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1
Rohrlack, Thomas, Elke Dittmann, Thomas Börner e Kirsten Christoffersen. "Effects of Cell-Bound Microcystins on Survival and Feeding of Daphnia spp". Applied and Environmental Microbiology 67, n. 8 (1 agosto 2001): 3523–29. http://dx.doi.org/10.1128/aem.67.8.3523-3529.2001.
Testo completoAbstract (sommario):
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.
2
Johansson, Emma, Catherine Legrand, Caroline Björnerås, Anna Godhe, Hanna Mazur-Marzec, Torbjörn Säll e Karin Rengefors. "High Diversity of Microcystin Chemotypes within a Summer Bloom of the Cyanobacterium Microcystis botrys". Toxins 11, n. 12 (1 dicembre 2019): 698. http://dx.doi.org/10.3390/toxins11120698.
Testo completoAbstract (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.
3
Ballot, Andreas, Morten Sandvik, Thomas Rundberget, Christo J. Botha e Christopher O. Miles. "Diversity of cyanobacteria and cyanotoxins in Hartbeespoort Dam, South Africa". Marine and Freshwater Research 65, n. 2 (2014): 175. http://dx.doi.org/10.1071/mf13153.
Testo completoAbstract (sommario):
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.
4
Vaitomaa, Jaana, Anne Rantala, Katrianna Halinen, Leo Rouhiainen, Petra Tallberg, Lena Mokelke e 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, n. 12 (dicembre 2003): 7289–97. http://dx.doi.org/10.1128/aem.69.12.7289-7297.2003.
Testo completoAbstract (sommario):
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.
5
Wang, Suqin, Siyu Yang, Jun Zuo, Chenlin Hu, Lirong Song, Nanqin Gan e 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, n. 8 (27 luglio 2021): 1594. http://dx.doi.org/10.3390/microorganisms9081594.
Testo completoAbstract (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.
6
Ho, Lionel, Nawal Kayal, Rino Trolio e Gayle Newcombe. "Determining the fate of Microcystis aeruginosa cells and microcystin toxins following chloramination". Water Science and Technology 62, n. 2 (1 luglio 2010): 442–50. http://dx.doi.org/10.2166/wst.2010.448.
Testo completoAbstract (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.
7
Kurmayer, Rainer, Guntram Christiansen e 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, n. 2 (febbraio 2003): 787–95. http://dx.doi.org/10.1128/aem.69.2.787-795.2003.
Testo completoAbstract (sommario):
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.
8
Bittencourt-Oliveira, MC, MC Oliveira e E. Pinto. "Diversity of microcystin-producing genotypes in Brazilian strains of Microcystis (Cyanobacteria)". Brazilian Journal of Biology 71, n. 1 (febbraio 2011): 209–16. http://dx.doi.org/10.1590/s1519-69842011000100030.
Testo completoAbstract (sommario):
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.
9
Wang, Hui, Cyndee L. Gruden, Thomas B. Bridgeman e 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, n. 7 (1 ottobre 2009): 1837–46. http://dx.doi.org/10.2166/wst.2009.517.
Testo completoAbstract (sommario):
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<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<0.05) were associated with the production of microcystin-LR.
10
Oh, Hee-Mock, Seog June Lee, Jee-Hwan Kim, Hee-Sik Kim e Byung-Dae Yoon. "Seasonal Variation and Indirect Monitoring of Microcystin Concentrations in Daechung Reservoir, Korea". Applied and Environmental Microbiology 67, n. 4 (1 aprile 2001): 1484–89. http://dx.doi.org/10.1128/aem.67.4.1484-1489.2001.
Testo completoAbstract (sommario):
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.
11
Rohrlack, Thomas, Elke Dittmann, Manfred Henning, Thomas Börner e Johannes-Günter Kohl. "Role of Microcystins in Poisoning and Food Ingestion Inhibition of Daphnia galeata Caused by the Cyanobacterium Microcystis aeruginosa". Applied and Environmental Microbiology 65, n. 2 (1 febbraio 1999): 737–39. http://dx.doi.org/10.1128/aem.65.2.737-739.1999.
Testo completoAbstract (sommario):
ABSTRACT The effects of microcystins on Daphnia galeata, a typical filter-feeding grazer in eutrophic lakes, were investigated. To do this, the microcystin-producing wild-type strain Microcystis aeruginosa PCC7806 was compared with a mcy− PCC7806 mutant, which could not synthesize any variant of microcystin due to mutation of a microcystin synthetase gene. The wild-type strain was found to be poisonous toD. galeata, whereas the mcy− mutant did not have any lethal effect on the animals. Both variants of PCC7806 were able to reduce the Daphnia ingestion rate. Our results suggest that microcystins are the most likely cause of the daphnid poisoning observed when wild-type strain PCC7806 is fed to the animals, but these toxins are not responsible for inhibition of the ingestion process.
12
Zilliges, Yvonne, Jan-Christoph Kehr, Stefan Mikkat, Christiane Bouchier, Nicole Tandeau de Marsac, Thomas Börner e Elke Dittmann. "An Extracellular Glycoprotein Is Implicated in Cell-Cell Contacts in the Toxic Cyanobacterium Microcystis aeruginosa PCC 7806". Journal of Bacteriology 190, n. 8 (15 febbraio 2008): 2871–79. http://dx.doi.org/10.1128/jb.01867-07.
Testo completoAbstract (sommario):
ABSTRACT 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 aeruginosa; however, the role of the peptide for the producing organism is poorly understood. Differences in the cellular aggregation of M. aeruginosa PCC 7806 and a microcystin-deficient ΔmcyB mutant guided the discovery of a surface-exposed protein that shows increased abundance in PCC 7806 mutants deficient in microcystin production compared to the abundance of this protein in the wild type. Mass spectrometric and immunoblot analyses revealed that the protein, designated microcystin-related protein C (MrpC), is posttranslationally glycosylated, suggesting that it may be a potential target of a putative O-glycosyltransferase of the SPINDLY family encoded downstream of the mrpC gene. Immunofluorescence microscopy detected MrpC at the cell surface, suggesting an involvement of the protein in cellular interactions in strain PCC 7806. Further analyses of field samples of Microcystis demonstrated a strain-specific occurrence of MrpC possibly associated with distinct Microcystis colony types. Our results support the implication of microcystin in the colony specificity of and colony formation by Microcystis.
13
Murphy, Tom, Kim Irvine, Jay Guo, John Davies, Henry Murkin, Murray Charlton e Susan Watson. "New Microcystin Concerns in the Lower Great Lakes". Water Quality Research Journal 38, n. 1 (1 febbraio 2003): 127–40. http://dx.doi.org/10.2166/wqrj.2003.008.
Testo completoAbstract (sommario):
Abstract Water samples were collected in the summer of 2001 for microcystin analysis, nutrients and algal enumeration from Hamilton Harbour (Lake Ontario), Wendt Beach (Lake Erie) and Presque Isle (Lake Erie). Microcystin concentrations varied largely and were present at acute toxicity levels only in some wind-concentrated scums of blue-green algae (>90% Microcystis, primarily M. botrys, M. viridis and some M. wesenbergii) in Hamilton Harbour. In Hamilton Harbour, microcystin-RR was the main microcystin with microcystin-YR and -LR also present. The two samples of August 17 and September 7, taken during the peak of the cyanobacterial bloom, contained 60 and 400 μg/L, respectively. A few dying birds were seen in the Hamilton scums. The concentrations of microcystins at the Lake Erie sites were less than 1 μg/L, yet dead birds were common. The major limitation with this approach is that current analysis (ELISA and HPLC) methods are unable to measure covalently bound microcystins, the form that is assimilated into the food chain.
14
Wiedner, Claudia, Petra M. Visser, Jutta Fastner, James S. Metcalf, Geoffrey A. Codd e Luuc R. Mur. "Effects of Light on the Microcystin Content of Microcystis Strain PCC 7806". Applied and Environmental Microbiology 69, n. 3 (marzo 2003): 1475–81. http://dx.doi.org/10.1128/aem.69.3.1475-1481.2003.
