Cyanotoxins are chemical compounds produced by cyanobacterial mats grown in aquatic ecosystems. These may threaten human health and aquatic organisms. Extraction of these toxins is usually associated with many difficu...Cyanotoxins are chemical compounds produced by cyanobacterial mats grown in aquatic ecosystems. These may threaten human health and aquatic organisms. Extraction of these toxins is usually associated with many difficulties due to their concentration in aquatic ecosystems. This study is designed to provide suitable and effective extraction procedures that can effectively extract low concentration cyanotoxin from water and bacterial cells. The methodology is based on collecting raw material of cyanobacterial mats from naturally growing sites such as Wadi Gaza along with 16 liters of aquatic surrounding media. The materials were left in the Lab for 24 - 48 h for stabilization of the mats. The floating mats were collected using special funnel and allowed to air drying. The aqueous phase was extracted by liquid/liquid extraction using solvent mixture (hexane + ethylacetate 10% w:w), and by liquid solid extraction using several types of organoclays complexes. The solid phase was extracted by acetone and ultrasonic device. Results showed some difficulties were associated with liquid/liquid extraction whereas effective and easy extraction procedures were obtained by liquid solid extraction using either organoclay complex or activated charcoal. In contrast combination of both solid materials did not show improvement in the extracted cyanotoxin. Thus we recommend the use of organoclays or activated charcoal separately for extracting cyanotoxin. Further improvement of extraction can be tailored by using a specific organoclay complex that has some similarity in the chemical structure between the pre-adsorbed organic cation to the clay mineral and the chemical structure of cyanotoxin.展开更多
Harmful algal blooms(HABs)that are formed by cyanobacteria have become a serious issue worldwide in recent years.Cyanobacteria can release a type of secondary metabolites called cyanotoxins into aquatic systems which ...Harmful algal blooms(HABs)that are formed by cyanobacteria have become a serious issue worldwide in recent years.Cyanobacteria can release a type of secondary metabolites called cyanotoxins into aquatic systems which may indirectly or directly provide health risks to the environment and humans.Cyanotoxins provide some of the most powerful natural poisons including potent neurotoxins,hepatotoxins,cytotoxins,and endotoxins that may result in environmental health risks,and long-term morbidity and mortality to animals and humans.In this research,we used the chemcomputational tool Molinspiration for molecular property predictions,Pred-hERG 4.2 web software for cardiac toxicity prediction,and Pred-Skin 2.0 web software for predicting skin sensitization.We are predicting some toxicological aspects of cyanobacteria here using chemcomputational tools with the hypothesis that cyanotoxins are providing a risk to human health.We are using the tool Pred-hERG 4.2 to predict hERG channel blocking potential and the Pred-skin tool to predict skin sensitization due to cyanotoxins.The potential of anatoxin,ambigol,the microcystin group,and lyngbyatoxin A,lyngbyatoxin B,nodularin-R,and saxitoxin were predicted to cause skin sensitization in the final results(consensus model).Anatoxin-a and lyngbyatoxin were predicted to allow GI absorption and blood–brain barrier penetration.Among the 20 predicted cyanotoxins only aeruginosin 103-A,ambigol A,and ambigol were predicted by Pred-hERG 4.2 according to the applicability domain results as potential cardiotoxins with weak or moderate potency.Lyngbyatoxin shows activity through the GPCR ligand and protease,kinase,and enzyme inhibitor.展开更多
Cyanotoxins produced by cyanobacteria pose significant challenges to water resource management due to the potential impacts they have on human health. Cylindrospermopsin (CYN) and microcystins (MC) are the more common...Cyanotoxins produced by cyanobacteria pose significant challenges to water resource management due to the potential impacts they have on human health. Cylindrospermopsin (CYN) and microcystins (MC) are the more commonly detected cyanotoxins in Singapore’s reservoirs. Among the MC congeners monitored locally, the most frequently detected variants are MC-RR (37.6%), followed by MC-LR (25.6%). MC-LA and MC-YR are the least frequently detected variants (7.1%). No cyanotoxins have been detected in Singapore’s treated drinking water. Singapore’s National Water Agency (PUB) and the National Environment Agency (NEA) developed recreational water quality guidelines using Chl <em>a</em> concentrations of 50 μg/L. In local surface waters, long-term data showed that at 50 μg/L of Chl <em>a</em>, MC-LR concentrations ranged from <0.025 μg/L to 1 μg/L. In addition to using Chl <em>a</em> concentrations, <em>Microcystis</em> cell counts in reservoir water have also been used to manage cyanotoxin risk in drinking water. Specifically, routinely monitored data from all 17 Singapore reservoirs indicated that to keep MC-LR concentrations below the WHO provisional guideline of 1 μg/L in drinking water, <em>Microcystis</em> cell counts needed to be <10,000 cells/ml. Culture experiments using local <em>Microcystis</em> isolates showed M. <em>aeruginosa</em> produced the most MC compared to <em>M</em>. <em>ichthyoblabe</em>, <em>M.</em> <em>flos-aquae</em>, and <em>M</em>. <em>viridis</em>. Based on the maximum toxin cell quota equivalent to the WHO provisional guideline for MC-LR of 1 μg/L in drinking water, a 5000 cells/ml cell count guideline was derived for <em>M</em>. <em>aeruginosa</em>. This cell count has also been incorporated into Singapore’s cyanotoxin risk management framework for reservoirs.展开更多
In this study,the distribution,transfer and fate of both polychlorinated biphenyls（PCBs）and cyanotoxins via phytoplankton routes were systematically investigated in two Chinese lakes.Results indicated that PCB adsor...In this study,the distribution,transfer and fate of both polychlorinated biphenyls（PCBs）and cyanotoxins via phytoplankton routes were systematically investigated in two Chinese lakes.Results indicated that PCB adsorption/bioaccumulation dynamics has significantly positive correlations with the biomass of green alga and diatoms.Total lipid content of phytoplankton is the major factor that influences PCB adsorption/bioaccumulation.Cyanobacterial blooms with relatively lower lipid content could also absorb high amount of PCBs due to their high cell density in the water columns,and this process was proposed as major route for the transfer of PCBs in Chinese eutrophic freshwater.According to these findings,a novel route on fates of PCBs via phytoplankton and a green bioadsorption concept were proposed and confirmed.In the practice of mechanical collections of bloom biomass from Lake Taihu,cyanotoxin/cyanobacteria and PCBs were found to be removed simultaneously very efficiently followed this theory.展开更多
The increasing occurrence of cyanobacterial blooms in water bodies is a serious threat to the environment. Efficient in-lake treatment methods for the control of cyanobacteria proliferation are needed, their in-vivo d...The increasing occurrence of cyanobacterial blooms in water bodies is a serious threat to the environment. Efficient in-lake treatment methods for the control of cyanobacteria proliferation are needed, their in-vivo detection to obtain a real-time response to their presence, as well as the information about their physiological state after the applied treatment. In-vivo fluorescence measurements of photosynthetic pigments have proved to be effective for quantitative and qualitative detection of phytoplankton in a water environment. In the experiment, chlorophyll and phycocyanin fluorescence sensors were used concurrently to detect stress caused by electrochemical oxidation applying an electrolytic cell equipped with borondoped diamond electrodes on a laboratory culture of cyanobacteria Microcystis aeruginosa PCC 7806. The inflicted injuries were reflected in a clear transient increase in the phycocyanin fluorescence signal(for 104 %? 43%) 24 h after the treatment, which was not the case for the chlorophyll fluorescence signal. In the next 72 h of observation, the fluorescence signals decreased(on 40% of the starting signal) indicating a reduction of cell number, which was confirmed by cell count(24% reduction of the starting concentration) and analysis of extracted chlorophyll and phycocyanin pigment. These results demonstrate the viability of the combined application of two sensors as a useful tool for in-vivo detection of induced stress, providing real-time information needed for the evaluation of the efficiency of the in-lake treatment and decision upon the necessity of its repetition. The electrochemical treatment also resulted in a lower free microcystins concentration compared to control.展开更多
