strain. We conclude that a low dose of PAC in combination with the recommended dose of LMB decreases C. raciborskii blooms and that the efficiency of the technique depends on the biomass of the bloom. A higher dose of LMB is needed to obtain a more efficient control of C. raciborskii blooms.

The cyanobacterial bloom is a consequence of eutrophication in a lentic environment. It is attributed to the contribution of nutrients related to anthropic action, as well as geographic and physico-chemical conditions. Water quality parameters of Alagados reservoir, which supplies Ponta Grossa, were determined between 08/2013 and 08/2014 to evaluate their effects on the occurrence of bloom. Some parameters, such as pH (9.1), DO (4.2 mg L-1), BOD (39 mg L-1), TP (0.86 mg L-1) and number of cyanobacterial cells (372,536 cells mL-1), were outside the limits recommended by CONAMA 357/05 for Class II and Decree 2,914/11 of the Ministry of Health. The bloom was predominantly caused by the overdevelopment of Cylindrospermopsis sp. and required additional use of chemical products in the treatment of municipal water supplies, to include coagulant (19.6%), polymer (21.0%) and activated carbon (1,889%), with a corresponding cost increase of 58%. The Water Quality Index confirmed the worsening of reservoir water quality during bloom. The Principal Component Analysis of historical data (01/2003 to 08/2014) did not discriminate the cyanobacteria levels classes (< 2,000, 2,000-20,000, 20,000-50,000 and > 50,000 cells mL-1) based on Brazilian standards, which was confirmed by the Hierarchical Cluster Analysis; although it confirmed a logical correlation between some parameters (climatic condition-reservoir rainfall-reservoir level and BOD-COD). The unidentified correlations can be attributed to the adaptability of Cylindrospermopsis sp. and the ecological complexity that requires higher sampling frequency. Resumo A floração de cianobactérias é consequência da eutrofização em ambiente lêntico e é atribuída ao aporte de nutrientes relacionado à ação antrópica, além de condições geográficas e físico-químicas. Parâmetros de qualidade da água da bacia de Alagados, que abastece Ponta Grossa, foram determinados entre 08/2013 e 08/2014 para avaliar seus efeitos na ocorrência de floração. Alguns parâmetros foram encontrados fora dos limites, como pH (9,1), OD (4,2 mg L-1), DBO (39 mg L-1), PT (0,86 mg L-1) e número de células de cianobactérias (372.536 céls mL-1); CONAMA 357/05 classe II e Portaria 2.914/11 do Ministério da Saúde. A piora da qualidade da água da represa durante a floração foi confirmada com uso do Índice de Qualidade de Água. A floração de Cylindrospermopsis sp. demandou uso suplementar de insumos químicos no tratamento de água, como coagulante (19,6%), polímero (21,0%) e carvão ativado (1.889%), com correspondente aumento de custo em 58%. A Análise de Componentes Principais de dados históricos (01/2003 a 08/2014) não discriminou as classes de níveis de cianobactérias (< 2.000, 2.000-20.000, 20.000-50.000 e > 50.000 cél ml-1) baseadas em normas brasileiras, o que foi confirmado pela Análise Hierárquica de Agrupamentos; embora tenha confirmado correlação lógica entre alguns parâmetros (condição climática, índice pluviométrico da bacia, nível da represa e DBO-DQO). As correlações não identificadas podem ser atribuídas à adaptabilidade da Cylindrospermopsis sp. e a complexidade ecológica que demanda maior frequência de amostragem.