Testo completoAbstract (sommario):
ABSTRACT Many cyanobacteria produce microcystins, hepatotoxic cyclic heptapeptides that can affect animals and humans. The effects of photosynthetically active radiation (PAR) on microcystin production by Microcystis strain PCC 7806 were studied in continuous cultures. Microcystis strain PCC 7806 was grown under PAR intensities between 10 and 403 μmol of photons m−2 s−1 on a light-dark rhythm of 12 h -12 h. The microcystin concentration per cell, per unit biovolume and protein, was estimated under steady-state and transient-state conditions and on a diurnal timescale. The cellular microcystin content varied between 34.5 and 81.4 fg cell−1 and was significantly positively correlated with growth rate under PAR-limited growth but not under PAR-saturated growth. Microcystin production and PAR showed a significant positive correlation under PAR-limited growth and a significant negative correlation under PAR-saturated growth. The microcystin concentration, as a ratio with respect to biovolume and protein, correlated neither with growth rate nor with PAR. Adaptation of microcystin production to a higher irradiance during transient states lasted for 5 days. During the period of illumination at a PAR of 10 and 40 μmol of photons m−2 s−1, the intracellular microcystin content increased to values 10 to 20% higher than those at the end of the dark period. Extracellular (dissolved) microcystin concentrations were 20 times higher at 40 μmol of photons m−2 s−1 than at 10 μmol of photons m−2 s−1 and did not change significantly during the light-dark cycles at both irradiances. In summary, our results showed a positive effect of PAR on microcystin production and content of Microcystis strain PCC 7806 up to the point where the maximum growth rate is reached, while at higher irradiances the microcystin production is inhibited.
15
Falcone-Dias, Maria Fernanda, Marianna Vaz Rodrigues, Jeppe Lund Nielsen, Nadieh de Jonge, Niels O. G. Jørgensen, Diego Peres Alonso, Gianmarco S. David, Reinaldo José da Silva e João Pessoa Araújo Júnior. "Occurrence of Cyanobacteria and microcystins in hydroelectric reservoirs used for fish farming". Journal of Water and Health 18, n. 6 (29 ottobre 2020): 983–94. http://dx.doi.org/10.2166/wh.2020.089.
Testo completoAbstract (sommario):
Abstract Fish farming can have a negative impact on water quality and aquatic organisms due to emerging blooms of Cyanobacteria and the production of cyanotoxins. In this study, the effect of aquaculture in hydroelectric reservoirs in Brazil was evaluated in six fish farms and in upstream and downstream water through analysis of the microbiome, Cyanobacteria and microcystin concentrations. Synechococcus and Microcystis were observed at all six locations, while Limnothrix was also observed abundantly at two locations. An increase in the relative abundance of Cyanobacteria inside the fish farms was observed at two locations, while an increase of Cyanobacteria was observed in downstream at five of the six locations. Microcystins were detected in significant and high values in all locations, with concentrations up to 1.59 μg/L. The trend in microcystin concentrations was mirrored in copy numbers of the mcyE gene (encodes microcystin synthetase) and presence of Microcystis, but not in any of the other observed cyanobacterial groups. In summary, the study shows that aquaculture production influenced the water microbiome inside and downstream the fish farms, and a direct correlation was found between mcyE gene copies, microcystin production and abundance of Microcystis, but not for the total abundance of Cyanobacteria.
16
Lahti, K., J. Rapala, A.-L. Kivimäki, J. Kukkonen, M. Niemelä e K. Sivonen. "Occurrence of microcystins in raw water sources and treated drinking water of Finnish waterworks". Water Science and Technology 43, n. 12 (1 giugno 2001): 225–28. http://dx.doi.org/10.2166/wst.2001.0744.
Testo completoAbstract (sommario):
Problems caused by cyanobacteria are common around the world and also in raw water sources of drinking water treatment plants. Strains belonging to genera Microcystis, Anabaena and Planktothrix produce potent hepatotoxins, the microcystins. Laboratory and pilot scale studies have shown that microcystins dissolved in water may pass the conventional surface water treatment processes. In 1998 the World Health Organization proposed a guide value of 1 μg/L for microcystin-LR (MC-LR) in drinking water. The purpose of this research was to study the occurrence of microcystins in raw water sources of surface waterworks and in bank filtration plants and to evaluate the removal of microcystins in operating waterworks. Four bank filtration plants and nine surface waterworks using different processes for water treatment were monitored. Phytoplankton was identified and quantified, and microcystins analysed with sensitive immunoassay. Microcystin occurrence in selected water samples was verified with HPLC and a protein phosphatase inhibition method. Microcystins were detected sporadically in raw water sources of most of the waterworks. In two raw water supplies toxins were detected for several months. The highest microcystin concentrations in incoming raw water were approximately 10 μg/L MC-LR equivalents. In treated drinking water microcystins were detected occasionally but the concentrations were always below the guide value proposed by WHO.
17
Et al., Abed. "Molecular and Immunological Methods to Confirm Toxiginicity (Microcystin Production) of Westiellopsis Prolifica Isolated from Tigris River – Iraq". Baghdad Science Journal 16, n. 4(Suppl.) (18 dicembre 2019): 0978. http://dx.doi.org/10.21123/bsj.2019.16.4(suppl.).0978.
Testo completoAbstract (sommario):
Several toxigenic cyanobacteria produce the cyanotoxin (microcystin). Being a health and environmental hazard, screening of water sources for the presence of microcystin is increasingly becoming a recommended environmental procedure in many countries of the world. This study was conducted to assess the ability of freshwater cyanobacterial species Westiellopsis prolifica to produce microcystins in Iraqi freshwaters via using molecular and immunological tools. The toxigenicity of W. prolifica was compared via laboratory experiments with other dominant bloom-forming cyanobacteria isolated from the Tigris River: Microcystis aeruginosa, Chroococcus turigidus, Nostoc carneum, and Lyngbya sp. significant expression of mcyE gene and microcystin production was most evident in W. prolifica. Contrary to the prevailing concept that M. aeruginosa is a main microcystin producer in freshwaters around the world, no significant microcystin production was observed with this species throughout the time points studied in our laboratory methods. As for C. turigidus, N. carneum and Lyngbya sp., neither mcyE expression nor microcystin production was significant. Data from mcyE expression by RT-qPCR were generally in agreement with those obtained from microcystin quantification by ELISA. Interestingly, W. prolifica, which showed clear microcystin-producing ability in this study and which was not reported before in the literature to produce microcystin, can be added as a new microcystin producer to the list of toxigenic cyanobacteria.
18
McElhiney, Jacqui, Mathew Drever, Linda A. Lawton e Andy J. Porter. "Rapid Isolation of a Single-Chain Antibody against the Cyanobacterial Toxin Microcystin-LR by Phage Display and Its Use in the Immunoaffinity Concentration of Microcystins from Water". Applied and Environmental Microbiology 68, n. 11 (novembre 2002): 5288–95. http://dx.doi.org/10.1128/aem.68.11.5288-5295.2002.
Testo completoAbstract (sommario):
ABSTRACT A naïve (unimmunized) human semisynthetic phage display library was employed to isolate recombinant antibody fragments against the cyanobacterial hepatotoxin microcystin-LR. Selected antibody scFv genes were cloned into a soluble expression vector and expressed in Escherichia coli for characterization against purified microcystin-LR by competition enzyme-linked immunosorbent assay (ELISA). The most sensitive single-chain antibody (scAb) isolated was capable of detecting microcystin-LR at levels below the World Health Organization limit in drinking water (1 μg liter−1) and cross-reacted with three other purified microcystin variants (microcystin-RR, -LW, and -LF) and the related cyanotoxin nodularin. Extracts of the cyanobacterium Microcystis aeruginosa were assayed by ELISA, and quantifications of microcystins in toxic samples showed good correlation with analysis by high-performance liquid chromatography. Immobilized scAb was also used to prepare immunoaffinity columns, which were assessed for the ability to concentrate microcystin-LR from water for subsequent analysis by high-performance liquid chromatography. Anti-microcystin-LR scAb was immobilized on columns via a hexahistidine tag, ensuring maximum exposure of antigen binding sites, and the performance of the columns was evaluated by directly applying 150 ml of distilled water spiked with 4 μg of purified microcystin-LR. The procedure was simple, and a recovery rate of 94% was achieved following elution in 1 ml of 100% methanol. Large-scale, low-cost production of anti-microcystin-LR scAb in E. coli is an exciting prospect for the development of biosensors and on-line monitoring systems for microcystins and will also facilitate a range of immunoaffinity applications for the cleanup and concentration of these toxins from environmental samples.
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Hu, Chenlin, Yanxia Zuo, Liang Peng, Nanqin Gan e Lirong Song. "Widespread Distribution and Adaptive Degradation of Microcystin Degrader (mlr-Genotype) in Lake Taihu, China". Toxins 13, n. 12 (3 dicembre 2021): 864. http://dx.doi.org/10.3390/toxins13120864.