The genetic diversity and the potential toxicity of bloom-forming cyanobacteria were studied in four lagoons located in the state of Sao Paulo (Campinas, Limeira and Piracicaba cities). Bloom samples were collected on...The genetic diversity and the potential toxicity of bloom-forming cyanobacteria were studied in four lagoons located in the state of Sao Paulo (Campinas, Limeira and Piracicaba cities). Bloom samples were collected on the water surface and cyanobacterial communities were evaluated using DGGE fingerprinting and 16S rDNA clone library. The amplification of genes encoding secondary metabolites such as microcystin (mcy), anatoxin (ana), cylindrospermopsin (cyr), saxitoxin (sxt), cyanopeptolin (mcn) and aeruginosin (aer) was performed and their production analyzed by LC-MS. The comparison of DGGE banding pattern among the different water samples suggested that some operational taxonomic units (OTUs) in these locations were predominant over others. The 16S rDNA clone libraries sequences matched with nine different known cyanobacterial genera available in NCBI, identified as Anabaena, Brasilonema, Cylindrospermopsis, Limnococcus, Microcystis, Nostoc, Pseudanabaena, Synechococcus and Woronichinia. The lagoons ESALQ2, Taquaral and Limeira had more than 80% of the cyanobacterial community assigned to the genus Microcystis. Genes encoding aeruginosin, cyanopeptolin and microcystin synthetases and saxitoxin synthase were amplified, and LC-MS/MS confirmed the production of aeruginosin, cyanopeptolin and microcystin. Rapid and sensitive methods for the detection of these secondary metabolites, especially toxins, using chemical and molecular tools together, can be used for a faster diagnostic of toxic cyanobacterial blooms.展开更多
Cyanobacterial blooms have become a worldwide concern due to the production of toxins harmful to humans and animals. In Brazil and worldwide, microcystins are the most frequently found cyanotoxin in water bodies. Four...Cyanobacterial blooms have become a worldwide concern due to the production of toxins harmful to humans and animals. In Brazil and worldwide, microcystins are the most frequently found cyanotoxin in water bodies. Four important reservoirs in Brazil’s Southeast and Northeast regions were sampled to identify the cyanobacteria community and the occurrence of potential toxin-producing species in the country’s public supply reservoirs. A total of 14 taxa were identi-fied, 11 of which are known as potential toxin producers. Potentially toxic cyanobacteria were recorded at concentra-tions above 20,000 cells.ml-1 in all samples from all four reservoirs, thus requiring microcystin monitoring in drinking water according to Brazilian legislation. Although the sample from Mundaú reservoir showed the highest concentration of microcystins in water, it had one of the lowest values of cells.ml-1, which demonstrates the non-correspondence between these two parameters. This calls into question the existence of a minimum level of potentially toxic cyanobacteria cells to merit the monitoring of microcystins in the treated water from these sources.展开更多
Cyanotoxins are distinctive molecules in Cyanobacteria whose evolutionary origin, radiation and ecological role are still controversial. The cyanobacterium Cylindrospermopsis raciborskii is alternately capable of prod...Cyanotoxins are distinctive molecules in Cyanobacteria whose evolutionary origin, radiation and ecological role are still controversial. The cyanobacterium Cylindrospermopsis raciborskii is alternately capable of producing two types of potent toxins, cylindrospermopsin (CYN) or saxitoxin and analogues (SAX). It has been proposed that this species spread to all continents early in its evolutionary history and biogeographical differences in toxin production are found between populations. Most reports indicate that American strains are able to produce SAX but not CYN, while Australian strains are described to produce CYN but not SAX. Here we describe the presence of three genes belonging to the cylindrospermopsin cluster (cyr), cyrA, cyrB and cyrC, in two SAX producing South American C. raciborskii strains, MVCC14 and MVCC19, which due to their differences in morphology, growth preferences, SAX production and genetic context are defined as different ecotypes. No CYN production was detected in either strain (by ELISA) after growth under nitrogen replete or nitrogen-free nutrient conditions. Phylogenetic analyses of cyrA, cyrB and cyrC partial sequences from both strains showed high similarity (>99%) with CYN genes belonging to C. raciborskii strains from Australia and Germany and to Aphanizomenon strains. This is the first report of the presence of cyr genes in strains known to produce only SAX.展开更多
The combined use of morphological identification and phylogenetic characterization employing primers that target the 16S rDNA region led to the identification of ten isolates belonging to eight cyanobacterial genera i...The combined use of morphological identification and phylogenetic characterization employing primers that target the 16S rDNA region led to the identification of ten isolates belonging to eight cyanobacterial genera in the Nile River. 16S-23S ITS region was amplified to confirm two isolates to be affiliated to genus Nostoc. Using MALDI-TOF/MS, we detected the production of the hepatotoxic demethylated MC-LR by one isolate that clustered together with the genus Nostoc. Protein phosphatase inhibition assay has confirmed toxicity. Our results add to the rising importance of Nostoc as a hepatotoxin-producing cyanobacterium. Furthermore, our results stress that water municipalities in the studied region need to assess the potential threat of toxic cyanobacteria that may pose to human health and economy.展开更多
Cyanobacterial blooms are ubiquitous in fresh and brackish eutrophic waters in India. The cyanotoxins produced by many bloom forming cyanobacteria severely affect the health of animals, fishes, birds and human beings....Cyanobacterial blooms are ubiquitous in fresh and brackish eutrophic waters in India. The cyanotoxins produced by many bloom forming cyanobacteria severely affect the health of animals, fishes, birds and human beings. Different physical and chemical factors contribute towards bloom formation. Ten bloom forming cyanobacteria were isolated from natural blooms of northern India. The strains were purified and enriched in the laboratory. The aim of this study was to understand the influence of iron on growth, pigmentation and antioxidative activity of enzymes-catalase and ascorbate peroxidase of bloom forming cyanobacteria. Results show that different strains of bloom forming cyanobacteria attain optimum growth at varied concentration of iron. The cyanobacterial strains like Synechocystis aquatalis, Merismopedia glauca, Anabaena variabilis and Anabaena iyengarii exhibit maximum growth at low iron concentration （2 pM） while some species require higher concentration of iron for their optimum growth namely, Arthrospira platensis show optimum growth at 10uM, and Nostocpaludosum shows maximum growth at 100uM concentration of iron. It was also noticed that chlorophyll and phycobiliprotein content also varies with change in iron concentration. The activity of antioxidative enzymescatalase and ascorbate peroxidase was noticed in all ten cyanobacterial strains. In the light of the findings, it seems that Arthrospira platensis possess maximum catalase and ascorbate peroxidase activity. Increment in concentration beyond optimum value leads to deterioration in the growth, pigment content and enzymatic activity of the cyanobacterial strains. Knowledge about the factors influencing growth of bloom forming cyanobacteria will help to work out ways for eradication of hazardous cyanobacterial blooms.展开更多
