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Letteratura scientifica selezionata sul tema "Microcystin"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 9 giugno 2025

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Articoli di riviste sul tema "Microcystin"

Rohrlack, Thomas, Elke Dittmann, Thomas Börner, and Kirsten Christoffersen. "Effects of Cell-Bound Microcystins on Survival and Feeding of Daphnia spp." Applied and Environmental Microbiology 67, no. 8 (August 1, 2001): 3523–29. http://dx.doi.org/10.1128/aem.67.8.3523-3529.2001.

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ABSTRACT The influence of cell-bound microcystins on the survival time and feeding rates of six Daphnia clones belonging to five common species was studied. To do this, the effects of the microcystin-producing Microcystis strain PCC7806 and its mutant, which has been genetically engineered to knock out microcystin synthesis, were compared. Additionally, the relationship between microcystin ingestion rate by the Daphnia clones andDaphnia survival time was analyzed. Microcystins ingested with Microcystis cells were poisonous to allDaphnia clones tested. The median survival time of the animals was closely correlated to their microcystin ingestion rate. It was therefore suggested that differences in survival amongDaphnia clones were due to variations in microcystin intake rather than due to differences in susceptibility to the toxins. The correlation between median survival time and microcystin ingestion rate could be described by a reciprocal power function. Feeding experiments showed that, independent of the occurrence of microcystins, cells of wild-type PCC7806 and its mutant are able to inhibit the feeding activity of Daphnia. Both variants of PCC7806 were thus ingested at low rates. In summary, our findings strongly suggest that (i) sensitivity to the toxic effect of cell-bound microcystins is typical for Daphnia spp., (ii) Daphnia spp. and clones may have a comparable sensitivity to microcystins ingested with food particles, (iii) Daphnia spp. may be unable to distinguish between microcystin-producing and -lacking cells, and (iv) the strength of the toxic effect can be predicted from the microcystin ingestion rate of the animals.

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Johansson, Emma, Catherine Legrand, Caroline Björnerås, Anna Godhe, Hanna Mazur-Marzec, Torbjörn Säll, and Karin Rengefors. "High Diversity of Microcystin Chemotypes within a Summer Bloom of the Cyanobacterium Microcystis botrys." Toxins 11, no. 12 (December 1, 2019): 698. http://dx.doi.org/10.3390/toxins11120698.

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Abstract (sommario):

The fresh-water cyanobacterium Microcystis is known to form blooms world-wide, and is often responsible for the production of microcystins found in lake water. Microcystins are non-ribosomal peptides with toxic effects, e.g. on vertebrates, but their function remains largely unresolved. Moreover, not all strains produce microcystins, and many different microcystin variants have been described. Here we explored the diversity of microcystin variants within Microcystis botrys, a common bloom-former in Sweden. We isolated a total of 130 strains through the duration of a bloom in eutrophic Lake Vomb, and analyzed their microcystin profiles with tandem mass spectrometry (LC-MS/MS). We found that microcystin producing (28.5%) and non-producing (71.5%) M. botrys strains, co-existed throughout the bloom. However, microcystin producing strains were more prevalent towards the end of the sampling period. Overall, 26 unique M. botrys chemotypes were identified, and while some chemotypes re-occurred, others were found only once. The M. botrys chemotypes showed considerable variation both in terms of number of microcystin variants, as well as in what combinations the variants occurred. To our knowledge, this is the first report on microcystin chemotype variation and dynamics in M. botrys. In addition, our study verifies the co-existence of microcystin and non-microcystin producing strains, and we propose that environmental conditions may be implicated in determining their composition.

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Ballot, Andreas, Morten Sandvik, Thomas Rundberget, Christo J. Botha, and Christopher O. Miles. "Diversity of cyanobacteria and cyanotoxins in Hartbeespoort Dam, South Africa." Marine and Freshwater Research 65, no. 2 (2014): 175. http://dx.doi.org/10.1071/mf13153.

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The South African Hartbeespoort Dam is known for the occurrence of heavy Microcystis blooms. Although a few other cyanobacterial genera have been described, no detailed study on those cyanobacteria and their potential toxin production has been conducted. The diversity of cyanobacterial species and toxins is most probably underestimated. To ascertain the cyanobacterial composition and presence of cyanobacterial toxins in Hartbeespoort Dam, water samples were collected in April 2011. In a polyphasic approach, 27 isolated cyanobacterial strains were classified morphologically and phylogenetically and tested for microcystins (MCs), cylindrospermopsin (CYN), saxitoxins (STXs) and anatoxin-a (ATX) by liquid chromatography–tandem mass spectrometry (LC–MS/MS) and screened for toxin-encoding gene fragments. The isolated strains were identified as Sphaerospermopsis reniformis, Sphaerospermopsis aphanizomenoides, Cylindrospermopsis curvispora, Raphidiopsis curvata, Raphidiopsis mediterrranea and Microcystis aeruginosa. Only one of the Microcystis strains (AB2011/53) produced microcystins (35 variants). Forty-one microcystin variants were detected in the environmental sample from Hartbeespoort Dam, suggesting the existence of other microcystin producing strains in Hartbeespoort Dam. All investigated strains tested negative for CYN, STXs and ATX and their encoding genes. The mcyE gene of the microcystin gene cluster was found in the microcystin-producing Microcystis strain AB2011/53 and in eight non-microcystin-producing Microcystis strains, indicating that mcyE is not a good surrogate for microcystin production in environmental samples.

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Vaitomaa, Jaana, Anne Rantala, Katrianna Halinen, Leo Rouhiainen, Petra Tallberg, Lena Mokelke, and Kaarina Sivonen. "Quantitative Real-Time PCR for Determination of Microcystin Synthetase E Copy Numbers for Microcystis and Anabaena in Lakes." Applied and Environmental Microbiology 69, no. 12 (December 2003): 7289–97. http://dx.doi.org/10.1128/aem.69.12.7289-7297.2003.

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ABSTRACT Cyanobacterial mass occurrences in freshwater lakes are generally formed by Anabaena, Microcystis, and Planktothrix, which may produce cyclic heptapeptide hepatotoxins, microcystins. Thus far, identification of the most potent microcystin producer in a lake has not been possible due to a lack of quantitative methods. The aim of this study was to identify the microcystin-producing genera and to determine the copy numbers of microcystin synthetase gene E (mcyE) in Lake Tuusulanjärvi and Lake Hiidenvesi in Finland by quantitative real-time PCR. The microcystin concentrations and cyanobacterial cell densities of these lakes were also determined. The microcystin concentrations correlated positively with the sum of Microcystis and Anabaena mcyE copy numbers from both Lake Tuusulanjärvi and Lake Hiidenvesi, indicating that mcyE gene copy numbers can be used as surrogates for hepatotoxic Microcystis and Anabaena. The main microcystin producer in Lake Tuusulanjärvi was Microcystis spp., since average Microcystis mcyE copy numbers were >30 times more abundant than those of Anabaena. Lake Hiidenvesi seemed to contain both nontoxic and toxic Anabaena as well as toxic Microcystis strains. Identifying the most potent microcystin producer in a lake could be valuable for designing lake restoration strategies, among other uses.

