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1
Cross, David Michael. "Analytical methods for cyanobacterial toxins". Thesis, University of Bath, 1997. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390310.
Testo completo
2
Froscio, Suzanne M. "Investigation of the mechanisms involved in cylindrospermopsin toxicity : hepatocyte culture and reticulocyte lysate studies". Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phf938.pdf.
Testo completoAbstract (sommario):
Bibliography: leaves 121-139. The aim of this study was to determine the extent to which protein synthesis inhibition, lowered glutathione (GSH) levels and toxin metabolism contribute to the toxicity of cyclindrospermopsin. Both hepatocyte cultures and reticulocyte lysates were utilized as in vitro tools of investigation. The findings imply that the inhibition of protein synthesis by direct action of the toxin cannot be considered a primary cause of hepatocyte cell death over an acute time frame. Cytochrome P450-derived metabolites may play a crucial role in cytotoxicity, and the toxicity process does not appear to involve oxidative damage.
3
Engelke, Clemens J. "Cyanobacterial chemical ecology". Thesis, University of Aberdeen, 2001. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU485501.
Testo completoAbstract (sommario):
This thesis reports the effect of the non-toxic cyanobacterium Oscillatoria agardhii CYA29 and its spent medium on the cell-bound toxin levels in Microcystis aeruginosa PCC7820 and Nodularia sp. PCC7804. Microcystin levels were elevated when O. agardhii or its spent medium were added to cultures of M. aeruginosa PCC7820. This effect was also observed for two nodularin variants in Nodularia PCC7804. However, growth of M. aeruginosa in its own spent medium did not lead to elevated microcystin levels. Some Gram-negative bacteria use quorum sensing, the determination of population density by pheromones, to regulate the expression of traits in a density dependent manner. The presence of the bacterial pheromones, acyl-homoserine lactones (AHLs), was investigated in cyanobacteria and a simple and fast synthesis for AHLs employed. No AHLs have been found in the cyanobacterial species tested, neither by Chromobacterium violaceum CV026 nor by Escherichia coli HB101 pUCD607 bioassay. No changes in dry weight or microcystin concentration were observed in M. aeruginosa PCC7820 grown in the presence of the AHL N-hexanoyl-DL-homoserine lactone. The activity of the spent medium of O. agardhii CYA29 was retained when it was heated up to 100°C for 20 min, frozen or freeze-dried. Molecular weight cut-off filtration showed the active compound to be less than 1 kD in size. The active component could not be extracted by dichloromethane or methanol, and activity was lost upon acidification. A small peptide of five amino acid moieties was isolated from an active fraction of the spent medium, four of which have been identified by 1H NMR to be serine, glycine, alanine, and the modified serine(thiazole). To my knowledge this is the first report of serine(thiazole) in natural products and the first thiazole containing peptide from O. agardhii.
4
McElhiney, Jacqueline. "Purification, detection and biological effects of cyanobacterial toxins". Thesis, Robert Gordon University, 1999. http://hdl.handle.net/10059/528.
Testo completoAbstract (sommario):
The aesthetic beauty of a landscape is a very subjective issue: every person has their own opinions and their own idea of what beauty is. However, all people have a common evolutionary history, and, according to the Biophilia hypothesis, a genetic predisposition to liking certain types of landscapes. It is possible that this common inheritance allows us to attempt to model scenic preference for natural landscapes. The ideal type of model for such predictions is the psychophysical preference model, integrating psychological responses to landscapes with objective measurements of quantitative and qualitative landscape variables. Such models commonly predict two thirds of the variance in the predications of the general public for natural landscapes. In order to create such a model three sets of data were required: landscape photographs (surrogates of the actual landscape), landscape preference data and landscape component variable measurements. The Internet was used to run a questionnaire survey; a novel, yet flexible, environmentally friendly and simple method of data gathering, resulting in one hundred and eighty responses. A geographic information system was used to digitise ninety landscape photographs and measure their landforms (based on elevation) in terms of areas and perimeters, their colours and proxies for their complexity and coherence. Landscape preference models were created by running multiple linear regressions using normalised preference data and the landscape component variables, including mathematical transformations of these variables. The eight models created predicted over sixty percent of variance in the responses and had moderate to high correlations with a second set of landscape preference data. A common base to the models were the variables of complexity, water and mountain landform, in particular the presence or absence of water and mountains was noted as being significant in determining landscape scenic preference. In order to fully establish the utility of these models, they were further tested against: changes in weather and season; the addition of cultural structures; different photographers; alternate film types; different focal lengths; and composition. Results showed that weather and season were not significant in determining landscape preference; cultural structures increased preferences for landscapes; and photographs taken by different people did not produce consistent results from the predictive models. It was also found that film type was not significant and that changes in focal length altered preferences for landscapes.