Alosa pseudoharengus<span style="font-family:;" "=""><span style="font-family:Verdana;"> is an anadromous fish that migrates from marine to freshwaters to spawn. The earl...Alosa pseudoharengus<span style="font-family:;" "=""><span style="font-family:Verdana;"> is an anadromous fish that migrates from marine to freshwaters to spawn. The early larval and juvenile forms are known to be planktivorous, where heavy feeding upon their preferred food source of large crustacean zooplankton often results in changes to composition and size structure within this trophic guild which in turn can result in shifts within the trophic spectrum and a classic trophic cascade. In this study of Lower Mill Pond, Brewster MA, we evaluated the feeding strategy of juvenile </span><i><span style="font-family:Verdana;">Alosa</span></i><span style="font-family:Verdana;"> to </span><span style="font-family:Verdana;">determine whether juvenile alewife switch</span></span><span style="font-family:Verdana;">es</span><span style="font-family:Verdana;"> to feeding</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">largely on cyanobacteria and whether cyanotoxins microcystin (MC) and</span><span style="font-family:;" "=""> <i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-methlyamino-L-alanine (BMAA) bioaccumulate in their muscle tissue. Within 15</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">30 days of their estimated spawning date, overexploitation of crustacean zooplankton resulted in a shift from planktivory to benthic detritivory for the majority of their life history, although this did not reduce their condition based on weight-length relationships (Log Wwt. = <sub>-</sub></span><span style="font-family:;" "=""><span style="font-family:Verdana;">5.503 + (3.101 </span><span style="font-family:Verdana;">×</span><span><span style="font-family:Verdana;"> Log Length). Mean MC (0.003 μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>g<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;"> dwt) and BMAA (4.49 μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>g<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;"> dwt) concentrations in the muscle tissue of out-migrating juveniles were presumably derived from benthic subsidies, exporting freshwater cyanotoxins and creating a potential transfer to consumer of 0.0012 μg MC and 1.85 μg BMAA. Biodilution of MC and biomagnification of BMAA were observed. Depletion of the crustacean biomass by >95% resulted in an increase in the rotifer biomass, where Log crustacean (μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;"> dwt) = - </span></span><span style="font-family:Verdana;">5.642 -</span><span style="font-family:Verdana;"> (7.976 </span><span style="font-family:Verdana;">×</span><span><span style="font-family:Verdana;"> Log rotifer (μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;"> dwt), and an increase in the amount of potentially edible <50 μm cyanobacterial biomass (r(8) =</span></span></span><span style="font-family:;" "=""> - </span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">0.676, </span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> = 0.046). A secondary cascade appears to have been maintained via invertebrate planktivory by </span><i><span style="font-family:Verdana;">Chaoborus </span></i><span style="font-family:Verdana;">spp.</span></span></span><span style="font-family:Verdana;">;</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> however for a period of time edible cyanobacteria growth exceeded grazing pressure, resulting in a bloom of edible cyanobacteria. Continued grazing resulted in a shift to larger, inedible cyanobacterial communities where late season (October) surface accumulations were observed. The mass occurrence of juvenile </span><i><span style="font-family:Verdana;">Alosa</span></i> <i><span style="font-family:Verdana;">pseudoharengus</span></i><span style="font-family:Verdana;"> appears to be coupled to the sequential increases of cyanobacterial biomass via its influence on the trophic spectrum. Overall, the rotifer biomass (μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) was positively correlated with MC (pg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>mL<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) (r(8) = 0.577, </span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> = 0.104), and negatively correlated with BMAA (μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) (r(8) = </span><span style="font-family:'Verdana, Helvetica, Arial';"><span style="background-color:#FFFFFF;">- </span></span></span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">0.388, </span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> = 0.373) in the edible cyanobacterial fraction of the water column, although neither of these were significant.</span></span></span>展开更多
Aphanizomenon ovalisporum is a cylindrospermopsin (CYN)-producing cyanobacteria species that due to its increasing worldwide distribution has become an important health alarm in the last few years. Several clusters of...Aphanizomenon ovalisporum is a cylindrospermopsin (CYN)-producing cyanobacteria species that due to its increasing worldwide distribution has become an important health alarm in the last few years. Several clusters of genes involved in CYN production have been described in different CYN+ cyanobacteria genera, named aoa for Aphanizomenon and cyr for Cylindrospermopsis and others strains. The sequences of those genes are highly similar, but a rearrangement in gene order is also observed. The information on the control of CYN production by gene expression is still scarce, especially in Aphanizomenon. To obtain further information about the control of CYN production in A. ovalisporum, we have quantified the intra and extracellular CYN content, during nine days in BG11 batch cultures under optimal conditions. In parallel, the expression of four genes related to CYN synthesis, aoaA-C and cyrJ, has been analyzed by real time q-PCR. The results show a similar pattern of total CYN accumulation and gene expression. Most of the CYN is found intracellularly. Considering the high nitrogen content in the CYN molecule, we have explored if nitrogen assimilation could be related to CYN synthesis. We found inside the aoaA and aoaC sequences several putative binding domains for the global nitrogen regulator NtcA. The pattern of the ntcA expression along the culture is similar to that of CYN accumulation. Our data suggest that CYN production in A. ovalisporum seems to be controlled both by the expression of genesaoa and ntcA, this last one suggesting the influence of available nitrogen;however, other regulation mechanisms of CYN synthesis cannot be discarded.展开更多
This study presented the results of HPLC-DAD microcystin and nodularin analyses from five Bulgarian water bodies (reservoirs Stoudena, Pchelina and Bistritsa, and lakes Dourankoulak and Vaya) carried out in 2012-2014,...This study presented the results of HPLC-DAD microcystin and nodularin analyses from five Bulgarian water bodies (reservoirs Stoudena, Pchelina and Bistritsa, and lakes Dourankoulak and Vaya) carried out in 2012-2014, as a continuation of our work from 2004 to 2005 and in 2011, and first data on microcystins in the lake Momin Brod were detected in the period 2012-2014. The total concentration of microcystins in water samples ranged from 0.1 to 1.8 μg/l and their amount in the concentrated biomasses from net samples ranged from 1.35 to 296 μg/g (d.w.). The presence of the most toxic microcystin-LR was recorded in all studied lakes and reservoirs, where also microcystins RR and YR were detected, but no microcystin-LA and nodularin were found.展开更多
Microcystins cause acute hepatotoxicity and chronic liver tumor promotion. This study presents the results of HPLC DAD analyses and their LC-MS confirmation of samples from five Bulgarian water bodies (reservoirs Stou...Microcystins cause acute hepatotoxicity and chronic liver tumor promotion. This study presents the results of HPLC DAD analyses and their LC-MS confirmation of samples from five Bulgarian water bodies (reservoirs Stoudena, Pchelina, Bistritsa and lakes Dourankoulak, Vaya). The total concentration of microcystins in water samples ranged from 0.1 to 26.5 μg/l. The amount of microcystins in the biomasses ranged from 11.4 to 49.6 μg/g (d.w.). The high percent of positive samples in which the most toxic microcystin-LR is recorded, can serve as a strong alarm for the necessity of a serious study and relevant discussion of the problem with responsible authorities at national level.展开更多