Testo completoAbstract (sommario):
Microbial degradation is an important route for removing environmental microcystins (MCs). Here, we investigated the ecological distribution of microcystin degraders (mlr-genotype), and the relationship between the substrate specificity of the microcystin degrader and the profile of microcystin congener production in the habitat. We showed that microcystin degraders were widely distributed and closely associated with Microcystis abundance in Lake Taihu, China. We characterized an indigenous degrader, Sphingopyxis N5 in the northern Lake Taihu, and it metabolized six microcystin congeners in increasing order (RR > LR > YR > LA > LF and LW). Such a substrate-specificity pattern was congruent to the order of the dominance levels of these congeners in northern Lake Taihu. Furthermore, a meta-analysis on global microcystin degraders revealed that the substrate-specificity patterns varied geographically, but generally matched the profiles of microcystin congener production in the degrader habitats, and the indigenous degrader typically metabolized well the dominant MC congeners, but not the rare congeners in the habitat. This highlighted the phenotypic congruence between microcystin production and degradation in natural environments. We theorize that such congruence resulted from the metabolic adaptation of the indigenous degrader to the local microcystin congeners. Under the nutrient microcystin selection, the degraders might have evolved to better exploit the locally dominant congeners. This study provided the novel insight into the ecological distribution and adaptive degradation of microcystin degraders.
20
Koreivienė, Judita, Olga Belous e Jūratė Kasperovičienė. "Variations of microcystins in freshwater ecosystems". Botanica Lithuanica 19, n. 2 (1 dicembre 2013): 139–48. http://dx.doi.org/10.2478/botlit-2013-0017.
Testo completoAbstract (sommario):
Abstract Koreivienė J., Belous O., Kasperovičienė J., 2012: Variations of microcystins in freshwater ecosystems [Mikrocystinai gėlavandenėse ekosistemose]. - Bot. Lith., 19(2): 139-148 Increased frequency, severity of harmful algae blooms and their extent worldwide have become a global challenge due to the production of toxins that are released to the water. Cyanotoxins are detected in 25-75% of blooms. Hazardous hepatotoxin-microcystin potential producers, spatial and temporal variations of toxins as well as their variations depending on environmental variables are discussed in this overview. The most common species among microcystin producers belong to the genera Dolichospermum and Microcystis. Variations of the amount of microcystins detected through the bloom are associated with the dominant cyanobacteria species or its genotype. The abundance of toxic cyanobacteria genotype and cyanotoxin values increase with the rise of water temperature and nutrient concentrations in the freshwaters. On the seasonal basis, cell-bound microcystin concentrations increase with bloom development, whereas extracellular cyanotoxin values rise with the senescing of bloom after cyanobacterial cell lysis.
21
Puddick, Jonathan, Eric O. Goodwin, Ian Hawes, David P. Hamilton e Susanna A. Wood. "In Situ Collection and Preservation of Intact Microcystis Colonies to Assess Population Diversity and Microcystin Quotas". Toxins 11, n. 8 (24 luglio 2019): 435. http://dx.doi.org/10.3390/toxins11080435.
Testo completoAbstract (sommario):
Understanding of colony specific properties of cyanobacteria in the natural environment has been challenging because sampling methods disaggregate colonies and there are often delays before they can be isolated and preserved. Microcystis is a ubiquitous cyanobacteria that forms large colonies in situ and often produces microcystins, a potent hepatotoxin. In the present study a new cryo-sampling technique was used to collect intact Microcystis colonies in situ by embedding them in a sheet of ice. Thirty-two of these Microcystis colonies were investigated with image analysis, liquid chromatography-mass spectrometry, quantitative polymerase chain reaction and high-throughput sequencing to assess their volume, microcystin quota and internal transcribed spacer (ITS) genotype diversity. Microcystin quotas were positively correlated to colony volume (R2 = 0.32; p = 0.004). Individual colonies had low Microcystis ITS genotype diversity and one ITS operational taxonomic unit predominated in all samples. This study demonstrates the utility of the cryo-sampling method to enhance the understanding of colony-specific properties of cyanobacteria with higher precision than previously possible.
22
Pilkaitytė, Renata, Donata Overlingė, Zita Rasuolė Gasiūnaitė e Hanna Mazur-Marzec. "Spatial and Temporal Diversity of Cyanometabolites in the Eutrophic Curonian Lagoon (SE Baltic Sea)". Water 13, n. 13 (25 giugno 2021): 1760. http://dx.doi.org/10.3390/w13131760.
Testo completoAbstract (sommario):
This work aims to determine the profiles of cyanopeptides and anatoxin synthetized by cyanobacteria in the Lithuanian part of the Curonian Lagoon (SE Baltic Sea) and to characterize their spatial and temporal patterns in this ecosystem. Cyanometabolites were analysed by a LC-MS/MS system and were coupled to a hybrid triple quadrupole/linear ion trap mass spectrometer. During the investigation period (2013–2017), 10 microcystins, nodularin, anatoxin-a, 16 anabaenopeptins, including 1 oscillamide, 12 aeruginosins, 1 aeruginosamide, 3 cyanopeptolins and 4 microginins were detected. The most frequently detected metabolites were found at all investigated sites. Demethylated microcystin variants and anabaenopeptins had the strongest relationship with Planktothrix agardhii, while non-demethylated microcystin variants and anatoxin had the strongest relationship with Microcystis spp. Low concentrations of some microcystins: [Asp3]MC-RR, MC-RR, MC-LR, as well as a few other cyanopeptides: AP-A and AEG-A were found during the cold period (December–March). Over the study period, Aphanizomenon, Planktothrix and Microcystis were the main dominant cyanobacteria species, while Planktothrix, Microcystis, and Dolichospermum were potentially producers of cyanopeptides and anatoxin detected in samples from the Curonian Lagoon.
23
Knoll, Lesley B., Orlando Sarnelle, Stephen K. Hamilton, Carrie E. H. Kissman, Alan E. Wilson, Joan B. Rose e Mechelle R. Morgan. "Invasive zebra mussels (Dreissena polymorpha) increase cyanobacterial toxin concentrations in low-nutrient lakes". Canadian Journal of Fisheries and Aquatic Sciences 65, n. 3 (1 marzo 2008): 448–55. http://dx.doi.org/10.1139/f07-181.
Testo completoAbstract (sommario):
We investigated whether concentrations of the cyanobacterial toxin microcystin were positively associated with Dreissena polymorpha invasion by conducting surveys of 39 inland lakes in southern Michigan with low to moderate total phosphorus concentrations (≤20 µg·L–1). Lakes with D. polymorpha had 3.3 times higher microcystin concentrations and 3.6 times higher biomass of Microcystis aeruginosa (a major producer of microcystin) than comparable lakes without D. polymorpha. In contrast, the biomass of Anabaena spp. (another potential producer of microcystin) was 4.6 times higher in lakes without D. polymorpha. We also conducted a large-scale enclosure manipulation of D. polymorpha density in Gull Lake, a low-nutrient lake containing D. polymorpha. The experiment revealed a positive effect of D. polymorpha on microcystin concentrations and M. aeruginosa biomass. The congruence between survey and experimental results provides strong evidence that D. polymorpha invasion causes an increase in toxin concentrations in lakes with low to moderate nutrients. An increase in M. aeruginosa biomass may negatively impact food webs and public health because microcystins are known to be toxic to aquatic and terrestrial organisms.
24
Sevilla, E., H. Smienk, P. Razquin, L. Mata e M. L. Peleato. "Optimization of intracellular microcystin-LR extraction for its analysis by protein phosphatase inhibition assay". Water Science and Technology 60, n. 7 (1 ottobre 2009): 1903–9. http://dx.doi.org/10.2166/wst.2009.527.
Testo completoAbstract (sommario):
Microcystins are toxins produced by some strains of cyanobacteria. Several methods have been developed to allow the quantification of microcystins, which are mainly endotoxins. Among those methods, the protein phosphatase inhibition assay is a good candidate as a screening method because of its sensitivity, simplicity and specificity. In this work a method for intracellular microcystin extraction in field water samples and lab cyanobacterial cultures prior to their analysis by protein phosphatase inhibition assay has been optimized. Microcystin-LR and Microcystis aeruginosa PCC 7806 were used as reference microcystin and strain, respectively, in order to optimize the protocol. The protocol consists on filtering the sample through a nylon filter of 0.8 μm, filter extraction with methanol 80% 0.1% trifluoroacetic acid (TFA) 0.1% tween 20, extract centrifugation and supernatant dilution (1/20). The establishment of an extraction protocol was carried out determining the extraction volume, time of extraction and number of extractions. The advantages of the method developed in this work are basically its simplicity and avoiding the use of specific and expensive equipment.
25
SIELAFF, Heike, Elke DITTMANN, Nicole TANDEAU de MARSAC, Christiane BOUCHIER, Hans von DÖHREN, Thomas BÖRNER e Torsten SCHWECKE. "The mcyF gene of the microcystin biosynthetic gene cluster from Microcystis aeruginosa encodes an aspartate racemase". Biochemical Journal 373, n. 3 (1 agosto 2003): 909–16. http://dx.doi.org/10.1042/bj20030396.