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Wang, Suqin, Siyu Yang, Jun Zuo, Chenlin Hu, Lirong Song, Nanqin Gan, and Peng Chen. "Simultaneous Removal of the Freshwater Bloom-Forming Cyanobacterium Microcystis and Cyanotoxin Microcystins via Combined Use of Algicidal Bacterial Filtrate and the Microcystin-Degrading Enzymatic Agent, MlrA." Microorganisms 9, no. 8 (July 27, 2021): 1594. http://dx.doi.org/10.3390/microorganisms9081594.

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Abstract (sommario):

Freshwater cyanobacterial blooms (e.g., Microcystis blooms) constitute a major global environmental problem because of their risks to public health and aquatic ecological systems. Current physicochemical treatments of toxic cyanobacteria cause the significant release of cyanotoxin microcystins from damaged cells. Biological control is a promising eco-friendly technology to manage harmful cyanobacteria and cyanotoxins. Here, we demonstrated an efficient biological control strategy at the laboratory scale to simultaneously remove Microcystis and microcystins via the combined use of the algicidal bacterial filtrate and the microcystin-degrading enzymatic agent. The algicidal indigenous bacterium Paenibacillus sp. SJ-73 was isolated from the sediment of northern Lake Taihu, China, and the microcystin-degrading enzymatic agent (MlrA) was prepared via the heterologous expression of the mlrA gene in the indigenous microcystin-degrading bacterium Sphingopyxis sp. HW isolated from Lake Taihu. The single use of a fermentation filtrate (5%, v/v) of Paenibacillus sp. SJ-73 for seven days removed the unicellular Microcystis aeruginosa PCC 7806 and the native colonial Microcystis strain TH1701 in Lake Taihu by 84% and 92%, respectively, whereas the single use of MlrA removed 85% of microcystins. Used in combination, the fermentation filtrate and MlrA removed Microcystis TH1701 and microcystins by 92% and 79%, respectively. The present biological control thus provides an important technical basis for the further development of safe, efficient, and effective measures to manage Microcystis blooms and microcystins in natural waterbodies.

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Ho, Lionel, Nawal Kayal, Rino Trolio, and Gayle Newcombe. "Determining the fate of Microcystis aeruginosa cells and microcystin toxins following chloramination." Water Science and Technology 62, no. 2 (July 1, 2010): 442–50. http://dx.doi.org/10.2166/wst.2010.448.

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Abstract (sommario):

The cyanobacterium Microcystis aeruginosa can produce potent toxins known as microcystins. While many studies have focussed on the chlorination of microcystin toxins, little work has been conducted with respect to the chloramination of the microcystins. In addition, no studies have been reported on the effect of chloramination on intact Microcystis cells. This study was conducted to determine the fate of M. aeruginosa cells and microcystin toxins following chloramination of a drinking water source. Results indicate that monochloramine could effectively oxidise dissolved microcystin-LR (MCLR) provided high CT values were employed, typically greater than 30,000 mg min L−1. The decay of MCLR was demonstrated to be a pseudo first-order reaction with rate constants ranging from 9.3 × 10−7 to 1.1 × 10−5 s−1 at pH 8.5. However, in the presence of Microcystis cells, monochloramine was ineffective in oxidising microcystin toxins due to the cells exerting a demand on the oxidant. The doses of monochloramine applied (2.8 and 3.5 mg L−1) were shown to rapidly release intracellular microcystins into the dissolved state. Flow cytometric analysis of the cells determined that the lower monochloramine dose did not compromise the cell membrane integrity, even though microcystins were rapidly released from the cells. In contrast the higher monochloramine dose resulted in cell membrane disruption with up to 90% of the cells shown to be non-viable after the high dose was applied.

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Kurmayer, Rainer, Guntram Christiansen, and Ingrid Chorus. "The Abundance of Microcystin-Producing Genotypes Correlates Positively with Colony Size in Microcystis sp. and Determines Its Microcystin Net Production in Lake Wannsee." Applied and Environmental Microbiology 69, no. 2 (February 2003): 787–95. http://dx.doi.org/10.1128/aem.69.2.787-795.2003.

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ABSTRACT The working hypotheses tested on a natural population of Microcystis sp. in Lake Wannsee (Berlin, Germany) were that (i) the varying abundance of microcystin-producing genotypes versus non-microcystin-producing genotypes is a key factor for microcystin net production and (ii) the occurrence of a gene for microcystin net production is related to colony morphology, particularly colony size. To test these hypotheses, samples were fractionated by colony size with a sieving procedure during the summer of 2000. Each colony size class was analyzed for cell numbers, the proportion of microcystin-producing genotypes, and microcystin concentrations. The smallest size class of Microcystis colonies (<50 μm) showed the lowest proportion of microcystin-producing genotypes, the highest proportion of non-microcystin-producing cells, and the lowest microcystin cell quotas (sum of microcystins RR, YR, LR, and WR). In contrast, the larger size classes of Microcystis colonies (>100 μm) showed the highest proportion of microcystin-producing genotypes, the lowest proportion of non-microcystin-producing cells, and the highest microcystin cell quotas. The microcystin net production rate was nearly one to one positively related to the population growth rate for the larger colony size classes (>100 μm); however, no relationship could be found for the smaller size classes. It was concluded that the variations found in microcystin net production between colony size classes are chiefly due to differences in genotype composition and that the microcystin net production in the lake is mainly influenced by the abundance of the larger (>100-μm) microcystin-producing colonies.

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Bittencourt-Oliveira, MC, MC Oliveira, and E. Pinto. "Diversity of microcystin-producing genotypes in Brazilian strains of Microcystis (Cyanobacteria)." Brazilian Journal of Biology 71, no. 1 (February 2011): 209–16. http://dx.doi.org/10.1590/s1519-69842011000100030.

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Microcystis Kützing ex Lemmermann is among the genera of cyanobacteria often associated to toxic blooms with the release of microcystins. A gene cluster codes for microcystin synthetases, which are involved in the biosynthesis of this toxin. The aim of the present study was to investigate the genetic diversity of the mcyB gene, specifically the B1 module, in Brazilian strains of Microcystis spp. and its microcystin variants. Broad genetic diversity was revealed in this region. From the phylogenetic analysis, three clusters were obtained that were not related to the geographic origin or morphospecies of the strains, nor with the variant of the microcystin produced. A group of strains that did not produce microcystins was found, despite the presence of the mcyB1 fragment. Eight microcystin isoforms were detected: MC-LR, [D-Asp³]-MC-LR, [Asp³]-MC-LR, MC-RR, [Dha7]-MC-LR, MC-LF, MC-LW and [D-Asp³, EtAdda5]-MC-LH, the latter of which is described for the first time in Brazil. Moreover, five other variants were not identified and indicate being new.

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Wang, Hui, Cyndee L. Gruden, Thomas B. Bridgeman, and Justin D. Chaffin. "Detection and quantification of Microcystis spp. and microcystin-LR in Western Lake Erie during the summer of 2007." Water Science and Technology 60, no. 7 (October 1, 2009): 1837–46. http://dx.doi.org/10.2166/wst.2009.517.