Cyanobacteria are oxygenic photosynthetic Gram-negative bacteria that can form potentially toxic blooms in eutrophic and slow flowing aquatic ecosystems. Bloom toxicity varies spatially and temporally, but understandi...Cyanobacteria are oxygenic photosynthetic Gram-negative bacteria that can form potentially toxic blooms in eutrophic and slow flowing aquatic ecosystems. Bloom toxicity varies spatially and temporally, but understanding the mechanisms that drive these changes remains largely a mystery. Changes in bloom toxicity may result from changes in intracellular toxin pool sizes of cyanotoxins with differing molecular toxicities, and/or from changes in the cell concentrations of toxic and non-toxic cyanobacterial species or strains within bloom populations. We show here how first-order rate kinetics at the cellular level can be used to explain how environmental conditions drive changes in bloom toxicity at the ecological level. First order rate constants can be calculated for changes in cell concentration( μ_c : specific cell division rate) or the volumetric biomass concentration( μ_g : specific growth rate) between short time intervals throughout the cell cycle. Similar first order rate constants can be calculated for changes in nett volumetric cyanotoxin concentration( μ_(tox) : specific cyanotoxin production rate) over similar time intervals. How μ_c(or μ_g) covaries with μ tox over the cell cycle shows conclusively when cyanotoxins are being produced and metabolised, and how the toxicity of cells change in response to environment stressors. When μ_(tox)/μ_c >1, cyanotoxin cell quotas increase and individual cells become more toxic because the nett cyanotoxin production rate is higher than the cell division rate. When μ_(tox)/μ_c =1, cell cyanotoxin quotas remains fixed because the nett cyanotoxin production rate matches the cell division rate. When μ_(tox)/μ_c <1, the cyanotoxin cell quota decreases because either the nett cyanotoxin production rate is lower than the cell division rate, or metabolic breakdown and/or secretion of cyanotoxins is occurring. These fundamental equations describe cyanotoxin metabolism dynamics at the cellular level and provide the necessary physiological background to understand how environmental stressors drive changes in bloom toxicity.展开更多
Microcystins produced by cyanobacteria pose a great threat to human health by releasing toxins upon cell death. In the present study, we studied microcystin production in the cyanobacterial strains Anabaena cylindrica...Microcystins produced by cyanobacteria pose a great threat to human health by releasing toxins upon cell death. In the present study, we studied microcystin production in the cyanobacterial strains Anabaena cylindrica (B629 and 2949) and Fremyella diplosiphon (SF33) exposed to 1, 2 and 4 g/L sodium chloride (NaCl). Cultures grown for 7 days in BG11/HEPES medium were pelleted, re-grown in the corresponding NaCl levels, and enzyme linked immunosorbent assay (ELISA) performed. ELISA assays revealed enhanced microcystin production in A. cylindrica B629 exposed to 4 g/L NaCl and A. cylindrica 29414 exposed to 2 and 4 g/L NaCl, after growth in the corresponding NaCl levels for 14 days. We observed a significant decrease (p > 0.05) in microcystin levels in the control strains after exposure to NaCl for 5 days. After exposure to 1, 2, or 4 g/L NaCl for 10 days, no microcystin release was observed in A. cylindrica B629, A. cylindrica 29414 or F. diplosiphon SF33. Sodium dodecyl sulfate polyacrylamide gel electrophoresis identified the presence of an additional band at 120 - 130 kDa in A. cylindrica B629 exposed to 2 and 4 g/L NaCl, and at 14 kDa in cultures amended with 1 and 2 g/L NaCl as well as the untreated control, indicating that exposure to salinity induces alterations in protein expression.展开更多
In this study we show that cylindrospermopsin (a cyanotoxin) content of filaments of Aphanizomenon ovalisporum ILC164 depended on growth on combined nitrogen or nitrogen fixation. Our results also demonstrated that th...In this study we show that cylindrospermopsin (a cyanotoxin) content of filaments of Aphanizomenon ovalisporum ILC164 depended on growth on combined nitrogen or nitrogen fixation. Our results also demonstrated that the shift down of cyanobacterial filaments from combined nitrogen to dinitrogen fixing condition resulted in a significant decrease of cylindrospermopsin pool size which resumed a growth rate dependent manner as the heterocyst and nitrogenase formation appeared. The current study indicated that alteration of nitrogen metabolism of Aphanizomenon ovalisporum (Forti) induced changes in cyanotoxin (cylindrospermopsin) metabolism. In addition, this is the first report that isolated heterocysts, the differentiated anaerobic cells for nitrogen fixation of cyanobacteria, did not contain cylindrospermopsin.展开更多
Quaternary ammonium compounds(QACs)are commonly used in a variety of consumer and commercial products,typically as a component of disinfectants.During the COVID-19 pandemic,QACs became one of the primary agents utiliz...Quaternary ammonium compounds(QACs)are commonly used in a variety of consumer and commercial products,typically as a component of disinfectants.During the COVID-19 pandemic,QACs became one of the primary agents utilized to inactivate the SARS CoV-2 virus on surfaces.However,the ecotoxicological effects of QACs upon aquatic organisms have not been fully assessed.In this study,we examined the effects of a widely used QAC(benzalkonium chloride-C_(14),BAC-14)on two toxigenic Microcystis strains and one non-toxigenic freshwater Microcystis strain and carried out an analysis focused on primary,adaptive and compensatory stress responses at apical(growth and photosynthesis)and metabolic levels.This analysis revealed that the two toxic Microcystis strains were more tolerant than the non-toxic strain,with 96 hr-EC_(50)values of 0.70,0.76,and 0.38 mg/L BAC-14 for toxigenic M.aeruginosa FACHB-905,toxigenic M.aeruginosa FACHB-469,and non-toxigenic M.wesenbergii FACHB-908,respectively.The photosynthetic activities of the Microcystis,assessed via F_(v)/F_(m) values,were significantly suppressed under 0.4 mg/L BAC-14.Furthermore,this analysis revealed that BAC-14 altered 14,12,and 8 metabolic pathways in M.aeruginosa FACHB-905,M.aeruginosa FACHB-469,and M.wesenbergii FACHB-908,respectively.It is noteworthy that BAC-14 enhanced the level of extracellular microcystin production in the toxigenic Microcystis strains,although cell growth was not significantly affected.Collectively,these data show that BAC-14 disrupted the physiological and metabolic status of Microcystis cells and stimulated the production and release of microcystin,which could result in damage to aquatic systems.展开更多
Cyanobacteria can produce cyanotoxins such as microcystin-LR(MC),saxitoxin(STX),and anatoxin-a(ANTX-a)which are harmful to humans and other animals.Individual removal efficiencies of STX and ANTX-a by powdered activat...Cyanobacteria can produce cyanotoxins such as microcystin-LR(MC),saxitoxin(STX),and anatoxin-a(ANTX-a)which are harmful to humans and other animals.Individual removal efficiencies of STX and ANTX-a by powdered activated carbon(PAC)was investigated,aswell as when MC-LR and cyanobacteriawere present.Experimentswere conductedwith distilled water and then source water,using the PAC dosages,rapid mix/flocculation mixing intensities and contact times of two drinking water treatment plants in northeast Ohio.At pH 8 and 9,STX removal was 47%-81%in distilled water and 46%-79%in source water,whereas it was 0-28%for pH 6 in distilled water and 31%-52%in source water.When 1.6μg/L or 20μg/L MC-LR was present with STX,STX removal was increased with PAC simultaneously removing 45%-65%of the 1.6μg/L MC-LR and 25%-95%of the 20μg/L MC-LR depending on the pH.ANTX-a removal at pH 6 was 29%-37%for distilled water and 80%for source water,whereas it was 10%-26%for pH 8 in distilled water and 28%for pH 9 in source water.The presence of cyanobacteria cells decreased ANTX-a removal by at least 18%.When 20μg/L MC-LR was present with ANTX-a in source water,59%-73%ANTX-a and 48%-77%of MCLR was removed at pH 9 depending on the PAC dose.In general,a higher PAC dose led to higher cyanotoxin removals.This study also documented that multiple cyanotoxins can be effectively removed by PAC for water at pH’s between 6 and 9.展开更多