Toxic cyanobacterial blooms are a water quality issue worldwide whose incidence and severity are predicted to increase due to climate change and eutrophication. Argentina is not an exception to this trend, since those massive proliferations have increased in the last two decades as a consequence of water quality changes due to human activities. This work presents a thorough search and analysis of published literature on the occurrence of cyanobacterial blooms and cyanotoxins in Argentina. We retrieved 241 bloom events (1944?2014) covering 63 impacted water bodies, used either for recreational activities and/or drinking water supply. The highest incidence was concentrated in the central and eastern areas of the country (Chaco-Pampean Plain and Peripampean Sierras), the most densely populated regions, also highly impacted by agro-industrial activities. Intense blooms of Microcystis, Dolichospermum and Cylindrospermopsis species represent a potential hazard for both human beings and wild?life through oral ingestion and/or direct contact, although quantitative and systematic registers to estimate the extent of occurrence are still missing. Elevated microcystins concentrations, together with the presence of blooms of potential saxitoxin or anatoxin-a producers emphasize the need to increase monitoring of these toxins in drinking water supplies and recreational areas. The data presented are valuable for promoting the generation and implementation of guideline values and risk management frameworks at a national and regional scale. Fil: Aguilera, Anabella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; Argentina Fil: Haakonsson, Signe. Universidad de la República. Facultad de Ciencias; Uruguay Fil: Martin, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; Argentina Fil: Salerno, Graciela Lidia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología; Argentina. Fundación para Investigaciones Biológicas Aplicadas; Argentina Fil: Echenique, Ricardo Omar. Universidad Nacional de La Plata; Argentina

Controlling blooms of toxigenic phytoplankton, including cyanobacteria, is a high priority for managers of aquatic systems that are used for drinking water, recreation, and aquaculture production. Although a variety of treatment approaches exist, hydrogen peroxide (H2O2) has the potential to be an effective and ecofriendly algaecide given that this compound may select against cyanobacteria while not producing harmful residues. To broadly evaluate the effectiveness of H2O2 on toxigenic phytoplankton, we tested multiple concentrations of H2O2 on (1) four cyanobacterial cultures, including filamentous Anabaena, Cylindrospermopsis, and Planktothrix, and unicellular Microcystis, in a 5-day laboratory experiment and (2) a dense cyanobacterial bloom in a 7-day field experiment conducted in a nutrient-rich aquaculture pond. In the laboratory experiment, half-maximal effective concentrations (EC50) were similar for Anabaena, Cylindrospermopsis, and Planktothrix (average EC50 = 0.41 mg L−1) but were ∼10x lower than observed for Microcystis (EC50 = 5.06 mg L−1). Results from a field experiment in an aquaculture pond showed that ≥1.3 and ≥ 6.7 mg L−1 of H2O2 effectively eliminated Planktothrix and Microcystis, respectively. Moreover, 6.7 mg L−1 of H2O2 reduced microcystin and enhanced phytoplankton diversity, while causing relatively small negative effects on zooplankton abundance. In contrast, 20 mg L−1 of H2O2 showed the greatest negative effect on zooplankton. Our results demonstrate that H2O2 can be an effective, rapid algaecide for controlling toxigenic cyanobacteria when properly dosed.

Harmful cyanobacterial blooms have caused several problems in freshwater environments due to their prolific growth and the harmful cyanotoxins produced by some species. The occurrence of these organisms has increased in recent decades due to climate change and eutrophication, although most studies are from temperate regions in the Northern hemisphere. This review presents data about cyanobacteria occurrence, dominance, and toxicity events in freshwater bodies in a semiarid region of Northeast Brazil, in the tropical Southern hemisphere. We performed a literature survey of cyanobacteria publications from 1930 to 2016. We made a list of all the dominant species registered in each state, noted their distribution and occurrence of dominance events involving one or more species, and the registered records of toxic blooms, including information about the toxins involved and the range of values. We selected 102 publications that described cyanobacteria occurrence from states in Northeast Brazil; these publications included relevant contributions regarding cyanobacteria distribution, richness, density, and biomass. Forty-nine dominant species were recorded, with the most representation found in the state of Pernambuco (30 spp.). The genera with the highest occurrences were Microcystis , Cylindrospermopsis , Planktothrix , Dolichospermum (= Anabaena ), and Geitlerinema , especially the species Cylindrospermopsis raciborskii , Microcystis aeruginosa , and Planktothrix agardhii . Episodes of toxic blooms were observed in four states. Microcystins, cylindrospermopsin, saxitoxins, and anatoxin-a(S) were found to be associated with these blooms. In Northeast Brazil, harmful cyanobacterial blooms are common in urban and public reservoirs. However, in recent years, cyanobacterial blooms in this region have been more intense and perennial, with high biomass occurring throughout the year.