5
Williams, Philip. "Chemical investigations of marine cyanobacteria : the search for new anticancer agents from the sea /". Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/6878.
Testo completo
6
Man, Kwok Wai. "The development of surfactant-medicated analytical methods for the determination of cyanobacterial toxins in natural waters /". access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-bch-b19887875a.pdf.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--City University of Hong Kong, 2005."Submitted to Department of Biology and Chemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references.
7
Lotierzo, Manuela. "Biological and artificial receptors in affinity sensor for water toxins detection". Thesis, Cranfield University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274040.
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8
Dale, Vanessa Cordelia Meriel. "The study of cyanobacterial toxins by means of tandem mass spectroscopy". Thesis, University of Warwick, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282458.
Testo completo
9
Coyle, Sadie Marie. "Investigations of microcystins (cyanobacterial peptide toxins) : detection, purification and analysis". Thesis, Robert Gordon University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360091.
Testo completo
10
Shams, Shiva. "Diversity, impact and fate of cyanobacterial toxins in freshwater ecosytems". Doctoral thesis, country:DE, 2015. http://hdl.handle.net/10449/24890.
Testo completoAbstract (sommario):
Massive proliferations of cyanobacteria (bloom) are common in aquatic environments worldwide. These blooms are often toxic due to the presence of hepatotoxins or neurotoxins and have become a worldwide environmental problem. Various incidents of animal and human poisonings have been
attributed to these toxins. Therefore, monitoring of potentially toxic cyanobacteria and the associated toxins need to be investigated routinely in each water body. In the first part of present study, LC-MS methods were applied for identifying and quantifying cyanotoxins diversity in Lake Garda. Anatoxin-a (ATX) and microcystins (MC) were always present in this lake with a different seasonal pattern. ATX represented an early summer peak, while MC showed a typical late summer-early autumn peak.The results of toxin analysis also revealed the
presence of 5 variants of MC in this lake, but the variants MC-RRdm was always dominant over the others. In another chapter of this thesis the kinetic aspects of MC transfer from Planktothrix rubescens to Daphnia magna was investigated. Models of MC accumulation obtained from this part of study differed largely as a result of the duration of exposure and initial MC concentrations used. Within the first 24 h of exposure, MC accumulation in D. magna was linear, irrespective of the initial densities
of toxic P. rubescens and MC concentrations. After 48h of exposure, MC accumulation in D. magna showed an exponential pattern. In the last part of this study, the taxonomic identification of new Oscillatoriales was carried out adopting a polyphasic approach and new potential ATX producers were screened through chemical characterization and identification of specific toxins encoding genes. The analyses were made on
several strains isolated from environmental samples collected in Lake Garda. The results allowed identifying a new ATX producer, Tychonema bourrellyi. This is the first
discovery of a planktonic genus belonging to the Oscillatoriales able to produce ATX
11
Phelan, Richard Reginald. "Microcystin enhances the fitness of microcystin producing cyanobacteria at high light intensities by either preventing or retarding photoinhibition". Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020957.