Testo completoAbstract (sommario):
Microcystins are hepatotoxic, non-ribosomal peptides produced by several genera of freshwater cyanobacteria. Among other enzymic activities, in particular those of peptide synthetases and polyketide synthases, microcystin biosynthesis requires racemases that provide d-aspartate and d-glutamate. Here, we report on the cloning, expression and characterization of an open reading frame, mcyF, that is part of the mcy gene cluster involved in microcystin biosynthesis in the Microcystis aeruginosa strain PCC 7806. Conserved amino acid sequence motifs suggest a function of the McyF protein as an aspartate racemase. Heterologous expression of mcyF in the unicellular cyanobacterium Synechocystis PCC 6803 yielded an active His6-tagged protein that was purified to homogeneity by Ni2+-nitriloacetate affinity chromatography. The purified recombinant protein racemized in a pyridoxal-5′-phosphate-independent manner l-aspartate, but not l-glutamate. Furthermore, we have identified a putative glutamate racemase gene that is located outside the mcy gene cluster in the M. aeruginosa PCC 7806 genome. Whereas homologues of this glutamate racemase gene are present in all the Microcystis strains examined, mcyF could only be detected in microcystin-producing strains.
26
Czyżewska, Wanda, Marlena Piontek e Katarzyna Łuszczyńska. "The Occurrence of Potential Harmful Cyanobacteria and Cyanotoxins in the Obrzyca River (Poland), a Source of Drinking Water". Toxins 12, n. 5 (28 aprile 2020): 284. http://dx.doi.org/10.3390/toxins12050284.
Testo completoAbstract (sommario):
Harmful cyanobacteria and their cyanotoxins may contaminate drinking water resources and their effective control remains challenging. The present study reports on cyanobacterial blooms and associated cyanotoxins in the Obrzyca River, a source of drinking water in Poland. The river was examined from July to October 2019 and concentrations of microcystins, anatoxin-a, and cylindrospermopsin were monitored. The toxicity of water samples was also tested using an ecotoxicological assay. All studied cyanotoxins were detected with microcystins revealing the highest levels. Maximal microcystin concentrations (3.97 μg/L) were determined in September at Uście point, exceeding the provisional guideline. Extracts from Uście point, where the dominant species were Dolichospermum flos-aquae (August), Microcystis aeruginosa (September), and Planktothrix agardhii (October), were toxic for Dugesia tigrina Girard. Microcystin concentrations (MC-LR and MC-RR) were positively correlated with cyanobacteria biovolume. Analysis of the chemical indicators of water quality has shown relationships between them and microcystins as well as cyanobacteria abundance.
27
D'ors, A., M. C. Bartolomé e S. Sánchez-Fortún. "Importance of strain type to predict the toxicological risk associated with Microcystis aeruginosa blooms: comparison of Microtox® analysis and immunoassay". Journal of Water and Health 10, n. 2 (23 marzo 2012): 256–61. http://dx.doi.org/10.2166/wh.2012.081.
Testo completoAbstract (sommario):
The occurrence of toxic cyanobacterial blooms in aquatic environments, associated with human health problems and animal deaths, has increased the need for rapid, reliable and sensitive methods to determine the toxicity of microcystin produced by cyanobacteria. An in vitro Microtox® system and a commercially available microcystin ELISA were used to screen out the potential risk associated with selected Microcystis aeruginosa strains (Ma1D–Ma8D). Results showed the existence of three differentiated groups in the selected M. aeruginosa strains. Strains Ma7D and Ma6D were determined to be very toxic, strains Ma2D, Ma1D and Ma5D as moderately toxic and strains Ma8D, Ma4D and MA3D as non-toxic. These results agreed with the microcystin concentration values obtained by immunoassay. Although the data obtained by other authors clearly show that Microtox® is not sensitive to microcystins, our results suggested that this bioluminescence assay may prove useful in the preliminary screening of cyanobacterial blooms for microcystin-based toxicity. Additionally, the combination of immunodetection and toxicity-based Microtox® provides a useful addition to the methods already available for detection of cyanobacterial toxins.
28
Aragão, Marianna Correia, Kelly Cristina dos Reis, Allan Clemente Souza, Maria Aparecida Melo Rocha e Jose Capelo Neto. "Modeling total microcystin production by Microcystis aeruginosa using multiple regression". Journal of Water Supply: Research and Technology-Aqua 69, n. 5 (9 aprile 2020): 415–26. http://dx.doi.org/10.2166/aqua.2020.128.
Testo completoAbstract (sommario):
Abstract Microcystis sp. is one of the most studied genus of cyanobacteria worldwide. Once it has been identified in raw water, frequent analyses of cell density and toxic metabolites (microcystins) are recommended at the water treatment plants. However, both analytical procedures are highly time-consuming and labor-intensive, allowing the potentially contaminated finished water to reach customers. The identification of easily measurable parameters related to toxin production, preferably by on-line equipment, would mitigate this issue and help water companies to improve water safety and decrease operating costs. However, these devices still have precision limitations and need efficient mathematical models for converting light signals into cyanobacteria densities or cyanotoxin concentrations. In this scenario, this research aimed to develop a mathematical correlation between microcystin production and cell age and density, chlorophyll-a, pheophytin and phycocyanin in a Microcystis aeruginosa culture using a multiple linear regression model. Despite the significant correlation (p < 0.05) found between all the variables and total microcystin, a simplified and precise model (Adjusted R2 = 0.824) involving only phycocyanin and pheophytin concentrations was developed in order to provide an initial attempt to easily and cheaply predict microcystin concentration in raw water.
29
Saitou, T., N. Sugiura, T. Itayama, Y. Inamori e M. Matsumura. "Degradation of microcystin by biofilm in practical treatment facility". Water Science and Technology 46, n. 11-12 (1 dicembre 2002): 237–44. http://dx.doi.org/10.2166/wst.2002.0744.
Testo completoAbstract (sommario):
Potential for degradation of microcystin by biofilm was examined by some batch experiments using biofilm scraped from practical biological treatment facility combined with conventional treatment processes. The viable cells of Microcystis viridis, which produced microcystin LR, RR and YR were degraded at 6 to 10 days by the addition of biofilm. Biofilm collected in summer season had especially higher potential for degradation of Microcystis with complete degradation at 6 days. In all seasons, Monas spp. grew remarkably, accompanied with the higher decrease of the viable cells of Microcystis and the micro-animals were considered as a main predator for Microcystis cells. Intracellular microcystin LR, RR, YR were degraded simultaneously with high reduction of Microcystis cells. Dissolved microcystin LR of 1,000 μg l−1 was effectively degraded by indigenous aquatic bacteria on biofilm during 5 days, the degradability became higher with the increase in the concentration of microcystin LR. From the results of our research, it was clarified that the aggregated microorganisms consisting of biofilm had high potential for degradation of intracellular and dissolved microcystin.
30
Botha, C. J., P. N. Laver, A. Singo, E. A. Venter, G. C. H. Ferreira, M. Rösemann e J. G. Myburgh. "Evaluation of a Norwegian-developed ELISA to determine microcystin concentrations in fresh water". Water Supply 19, n. 3 (27 giugno 2018): 743–52. http://dx.doi.org/10.2166/ws.2018.118.
Testo completoAbstract (sommario):
Abstract Cyanobacteria are known for their extensive and highly visible blooms in rivers or dams in Africa. One of the most important cyanobacteria is Microcystis aeruginosa which can synthesise various microcystins that may affect the health of humans and animals. Accurate and efficient detection of microcystins in water is thus important for public and veterinary health. Two enzyme-linked immunosorbent assays (ELISA), a commercially-available ELISA kit (Abraxis) and a newly-developed Norwegian ELISA (putatively cheaper and more robust) were used to detect microcystins in fresh water in South Africa. Water samples were collected monthly at two sites, the Hartbeespoort Dam and a crocodile breeding dam. Extremely high microcystin concentrations (exceeding 360 μg L−1) were detected in the Hartbeespoort Dam during January 2015, whereas the microcystin concentrations in the crocodile breeding dam peaked during March–April 2015. Both ELISAs were positively correlated when analysing water samples ‘as is’ and following resin adsorption and methanol extraction. However, following resin adsorption and methanol extraction of the water samples, the correlation between the two assays was much stronger. These results suggests that the two ELISAs provide comparable results. If the Norwegian-developed ELISA can be packaged and made available as a user-friendly kit, it could be used successfully in surveillance programmes to monitor microcystin concentrations in fresh water bodies in Africa.