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Microcystis spp. blooms have occurred annually in western Lake Erie since about 1995. Microcystis produce a group of toxins known as microcystins which can be harmful to livestock and to humans. In this study, surface water samples were collected from six sites during six sampling events from July to October in 2007. In situ environmental data (e.g. pH, temperature) and laboratory analyses (e.g. nutrients) were carried out to characterize the six sites. The Microcystis spp. density ranged from 102 to 107 cells/ml. Microcystin-LR concentration of 20 of all 36 samples were below the detection limit (0.15–5 ppb), while the microcystin-LR concentration in the 16 remaining samples ranged from 0.5 to 3 × 103 μg per gram dry weight. The aim of this research was to investigate the relationships between sampling location, environmental parameters, Microcystis spp. concentration, and microcystin-LR concentration. The results suggest that temperature, nutrient concentration, turbidity, and wind speed and direction (P&lt;0.05) are factors which affected Microcystis spp. density. Sampling site 8M, located 13 m from the Maumee River, provided an advantage for Microcystis spp. growth, presumably due to intermediate water depth (5.5 m) combined with impact from the river. No relationship was found between Microcystis spp. density and microcystin-LR concentration. Temperature, nutrient concentration and DO (P&lt;0.05) were associated with the production of microcystin-LR.

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Oh, Hee-Mock, Seog June Lee, Jee-Hwan Kim, Hee-Sik Kim, and Byung-Dae Yoon. "Seasonal Variation and Indirect Monitoring of Microcystin Concentrations in Daechung Reservoir, Korea." Applied and Environmental Microbiology 67, no. 4 (April 1, 2001): 1484–89. http://dx.doi.org/10.1128/aem.67.4.1484-1489.2001.

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ABSTRACT Physicochemical and biological water quality, including the microcystin concentration, was investigated from spring to autumn 1999 in the Daechung Reservoir, Korea. The dominant genus in the cyanobacterial blooming season was Microcystis. The microcystin concentration in particulate form increased dramatically from August up to a level of 200 ng liter−1 in early October and thereafter tended to decrease. The microcystin concentration in dissolved form was about 28% of that of the particulate form. The microcystins detected using a protein phosphatase (PP) inhibition assay were highly correlated with those microcystins detected by a high-performance liquid chromatograph (r= 0.973; P < 0.01). Therefore, the effectiveness of a PP inhibition assay for microcystin detection in a high number of water samples was confirmed as easy, quick, and convenient. The microcystin concentration was highly correlated with the phytoplankton number (r = 0.650; P < 0.01) and chlorophyll-a concentration (r = 0.591;P < 0.01). When the microcystin concentration exceeded about 100 ng liter−1, the ratio of particulate to dissolved total nitrogen (TN) or total phosphorus (TP) converged at a value of 0.6. Furthermore, the microcystin concentration was lower than 50 ng liter−1 at a particulate N/P ratio below 8, whereas the microcystin concentration varied quite substantially from 50 to 240 ng liter−1 at a particulate N/P ratio of >8. Therefore, it seems that the microcystin concentration in water can be estimated and indirectly monitored by analyzing the following: the phytoplankton number and chlorophyll-a concentration, the ratio of the particulate and the dissolved forms of N and P, and the particulate N/P ratio when the dominant genus is toxigenic Microcystis.

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Più fonti

Tesi sul tema "Microcystin"

Zilliges, Yvonne. "Molekulare Funktionsanalyse von Microcystin in Microcystis aeruginosa PCC 7806." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2008. http://dx.doi.org/10.18452/15782.

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Microcystine sind die wohl bekanntesten cyanobakteriellen Toxine. Sie werden im Wesentlichen durch die im Süßwasser weltweit verbreitete, koloniebildende Gattung Microcystis synthetisiert. Die biologische Funktion dieser Peptide ist jedoch ungeklärt. In dieser Studie wurde die Fragestellung erstmals über einen globalen Ansatz auf molekularer Ebene analysiert. Die proteomischen Analysen zwischen M. aeruginosa PCC 7806/ Wildtyp und einigen Microcystin-freien Mutanten deuten auf eine physiologische Rolle der Microcystine. Microcystine beeinflussen die Abundanz zahlreicher Proteine. Prominentester Vertreter ist RubisCO – Schlüsselenzym des Calvin Zyklus. RubisCO und andere im 2D selektierte Proteine konnten außerdem als mögliche zelluläre Bindepartner des Microcystins identifiziert werden. Möglicherweise bindet MC an bestimmte Cysteinreste dieser Proteine. Mit dem Knockout der mcy-Gene geht außerdem eine Überexpression eines Morphotyp-spezifischen Proteins einher, das MrpC genannt wurde. Dieses Protein vermittelt möglicherweise Zell-Zell-Interaktionen in Microcystis.<br>Microcystins are the most common cyanobacterial toxins found in freshwater lakes and reservoirs throughout the world. They are frequently produced by the unicellular, colonial cyanobacterium Microcystis; however, the role of the peptide for the producing organismen is poorly understood. In this study we describe the first global approach to investigate this topic on a molecular level. Proteomic studies with M. aeruginosa PCC 7806 wild-type and several microcystin-deficient mutants indicated a physiological function for microcystin. Microcystin was shown to influence the abundance of several proteins which have an intra- or extracellular function. A prominent candidate is RubisCO, the key enzyme of the calvin cycle. RubisCO and other proteins, initially selected by 2D analysis, are putative cellular binding partners of microcystin. A potentially interaction mechanismen is the kovalent binding of microcystin to cysteine residues of the protein. Moreover, several knockouts of microcystin biosynthesis genes result in an overexpression of a putative morpho-type specific factor, named MrpC. This protein possibly mediates cell-cell interactions in Microcystis.

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Phelan, Richard Reginald. "Microcystin enhances the fitness of microcystin producing cyanobacteria at high light intensities by either preventing or retarding photoinhibition." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020957.

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Several genera of cyanobacteria produce microcystin, a monocyclic peptide, with a unique chemical structure. To date, there have been over a 100 different structural variants of microcystin which have been identified. Microcystin production is affected by numerous environmental factors. However, the primary modulating factor for intracellular microcystin quota is the intracellular N:C ratio. No clearly defined biological role has been described for microcystin. Proposed roles for microcystin include defence against plankton grazers, metal chelation, an infochemical and a protectant against oxidative stress. There is sufficient evidence to support a biological role for microcystin in photosynthesis: microcystin is predominantly located in the thylakoid membranes, the microcystin gene cluster is differentially expressed as a function of light and a growth advantage for the microcystin producer in saturating light intensities. The purpose of this study is to investigate a possible biological role for microcystin in preventing photoinhibition and thus explaining the growth advantage observed in toxin-producers over non-toxin-producers. The uptake of exogenous microcystin was observed in Synechocystis PCC 6803 which was internalized and located in the thylakoid membranes and caused the inhibition of photosynthesis. Microcystin variants and increasing concentrations of microcystin-LR had no effect on the fluidity of the thylakoid membranes. The exposure of thylakoid membranes from Synechocystis PCC 6803 to physiologically relevant concentrations of different microcystin variants resulted in the inhibition of photosystem II activity but not photosystem I activity. The inhibition of photosystem II was variant dependent and concentration dependent for microcystin-LR and microcystin-RR. Chlorophyll a fluorescence data showed that photosystem II inhibition was caused by the inhibition of the oxygen evolving complex. Furthermore, a completion study revealed that the microcystin-producing Microcystis PCC 7806 had a competitive advantage over the non-microcystin producing ΔmcyA mutant of Microcystis PCC 7806 at high light intensities. The data indicates that microcystin protects the toxin-producer by either retarding or preventing photoinhibition and thus identifying the first data supported function for microcystin in cyanobacteria.