Saxitoxins (STX), neurotoxic alkaloids, fall under the umbrella of paralytic shellfish toxins produced by marine dinoflagellates and freshwater cyanobacteria. The genes responsible for the production of STX have been proposed, but factors that influence their expression and induce toxin efflux remain unclear. Here we characterize the putative STX NorM-like MATE transporters SxtF and SxtM. Complementation of the antibiotic-sensitive strain Escherichia coli KAM32 with these transporters decreased fluoroquinolone sensitivity, indicating that while becoming evolutionary specialized for STX transport these transporters retain relaxed specificity typical of this class. The transcriptional response of STX biosynthesis (sxtA) along with that of the STX transporters (sxtM and sxtF from Cylindrospermopsis raciborskii T3, and sxtM from Anabaena circinalis AWQC131C) were assessed in response to ionic stress. These data, coupled with a measure of toxin intracellular to extracellular ratios, provide an insight into the physiology of STX export. Cylindrospermopsis raciborskii and Anabaena circinalis exhibited opposing responses under conditions of ionic stress. High Na(+) (10 mM) induced moderate alterations of transcription and STX localization, whereas high pH (pH 9) stimulated the greatest physiological response. Saxitoxin production and cellular localization are responsive to ionic strength, indicating a role of this molecule in the maintenance of cellular homeostasis.

We combined the use of polyclonal antibodies against saxitoxin with catalyzed reporter deposition to detect production of saxitoxin by the cyanobacterium Cylindrospermopsis raciborskii. The procedure is simple, allows detection of intracellular saxitoxin in cyanobacteria filaments by confocal laser microscopy and is a promising tool to study toxin production and metabolism.

Summary In the forthcoming decades, it is widely believed that the dominance of colonial and filamentous bloom- forming cyanobacteria (e.g. Microcystis, Planktothrix, Anabaena and Cylindrospermopsis) will increase in freshwater systems as a combined result of anthropogenic nutrient input into freshwater bodies and climate change. While the physicochemical parameters controlling bloom dynamics are well known, the role of biotic factors remains compara- tively poorly studied. Morphology and toxicity often - but not always - limit the availability of cyanobacteria to filter feeding zooplankton (e.g. cladocerans). Fila- mentous and colonial cyanobacteria are widely regarded as trophic dead-ends mostly inedible for zooplankton, but substantial evidence shows that some grazers (e.g. copepods) can bypass this size constraint by breaking down filaments, making the bloom biomass available to other zooplankton species. A wide range of algicidal bacteria (mostly from the Alcaligenes, Flavobacterium/Cytophaga group and Pseudomonas) and viruses (Podoviridae, Siphoviridae and Myoviridae) may also contribute to bloom control, via their lytic activity underpinned by a diverse array of mechanisms. Fungal parasitism by the Chytridiomycota remains the least studied. While each of these biotic factors has traditionally been studied in isolation, emerging research consistently point to complex interwoven interactions between biotic and environmental factors.

Cylindrospermopsin (CYN) and 7-deoxy-cylindrospermopsin (dCYN) are potent hepatotoxic alkaloids produced by numerous species of cyanobacteria, including the freshwater Cylindrospermopsis raciborskii . C. raciborskii is an invasive cyanobacterium, and the study of how environmental parameters drive CYN production has received significant interest from water managers and health authorities. Light and CO 2 affect cell growth and physiology in photoautotrophs, and these are potential regulators of cyanotoxin biosynthesis. In this study, we investigated how light and CO 2 affect CYN and dCYN pool size as well as the expression of the key genes, cyrA and cyrK , involved in CYN biosynthesis in a toxic C. raciborskii strain. For cells growing at different light intensities (10 and 100 μmol photons m −2 s −1 ), we observed that the rate of CYN pool size production (μ CYN ) was coupled to the cell division rate (μ c ) during batch culture. This indicated that CYN pool size under our experimental conditions is constant and cell quotas of CYN (Q CYN ) and dCYN (Q dCYN ) are fixed. Moreover, a lack of correlation between expression of cyrA and total CYN cell quotas (Q CYNs ) suggests that the CYN biosynthesis is regulated posttranscriptionally. Under elevated CO 2 (1,300 ppm), we observed minor effects on Q CYN and no effects on expression of cyrA and cyrK . We conclude that the CYN pool size is constitutive and not affected by light and CO 2 conditions. Thus, C. raciborskii bloom toxicity is determined by the absolute abundance of C. raciborskii cells within the water column and the relative abundance of toxic and nontoxic strains.

