Fatal dog poisoning after uptake of neurotoxic cyanobacteria associated with aquatic macrophytes in Tegeler See (Berlin, Germany) raised concerns about critical exposure of humans, especially children, to cyanotoxins produced by macrophyte associated cyanobacteria during recreational activity. From 2017 to 2021 a total of 398 samples of macrophytes washed ashore at bathing sites located at 19 Berlin lakes were analysed for anatoxins, microcystins, and cylindrospermopsins, as were 463 water samples taken in direct proximity to macrophyte accumulations. Cyanotoxins were detected in 66 % of macrophyte samples and 50 % of water samples, with anatoxins being the most frequently detected toxin group in macrophyte samples (58 %) and cylindrospermopsins in water samples (41 %). Microcoleus sp. associated with the water moss Fontinalis antipyretica was identified as anatoxin producing cyanobacterium in isolated strains as well as in field samples from Tegeler See. Anatoxin contents in macrophyte samples rarely exceeded 1 (micro)g/g macrophyte fresh weight and peaked at 9. 2 (micro)g/g f.w. Based on established toxicological points of departure, a critical anatoxin content of macrophyte samples of 3 (micro)g/g f.w. is proposed. Five samples, all taken in Tegeler See and all associated with the water moss Fontinalis antipyretica, exceeded this value. Contents and concentrations of microcystins and cylindrospermopsins did not reach critical levels. The potential exposure risks to anatoxins for children and dogs are assessed and recommendations are given. © 2022 The Authors
Cyanobacteria are favored by climate change and global warming; however, to date, mostresearch and monitoring programs have focused on planktic cyanobacteria. Benthic cyanobacte-ria blooms also increase and pose a risk to animal and human health; however, there is limitedknowledge of their occurrence, distribution and the toxins involved, especially in relation to theirplanktic conspeciï Ącs. Therefore, we analyzed the benthic and planktic life forms of cyanobacterialcommunities in 34 lakes in Germany, including a monitoring of cyanotoxins. Community analyseswere based on microscopic examination and Illumina sequencing of the 16S rRNA gene. The analysesof cyanotoxins were carried out using LC-MS/MS and ELISA. Observed benthic mats containingcyanobacteria consisted mainly of Nostocales and Oscillatoriales, being present in 35% of the lakes. Ana-toxin was the most abundant cyanotoxin in the benthic samples, reaching maximum concentrationsof 45,000Ìg/L, whereas microcystin was the predominate cyanotoxin in the open-water samples,reaching concentrations of up to 18,000Ìg/L. Based on the results, speciï Ąc lakes at risk of toxiccyanobacteria could be identiï Ąed. Our ï Ąndings suggest that monitoring of benthic cyanobacteria andtheir toxins should receive greater attention, ideally complementing existing open-water samplingprograms with little additional effort. © 2023 by the authors.
Chytrid parasites are increasingly recognized as ubiquitous and potent control agents of phytoplankton, including bloom-forming toxigenic cyanobacteria. In order to explore the fate of the cyanobacterial toxin microcystins (MCs) and assess potential upregulation of their production under parasite attack, a laboratory experiment was conducted to evaluate short- and long-term variation in extracellular and intracellular MC in the cyanobacteria Planktothrix agardhii and P. rubescens, both under chytrid infection and in the presence of lysates of previously infected cyanobacteria. MCs release under parasite infection was limited and not different to uninfected cyanobacteria, with extracellular toxin shares never exceeding 10%, substantially below those caused by mechanical lysis induced by a cold-shock. Intracellular MC contents in P. rubescens under infection were not significantly different from uninfected controls, whereas infected P. agardhii showed a 1.5-fold increase in intracellular MC concentrations, but this was detected within the first 48 hours after parasite inoculation and not later, indicating no substantial MC upregulation in cells being infected. The presence of lysates of previously infected cyanobacteria did not elicit higher intracellular MC contents in exposed cyanobacteria, speaking against a putative upregulation of toxin production induced via quorum sensing in response to parasite attack. These results indicate that chytrid epidemics can constitute a bloom decay mechanism that is not accompanied by massive release of toxins into the medium. © 2022 Elsevier
Although the use of genetically modified plants for bioremediation, or the in situ cleaning of contaminated sites, has been known for quite some time, little attention has so far been paid to the production of antibodies in plants and their ex vivo application in selective depletion. Therefore, highly affine and specific antibodies against algal toxins using microcystin as an example will be produced in plants at low cost within this research project. The basis is a monoclonal antibody (Mab 10E7, species: mouse) generated in a former research project. The sequence of the variable domains will be determined, optimized for plants and sub cloned into suitable plant transformation vectors, which already contain constant antibody sequences. In addition, a scFv fragment containing different tag sequences and fusion proteins will be constructed. Leaf-based (tobacco) as well as seed-based (barley) systems will be used.Affinity-purified plant-produced antibodies (plantibodies) will be characterized in detail for their binding properties using microtitre plate-ELISA and surface plasmon resonance (SPR). The monoclonal mouse antibody will be used as reference. To assure cost-efficiency for future applications, roughly purified fractions (sequential pH and temperature treatment followed by filtration) will be tested for the upscaling. Following immobilization of the plantibody fractions on suitable substrates, for instance membranes, porous polymer monoliths or in porous glasses, their application for depletion will be defined using model water samples spiked fortified with microcystins.