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Phelan, Richard Reginald. "A potential biological role for microcystin in photosynthesis in Microcystis Aeruginosa." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1285.

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Neither the ecological role nor the metabolic function of microcystin is known. Cellular microcystin concentrations correlate to cellular nitrogen status for a given environmental phosphorous concentration and specific growth rate. Microcystin production is enhanced when the rate of nitrogen accumulation exceeds the relative specific growth rate and/or when cellular N:C ratios exceed the Redfield ratio as a function of reduced carbon fixation, suggesting enhanced production of microcystin under carbon stress. Additionally, a strong correlation between medium phosphate and carbon fixation, and the negative correlation between medium phosphate and microcystin combined with the cellular localization of microcystin in thylakoids supports a possible role for microcystin in enhancement of photosynthesis. Batch cultures of both Microcystis aeruginosa PCC7806 and a mcyA- knockout mutant of PCC7806 were therefore cultured at different light intensities and media treatments, so as to vary cellular N:C ratios and concentrations, and sampled for analysis of microcystin concentration, cell numbers and residual medium nitrates. Inter-strain differences in photosynthetic electron transfer rates and levels were monitored using a Hansatech PEA fluorometer and compared to cellular microcystin concentrations. An enhanced survival was observed at high light, where the toxic strain survived while the nontoxic strain became chlorotic. A strong correlation (r2 = 0.907, p< 0.001, N=22) between microcystin concentration and growth rate was observed at high light conditions. No such advantage was observed at optimal or low-light conditions and media composition had no significant effect on the relationship between toxicity and survival at high light. PCC7806 showed elevated PI(abs) values compared to the mcyA knockout strain, which indicates an increased stability of PSII. A strong correlation between PI(abs) and microcystin (r = 0.88, p< 0.005, N=15) was observed for cultures grown in modified BG11 containing 25 mM under continuous illumination of 37 μmol of photons m-2.s-1. No correlation was observed between PI(abs) and microcystin for the other treatments. The toxin producer had significantly higher values for density of active reaction centers and ii quantum efficiency compared to the mutant. A decrease in F0 in the mutant suggests degradation of the phycobiliproteins, whereas PCC7806 didn’t show a significant decrease in F0 Data indicate that microcystins play a role in photosynthesis by preventing chlorosis in saturating light conditions either by enhancing the redox stability of the phycobiliproteins or PS II, thus preventing photooxidation.

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Downing, T. G. "The role of nitrogen in the regulation of microcystin content in Microcystis aeruginosa." Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/50523.

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Thesis (PhD)--University of Stellenbosch, 2005.<br>ENGLISH ABSTRACT: Several genera of cyanobacteria produce a range of toxins. The increased rate of eutrophication of surface fresh waters due to anthropogenic inputs has resulted in more frequent and severe cyanobacterial bloom events. Such bloom events make impoundments unsuitable for recreational use and increase the cost of production of potable water due to the necessity for removal of toxins released from cells during the purification process. Microcystis aeruginosa is the major freshwater bloom-forming toxic cyanobacterium. Concentrations of the hepatotoxin, microcystin, are highly variable in blooms. Published literature on environmental conditions leading to increased microcystin production was often contradictory and in many cases did not consider all relevant parameters. However, environmental nitrogen and phosphorus, temperature and light, and growth rate were implicated in regulation of toxin content. The purpose of this work was therefore to investigate environmental factors (specifically nitrogen and phosphorus) and cellular activities (specifically carbon fixation and nitrogen uptake rates and growth rate) involved in the modulation of microcystin production in M. aeruginosa in order to clarify the role of these parameters, and in an attempt to identify regulatory mechanisms for microcystin production. Environmental nitrogen, phosphorus and growth rate were shown to co-modulate microcystin production in M. aeruginosa. Adequate phosphorus is required for photosynthetic carbon fixation. Phosphorus uptake by M. aeruginosa is strongly correlated with carbon fixation rate. Although microcystin content increased with increasing nitrogen:phosphorus ratios in culture medium, under phosphorus limitation microcystin content was lower irrespective of nitrogen concentrations. This observation and the requirements for fixed carbon for nitrogen assimilation therefore prompted investigation of the effects of cellular carbon fixation and nitrogen uptake in the modulation of microcystin production. Microcystin production was found to be enhanced when nitrogen uptake rate relative to carbon fixation rate was higher than that required for balanced growth. The cellular nitrogen:carbon ratio above which microcystin concentrations increased substantially, corresponded to the Redfield ratio for balanced growth. Investigation of potential regulatory mechanisms involving the cyanobacterial nitrogen regulator, NtcA, yielded putative NtcA binding sites indicative of repression in the microcystin synthetase gene cluster. In culture, the polypeptide synthetase module gene, mcyA, and ntcA were inversely expressed as a function of carbon-fixation:nitrogen-uptake potential. However, no increase or decrease in microcystin production could be linked to either glutamine, glutamate or a-ketoglutarate, metabolites that are involved in regulation of ntcA. The role of NtcA in regulation of microcystin production could therefore not be confirmed. In conclusion, these data suggest that microcystin production is metabolically regulated by cellular C:N balance and specific growth rate. The primary importance of nitrogen and carbon was demonstrated by a simple model where only nitrogen uptake, carbon fixation and growth rate were used to predict microcystin levels. The model also explains results previously described in literature. Similarly, an artificial neural network model was used to show that the carbon fixation dependence on phosphorus allows accurate prediction of microcystin levels based on growth rate and environmental nitrogen and phosphorus.<br>AFRIKAANSE OPSOMMING: Verskeie genera van sianobakterieë produseer 'n verskeidenheid van toksiene. Die toename in die tempo van eutrofikasie van varswater oppervlaktes as gevolg van antropogeniese insette veroorsaak al hoe meer en al hoe erger sianobakteriële infestasies. Dit veroorsaak probleme vir ontspanninggebruik van hierdie waters en verhoog die koste van produksie van drinkbare water as gevolg van die noodsaak om die toksiene wat deur die selle gedurende die suiweringsproses vrygelaat word te verwyder. Microcystis aeruginosa is die belangrikste varswater bloeisel-vormende toksiese sianobakterium. Die konsentrasie van die hepatotoksien mikrosistien is hoogs varieerbaar in sulke bloeisels. Gepubliseerde literatuur oor die omgewingskondisies wat lei na verhoogde mikrosistienproduksie is dikwels weersprekend en neem in vele gevalle nie al die relevante parameters in ag nie. Desnieteenstaande word omgewingstikstof, fosfor, temperatuur en lig, asook groeisnelheid, geïmpliseer in die regulering van toksieninhoud. Die doel van hierdie navorsing was dus om omgewingsfaktore (spesifiek stikstof en fosfor) en sellulêre aktiwiteite (spesifiek koolstoffiskering en die snelheid van stikstofopname en van groei) betrokke by die modulering van mikrosistienproduksie in M. aeruginosa te ondersoek in 'n poging om die rol van hierdie parameters te verstaan en om regulatoriese meganismes vir mikrosistienproduksie te identifiseer. In hierdie studie is aangetoon dat omgewingstikstof en fosfor sowel as groeisnelheid mikrosistienproduksie in M. aeruginosa ko-moduleer. Genoegsame fosfor word benodig vir fotosintetiese koolstoffiksering. Fosforopname deur M. aeruginosa korreleer sterk met die snelheid van koolstoffiksering. Alhoewel mikrosistieninhoud toegeneem het met 'n toename in die stikstof:fosfor verhouding in die kultuurmedium, was die mikrosistieninhoud onder kondisies van fosforlimitering laer ongeag die stikstofkonsentrasie. Hierdie waarneming, tesame met die noodsaak van gefikseerde koolstof vir stikstofassimilering, het gelei na 'n studie van die effekte van sellulêre koolstoffiksering and stikstofopname op die modulering van mikrosistienproduksie. Dit is gevind dat mikrosistienproduksie verhoog was wanneer die snelheid van stikstofopname relatief tot die snelheid van koolstoffiksering hoër was as die waarde wat benodig word vir gebalanseerde groei. Die sellulêre stikstof:koolstof verhouding waarbo mikrosistienkonsentrasies beduidend verhoog is stem ooreen met die Redfield verhouding vir gebalanseerde groei. 'n Ondersoek na potensiële reguleringsmeganismes waarby die sianobakteriële stikstofreguleerder NtcA betrokke is het gelei na die ontdekking van moontlike NtcA bindingseteis; dit kan dui op die repressie van die mikrosistiensintetase geengroepering. Onder kultuurkondisies is gevind dat die geen vir die polipeptiedsintetase module, mcyA, en ntcA omgekeerd uitgedruk word as 'n funksie van koolstofopname:stikstofopname potensiale. Geen toename of afname in mikrosistienproduksie kon egter gekoppel word aan óf glutamien, óf glutamaat, óf a-ketoglutaraat nie, metaboliete wat betrokke is by die regulering van ntcA. Die rol van NtcA in die regulering van mikrosistienproduksie kon dus nie bevestig word nie. Die gevolgtrekking is dus gemaak dat mikrosistienproduksie metabolies gereguleer word deur die C:N balans en die spesifieke groeisnelheid. Die primêre belang van stikstof en koolstof is gedemonstreer deur 'n eenvoudige model waarin slegs stikstofopname, koolstoffiksering en groeisnelheid gebruik word om mikrosistienvlakke te voorspel. Die model verklaar ook resultate wat tevore in die literatuur beskryf is. Soortgelyk is 'n artifisiële neurale netwerkmodel gebruik om te toon dat die afhanklikheid van koolstoffiksering van fosfor akkurate voorspelling van mikrosistienvlakke gebaseer of groeisnelheid en omgewingstikstof en fosfor moontlik maak.