31
Paes, T. A. S. V., I. A. S. Costa, A. P. C. Silva e E. M. Eskinazi-Sant’Anna. "Can microcystins affect zooplankton structure community in tropical eutrophic reservoirs?" Brazilian Journal of Biology 76, n. 2 (8 marzo 2016): 450–60. http://dx.doi.org/10.1590/1519-6984.21014.
Testo completoAbstract (sommario):
Abstract The aim of our study was to assess whether cyanotoxins (microcystins) can affect the composition of the zooplankton community, leading to domination of microzooplankton forms (protozoans and rotifers). Temporal variations in concentrations of microcystins and zooplankton biomass were analyzed in three eutrophic reservoirs in the semi-arid northeast region of Brazil. The concentration of microcystins in water proved to be correlated with the cyanobacterial biovolume, indicating the contributions from colonial forms such as Microcystis in the production of cyanotoxins. At the community level, the total biomass of zooplankton was not correlated with the concentration of microcystin (r2 = 0.00; P > 0.001), but in a population-level analysis, the biomass of rotifers and cladocerans showed a weak positive correlation. Cyclopoid copepods, which are considered to be relatively inefficient in ingesting cyanobacteria, were negatively correlated (r2 = – 0.01; P > 0.01) with the concentration of cyanotoxins. Surprisingly, the biomass of calanoid copepods was positively correlated with the microcystin concentration (r2 = 0.44; P > 0.001). The results indicate that allelopathic control mechanisms (negative effects of microcystin on zooplankton biomass) do not seem to substantially affect the composition of mesozooplankton, which showed a constant and high biomass compared to the microzooplankton (rotifers). These results may be important to better understand the trophic interactions between zooplankton and cyanobacteria and the potential effects of allelopathic compounds on zooplankton.
32
Chia, Mathias Ahii, Ilu Ameh, Korie Chibuike George, Emmanuel Oluwadare Balogun, Suwebat Ayanronke Akinyemi e Adriana Sturion Lorenzi. "Genetic Diversity of Microcystin Producers (Cyanobacteria) and Microcystin Congeners in Aquatic Resources across Africa: A Review Paper". Toxics 10, n. 12 (10 dicembre 2022): 772. http://dx.doi.org/10.3390/toxics10120772.
Testo completoAbstract (sommario):
Microcystins are produced by multifaceted organisms called cyanobacteria, which are integral to Africa’s freshwater environments. The excessive proliferation of cyanobacteria caused by rising temperature and eutrophication leads to the production and release of copious amounts of microcystins, requiring critical management and control approaches to prevent the adverse environmental and public health problems associated with these bioactive metabolites. Despite hypotheses reported to explain the phylogeography and mechanisms responsible for cyanobacterial blooms in aquatic water bodies, many aspects are scarcely understood in Africa due to the paucity of investigations and lack of uniformity of experimental methods. Due to a lack of information and large-scale studies, cyanobacteria occurrence and genetic diversity are seldom reported in African aquatic ecosystems. This review covers the diversity and geographical distribution of potential microcystin-producing and non-microcystin-producing cyanobacterial taxa in Africa. Molecular analyses using housekeeping genes (e.g., 16S rRNA, ITS, rpoC1, etc.) revealed significant sequence divergence across several cyanobacterial strains from East, North, West, and South Africa, but the lack of uniformity in molecular markers employed made continent-wise phylogenetic comparisons impossible. Planktothrix agardhii, Microcystis aeruginosa, and Cylindrospermopsis raciborskii (presently known as Raphidiopsis raciborskii) were the most commonly reported genera. Potential microcystin (MCs)-producing cyanobacteria were detected using mcy genes, and several microcystin congeners were recorded. Studying cyanobacteria species from the African continent is urgent to effectively safeguard public and environmental health because more than 80% of the continent has no data on these important microorganisms and their bioactive secondary metabolites.
33
Yuan, Jian, Hyun-Joong Kim, Christopher T. Filstrup, Baoqing Guo, Paula Imerman, Steve Ensley e Kyoung-Jin Yoon. "Utility of a PCR-based method for rapid and specific detection of toxigenic Microcystis spp. in farm ponds". Journal of Veterinary Diagnostic Investigation 32, n. 3 (20 aprile 2020): 369–81. http://dx.doi.org/10.1177/1040638720916156.
Testo completoAbstract (sommario):
Microcystis is a widespread freshwater cyanobacterium that can produce microcystin, a potent hepatotoxin harmful to animals and humans. Therefore, it is crucial to monitor for the presence of toxigenic Microcystis spp. to provide early warning of potential microcystin contamination. Microscopy, which has been used traditionally to identify Microcystis spp., cannot differentiate toxigenic from non-toxigenic Microcystis. We developed a PCR-based method to detect toxigenic Microcystis spp. based on detection of the microcystin synthetase C ( mcyC) gene and 16S rRNA gene. Specificity was validated against toxic and nontoxic M. aeruginosa strains, as well as 4 intergeneric freshwater cyanobacterial strains. Analytical sensitivity was as low as 747 fg/µL genomic DNA (or 3 cells/µL) for toxic M. aeruginosa. Furthermore, we tested 60 water samples from 4 farm ponds providing drinking water to swine facilities in the midwestern United States using this method. Although all water samples were positive for Microcystis spp. (i.e., 16S rRNA gene), toxigenic Microcystis spp. were detected in only 34 samples (57%). Seventeen water samples contained microcystin (0.1–9.1 μg/L) determined with liquid chromatography–mass spectrometry, of which 14 samples (82%) were positive for mcyC. A significant correlation was found between the presence of toxigenic Microcystis spp. and microcystin in water samples ( p = 0.0004). Our PCR method can be a low-cost molecular tool for rapid and specific identification of toxigenic Microcystis spp. in farm ponds, improving detection of microcystin contamination, and ensuring water safety for farm animals.
34
Oksanen, Ilona, Jouni Jokela, David P. Fewer, Matti Wahlsten, Jouko Rikkinen e Kaarina Sivonen. "Discovery of Rare and Highly Toxic Microcystins from Lichen-Associated Cyanobacterium Nostoc sp. Strain IO-102-I". Applied and Environmental Microbiology 70, n. 10 (ottobre 2004): 5756–63. http://dx.doi.org/10.1128/aem.70.10.5756-5763.2004.
Testo completoAbstract (sommario):
ABSTRACT The production of hepatotoxic cyclic heptapeptides, microcystins, is almost exclusively reported from planktonic cyanobacteria. Here we show that a terrestrial cyanobacterium Nostoc sp. strain IO-102-I isolated from a lichen association produces six different microcystins. Microcystins were identified with liquid chromatography-UV mass spectrometry by their retention times, UV spectra, mass fragmentation, and comparison to microcystins from the aquatic Nostoc sp. strain 152. The dominant microcystin produced by Nostoc sp. strain IO-102-I was the highly toxic [ADMAdda5]microcystin-LR, which accounted for ca. 80% of the total microcystins. We assigned a structure of [DMAdda5]microcystin-LR and [d-Asp3,ADMAdda5]microcystin-LR and a partial structure of three new [ADMAdda5]-XR type of microcystin variants. Interestingly, Nostoc spp. strains IO-102-I and 152 synthesized only the rare ADMAdda and DMAdda subfamilies of microcystin variants. Phylogenetic analyses demonstrated congruence between genes involved directly in microcystin biosynthesis and the 16S rRNA and rpoC1 genes of Nostoc sp. strain IO-102-I. Nostoc sp. strain 152 and the Nostoc sp. strain IO-102-I are distantly related, revealing a sporadic distribution of toxin production in the genus Nostoc. Nostoc sp. strain IO-102-I is closely related to Nostoc punctiforme PCC 73102 and other symbiotic Nostoc strains and most likely belongs to this species. Together, this suggests that other terrestrial and aquatic strains of the genus Nostoc may have retained the genes necessary for microcystin biosynthesis.
35
Wood, Susanna A., Jonathan Puddick, Ian Hawes, Konstanze Steiner, Daniel R. Dietrich e David P. Hamilton. "Variability in microcystin quotas during a Microcystis bloom in a eutrophic lake". PLOS ONE 16, n. 7 (21 luglio 2021): e0254967. http://dx.doi.org/10.1371/journal.pone.0254967.