E crescente a preocupacao com a poluicao dos recursos hidricos, principalmente sobre as aguas destinadas ao abastecimento publico. Nos ecossistemas aquaticos, alem do processo de eutrofizacao, outros fatores como a sazonalidade favorecem a quebra do equilibrio ecologico. A presente pesquisa verificou a influencia da sazonalidade na ocorrencia de cianobacterias como parâmetro da qualidade da agua do reservatorio Mororo, situado no municipio de Pedra (Pernambuco, Brasil). As caracteristicas fisico-quimicas estudadas foram: cor aparente, turbidez, pH e fosfato total. As cianobacterias estiveram representadas por 10 generos, distribuidos entre 4 ordens e 4 familias. Destacam-se Planktothrix Anagnostidis & Komarek, Aphanocapsa Nageli, Dolichospermum Bory ex Bornet et Flahault e Cylindrospermopsis Seenayya et Subba Raju por serem potencialmente toxicas. Os resultados mostraram densidades de cianobacterias acima dos limites estabelecidos pela Resolucao no 357/2005 do CONAMA. O reservatorio foi considerado supereutrofico durante todo o estudo. Os resultados indicaram a influencia da sazonalidade na qualidade da agua, em funcao da pluviosidade na dinâmica das variaveis limnologicas, em especial quanto a disponibilidade e diluicao de nutrientes nos reservatorios. Normal 0 21 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabela normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; color:black; mso-themecolor:text1; mso-ansi-language:EN-US; mso-fareast-language:EN-US;} ABSTRACT There is growing concern about the pollution of water resources, especially on the water for public supply. In aquatic ecosystems, in addition to the eutrophication process, other factors such as seasonality favor the breakdown of ecological balance. This research analyzes the influence of seasonality in the occurrence of cyanobacteria and water quality of the Mororo reservoir, located in the city of Pedra, (Pernambuco, Brazil). The physicochemical parameters studied were: apparent color, turbidity, pH and total phosphate. Cyanobacteria were represented by 10 genera, distributed among four orders and four families. Planktothrix Anagnostidis & Komarek , Aphanocapsa Nageli, Dolichospermum Bory ex Bornet et Flahault and Cylindrospermopsis Seenayya et Subba Raju are highlighted for being potentially toxic. The results showed densities of cyanobacteria above the limits established by CONAMA Resolution No. 357/2005. The reservoir was considered in supereutrophic state throughout the study. The results showed the influence of seasonality on water quality, depending on the rainfall in the dynamics of limnological variables, especially for availability and dilution of nutrients in the reservoirs. Keywords: reservoirs, cyanobacteria, public water supply, water quality .

The genetic diversity and the potential toxicity of bloom-forming cyanobacteria were studied in four lagoons located in the state of Sao Paulo (Campinas, Limeira and Piracicaba cities). Bloom samples were collected on the water surface and cyanobacterial communities were evaluated using DGGE fingerprinting and 16S rDNA clone library. The amplification of genes encoding secondary metabolites such as microcystin (mcy), anatoxin (ana), cylindrospermopsin (cyr), saxitoxin (sxt), cyanopeptolin (mcn) and aeruginosin (aer) was performed and their production analyzed by LC-MS. The comparison of DGGE banding pattern among the different water samples suggested that some operational taxonomic units (OTUs) in these locations were predominant over others. The 16S rDNA clone libraries sequences matched with nine different known cyanobacterial genera available in NCBI, identified as Anabaena, Brasilonema, Cylindrospermopsis, Limnococcus, Microcystis, Nostoc, Pseudanabaena, Synechococcus and Woronichinia. The lagoons ESALQ2, Taquaral and Limeira had more than 80% of the cyanobacterial community assigned to the genus Microcystis. Genes encoding aeruginosin, cyanopeptolin and microcystin synthetases and saxitoxin synthase were amplified, and LC-MS/MS confirmed the production of aeruginosin, cyanopeptolin and microcystin. Rapid and sensitive methods for the detection of these secondary metabolites, especially toxins, using chemical and molecular tools together, can be used for a faster diagnostic of toxic cyanobacterial blooms.