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Sember, Craig Stewart. "The effect of nutrient levels and ratios on the growth of Microcystis aeruginosa and microcystin production." Thesis, University of Port Elizabeth, 2002. http://hdl.handle.net/10948/287.

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This study reports the findings on the effect of nitrates and phosphates on the biomass and toxin production of various strains of the unicellular non-nitrogen fixing cyanobacterium, Microcystis aeruginosa. The occurrence of blooms of Microcystis aeruginosa and microcystin in freshwater impoundments across the globe has been on the increase lately due to increased levels of eutrophication, resulting in human and animal deaths and illness, as well as drinking and recreational water foulment. A range of environmental factors have been shown to effect growth and microcystin production. Existing literature however is somewhat contradictory as to the effects of these physical and chemical factors on toxin production. Therefore Microcystis aeruginosa strains were cultured under batch and continuous conditions to determine the effect of nitrate and phosphate concentrations and ratios on biomass and toxin production. Cultures were analysed with regards to internal nutrient stores, biomass production, nutrient depletion, photosynthetic efficiency and microcystin production. Results showed that microcystin production correlated to growth rate, photosynthetic efficiency and internal nitrogen stores and that an optimal N:P ratio was associated with microcystin levels, growth rate and photosynthetic efficiency. Results therefore led to the conclusion that the nitrogen, carbon, and phosphate balance within the cell is closely associated with microcystin production. Whether or not microcystin is produced to maintain this balance or produced as a function of this balance remains to be determined.

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Delaney, James M. "The biological activity of microcystin-LR, isolated from the cyanobacterium Microcystis aeruginosa against insects." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308015.

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Zemskov, Ivan [Verfasser]. "Total Synthesis of Microcystin-LR, Microcystin-LF, and Unnatural Derivatives thereof / Ivan Zemskov." Konstanz : Bibliothek der Universität Konstanz, 2016. http://d-nb.info/1169046711/34.

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Meissner, Sven Verfasser], and Elke [Akademischer Betreuer] [Dittmann. "Implications of Microcystin Production in Microcystis aeruginosa PCC 7806 / Sven Meissner ; Betreuer: Elke Dittmann-Thünemann." Potsdam : Universität Potsdam, 2015. http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-75199.

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Meissner, Sven [Verfasser], and Elke [Akademischer Betreuer] Dittmann-Thünemann. "Implications of Microcystin Production in Microcystis aeruginosa PCC 7806 / Sven Meissner ; Betreuer: Elke Dittmann-Thünemann." Potsdam : Universität Potsdam, 2015. http://d-nb.info/1218398965/34.

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Velkme, Erik. "A novel method for antisense oligonucleotide gene expression manipulation in toxigenic cyanobacterial species, Microcystis aeruginosa." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2781.

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Algal blooms caused by toxigenic cyanobacterial species are an increasing economic burden globally, as high anthropogenic inputs of nitrogen and phosphorous, coupled with rising levels of atmospheric CO2, promote eutrophication and enhance bloom proliferation. Of the freshwater bloom forming species, Microcystis aeruginosa has garnered the most attention due to the production of toxic secondary metabolites known as microcystins. These cyclic peptides are potent eukaryotic protein phosphatase 1 and 2A inhibitors, and can induce hepatic damage if concentration levels reach above the World Health Organization level of 1 µg/L. Current mitigation strategies of water column disruption or by use of broad acting chemicals, are limited in their range and may cause unwanted off target effects to the surrounding biota. Antisense oligonucleotides are short single-stranded DNA polymers that hybridize with transcribed mRNA, and suppress translation of protein products through steric hindrance of ribosomes, or by RNAse H degradation of the DNA/RNA bound complex. While antisense oligonucleotide applications have proven successful in the pharmaceutical industry, their potential remains largely unexplored in environmental contexts. For this reason, we investigated the knockdown of microcystin synthetase gene cluster mcyE in M. aeruginosa. We found that ionic charge neutralization coupled with heat shock were effective chemical competence based methods for delivery, mcyE transcript abundance in cells treated with phosphodiester linked antisense oligonucleotides significantly decreased in RT-qPCR analysis, and production of intracellular microcystin significantly decreased over a 24 hour period (-1.9 fg/cell). This work demonstrates a novel proof of concept for the potential use of exogenous antisense oligonucleotides to target M. aeruginosa in harmful algal bloom occurrences.

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Più fonti

Libri sul tema "Microcystin"

F, Watanabe Mariyo, ed. Toxic microcystis. Boca Raton, FL: CRC Press, 1996.

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Standing Committee of Analysts., ed. Determination of microcystin-LR in drinking waters by HPLC 1994. London: HMSO, 1994.

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Jones, Geoffrey Brent. Phytoplankton and microcystin-LR in the Assiniboine River at Portage la Prairie, Manitoba, 1997-2001. Winnipeg, MB: Manitoba Conservation, 2002.

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Zurawell, Ronald William. An initial assessment of microcystin in raw and treated municipal drinking water derived from eutrophic surface waters in Alberta. Edmonton: Alberta Environment, Science and Standards Branch, 2002.