Testo completoAbstract (sommario):
Microcystis is a bloom-forming genus of cyanobacteria with some genotypes that produce highly toxic microcystin hepatotoxins. In waterbodies where biological and physical factors are relatively homogenous, toxin quotas (the average amount of toxin per cell), at a single point in time, are expected to be relatively constant. In this study we challenged this assumption by investigating the spatial distribution of microcystin quotas at a single point in time on two separate occasions in a lake with a major Microcystis bloom. Microcystis cell concentrations varied widely across the lake on both sampling occasions (730- and 137-fold) together with microcystin quotas (148- and 362-fold). Cell concentrations and microcystin quotas were strongly positively correlated (R2 = 0.89, P < 0.001, n = 28; R2 = 0.67, P < 0.001, n = 25). Analysis of Microcystis strains using high-throughput sequencing of the 16S-23S rRNA intergenic spacer region showed no relationship between microcystin quota and the relative abundance of specific sequences. Collectively, the results of this study indicate an association between microcystin production and cell density that magnifies the potential for bloom toxicity at elevated cell concentrations.
36
Janse, Ingmar, W. Edwin A. Kardinaal, Marion Meima, Jutta Fastner, Petra M. Visser e Gabriel Zwart. "Toxic and Nontoxic Microcystis Colonies in Natural Populations Can Be Differentiated on the Basis of rRNA Gene Internal Transcribed Spacer Diversity". Applied and Environmental Microbiology 70, n. 7 (luglio 2004): 3979–87. http://dx.doi.org/10.1128/aem.70.7.3979-3987.2004.
Testo completoAbstract (sommario):
ABSTRACT Assessing and predicting bloom dynamics and toxin production by Microcystis requires analysis of toxic and nontoxic Microcystis genotypes in natural communities. We show that genetic differentiation of Microcystis colonies based on rRNA internal transcribed spacer (ITS) sequences provides an adequate basis for recognition of microcystin producers. Consequently, ecological studies of toxic and nontoxic cyanobacteria are now possible through studies of rRNA ITS genotypic diversity in isolated cultures or colonies and in natural communities. A total of 107 Microcystis colonies were isolated from 15 lakes in Europe and Morocco, the presence of microcystins in each colony was examined by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and they were grouped by rRNA ITS denaturing gradient gel electrophoresis (DGGE) typing. Based on DGGE analysis of amplified ITSa and ITSc fragments, yielding supplementary resolution (I. Janse et al., Appl. Environ. Microbiol. 69:6634-6643, 2003), the colonies could be differentiated into 59 classes. Microcystin-producing and non-microcystin-producing colonies ended up in different classes. Sequences from the rRNA ITS of representative strains were congruent with the classification based on DGGE and confirmed the recognition of microcystin producers on the basis of rRNA ITS. The rRNA ITS sequences also confirmed inconsistencies reported for Microcystis identification based on morphology. There was no indication for geographical restriction of strains, since identical sequences originated from geographically distant lakes. About 28% of the analyzed colonies gave rise to multiple bands in DGGE profiles, indicating either aggregation of different colonies, or the occurrence of sequence differences between multiple operons. Cyanobacterial community profiles from two Dutch lakes from which colonies had been isolated showed different relative abundances of genotypes between bloom stages and between the water column and surface scum. Although not all bands in the community profiles could be matched with isolated colonies, the profiles suggest a dominance of nontoxic colonies, mainly later in the season and in scums.
37
Radkova, Mariana, Katerina Stefanova, Blagoy Uzunov, Georg Gärtner e Maya Stoyneva-Gärtner. "Morphological and Molecular Identification of Microcystin-Producing Cyanobacteria in Nine Shallow Bulgarian Water Bodies". Toxins 12, n. 1 (8 gennaio 2020): 39. http://dx.doi.org/10.3390/toxins12010039.
Testo completoAbstract (sommario):
The paper presents results from the first application of polyphasic approach in studies of field samples from Bulgaria. This approach, which combined the conventional light microscopy (LM) and molecular-genetic methods (based on PCR amplified fragments of microcystin synthetase gene mcyE), revealed that almost all microcystin-producers in the studied eutrophic waterbodies belong to the genus Microcystis. During the molecular identification of toxin-producing strains by use of HEPF × HEPR pair of primers, we obtained 57 sequences, 56 of which formed 28 strains of Microcystis, spread in six clusters of the phylogenetic tree. By LM, seven Microcystis morphospecies were identified (M. aeruginosa, M. botrys, M. flos-aquae, M. natans, M. novacekii, M. smithii, and M. wesenbergii). They showed significant morphological variability and contributed from <1% to 98% to the total biomass. All data support the earlier opinions that taxonomic revision of Microcystis is needed, proved the presence of toxigenic strains in M. aeruginosa and M. wesenbergii, and suppose their existence in M. natans. Our results demonstrated also that genetic sequencing, and the use of HEPF × HEPR pair in particular, can efficiently serve in water quality monitoring for identifying the potential risk from microcystins, even in cases of low amounts of Microcystis in the water.
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Arruda-Neto, Joao Dias Toledo, Erika Cavalcante-Silva, Henriette Righi, Odete Rocha, Maria do Carmo Bitten court-Oliveira e Micheline K. Cordeiro-Araújo. "Attenuation of Microcystins Using Electron Beams and Gamma Radiation: A Study with Environment-Bound Conditions". Journal of Experimental and Clinical Toxicology 1, n. 3 (11 ottobre 2021): 30–44. http://dx.doi.org/10.14302/issn.2641-7669.ject-21-3970.
Testo completoAbstract (sommario):
Microcystins (MCs) are toxins profusely synthesized by cyanobacteria, causing livestock poisonings and endangering human health. We design and execute an experiment to investigate the attenuation (degradation) of microcystins by exposing them to gamma radiation and electron beams at doses of 0 (control), 3, 5, 10 and 15 kGy. The experimental conditions simulate microcystin contamination of aquatic environments; we thus consider (1) microcystins inside whole cells and extracellular dissolved in water, simulated by non-sonicated and sonicated cells, respectively, and (2) two acute microcystin concentrations within water. Toxicity tests of Microcystis aeruginosa detected immobilization (i.e., paralysis) of Ceriodaphniasilvestrii exposed to aqueous crude extracts of irradiated and non-irradiated M. aeruginosa (NPLJ-4 strain) at concentrations of 45 and 90 mg.L-1 (mg dry weight of freeze-dried material), and the results were analyzed using the Trimmed Spearman-Karber statistical program to obtain 48-h EC50, the average effective concentration causing immobility in 50% of organisms after 48 hours. We conclude that electron beams are effective physical agents for toxin attenuation (degradation) and reach 100% effectiveness at 5 kGy and above; their efficiency is two orders of magnitude greater than that of gamma radiation. This new body of information contributes to (1) remediating environmental water sources; (2) designing water/wastewater treatment facilities; (3) combatting chronic microcystin environmental contamination; and (4) inspiring further studies to promote the use of biomonitors (e.g., Cladocerans) to detect and evaluate microalgae contamination.
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Liang, Shuang, Xing Li e Yan Ling Yang. "Effect and Mechanism of Microcystin Removal by Potassium Permanganate Loaded Zeolite". Advanced Materials Research 113-116 (giugno 2010): 521–24. http://dx.doi.org/10.4028/www.scientific.net/amr.113-116.521.
Testo completoAbstract (sommario):
A microcystin detection and Environmental Scanning Electron Microscope investigation were carried out to analyze the microcystin removal effect and the forms of Microcystis aeruginosa cells with different dosage of potassium permanganate loaded zeolite. The results showed that potassium permanganate loaded zeolite had significant microcystin-LR removal effect both in the Microcystis aeruginosa and Nostoc samples. The optimal dosage and the optimal removal rate were 96.0% at 220mg/L and 77% at 110mg/L separately. The cell wall of Microcystis aeruginosa was ruptured by dosing both potassium permanganate and potassium permanganate loaded zeolite, while algae cells were accumulated. Cell groups treated by potassium permanganate loaded zeolite appeared more compact to improve cells settling performance and wrapped exudates to avoid microcystin excessing into water. There were abundant adsorption sites to adsorb intracellular and extracellular microcystin after potassium permanganate released from zeolite.
40
Guljamow, Arthur, Tino Barchewitz, Rebecca Große, Stefan Timm, Martin Hagemann e Elke Dittmann. "Diel Variations of Extracellular Microcystin Influence the Subcellular Dynamics of RubisCO in Microcystis aeruginosa PCC 7806". Microorganisms 9, n. 6 (10 giugno 2021): 1265. http://dx.doi.org/10.3390/microorganisms9061265.