We investigated the accumulation and effects of cyanobacterial crude extract（CCE）containing microcystins（MCs） on the edible clam Corbicula leana P. Toxic effects were evaluated through the activity of antioxidant ...We investigated the accumulation and effects of cyanobacterial crude extract（CCE）containing microcystins（MCs） on the edible clam Corbicula leana P. Toxic effects were evaluated through the activity of antioxidant and detoxification enzymes： catalase（CAT）,superoxide dismutase（SOD）, and glutathione-S-transferases（GSTs） from gills, foot, mantle and remaining soft tissues. Clams were exposed to CCE containing 400 μg MC-LReq/L for10 days and were then kept in toxin-free water for 5 days. Clam accumulated MCs（up to 3.41 ± 0.63 μg/g dry weight（DW） of unbound MC and 0.31 ± 0.013 μg/g DW of covalently bound MC）. Detoxification and antioxidant enzymes in different organs responded differently to CCE during the experiment. The activity of SOD, CAT, and GST in the gills and mantle increased in MC-treated clams. In contrast, CAT and GST activity was significantly inhibited in the foot and mostly only slightly changed in the remaining tissues. The responses of biotransformation, antioxidant enzyme activity to CCE and the fast elimination of MCs during depuration help to explain how the clam can survive for long periods（over a week） during the decay of toxic cyanobacterial blooms in nature.展开更多
文摘Cyanotoxins are chemical compounds produced by cyanobacterial mats grown in aquatic ecosystems. These may threaten human health and aquatic organisms. Extraction of these toxins is usually associated with many difficulties due to their concentration in aquatic ecosystems. This study is designed to provide suitable and effective extraction procedures that can effectively extract low concentration cyanotoxin from water and bacterial cells. The methodology is based on collecting raw material of cyanobacterial mats from naturally growing sites such as Wadi Gaza along with 16 liters of aquatic surrounding media. The materials were left in the Lab for 24 - 48 h for stabilization of the mats. The floating mats were collected using special funnel and allowed to air drying. The aqueous phase was extracted by liquid/liquid extraction using solvent mixture (hexane + ethylacetate 10% w:w), and by liquid solid extraction using several types of organoclays complexes. The solid phase was extracted by acetone and ultrasonic device. Results showed some difficulties were associated with liquid/liquid extraction whereas effective and easy extraction procedures were obtained by liquid solid extraction using either organoclay complex or activated charcoal. In contrast combination of both solid materials did not show improvement in the extracted cyanotoxin. Thus we recommend the use of organoclays or activated charcoal separately for extracting cyanotoxin. Further improvement of extraction can be tailored by using a specific organoclay complex that has some similarity in the chemical structure between the pre-adsorbed organic cation to the clay mineral and the chemical structure of cyanotoxin.
基金funded by the Ministry of Science and Technology of Taiwan,R.O.C.to HUD,grant number MOST 107-2621-M-037-001,MOST108-2621-M-037-001,MOST 109-2621-M-037-001 provided for Tan,Han-Shihsupported by the Research Center for Environmental Medicine,Kaohsiung Medical University,Kaohsiung,Taiwan from The Featured Areas Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education(MOE)in TaiwanAn NSYSU/KMU collaboration is acknowledged(108-PO25).
文摘Harmful algal blooms(HABs)that are formed by cyanobacteria have become a serious issue worldwide in recent years.Cyanobacteria can release a type of secondary metabolites called cyanotoxins into aquatic systems which may indirectly or directly provide health risks to the environment and humans.Cyanotoxins provide some of the most powerful natural poisons including potent neurotoxins,hepatotoxins,cytotoxins,and endotoxins that may result in environmental health risks,and long-term morbidity and mortality to animals and humans.In this research,we used the chemcomputational tool Molinspiration for molecular property predictions,Pred-hERG 4.2 web software for cardiac toxicity prediction,and Pred-Skin 2.0 web software for predicting skin sensitization.We are predicting some toxicological aspects of cyanobacteria here using chemcomputational tools with the hypothesis that cyanotoxins are providing a risk to human health.We are using the tool Pred-hERG 4.2 to predict hERG channel blocking potential and the Pred-skin tool to predict skin sensitization due to cyanotoxins.The potential of anatoxin,ambigol,the microcystin group,and lyngbyatoxin A,lyngbyatoxin B,nodularin-R,and saxitoxin were predicted to cause skin sensitization in the final results(consensus model).Anatoxin-a and lyngbyatoxin were predicted to allow GI absorption and blood–brain barrier penetration.Among the 20 predicted cyanotoxins only aeruginosin 103-A,ambigol A,and ambigol were predicted by Pred-hERG 4.2 according to the applicability domain results as potential cardiotoxins with weak or moderate potency.Lyngbyatoxin shows activity through the GPCR ligand and protease,kinase,and enzyme inhibitor.
文摘Cyanotoxins produced by cyanobacteria pose significant challenges to water resource management due to the potential impacts they have on human health. Cylindrospermopsin (CYN) and microcystins (MC) are the more commonly detected cyanotoxins in Singapore’s reservoirs. Among the MC congeners monitored locally, the most frequently detected variants are MC-RR (37.6%), followed by MC-LR (25.6%). MC-LA and MC-YR are the least frequently detected variants (7.1%). No cyanotoxins have been detected in Singapore’s treated drinking water. Singapore’s National Water Agency (PUB) and the National Environment Agency (NEA) developed recreational water quality guidelines using Chl <em>a</em> concentrations of 50 μg/L. In local surface waters, long-term data showed that at 50 μg/L of Chl <em>a</em>, MC-LR concentrations ranged from <0.025 μg/L to 1 μg/L. In addition to using Chl <em>a</em> concentrations, <em>Microcystis</em> cell counts in reservoir water have also been used to manage cyanotoxin risk in drinking water. Specifically, routinely monitored data from all 17 Singapore reservoirs indicated that to keep MC-LR concentrations below the WHO provisional guideline of 1 μg/L in drinking water, <em>Microcystis</em> cell counts needed to be <10,000 cells/ml. Culture experiments using local <em>Microcystis</em> isolates showed M. <em>aeruginosa</em> produced the most MC compared to <em>M</em>. <em>ichthyoblabe</em>, <em>M.</em> <em>flos-aquae</em>, and <em>M</em>. <em>viridis</em>. Based on the maximum toxin cell quota equivalent to the WHO provisional guideline for MC-LR of 1 μg/L in drinking water, a 5000 cells/ml cell count guideline was derived for <em>M</em>. <em>aeruginosa</em>. This cell count has also been incorporated into Singapore’s cyanotoxin risk management framework for reservoirs.
基金supported by the National Natural Science Foundation of China(Nos.41276150,51679169 and 40971249)
文摘In this study,the distribution,transfer and fate of both polychlorinated biphenyls（PCBs）and cyanotoxins via phytoplankton routes were systematically investigated in two Chinese lakes.Results indicated that PCB adsorption/bioaccumulation dynamics has significantly positive correlations with the biomass of green alga and diatoms.Total lipid content of phytoplankton is the major factor that influences PCB adsorption/bioaccumulation.Cyanobacterial blooms with relatively lower lipid content could also absorb high amount of PCBs due to their high cell density in the water columns,and this process was proposed as major route for the transfer of PCBs in Chinese eutrophic freshwater.According to these findings,a novel route on fates of PCBs via phytoplankton and a green bioadsorption concept were proposed and confirmed.In the practice of mechanical collections of bloom biomass from Lake Taihu,cyanotoxin/cyanobacteria and PCBs were found to be removed simultaneously very efficiently followed this theory.