Cyanobacteria are known to produce a wide array of metabolites, including various classes of toxins. Among these, hepatotoxins (Microcystins), neurotoxins (Anatoxin-A and PSP toxins) or cytotoxins (Cylindrospermopsins) have been subjected to numerous, individual studies during the past twenty years. Reports of toxins co-occurrences, however, remain scarce in the literature. The present work is an inventory of cyanobacteria with a particular focus on Nostocales and their associated toxin classes from 2007 to 2010 in ten lakes used for drinking water production in France. The results show that potential multiple toxin producing species are commonly encountered in cyanobacteria populations. Individual toxin classes were detected in 75% of all samples. Toxin co-occurrences appeared in 40% of samples as two- or three-toxin combinations (with 35% for the microcystinsâ€Ìanatoxin combination), whereas four-toxin class combinations only appeared in 1% of samples. Toxin co-occurrences could be partially correlated to species composition and water temperature. Peak concentrations however could never be observed simultaneously and followed distinct, asymmetrical distribution patterns. As observations are the key for preventive management and risk assessment, these results indicate that water monitoring should search for all four toxin classes simultaneously instead of focusing on the most frequent toxins, i.e., microcystins Quelle: https://www.mdpi.com
Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains. Quelle: https://www.mdpi.com
Man-made eutrophication of lakes has caused increased frequencies of cyanobacterial blooms, which go along with a reduction in abundance of Daphnia, the major herbivore of the phytoplankton. This reduced abundance of Daphnia is a major cause for the fact that food web manipulations frequently cause only short term improvements of water quality. The most frequently reported toxins of cyanobacterial blooms are microcystins, which are hepatotoxic to mammals and increase mortality in Daphnia. Although it has frequently been shown that Daphnia coexisting with cyanobacteria show increased tolerance to toxic cyanobacteria, the genetic basis of this tolerance is entirely unknown. Here the genetic basis of tolerance to microcystins in Daphnia will be investigated. A microcystin-producing strain and a mutant of that strain, which is deficient in microcystins, will be fed to a microcystin-tolerant and a microcystin-sensitive clone of Daphnia magna. Transcriptome analysis based on RNASeq will be used to identify differentially expressed genes that either differ constitutively in expression among the two Daphnia clones or are differentially expressed upon ingestion of microcystins. Bioinformatic analysis of the data and metabolic mapping will be used to identify key enzymes and genes that mediate tolerance to microcystins. Expression of selected differentially expressed genes will be validated in an independent experiment using qPCR. Further evidences for a mediation of microcystin tolerance by selected differentially expressed genes will be gained by investigating how the concentration of dietary microcystins affect gene expression. This will be achieved by feeding liposomes that are loaded with microcystins to Daphnia. Understanding the molecular mechanisms is indispensable for the understanding of the evolution of microcystin tolerance in Daphnia and is of potentially pivotal importance for the management of lakes with toxic cyanobacterial blooms.
Blooms of toxic cyanobacteria in freshwater ecosystems have received considerable attention in recent years, but their occurrence and potential importance at the land-sea interface has not been widely recognized. Here we present the results of a survey of discrete samples conducted in more than fifty brackish water sites along the coastline of southern California. Our objectives were to characterize cyanobacterial community composition and determine if specific groups of cyanotoxins (anatoxins, cylindrospermopsins, microcystins, nodularins, and saxitoxins) were present. We report the identification of numerous potentially harmful taxa and the co-occurrence of multiple toxins, previously undocumented, at several locations. Our findings reveal a potential health concern based on the range of organisms present and the widespread prevalence of recognized toxic compounds. Our results raise concerns for recreation, harvesting of finfish and shellfish, and wildlife and desalination operations, highlighting the need for assessments and implementation of monitoring programs. Such programs appear to be particularly necessary in regions susceptible to urban influence. Quelle: Verlagsinformation
Lentic water bodies and large rivers have long been recognized as being susceptible, under certain conditions, to toxin-producing ("toxigenicŁ) planktonic cyanobacterial blooms. Although benthic cyanobacteria commonly inhabit wadeable (i.e., shallow) streams, little has been published on the potential for cyanotoxin (e.g., microcystin) production in this water body type. Recent research in Monterey Bay, California, USA has linked inland-derived microcystins to numerous sea otter mortalities in the marine environment, a finding that illustrates the negative effects cyanotoxins can have on ecosystem services, even far downstream from their origin, due to fluvial transport. For the present study, surveys of >1200 wadeable stream segments were conducted throughout California during the spring and summer of 2007 through 2013, and revealed a high occurrence of potentially toxigenic benthic cyanobacteria. In addition, benthic microcystins were detected in one-third of sites, where tested (N = 368), based primarily on one-time sampling, from 2011 to 2013 (mean concentration was 46 ìg/m2 of stream-bottom). Sites where microcystins were detected spanned a variety of surrounding land-use types, from open space (i.e., undeveloped land) to heavily urbanized/agricultural. Lyngbyatoxin (n = 14), saxitoxins (n = 99), and anatoxin-a (n = 33) were also measured, at subsets of sites, and were also detected, albeit at lower rates than microcystins. Results of this study provide strong evidence that wadeable streams could be significant sources of cyanotoxin inputs to receiving waters, a finding that has implications for the management of drinking water, wildlife, and recreational resources, within both the streams themselves and in downstream rivers, lentic water bodies, and the ocean.<BR>Quelle: http://www.sciencedirect.com/
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