Testo completoAbstract (sommario):
The ubiquitous freshwater cyanobacterium Microcystis is remarkably successful, showing a high tolerance against fluctuations in environmental conditions. It frequently forms dense blooms which can accumulate significant amounts of the hepatotoxin microcystin, which plays an extracellular role as an infochemical but also acts intracellularly by interacting with proteins of the carbon metabolism, notably with the CO2 fixing enzyme RubisCO. Here we demonstrate a direct link between external microcystin and its intracellular targets. Monitoring liquid cultures of Microcystis in a diel experiment revealed fluctuations in the extracellular microcystin content that correlate with an increase in the binding of microcystin to intracellular proteins. Concomitantly, reversible relocation of RubisCO from the cytoplasm to the cell’s periphery was observed. These variations in RubisCO localization were especially pronounced with cultures grown at higher cell densities. We replicated these effects by adding microcystin externally to cultures grown under continuous light. Thus, we propose that microcystin may be part of a fast response to conditions of high light and low carbon that contribute to the metabolic flexibility and the success of Microcystis in the field.
41
Luu, Pham Thanh, e Ngo Xuan Quang. "DETECTION OF POTENTIALLY TOXIGENIC MICROCYSTIS STRAINS FROM DAU TIENG RESERVOIR". Vietnam Journal of Biotechnology 15, n. 4 (14 dicembre 2018): 745–52. http://dx.doi.org/10.15625/1811-4989/15/4/13418.
Testo completoAbstract (sommario):
Microcystis is a bloom-forming, common cyanobacterium in Dau Tieng reservoir used for public water supply. To assess the presence of potentially microcystin-producing Microcystis, molecular techniques were conducted and acute toxicity bioassays were performed with the microcrustacean Daphnia magna exposed to cyanobacterial crude extracts. Potentially toxigenic of isolated strains was characterized by amplifying mcyD genes and identification of Microcystis was confirmed by 16S rRNA amplification. Microcystins (MCs) concentration in bloom samples and cultured strains were quantified by High Performance Liquid Chromatography (HPLC). Results showed that there were 9/15 strains showed positive with the mcyD marker indicating that they are toxic strains. Three MCs variants including MC-RR, -LR and -YR were found in all extracts of toxic strains with the highest concentration of 1,218 μg/g dry weight (DW). The acute toxicity bioassays revealed that both toxic and non-toxic crude extracts elicited significant lethal effects on the tested animal with LC50 values ranged from 189-411 mg DW/L. The toxic effects of isolated strains were independent from the MCs concentration in some strains suggesting the presence of other metabolites contributed to the biological effects. In conclusion, microcystin-producing Microcystis from the Dau Tieng reservoir warn about possible toxic effects for aquatic biota and human health.
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Gandhi, Vikram Pal, e Anil Kumar. "Isolation and Characterization of Microcystin Degrading Bacteria from Holy Ponds in India". International Journal of Applied Sciences and Biotechnology 4, n. 4 (6 gennaio 2017): 436–47. http://dx.doi.org/10.3126/ijasbt.v4i4.16249.
Testo completoAbstract (sommario):
Microcystins (MCs) are toxic cyclic heptapeptides produced by few toxic cyanobacteria and generally form blooms in eutrophic surface fresh water bodies. They cause acute to chronic poisoning and other health related problems mainly by irreversible inhibition of protein phosphatases (PP1 and PP2A) and increased formation of reactive oxygen species (ROS). Due to limitation of non-biological methods of water treatments the exploration of MCs degrading bacteria is emerging at a quite pace to address, through bioremediation, the problems posed by MCs in water and water-bodies. Report and study of MCs biodegrading bacteria from India were lacking. However it was evident, from our previous study, that microcystin degradation can be achieved by indigenous microcystin degrading bacterial population in its natural place where microcystin producing blooms occur. This study has presented isolation and characterization of indigenous microcystin degrading bacteria from holy ponds in Utter Pradesh of India. Overall 20 bacterial isolates were isolated from Microcystis infested different ponds. Out of these 13 isolates were mlrA positive by PCR and were found to be distinct isolates by amplified ribosomal DNA restriction analysis (ARDRA). However, ARDRA analysis revealed overall four bacterial groups. On the basis of 16S-rRNA gene sequence the Gram-positive-rod isolate PM1 was identified, with 99% identity, as Bacillus licheniformis which was shown earlier to cluster with microcystin degrading bacterium B. subtilis. Thus the present study revealed, for the first time, probable microcystin degrading bacteria in water-bodies from India. The potential and the metabolic pathway of PM1 and other mlrA positive isolates need to be further studied and validated to confirm their application in microcystin bioremediation. Int J Appl Sci Biotechnol, Vol 4(4): 436-447
43
Fastner, Jutta, Marcel Erhard e Hans von Döhren. "Determination of Oligopeptide Diversity within a Natural Population of Microcystis spp. (Cyanobacteria) by Typing Single Colonies by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry". Applied and Environmental Microbiology 67, n. 11 (1 novembre 2001): 5069–76. http://dx.doi.org/10.1128/aem.67.11.5069-5076.2001.
Testo completoAbstract (sommario):
ABSTRACT Besides the most prominent peptide toxin, microcystin, the cyanobacteria Microcystis spp. have been shown to produce a large variety of other bioactive oligopeptides. We investigated for the first time the oligopeptide diversity within a naturalMicrocystis population by analyzing single colonies directly with matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS). The results demonstrate a high diversity of known cyanobacterial peptides such as microcystins, anabaenopeptins, microginins, aeruginosins, and cyanopeptolins, but also many unknown substances in the Microcystis colonies. Oligopeptide patterns were mostly related to specificMicrocystis taxa. Microcystis aeruginosa(Kütz.) Kütz. colonies contained mainly microcystins, occasionally accompanied by aeruginosins. In contrast, microcystins were not detected in Microcystis ichthyoblabeKütz.; instead, colonies of this species contained anabaenopeptins and/or microginins or unknown peptides. Within a third group, Microcystis wesenbergii (Kom.) Kom. in Kondr., chiefly a cyanopeptolin and an unknown peptide were found. Similar patterns, however, were also found in colonies which could not be identified to species level. The significance of oligopeptides as a chemotaxonomic tool within the genus Microcystis is discussed. It could be demonstrated that the typing of single colonies by MALDI-TOF MS may be a valuable tool for ecological studies of the genus Microcystis as well as in early warning of toxic cyanobacterial blooms.
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Arman, Tarana, e John D. Clarke. "Microcystin Toxicokinetics, Molecular Toxicology, and Pathophysiology in Preclinical Rodent Models and Humans". Toxins 13, n. 8 (29 luglio 2021): 537. http://dx.doi.org/10.3390/toxins13080537.
Testo completoAbstract (sommario):
Microcystins are ubiquitous toxins produced by photoautotrophic cyanobacteria. Human exposures to microcystins occur through the consumption of contaminated drinking water, fish and shellfish, vegetables, and algal dietary supplements and through recreational activities. Microcystin-leucine-arginine (MCLR) is the prototypical microcystin because it is reported to be the most common and toxic variant and is the only microcystin with an established tolerable daily intake of 0.04 µg/kg. Microcystin toxicokinetics is characterized by low intestinal absorption, rapid and specific distribution to the liver, moderate metabolism to glutathione and cysteinyl conjugates, and low urinary and fecal excretion. Molecular toxicology involves covalent binding to and inhibition of protein phosphatases, oxidative stress, cell death (autophagy, apoptosis, necrosis), and cytoskeleton disruption. These molecular and cellular effects are interconnected and are commonly observed together. The main target organs for microcystin toxicity are the intestine, liver, and kidney. Preclinical data indicate microcystins may also have nervous, pulmonary, cardiac, and reproductive system toxicities. Recent evidence suggests that exposure to other hepatotoxic insults could potentiate microcystin toxicity and increase the risk for chronic diseases. This review summarizes the current knowledge for microcystin toxicokinetics, molecular toxicology, and pathophysiology in preclinical rodent models and humans. More research is needed to better understand human toxicokinetics and how multifactorial exposures contribute to disease pathogenesis and progression.
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Van Hassel, Wannes Hugo R., Mirjana Andjelkovic, Benoit Durieu, Viviana Almanza Marroquin, Julien Masquelier, Bart Huybrechts e Annick Wilmotte. "A Summer of Cyanobacterial Blooms in Belgian Waterbodies: Microcystin Quantification and Molecular Characterizations". Toxins 14, n. 1 (16 gennaio 2022): 61. http://dx.doi.org/10.3390/toxins14010061.