基金Supported by the ARRS Project L1-5456(Control of Harmful Cyanobacteria Bloom in Fresh-Water Bodies)LIFE+Project:LIFE12 ENV/SI/00083 LIFE Stop CyanoBloom
文摘The increasing occurrence of cyanobacterial blooms in water bodies is a serious threat to the environment. Efficient in-lake treatment methods for the control of cyanobacteria proliferation are needed, their in-vivo detection to obtain a real-time response to their presence, as well as the information about their physiological state after the applied treatment. In-vivo fluorescence measurements of photosynthetic pigments have proved to be effective for quantitative and qualitative detection of phytoplankton in a water environment. In the experiment, chlorophyll and phycocyanin fluorescence sensors were used concurrently to detect stress caused by electrochemical oxidation applying an electrolytic cell equipped with borondoped diamond electrodes on a laboratory culture of cyanobacteria Microcystis aeruginosa PCC 7806. The inflicted injuries were reflected in a clear transient increase in the phycocyanin fluorescence signal(for 104 %? 43%) 24 h after the treatment, which was not the case for the chlorophyll fluorescence signal. In the next 72 h of observation, the fluorescence signals decreased(on 40% of the starting signal) indicating a reduction of cell number, which was confirmed by cell count(24% reduction of the starting concentration) and analysis of extracted chlorophyll and phycocyanin pigment. These results demonstrate the viability of the combined application of two sensors as a useful tool for in-vivo detection of induced stress, providing real-time information needed for the evaluation of the efficiency of the in-lake treatment and decision upon the necessity of its repetition. The electrochemical treatment also resulted in a lower free microcystins concentration compared to control.
文摘The genetic diversity and the potential toxicity of bloom-forming cyanobacteria were studied in four lagoons located in the state of Sao Paulo (Campinas, Limeira and Piracicaba cities). Bloom samples were collected on the water surface and cyanobacterial communities were evaluated using DGGE fingerprinting and 16S rDNA clone library. The amplification of genes encoding secondary metabolites such as microcystin (mcy), anatoxin (ana), cylindrospermopsin (cyr), saxitoxin (sxt), cyanopeptolin (mcn) and aeruginosin (aer) was performed and their production analyzed by LC-MS. The comparison of DGGE banding pattern among the different water samples suggested that some operational taxonomic units (OTUs) in these locations were predominant over others. The 16S rDNA clone libraries sequences matched with nine different known cyanobacterial genera available in NCBI, identified as Anabaena, Brasilonema, Cylindrospermopsis, Limnococcus, Microcystis, Nostoc, Pseudanabaena, Synechococcus and Woronichinia. The lagoons ESALQ2, Taquaral and Limeira had more than 80% of the cyanobacterial community assigned to the genus Microcystis. Genes encoding aeruginosin, cyanopeptolin and microcystin synthetases and saxitoxin synthase were amplified, and LC-MS/MS confirmed the production of aeruginosin, cyanopeptolin and microcystin. Rapid and sensitive methods for the detection of these secondary metabolites, especially toxins, using chemical and molecular tools together, can be used for a faster diagnostic of toxic cyanobacterial blooms.
文摘Cyanobacterial blooms have become a worldwide concern due to the production of toxins harmful to humans and animals. In Brazil and worldwide, microcystins are the most frequently found cyanotoxin in water bodies. Four important reservoirs in Brazil’s Southeast and Northeast regions were sampled to identify the cyanobacteria community and the occurrence of potential toxin-producing species in the country’s public supply reservoirs. A total of 14 taxa were identi-fied, 11 of which are known as potential toxin producers. Potentially toxic cyanobacteria were recorded at concentra-tions above 20,000 cells.ml-1 in all samples from all four reservoirs, thus requiring microcystin monitoring in drinking water according to Brazilian legislation. Although the sample from Mundaú reservoir showed the highest concentration of microcystins in water, it had one of the lowest values of cells.ml-1, which demonstrates the non-correspondence between these two parameters. This calls into question the existence of a minimum level of potentially toxic cyanobacteria cells to merit the monitoring of microcystins in the treated water from these sources.
文摘Cyanotoxins are distinctive molecules in Cyanobacteria whose evolutionary origin, radiation and ecological role are still controversial. The cyanobacterium Cylindrospermopsis raciborskii is alternately capable of producing two types of potent toxins, cylindrospermopsin (CYN) or saxitoxin and analogues (SAX). It has been proposed that this species spread to all continents early in its evolutionary history and biogeographical differences in toxin production are found between populations. Most reports indicate that American strains are able to produce SAX but not CYN, while Australian strains are described to produce CYN but not SAX. Here we describe the presence of three genes belonging to the cylindrospermopsin cluster (cyr), cyrA, cyrB and cyrC, in two SAX producing South American C. raciborskii strains, MVCC14 and MVCC19, which due to their differences in morphology, growth preferences, SAX production and genetic context are defined as different ecotypes. No CYN production was detected in either strain (by ELISA) after growth under nitrogen replete or nitrogen-free nutrient conditions. Phylogenetic analyses of cyrA, cyrB and cyrC partial sequences from both strains showed high similarity (>99%) with CYN genes belonging to C. raciborskii strains from Australia and Germany and to Aphanizomenon strains. This is the first report of the presence of cyr genes in strains known to produce only SAX.
文摘The combined use of morphological identification and phylogenetic characterization employing primers that target the 16S rDNA region led to the identification of ten isolates belonging to eight cyanobacterial genera in the Nile River. 16S-23S ITS region was amplified to confirm two isolates to be affiliated to genus Nostoc. Using MALDI-TOF/MS, we detected the production of the hepatotoxic demethylated MC-LR by one isolate that clustered together with the genus Nostoc. Protein phosphatase inhibition assay has confirmed toxicity. Our results add to the rising importance of Nostoc as a hepatotoxin-producing cyanobacterium. Furthermore, our results stress that water municipalities in the studied region need to assess the potential threat of toxic cyanobacteria that may pose to human health and economy.
文摘Cyanobacterial blooms are ubiquitous in fresh and brackish eutrophic waters in India. The cyanotoxins produced by many bloom forming cyanobacteria severely affect the health of animals, fishes, birds and human beings. Different physical and chemical factors contribute towards bloom formation. Ten bloom forming cyanobacteria were isolated from natural blooms of northern India. The strains were purified and enriched in the laboratory. The aim of this study was to understand the influence of iron on growth, pigmentation and antioxidative activity of enzymes-catalase and ascorbate peroxidase of bloom forming cyanobacteria. Results show that different strains of bloom forming cyanobacteria attain optimum growth at varied concentration of iron. The cyanobacterial strains like Synechocystis aquatalis, Merismopedia glauca, Anabaena variabilis and Anabaena iyengarii exhibit maximum growth at low iron concentration （2 pM） while some species require higher concentration of iron for their optimum growth namely, Arthrospira platensis show optimum growth at 10uM, and Nostocpaludosum shows maximum growth at 100uM concentration of iron. It was also noticed that chlorophyll and phycobiliprotein content also varies with change in iron concentration. The activity of antioxidative enzymescatalase and ascorbate peroxidase was noticed in all ten cyanobacterial strains. In the light of the findings, it seems that Arthrospira platensis possess maximum catalase and ascorbate peroxidase activity. Increment in concentration beyond optimum value leads to deterioration in the growth, pigment content and enzymatic activity of the cyanobacterial strains. Knowledge about the factors influencing growth of bloom forming cyanobacteria will help to work out ways for eradication of hazardous cyanobacterial blooms.