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Watanabe, Mariyo F., Ken-ichi Harada, Wayne W. Carmichael, and Hirota Fujiki. Toxic Microcystis. Boca Raton: CRC Press, 2024. http://dx.doi.org/10.1201/9781003575078.

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Ino, Tomio. Strukturaufklärung von toxischen und nicht toxischen Peptiden aus Cyanobakterien der Gattung Microcystis und Partialsynthese von Adda, der Schlüsselkomponente der Microcystine. [s.l.]: [s.n.], 1994.

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Watanabe, Masayuki. Nihon aoko daizukan: The freshwater planktonic blue-greens of Japan with photographs and illustrations / by Masayuki Watanabe. Tōkyō: Seibundō Shinkōsha, 2007.

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Toivola, Diana. Microcystins: Potent tools to study serine/threonine protein phosphatases and their role in cytoskeletal regulation. Åbo: Åbo Akademi University Press, 1998.

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Meriluoto, Jussi. Liquid chromatographic analysis of cyanobacterial peptide hepatotoxins. Åbo: Åbo Akademis förlag, 1990.

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Kovermann, Georg. Süsswasserblaualgen (Microcystis aeruginosa, Anabaena flos-aquae, Aphanizomenon flos-aquae): Entwicklung, Vorkommen, Pharmakologie u. Toxizität. [s.l.]: [s.n.], 1988.

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Capitoli di libri sul tema "Microcystin"

Fujiki, Hirota. "Microcystin-LR." In Encyclopedia of Cancer, 1–5. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-27841-9_7069-3.

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Fujiki, Hirota. "Microcystin-LR." In Encyclopedia of Cancer, 2828–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-662-46875-3_7069.

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Chorus, Ingrid. "Factors Controlling Cellular Microcystin Content." In Cyanotoxins, 102–47. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-59514-1_3.

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Kim, Hye Ryoung, Chi Kyung Kim, Tae Seok Ahn, Soon Ae Yoo, and Dong Hun Lee. "Effects of Temperature and Light on Microcystin Synthetase Gene Transcription in Microcystis Aeruginosa." In Key Engineering Materials, 606–11. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-958-x.606.

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Xin, Qing, Yi Zhang, and Gaofeng Yan. "Adsorption of Microcystin-LR by Carbon Xerogel." In Lecture Notes in Electrical Engineering, 197–203. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-25905-0_27.

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Liyanage, G. Y., S. P. Manage, H. A. S. N. Abeysiri, P. M. Manage, and S. A. Kulasooriya. "Rapid Detection Method of Microcystin in Water." In Protocols for Cyanobacteria Sampling and Detection of Cyanotoxin, 363–72. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-4514-6_50.

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Abeyrathne, P. A. B. P., K. P. A. Imanthi, H. A. S. N. Abeysiri, G. Y. Liyanage, M. M. Pathmalal, and S. A. Kulasooriya. "Risk Assessment of Microcystin in Water Resources." In Protocols for Cyanobacteria Sampling and Detection of Cyanotoxin, 165–72. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-4514-6_24.

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Ferrari, Alejandro, Marcia Andrea Ruiz, and Ana Laura Ruibal-Conti. "Antibodies as Biomarkers: Effect of Microcystin Exposure." In Biomarkers in Toxicology, 85–106. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-07392-2_6.

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Ferrari, Alejandro, Marcia Andrea Ruiz, and Ana Laura Ruibal-Conti. "Antibodies as Biomarkers: Effect of Microcystin Exposure." In Biomarkers in Toxicology, 1–22. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-87225-0_6-1.

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Chang, Shu-Chi, Bo-Li Lu, Jiang-Jen Lin, Yen-Hsien Li, and Maw-Rong Lee. "A Method to Prepare Magnetic Nanosilicate Platelets for Effective Removal of Microcystis aeruginosa and Microcystin-LR." In Methods in Molecular Biology, 85–94. New York, NY: Springer New York, 2017. http://dx.doi.org/10.1007/978-1-4939-6958-6_8.

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Atti di convegni sul tema "Microcystin"

Yi, Cheng-wu, Jing Cai, Hong-xiang Ou, Hong Liu, Qian-qian Li, Jin-yu Chu, and Cheng-gang He. "Extraction and Detection of Microcystin-LR from Microcystic Aeruginosa." In 2010 International Conference on E-Product E-Service and E-Entertainment (ICEEE 2010). IEEE, 2010. http://dx.doi.org/10.1109/iceee.2010.5660565.

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Hendrickson, Olga Dmitrievna, Elena Anatolievna Zvereva, Ksenia Alekseevna Maksimova, Alexandra Pavlovna Bondarenko, and Sergey Aleksandrovich Eremin. "FLUORESCENT POLARIZATION IMMUNOASSAY OF MICROCYSTIN-LR." In NEW TECHNOLOGIES IN MEDICINE, BIOLOGY, PHARMACOLOGY AND ECOLOGY. Institute of information technology, 2021. http://dx.doi.org/10.47501/978-5-6044060-1-4.31.

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To control the highly toxic phycotoxin microcystin-LR, which comtaminates food, a test sys-tem based on polarizing fluorescent immunoassay has been developed allowing for rapid screening testing, the detection limit of microcystin-LR is up to 7.5 ng / ml; duration of analy-sis – 10 min.

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Fields, Chad. "SURVEILLANCE OF MICROCYSTIN IN IOWA’S DRINKING WATER." In 52nd Annual North-Central GSA Section Meeting - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018nc-312716.

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Huang, Pei, and An Xu. "Genotoxic Effects of Microcystin-LR in Mammalian Cells." In 2009 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2009. http://dx.doi.org/10.1109/icbbe.2009.5162883.

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Chen, Xiaoguo, Shenghu Zhang, Yang Zhang, and Bangding Xiao. "Purification of Microcystin-LR by Solid-Phase Extraction Procedure." In 2009 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2009. http://dx.doi.org/10.1109/icbbe.2009.5163264.

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Wu, Ming-Song, Ying Ji, Jun-Li Huang, Jiao Fu, Yu-Ling Zhang, and Yu Tian. "Effects and Kinetics of Chlorine Dioxide Removal Microcystin-RR." In 2009 3rd International Conference on Bioinformatics and Biomedical Engineering (iCBBE). IEEE, 2009. http://dx.doi.org/10.1109/icbbe.2009.5162728.

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Briscoe, Jayson L., and Sang-Yeon Cho. "Low level detection of microcystin using a plasmonic biosensor." In 2014 IEEE Sensors. IEEE, 2014. http://dx.doi.org/10.1109/icsens.2014.6984996.

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Xiaoguo Chen, Fan Hu, Weicheng Zhang, Yue Hu, Ruiting Yan, and Bangding Xiao. "Toxicities of microcystin LR on caenorhabditis elegans and their offspring." In 2011 International Symposium on Water Resource and Environmental Protection (ISWREP). IEEE, 2011. http://dx.doi.org/10.1109/iswrep.2011.5893485.

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Chen, Zhaozhe, and Ozeas Costa. "REMOVAL OF MICROCYSTIN USING ARTIFICIAL FLOATING ISLANDS IN RESIDENTIAL WASTEWATER." In GSA Connects 2023 Meeting in Pittsburgh, Pennsylvania. Geological Society of America, 2023. http://dx.doi.org/10.1130/abs/2023am-391976.