Cylindrospermopsis raciborskii is a toxic cyanobacterium with an invasive nature. The species is found in all the main continents but its origin and dispersal routes on a worldwide perspective remain yet mostly unknown. In this study, 27 isolates of C. raciborskii gathered worldwide have been used for an in-deep phylogenetic analyses with a concatenated system of three genetic markers (16 rRNA, 16S-23S ITS larger subunit, and RNA polymerase rpoC1) comprehending 3,188 bp. Our results provide support for an origin of C. raciborskii in the American continent. Dispersal routes included afterward a spread into the African continent and then Asia and Australia, being Europe the last continent to be colonized by this species. Our phylogenetic inferences suggest that C. raciborskii seem to have a well-defined dispersal behavior with a well-established population structure around the world.

Owing to the global warming and its strong adaptability, Cylindrospermopsis raciborskii has spread world-wide. However, as one of toxic cyanobacteria in many drinking water sources, it has not been drawn proper consideration in drinking water treatment plants so far. The investigation aimed at unveiling the fate of C. raciborskii during polyaluminum ferric chloride (PAFC) coagulation and sludge storage, revealing its differences from Microcystis aeruginosa. Results showed that C. raciborskii cells were effectively removed intactly under optimum coagulation conditions, but PAFC at higher dosages (>10 mg/L) triggered additional cylindrospermopsins release. In sludge storage, coagulated C. raciborskii cells suffered severe oxidative damage, leading to significant cylindrospermopsins release after day 6. C. raciborskii manifested different behaviors from M. aeruginosa which cells didn’t release much microcystins during coagulation and sludge storage. This was mostly due to their differences in physiology and morphology. In flocs, M. aeruginosa could be enveloped by coagulant which can protect cells against the nasty attack from outside, whereas C. raciborskii with long filaments was hard to be wrapped and prone to suffering oxidative damage. These results confirmed C. raciborskii had a higher risk of toxin release in water production process than M. aeruginosa, which should deserve more attention.

Saxitoxins are a class of toxins produced by at least two groups of evolutionarily distant organisms (cyanobacteria and dinoflagellates). While the toxicity of these toxins is relatively well characterized, to date little is known about their drivers and ecological functions, especially in lower latitude tropical and subtropical freshwater ecosystems. In the present study, we aimed to obtain a better understanding of the main drivers of saxitoxin concentrations in aquatic environments. We investigated the relationships among saxitoxin concentrations in a mesotrophic subtropical reservoir dominated by the cyanobacteria Cylindrospermopsis raciborskii with physical, chemical and biological water variables. The highest saxitoxin concentrations were 0.20 μg·L−1, which occurred in the samples with the highest densities of C. raciborskii (maximum of 4.3 × 104 org·mL−1) and the highest concentration of dissolved nutrients (nitrate from 0.2 to 0.8 μg·L−1, ortophosphate from 0.3 to 8.5 μg·L−1). These correlations were confirmed by statistical analyses. However, the highest saxitoxin relative concentrations (per trichome) were associated with lower C. raciborskii densities, suggesting that saxitoxin production or the selection of saxitoxin-producing strains was associated with the adaptation of this species to conditions of stress. Our results indicate that C. raciborskii toxin yields vary depending on the enrichment conditions having potential implications for reservoir management.

Much attention has been paid to ways of removing toxic cyanobacteria and cyanotoxins from water prior to its use due to public health concerns. The efficacy of treating the toxic filamentous cyanobacterium Cylindrospermopsis raciborskii (C. raciborskii) by electrolysis with a boron-doped diamond (BDD) in Chloride-free solution was investigated. At optimum current, about 87 and 93% removal of cell density at 60 and 180min and about 72 and 90% of Chl a, respectively. Additionally, a physiological test (FV/Fm) indicated that cells were completely inactivated in 45min. Furthermore, initial total cylindrospermopsin concentration 1.83μg/L was also degraded to below the detection limit (