文摘Alosa pseudoharengus<span style="font-family:;" "=""><span style="font-family:Verdana;"> is an anadromous fish that migrates from marine to freshwaters to spawn. The early larval and juvenile forms are known to be planktivorous, where heavy feeding upon their preferred food source of large crustacean zooplankton often results in changes to composition and size structure within this trophic guild which in turn can result in shifts within the trophic spectrum and a classic trophic cascade. In this study of Lower Mill Pond, Brewster MA, we evaluated the feeding strategy of juvenile </span><i><span style="font-family:Verdana;">Alosa</span></i><span style="font-family:Verdana;"> to </span><span style="font-family:Verdana;">determine whether juvenile alewife switch</span></span><span style="font-family:Verdana;">es</span><span style="font-family:Verdana;"> to feeding</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">largely on cyanobacteria and whether cyanotoxins microcystin (MC) and</span><span style="font-family:;" "=""> <i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-methlyamino-L-alanine (BMAA) bioaccumulate in their muscle tissue. Within 15</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">30 days of their estimated spawning date, overexploitation of crustacean zooplankton resulted in a shift from planktivory to benthic detritivory for the majority of their life history, although this did not reduce their condition based on weight-length relationships (Log Wwt. = <sub>-</sub></span><span style="font-family:;" "=""><span style="font-family:Verdana;">5.503 + (3.101 </span><span style="font-family:Verdana;">×</span><span><span style="font-family:Verdana;"> Log Length). Mean MC (0.003 μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>g<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;"> dwt) and BMAA (4.49 μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>g<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;"> dwt) concentrations in the muscle tissue of out-migrating juveniles were presumably derived from benthic subsidies, exporting freshwater cyanotoxins and creating a potential transfer to consumer of 0.0012 μg MC and 1.85 μg BMAA. Biodilution of MC and biomagnification of BMAA were observed. Depletion of the crustacean biomass by >95% resulted in an increase in the rotifer biomass, where Log crustacean (μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;"> dwt) = - </span></span><span style="font-family:Verdana;">5.642 -</span><span style="font-family:Verdana;"> (7.976 </span><span style="font-family:Verdana;">×</span><span><span style="font-family:Verdana;"> Log rotifer (μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;"> dwt), and an increase in the amount of potentially edible <50 μm cyanobacterial biomass (r(8) =</span></span></span><span style="font-family:;" "=""> - </span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">0.676, </span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> = 0.046). A secondary cascade appears to have been maintained via invertebrate planktivory by </span><i><span style="font-family:Verdana;">Chaoborus </span></i><span style="font-family:Verdana;">spp.</span></span></span><span style="font-family:Verdana;">;</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> however for a period of time edible cyanobacteria growth exceeded grazing pressure, resulting in a bloom of edible cyanobacteria. Continued grazing resulted in a shift to larger, inedible cyanobacterial communities where late season (October) surface accumulations were observed. The mass occurrence of juvenile </span><i><span style="font-family:Verdana;">Alosa</span></i> <i><span style="font-family:Verdana;">pseudoharengus</span></i><span style="font-family:Verdana;"> appears to be coupled to the sequential increases of cyanobacterial biomass via its influence on the trophic spectrum. Overall, the rotifer biomass (μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) was positively correlated with MC (pg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>mL<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) (r(8) = 0.577, </span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> = 0.104), and negatively correlated with BMAA (μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) (r(8) = </span><span style="font-family:'Verdana, Helvetica, Arial';"><span style="background-color:#FFFFFF;">- </span></span></span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">0.388, </span><i><span style="font-family:Verdana;">p</span></i><span style="font-family:Verdana;"> = 0.373) in the edible cyanobacterial fraction of the water column, although neither of these were significant.</span></span></span>
文摘Aphanizomenon ovalisporum is a cylindrospermopsin (CYN)-producing cyanobacteria species that due to its increasing worldwide distribution has become an important health alarm in the last few years. Several clusters of genes involved in CYN production have been described in different CYN+ cyanobacteria genera, named aoa for Aphanizomenon and cyr for Cylindrospermopsis and others strains. The sequences of those genes are highly similar, but a rearrangement in gene order is also observed. The information on the control of CYN production by gene expression is still scarce, especially in Aphanizomenon. To obtain further information about the control of CYN production in A. ovalisporum, we have quantified the intra and extracellular CYN content, during nine days in BG11 batch cultures under optimal conditions. In parallel, the expression of four genes related to CYN synthesis, aoaA-C and cyrJ, has been analyzed by real time q-PCR. The results show a similar pattern of total CYN accumulation and gene expression. Most of the CYN is found intracellularly. Considering the high nitrogen content in the CYN molecule, we have explored if nitrogen assimilation could be related to CYN synthesis. We found inside the aoaA and aoaC sequences several putative binding domains for the global nitrogen regulator NtcA. The pattern of the ntcA expression along the culture is similar to that of CYN accumulation. Our data suggest that CYN production in A. ovalisporum seems to be controlled both by the expression of genesaoa and ntcA, this last one suggesting the influence of available nitrogen;however, other regulation mechanisms of CYN synthesis cannot be discarded.
基金financial support of MESY scientific projects DDVU-02/77 and DFNI-T01/5 NANOSORBLABparticipates in the Project№BG051PO001-3.3.06-0045/18.07.2013 in Human Resources Development Operational Programme
文摘This study presented the results of HPLC-DAD microcystin and nodularin analyses from five Bulgarian water bodies (reservoirs Stoudena, Pchelina and Bistritsa, and lakes Dourankoulak and Vaya) carried out in 2012-2014, as a continuation of our work from 2004 to 2005 and in 2011, and first data on microcystins in the lake Momin Brod were detected in the period 2012-2014. The total concentration of microcystins in water samples ranged from 0.1 to 1.8 μg/l and their amount in the concentrated biomasses from net samples ranged from 1.35 to 296 μg/g (d.w.). The presence of the most toxic microcystin-LR was recorded in all studied lakes and reservoirs, where also microcystins RR and YR were detected, but no microcystin-LA and nodularin were found.
基金financial support of MESY scientific projects DDVU-02/77 and DFNI-T01/5 NANOSORBLAB.
文摘Microcystins cause acute hepatotoxicity and chronic liver tumor promotion. This study presents the results of HPLC DAD analyses and their LC-MS confirmation of samples from five Bulgarian water bodies (reservoirs Stoudena, Pchelina, Bistritsa and lakes Dourankoulak, Vaya). The total concentration of microcystins in water samples ranged from 0.1 to 26.5 μg/l. The amount of microcystins in the biomasses ranged from 11.4 to 49.6 μg/g (d.w.). The high percent of positive samples in which the most toxic microcystin-LR is recorded, can serve as a strong alarm for the necessity of a serious study and relevant discussion of the problem with responsible authorities at national level.
文摘Cyanobacteria are oxygenic photosynthetic Gram-negative bacteria that can form potentially toxic blooms in eutrophic and slow flowing aquatic ecosystems. Bloom toxicity varies spatially and temporally, but understanding the mechanisms that drive these changes remains largely a mystery. Changes in bloom toxicity may result from changes in intracellular toxin pool sizes of cyanotoxins with differing molecular toxicities, and/or from changes in the cell concentrations of toxic and non-toxic cyanobacterial species or strains within bloom populations. We show here how first-order rate kinetics at the cellular level can be used to explain how environmental conditions drive changes in bloom toxicity at the ecological level. First order rate constants can be calculated for changes in cell concentration( μ_c : specific cell division rate) or the volumetric biomass concentration( μ_g : specific growth rate) between short time intervals throughout the cell cycle. Similar first order rate constants can be calculated for changes in nett volumetric cyanotoxin concentration( μ_(tox) : specific cyanotoxin production rate) over similar time intervals. How μ_c(or μ_g) covaries with μ tox over the cell cycle shows conclusively when cyanotoxins are being produced and metabolised, and how the toxicity of cells change in response to environment stressors. When μ_(tox)/μ_c >1, cyanotoxin cell quotas increase and individual cells become more toxic because the nett cyanotoxin production rate is higher than the cell division rate. When μ_(tox)/μ_c =1, cell cyanotoxin quotas remains fixed because the nett cyanotoxin production rate matches the cell division rate. When μ_(tox)/μ_c <1, the cyanotoxin cell quota decreases because either the nett cyanotoxin production rate is lower than the cell division rate, or metabolic breakdown and/or secretion of cyanotoxins is occurring. These fundamental equations describe cyanotoxin metabolism dynamics at the cellular level and provide the necessary physiological background to understand how environmental stressors drive changes in bloom toxicity.