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Chen, Zhaozhe, Ozeas Costa, Jiyoung Lee, and Abigail Volk. "REMOVAL OF MICROCYSTIN USING ARTIFICIAL FLOATING ISLANDS IN RESIDENTIAL WASTEWATER." In 57th Annual GSA North-Central Section Meeting - 2023. Geological Society of America, 2023. http://dx.doi.org/10.1130/abs/2023nc-386665.

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Rapporti di organizzazioni sul tema "Microcystin"

Carrigee, Lyndsay, Carina Jung, Matthew Carr, and Karl Indest. Bacterial remediation of microsystin-HAB toxins utilizing microcystinase (MlrA). Engineer Research and Development Center (U.S.), April 2025. https://doi.org/10.21079/11681/49673.

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Microcystins are a class of hepatotoxins produced by some harmful algal bloom–associated cyanobacteria and are the most reported toxins in freshwaters. Their cyclic structure makes them resistant to conventional methods used in water treatment operations (boiling, chlorination, and UV treatment). Some bacteria can naturally degrade microcystins via the mlrABCD cluster, a pathway initiated by the primary enzyme microcystinase (MlrA). MlrA linearizes the cyclic microcystin, greatly reducing its toxicity. Protein fusion was employed to produce a recombinant MlrA enzyme fused to maltose-binding protein ([MBP] MBP-MlrA) and to evaluate long-term enzymatic stabilization and reconstitution for future applications. MBP-MlrA degraded cyclic microcystin in vitro and demonstrated stability across a range of biological pHs. At a concentration of 0.61 ng/μl in buffer, MBP-MlrA achieved and maintained an average degradation rate of approximately 101.95 μM/h/ng of protein across fifteen freeze/thaw cycles. Stability assays demonstrated that enzyme activity was preserved over 5 months at −20°C. Results also demonstrated the effectiveness of MBP-MlrA to linearize microcystin upwards of 55.59 μM/h/ng of protein at the bench scale in both buffer and various freshwater matrices. The presence of the linear metabolite is of concern regarding intermediate toxicity, and future studies to incorporate the MlrB peptidase are discussed.

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Robinson, Nancy A., Judith G. Pace, Charles F. Matson, George A. Miura, and Wade B. Lawrence. Toxicokinetics of (3H)Microcystin-LR in Mice. Fort Belvoir, VA: Defense Technical Information Center, March 1990. http://dx.doi.org/10.21236/ada221204.

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Maycock, Barry, Cath Mulholland, Emma French, and Joseph Shavila. Rapid Risk Assessment: What is the risk from microcystins in the edible flesh of fish caught from Lough Neagh? Food Standards Agency, March 2024. http://dx.doi.org/10.46756/sci.fsa.slz868.

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During the Summer and Autumn of 2023, Lough Neagh in Northern Ireland was affected by a cyanobacterial bloom. Testing of water from within the bloom reported high concentrations of one type of cyanobacterial toxin, microcystins. Samples were taken from the Lough of eels, roach, perch, pollan and bream and tested for a range of cyanobacterial toxins, including microcystins, nodularins, anatoxin, cylindrospermopsin and saxitoxin. Each sample comprised 10 fish, and five samples were taken of each species, except for bream for which a single sample was collected. The fish were dissected and the edible flesh, intestine, liver, roe, gonad and/or gills analysed separately. Microcystins were detected at a range of concentrations in the various parts of the fish that were sampled - intestine, liver, roe and/or gills, but were not detected in the edible flesh of any of the fish samples. Averaged across the samples, the highest concentrations of microcystins were quantified in the intestine samples, followed by the liver samples, with low concentrations were detected in the gills and a small number of the samples of gonads and roe. None of the other toxins were detected in any fish sample. The initial analysis for microcystins was of free toxins only. However, there is evidence that microcystins which are covalently bound to proteins are also bioavailable and therefore 22 fish tissue samples, including nine fish flesh samples, were also sent to another laboratory where they were analysed by a method which measures the total concentrations of microcystins, free and protein-bound. The viscera tissue samples chosen for the further analysis were those with the highest concentrations of the free toxins, while the fish flesh samples included 2-3 samples each of eels, roach, pollan and perch. The concentrations of total microcystins found in viscera samples were around one order of magnitude higher than the concentrations of free microcystins that had been measured. However, microcystins were still not detected in the edible fish flesh samples. It is possible that microcystins were not present at any level in any of the fish flesh samples. However, the presence of microcystins in the edible flesh of fish has been reported in the scientific literature, albeit at lower levels than those in the gastrointestinal tract or other parts of the viscera such as liver (Testai et al., 2016). Since microcystins were detected in other parts of the fish sampled from Lough Neagh it is also possible that they were also present in the fish flesh but at levels below the limits of detection of the analytical methods. The limit of detection of the analytical method for total (free + bound) microcystins was 10 µg/kg wet weight. An upper bound dietary exposure assessment was conducted. While a lower bound exposure assessment would assume the microcystins were not present in the edible flesh, i.e. a concentration of 0 µg/kg, the upper bound approach assumed they were present at the limit of detection of 10 µg/kg. The true concentrations may be between these levels. The exposure assessments consider high consumers of fish (97.5th percentile). For eels, consumption data were used from the National Diet and Nutrition Survey (NDNS). For roach, perch, pollan and bream. No consumption data were available from the NDNS and consumption data for trout were used instead as a proxy. The main target organ for toxicity of the microcystins is the liver, though other organs may also be affected. The microcystin most studied toxicologically is microcystin-LR, which is one of the most common microcystins. A WHO review established a provisional tolerable daily intake (TDI) for microcystin-LR of 0.04 µg per kg bodyweight (bw). WHO recommended that exposures to total microcystins should be compared to this provisional TDI, though there is uncertainty with this as individual microcystins are likely to differ significantly in their toxic potencies. Estimated dietary exposures of total microcystins were all within the provisional TDI, indicating no health concern from consuming the edible flesh of these species. Since fish may be caught and prepared for consumption not only by food business operators but by recreational anglers, concern has been raised that evisceration may be incomplete or the edible flesh may become contaminated in the process, and therefore this was also considered in the risk assessment. This was based on the sample of fish which contained the highest concentration of total microcystins in a viscera component, which was a sample of roach with a particularly high concentration of microcystins in intestine. It was assumed that 10% of the relative proportion of intestine to flesh in the fish would be inadvertently consumed with the flesh. In this scenario, dietary exposures would be within the provisional TDI in most age groups or would marginally exceed the TDI, but this would not be toxicologically significant. In addition, since this exposure scenario used an upper bound approach to the concentration in flesh, and used the highest concentration in any viscera sample, it is not clear that there would be any exceedance of the provisional TDI in practice. Overall, it appears unlikely that consumers will substantially exceed the provisional TDI on a long-term basis due to incomplete evisceration of fish. Overall, exposure to microcystins from eating the edible flesh of the tested fish species would not be expected to cause adverse effects in consumers, including if the fish is inadequately eviscerated. Therefore, we consider the frequency of adverse reactions in the general population to be negligible, so rare that it does not merit to be included. Based on the possible levels of exposure to microcystins from fish from Lough Neagh, it is considered that any liver injury, were it to occur in consumers of fish, would result from long term exposure and be mild. Overall, we consider the severity of illness that could potentially occur as a result of exposure to microcystins from consuming edible fish flesh from Lough Neagh to be medium (i.e. moderate illness, incapacitating but not usually life-threatening and of moderate duration). We consider the level of uncertainty to be medium (i.e. there are some but no complete data available), but that this does not affect the conclusion of the risk assessment since many of the key uncertainties are addressed within the risk assessment. However, future monitoring would be useful to assess whether microcystin concentrations in the fish change over time.