Testo completoAbstract (sommario):
In the context of increasing occurrences of toxic cyanobacterial blooms worldwide, their monitoring in Belgium is currently performed by regional environmental agencies (in two of three regions) using different protocols and is restricted to some selected recreational ponds and lakes. Therefore, a global assessment based on the comparison of existing datasets is not possible. For this study, 79 water samples from a monitoring of five lakes in Wallonia and occasional blooms in Flanders and Brussels, including a canal, were analyzed. A Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) method allowed to detect and quantify eight microcystin congeners. The mcyE gene was detected using PCR, while dominant cyanobacterial species were identified using 16S RNA amplification and direct sequencing. The cyanobacterial diversity for two water samples was characterized with amplicon sequencing. Microcystins were detected above limit of quantification (LOQ) in 68 water samples, and the World Health Organization (WHO) recommended guideline value for microcystins in recreational water (24 µg L−1) was surpassed in 18 samples. The microcystin concentrations ranged from 0.11 µg L−1 to 2798.81 µg L−1 total microcystin. For 45 samples, the dominance of the genera Microcystis sp., Dolichospermum sp., Aphanizomenon sp., Cyanobium/Synechococcus sp., Planktothrix sp., Romeria sp., Cyanodictyon sp., and Phormidium sp. was shown. Moreover, the mcyE gene was detected in 75.71% of all the water samples.
46
Zhu, Jing Ping, Shi Du e Xian Li. "Detection of microcystin-producingMicrocystisin Guanqiao Lake using a sandwich hybridization assay". Canadian Journal of Microbiology 58, n. 4 (aprile 2012): 442–47. http://dx.doi.org/10.1139/w2012-008.
Testo completoAbstract (sommario):
Based on sequence analyses of the mcyJ gene from Microcystis strains, a probe pair TJF and TJR was designed and a sandwich hybridization assay (SHA) was established to quantitatively detect microcystin-producing Microcystis. Through BLAST and cyanobacterial culture tests, TJF and TJR were demonstrated to be specific for microcystin-producing Microcystis. A calibration curve for the SHA was established, and the lowest detected concentration was 100 cells·mL–1. Laboratory cultures and field samples from Guanqiao Lake were analyzed with both the SHA and microscopy. The cell number of microcystin-producing Microcystis and that of total Microcystis were compared. The biotic and abiotic components of the samples were of little disturbance to the SHA. In this study, a SHA was established to detect Microcystis, providing an alternative to PCR–ELISA and real-time PCR technology.
47
Cunningham, Brady R., Rebekah E. Wharton, Christine Lee, Mike A. Mojica, Logan C. Krajewski, Shirley C. Gordon, Adam M. Schaefer, Rudolph C. Johnson e Elizabeth I. Hamelin. "Measurement of Microcystin Activity in Human Plasma Using Immunocapture and Protein Phosphatase Inhibition Assay". Toxins 14, n. 11 (21 novembre 2022): 813. http://dx.doi.org/10.3390/toxins14110813.
Testo completoAbstract (sommario):
Microcystins are toxic chemicals generated by certain freshwater cyanobacteria. These chemicals can accumulate to dangerous levels during harmful algal blooms. When exposed to microcystins, humans are at risk of hepatic injury, including liver failure. Here, we describe a method to detect microcystins in human plasma by using immunocapture followed by a protein phosphatase inhibition assay. At least 279 microcystins have been identified, and most of these compounds share a common amino acid, the Adda side chain. We targeted this Adda side chain using a commercial antibody and extracted microcystins from human samples for screening and analysis. To quantitate the extracted microcystins, we fortified plasma with microcystin-LR, one of the most well-studied, commonly detected, and toxic microcystin congeners. The quantitation range for the detection of microcystin in human plasma using this method is 0.030–0.50 ng/mL microcystin-LR equivalents. This method detects unconjugated and conjugated forms (cysteine and glutathione) of microcystins. Quality control sample accuracies varied between 98.9% and 114%, with a precision of 7.18–15.8%. Finally, we evaluated plasma samples from a community health surveillance project of Florida residents living or working near harmful algae blooms.
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Christiansen, Guntram, Jutta Fastner, Marcel Erhard, Thomas Börner e Elke Dittmann. "Microcystin Biosynthesis in Planktothrix: Genes, Evolution, and Manipulation". Journal of Bacteriology 185, n. 2 (15 gennaio 2003): 564–72. http://dx.doi.org/10.1128/jb.185.2.564-572.2003.
Testo completoAbstract (sommario):
ABSTRACT Microcystins represent an extraordinarily large family of cyclic heptapeptide toxins that are nonribosomally synthesized by various cyanobacteria. Microcystins specifically inhibit the eukaryotic protein phosphatases 1 and 2A. Their outstanding variability makes them particularly useful for studies on the evolution of structure-function relationships in peptide synthetases and their genes. Analyses of microcystin synthetase genes provide valuable clues for the potential and limits of combinatorial biosynthesis. We have sequenced and analyzed 55.6 kb of the potential microcystin synthetase gene (mcy) cluster from the filamentous cyanobacterium Planktothrix agardhii CYA 126. The cluster contains genes for peptide synthetases (mcyABC), polyketide synthases (PKSs; mcyD), chimeric enzymes composed of peptide synthetase and PKS modules (mcyEG), a putative thioesterase (mcyT), a putative ABC transporter (mcyH), and a putative peptide-modifying enzyme (mcyJ). The gene content and arrangement and the sequence of specific domains in the gene products differ from those of the mcy cluster in Microcystis, a unicellular cyanobacterium. The data suggest an evolution of mcy clusters from, rather than to, genes for nodularin (a related pentapeptide) biosynthesis. Our data do not support the idea of horizontal gene transfer of complete mcy gene clusters between the genera. We have established a protocol for stable genetic transformation of Planktothrix, a genus that is characterized by multicellular filaments exhibiting continuous motility. Targeted mutation of mcyJ revealed its function as a gene coding for a O-methyltransferase. The mutant cells produce a novel microcystin variant exhibiting reduced inhibitory activity toward protein phosphatases.
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Kardinaal, W. Edwin A., Linda Tonk, Ingmar Janse, Suzanne Hol, Pieter Slot, Jef Huisman e Petra M. Visser. "Competition for Light between Toxic and Nontoxic Strains of the Harmful Cyanobacterium Microcystis". Applied and Environmental Microbiology 73, n. 9 (2 marzo 2007): 2939–46. http://dx.doi.org/10.1128/aem.02892-06.
Testo completoAbstract (sommario):
ABSTRACT The cyanobacterium Microcystis can produce microcystins, a family of toxins that are of major concern in water management. In several lakes, the average microcystin content per cell gradually declines from high levels at the onset of Microcystis blooms to low levels at the height of the bloom. Such seasonal dynamics might result from a succession of toxic to nontoxic strains. To investigate this hypothesis, we ran competition experiments with two toxic and two nontoxic Microcystis strains using light-limited chemostats. The population dynamics of these closely related strains were monitored by means of characteristic changes in light absorbance spectra and by PCR amplification of the rRNA internal transcribed spacer region in combination with denaturing gradient gel electrophoresis, which allowed identification and semiquantification of the competing strains. In all experiments, the toxic strains lost competition for light from nontoxic strains. As a consequence, the total microcystin concentrations in the competition experiments gradually declined. We did not find evidence for allelopathic interactions, as nontoxic strains became dominant even when toxic strains were given a major initial advantage. These findings show that, in our experiments, nontoxic strains of Microcystis were better competitors for light than toxic strains. The generality of this finding deserves further investigation with other Microcystis strains. The competitive replacement of toxic by nontoxic strains offers a plausible explanation for the gradual decrease in average toxicity per cell during the development of dense Microcystis blooms.
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Orihel, Diane M., David F. Bird, Michael Brylinsky, Huirong Chen, Derek B. Donald, Dorothy Y. Huang, Alessandra Giani et al. "High microcystin concentrations occur only at low nitrogen-to-phosphorus ratios in nutrient-rich Canadian lakes". Canadian Journal of Fisheries and Aquatic Sciences 69, n. 9 (settembre 2012): 1457–62. http://dx.doi.org/10.1139/f2012-088.
Testo completoAbstract (sommario):
Although the cyanobacterial toxin microcystin has been detected in Canadian fresh waters, little is known about its prevalence on a national scale. Here, we report for the first time on microcystin in 246 water bodies across Canada based on 3474 analyses. Over the last 10 years, microcystins were detected in every province, often exceeding maximum guidelines for potable and recreational water quality. Microcystins were virtually absent from unproductive systems and were increasingly common in nutrient-rich waters. The probable risk of microcystin concentrations exceeding water quality guidelines was greatest when the ratio of nitrogen (N) to phosphorus (P) was low and rapidly decreased at higher N:P ratios. Maximum concentrations of microcystins occurred in hypereutrophic lakes at mass ratios of N:P below 23. Our models may prove to be useful screening tools for identifying potentially toxic “hotspots” or “hot times” of unacceptable microcystin levels. A future scientific challenge will be to determine whether there is any causal link between N:P ratios and microcystin concentrations, as this may have important implications for the management of eutrophied lakes and reservoirs.