文摘Microcystins produced by cyanobacteria pose a great threat to human health by releasing toxins upon cell death. In the present study, we studied microcystin production in the cyanobacterial strains Anabaena cylindrica (B629 and 2949) and Fremyella diplosiphon (SF33) exposed to 1, 2 and 4 g/L sodium chloride (NaCl). Cultures grown for 7 days in BG11/HEPES medium were pelleted, re-grown in the corresponding NaCl levels, and enzyme linked immunosorbent assay (ELISA) performed. ELISA assays revealed enhanced microcystin production in A. cylindrica B629 exposed to 4 g/L NaCl and A. cylindrica 29414 exposed to 2 and 4 g/L NaCl, after growth in the corresponding NaCl levels for 14 days. We observed a significant decrease (p > 0.05) in microcystin levels in the control strains after exposure to NaCl for 5 days. After exposure to 1, 2, or 4 g/L NaCl for 10 days, no microcystin release was observed in A. cylindrica B629, A. cylindrica 29414 or F. diplosiphon SF33. Sodium dodecyl sulfate polyacrylamide gel electrophoresis identified the presence of an additional band at 120 - 130 kDa in A. cylindrica B629 exposed to 2 and 4 g/L NaCl, and at 14 kDa in cultures amended with 1 and 2 g/L NaCl as well as the untreated control, indicating that exposure to salinity induces alterations in protein expression.
文摘In this study we show that cylindrospermopsin (a cyanotoxin) content of filaments of Aphanizomenon ovalisporum ILC164 depended on growth on combined nitrogen or nitrogen fixation. Our results also demonstrated that the shift down of cyanobacterial filaments from combined nitrogen to dinitrogen fixing condition resulted in a significant decrease of cylindrospermopsin pool size which resumed a growth rate dependent manner as the heterocyst and nitrogenase formation appeared. The current study indicated that alteration of nitrogen metabolism of Aphanizomenon ovalisporum (Forti) induced changes in cyanotoxin (cylindrospermopsin) metabolism. In addition, this is the first report that isolated heterocysts, the differentiated anaerobic cells for nitrogen fixation of cyanobacteria, did not contain cylindrospermopsin.
基金supported by the National Key Research and Development Program of China (Nos.2018YFD0900701 and 2019YFD0900604)the National Natural Science Foundation of China (Nos.42107150 and 32061143029)。
文摘Quaternary ammonium compounds(QACs)are commonly used in a variety of consumer and commercial products,typically as a component of disinfectants.During the COVID-19 pandemic,QACs became one of the primary agents utilized to inactivate the SARS CoV-2 virus on surfaces.However,the ecotoxicological effects of QACs upon aquatic organisms have not been fully assessed.In this study,we examined the effects of a widely used QAC(benzalkonium chloride-C_(14),BAC-14)on two toxigenic Microcystis strains and one non-toxigenic freshwater Microcystis strain and carried out an analysis focused on primary,adaptive and compensatory stress responses at apical(growth and photosynthesis)and metabolic levels.This analysis revealed that the two toxic Microcystis strains were more tolerant than the non-toxic strain,with 96 hr-EC_(50)values of 0.70,0.76,and 0.38 mg/L BAC-14 for toxigenic M.aeruginosa FACHB-905,toxigenic M.aeruginosa FACHB-469,and non-toxigenic M.wesenbergii FACHB-908,respectively.The photosynthetic activities of the Microcystis,assessed via F_(v)/F_(m) values,were significantly suppressed under 0.4 mg/L BAC-14.Furthermore,this analysis revealed that BAC-14 altered 14,12,and 8 metabolic pathways in M.aeruginosa FACHB-905,M.aeruginosa FACHB-469,and M.wesenbergii FACHB-908,respectively.It is noteworthy that BAC-14 enhanced the level of extracellular microcystin production in the toxigenic Microcystis strains,although cell growth was not significantly affected.Collectively,these data show that BAC-14 disrupted the physiological and metabolic status of Microcystis cells and stimulated the production and release of microcystin,which could result in damage to aquatic systems.
基金This work was supported by the Ohio Department of Higher Education Harmful Algal Bloom Research Initiative(No.60075961).Funding was solely for support of conducting the research.The authorswould like to thank Jessica Glowczewski fromCity of Akron and Amy Elliot fromCity of Alliance for providing water treatment details and permission for source water collection as well as Dr.Xiaozhen Mou and Madison Summers from Kent State University for assistance in conducting the toxin measurements.
文摘Cyanobacteria can produce cyanotoxins such as microcystin-LR(MC),saxitoxin(STX),and anatoxin-a(ANTX-a)which are harmful to humans and other animals.Individual removal efficiencies of STX and ANTX-a by powdered activated carbon(PAC)was investigated,aswell as when MC-LR and cyanobacteriawere present.Experimentswere conductedwith distilled water and then source water,using the PAC dosages,rapid mix/flocculation mixing intensities and contact times of two drinking water treatment plants in northeast Ohio.At pH 8 and 9,STX removal was 47%-81%in distilled water and 46%-79%in source water,whereas it was 0-28%for pH 6 in distilled water and 31%-52%in source water.When 1.6μg/L or 20μg/L MC-LR was present with STX,STX removal was increased with PAC simultaneously removing 45%-65%of the 1.6μg/L MC-LR and 25%-95%of the 20μg/L MC-LR depending on the pH.ANTX-a removal at pH 6 was 29%-37%for distilled water and 80%for source water,whereas it was 10%-26%for pH 8 in distilled water and 28%for pH 9 in source water.The presence of cyanobacteria cells decreased ANTX-a removal by at least 18%.When 20μg/L MC-LR was present with ANTX-a in source water,59%-73%ANTX-a and 48%-77%of MCLR was removed at pH 9 depending on the PAC dose.In general,a higher PAC dose led to higher cyanotoxin removals.This study also documented that multiple cyanotoxins can be effectively removed by PAC for water at pH’s between 6 and 9.
基金supported by the Ministry of Education, Culture, Sports, Science, and Technology of Japan (MEXT) under a Ph.D programsupported by Grants-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science (JSPS) and MEXT
文摘We investigated the accumulation and effects of cyanobacterial crude extract（CCE）containing microcystins（MCs） on the edible clam Corbicula leana P. Toxic effects were evaluated through the activity of antioxidant and detoxification enzymes： catalase（CAT）,superoxide dismutase（SOD）, and glutathione-S-transferases（GSTs） from gills, foot, mantle and remaining soft tissues. Clams were exposed to CCE containing 400 μg MC-LReq/L for10 days and were then kept in toxin-free water for 5 days. Clam accumulated MCs（up to 3.41 ± 0.63 μg/g dry weight（DW） of unbound MC and 0.31 ± 0.013 μg/g DW of covalently bound MC）. Detoxification and antioxidant enzymes in different organs responded differently to CCE during the experiment. The activity of SOD, CAT, and GST in the gills and mantle increased in MC-treated clams. In contrast, CAT and GST activity was significantly inhibited in the foot and mostly only slightly changed in the remaining tissues. The responses of biotransformation, antioxidant enzyme activity to CCE and the fast elimination of MCs during depuration help to explain how the clam can survive for long periods（over a week） during the decay of toxic cyanobacterial blooms in nature.