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Robinson, Nancy A., Judith G. Pace, Charles F. Matson, George A. Miura, and Wade B. Lawrence. Tissue Distribution, Excretion, and Hepatic Biotransformation of Microcystin-LR in Mice. Fort Belvoir, VA: Defense Technical Information Center, July 1990. http://dx.doi.org/10.21236/ada232418.

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Thomas, Catherine, Afrachanna Butler, Victor Medina, Chris Griggs, and Alan Katzenmeyer. Physicochemical treatment of cyanobacteria and microcystin by hydrodynamic cavitation and advanced oxidation. Engineer Research and Development Center (U.S.), March 2019. http://dx.doi.org/10.21079/11681/32313.

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McQueen, Andrew, Michael Habberfield,, Karen Keil, and Burton Suedel. Fate and effects of microcystin in nearshore and upland environments : a literature review. Engineer Research and Development Center (U.S.), January 2020. http://dx.doi.org/10.21079/11681/35274.

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Sperry, Benjamin, Bradley Sartain, Kurt Getsinger, Brianna Fernando, Kaytee Pokrzywinski, West Bishop, and Mark Heilman. Field demonstration of a peroxide-based algaecide for harmful algal bloom control in Lake Okeechobee. Engineer Research and Development Center (U.S.), September 2023. http://dx.doi.org/10.21079/11681/47624.

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Large-scale cyanobacterial harmful algal blooms (cHABs) in Lake Okeechobee, Florida, and connected waterways routinely impair water resources. This study conducted a field demonstration of a peroxide-based algaecide in 2020 in the Pahokee Marina on Lake Okeechobee to evaluate the algaecide’s suitability for near-future operational implementation. Within minutes of treatment, rapid oxidation of cHAB cells occurred in the form of bleaching and cell lysis. On average, levels in the treatment area decreased by 4 hours after treatment (HAT) and remained low out to 24 HAT: chlorophyll decreased 87%, phycocyanin decreased 85%, total microcystin levels decreased from 50 μg L−1 to 4 μg L⁻¹ at 4 HAT and then increased to 11 μg L⁻¹ by 24 HAT, hydrogen peroxide concentrations averaged 6.1 mg L⁻¹ 0.5 HAT and then dropped below detection limits by 24 HAT, and Microcystis spp. cell densities decreased at 4 HAT in all but four sampling sites. However, inflows of cHAB-infested lake water in some portions of the treatment area resulted in lack of control at these sites. Because of their vulnerability to influxes of cHABs from surrounding nontreated waters via water-exchange processes driven by wind-induced surface currents, future applications must therefore consider treatment area size.

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Calomeni, Alyssa, Andrew McQueen, Ciera Kinley-Baird, and Gerard Clyde. Identification and preventative treatment of overwintering cyanobacteria in sediments : a literature review. Engineer Research and Development Center (U.S.), August 2022. http://dx.doi.org/10.21079/11681/45063.

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Freshwaters can experience growths of toxin-producing cyanobacteria or harmful algal blooms (HABs). HAB-producing cyanobacteria can develop akinetes, which are thick-enveloped quiescent cells akin to seeds in vascular plants or quiescent colonies that overwinter in sediment. Overwintering cells produce viable “seed beds” for HAB resurgences and preventative treatments may diminish HAB intensity. The purpose of this literature review was to identify (1) environmental factors triggering germination and growth of overwintering cells, (2) sampling, identification, and enumeration methods, and (3) feasibility of preventative algaecide treatments. Conditions triggering akinete germination (light ≥0.5 μmol m-2s-1, temperature 22-27℃) differ from conditions triggering overwintering Microcystis growth (temperature 15-30℃, nutrients, mixing). Corers or dredges are used to collect surficial (0-2 cm) sediment layers containing overwintering cells. Identification and enumeration via microscopy are aided by dilution, sieving, or density separation of sediment. Grow-out studies simulate environmental conditions triggering cell growth and provide evidence of overwintering cell viability. Lines of evidence supporting algaecide efficacy for preventative treatments include (1) field studies demonstrating scalability and efficacy of algaecides against benthic algae, (2) data suggesting similar sensitivities of overwintering and planktonic Microcystis cells to a peroxide algaecide, and (3) a mesocosm study demonstrating a decrease in HAB severity following preventative treatments. This review informs data needs, monitoring techniques, and potential efficacy of algaecides for preventative treatments of overwintering cells.

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Moores, Lee C., P. U. Ashvin, I. Fernando, and Garret W. George. Synthesis of 2-Methoxypropyl Benzene for Epitope Imprinting. U.S. Army Engineer Research and Development Center, July 2022. http://dx.doi.org/10.21079/11681/44883.

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Harmful algal blooms (HABs) are occurring with increasing frequency and severity across the globe in part due to climate change and anthropogenic pollution (Bullerjahn et al. 2016). HABs produce several classes of toxins; however, microcystins (MCs) are the most commonly studied (Lone et al. 2015) and can be potent toxins with LD50s in the range of 50 μg/kg (Puddick et al. 2014). Sample analysis in laboratories, typically by high-pressure liquid chromatography tandem mass spectrometry (HPLC-MS/MS) or by Enzyme Linked Immunosorbent Assays (ELISAs) (USEPA 2015). These analytical techniques are highly sensitive and selective for the given toxins; however, the time it takes to collect, transfer, prepare, and analyze a sample before the data can be reported is significant; often, multiple days is the most expeditious.

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Pokrzywinski, Kaytee, Cliff Morgan, Scott Bourne, Molly Reif, Kenneth Matheson, and Shea Hammond. A novel laboratory method for the detection and identification of cyanobacteria using hyperspectral imaging : hyperspectral imaging for cyanobacteria detection. Engineer Research and Development Center (U.S.), June 2021. http://dx.doi.org/10.21079/11681/40966.

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To assist US Army Corps of Engineers resource managers in monitoring for cyanobacteria bloom events, a laboratory method using hyperspectral imaging has been developed. This method enables the rapid detection of cyanobacteria in large volumes and has the potential to be transitioned to aerial platforms for field deployment. Prior to field data collection, validation of the technology in the laboratory using monocultures was needed. This report describes the development of the detection method using hyperspectral imaging and the stability/reliability of these signatures for identification purposes. Hyperspectral signatures of different cyanobacteria were compared to evaluate spectral deviations between genera to assess the feasibility of using this imaging method in the field. Algorithms were then developed to spectrally deconvolute mixtures of cyanobacteria to determine relative abundances of each species. Last, laboratory cultures of Microcystis aeruginosa and Anabaena sp. were subjected to varying macro (nitrate and phosphate) and micro-nutrient (iron and magnesium) stressors to establish the stability of signatures within each species. Based on the findings, hyperspectral imaging can be a valuable tool for the detection and monitoring of cyanobacteria. However, it should be used with caution and only during stages of active growth for accurate identification and limited interference owing to stress.

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