Testo completoAbstract (sommario):
Several genera of cyanobacteria produce microcystin, a monocyclic peptide, with a unique chemical structure. To date, there have been over a 100 different structural variants of microcystin which have been identified. Microcystin production is affected by numerous environmental factors. However, the primary modulating factor for intracellular microcystin quota is the intracellular N:C ratio. No clearly defined biological role has been described for microcystin. Proposed roles for microcystin include defence against plankton grazers, metal chelation, an infochemical and a protectant against oxidative stress. There is sufficient evidence to support a biological role for microcystin in photosynthesis: microcystin is predominantly located in the thylakoid membranes, the microcystin gene cluster is differentially expressed as a function of light and a growth advantage for the microcystin producer in saturating light intensities. The purpose of this study is to investigate a possible biological role for microcystin in preventing photoinhibition and thus explaining the growth advantage observed in toxin-producers over non-toxin-producers. The uptake of exogenous microcystin was observed in Synechocystis PCC 6803 which was internalized and located in the thylakoid membranes and caused the inhibition of photosynthesis. Microcystin variants and increasing concentrations of microcystin-LR had no effect on the fluidity of the thylakoid membranes. The exposure of thylakoid membranes from Synechocystis PCC 6803 to physiologically relevant concentrations of different microcystin variants resulted in the inhibition of photosystem II activity but not photosystem I activity. The inhibition of photosystem II was variant dependent and concentration dependent for microcystin-LR and microcystin-RR. Chlorophyll a fluorescence data showed that photosystem II inhibition was caused by the inhibition of the oxygen evolving complex. Furthermore, a completion study revealed that the microcystin-producing Microcystis PCC 7806 had a competitive advantage over the non-microcystin producing ΔmcyA mutant of Microcystis PCC 7806 at high light intensities. The data indicates that microcystin protects the toxin-producer by either retarding or preventing photoinhibition and thus identifying the first data supported function for microcystin in cyanobacteria.
12
Shams, Shiva [Verfasser]. "Diversity, impact and fate of cyanobacterial toxins in freshwater ecosystems / Shiva Shams". Konstanz : Bibliothek der Universität Konstanz, 2015. http://d-nb.info/1114886548/34.
Testo completo
13
Fischer, Andreas [Verfasser]. "In vitro investigations on uptake and toxicity of cyanobacterial toxins / Andreas Fischer". Konstanz : Bibliothek der Universität Konstanz, 2010. http://d-nb.info/1028937717/34.
Testo completo
14
Norris, Ross L. G. "Toxicology of compounds from the cyanobacterium Cylindrospermopsis raciborskii /". [St. Lucia, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16950.pdf.
Testo completo
15
Ruebhart, David Robert. "Alternative Bioassays for the Detection of Cyanotoxins". Thesis, Griffith University, 2009. http://hdl.handle.net/10072/367103.
Testo completoAbstract (sommario):
Abstract: The presence of cyanobacteria, and their associated toxins, in drinking water supplies presents a public health risk. When specific cyanotoxins are suspected, analyte specific techniques such as HPLC are generally used. However, if there is a bloom of taxa not previously known as toxic, its potential risk has traditionally been determined by the mouse bioassay. Despite its long standing use, this bioassay has several constraints including a lack of precise quantification of cyanotoxins at low concentrations, insensitivity, difficulties in the interpretation of results and slow turnaround time. Additionally, animal ethics guidelines are calling for the elimination of the use of vertebrates for this application. Thus, the aim of this thesis was to investigate, optimise and validate alternative whole organism bioassays for the detection of cyanobacterial toxicity. As this study was industry funded via the Cooperative Research Centre for Water Quality and Treatment, the potential for research uptake in water industry and other laboratories contracted to undertake routine water quality monitoring, was a guiding factor for research outcomes. The general experimental approach was based on investigating dose-response relationships for selected bioassays tested against cyanotoxins and a variety of cyanobacterial aqueous extracts. It was found that neither the ToxScreen-II Test, a proprietary bioassay employing the bioluminescent test organism Photobacterium leiognathi, nor any of a comprehensive panel of bacteria tested in the disc diffusion bioassay, was sensitive to cylindrospermopsin or microcystin-LR at a maximum concentration of 800 µg/L. The bacteria species tested by disc diffusion technique were also not sensitive to a variety of aqueous cyanobacterial extracts; however, the yeast Saccharomyces cerevisiae indicated selective sensitivity to cylindrospermopsin and an aqueous extract Cylindrospermopsis raciborskii. It was recommended, that future studies of the suitability of S. cerevisiae for detecting cylindrospermopsin, utilise a growth inhibition bioassay utilising a liquid medium with the endpoint measured by photometric determination of turbidity. The importance of the correct taxonomic identification of Artemia species used in the brine shrimp nauplii bioassay was addressed. It was found that Artemia franciscana, not the commonly cited Artemia salina, represented the vast majority of studies in which Artemia was used as an experimental test organism. A validated and optimised A. franciscana nauplii bioassay was reported with maximum sensitivity at 72 h with LC50 values of 0.58 (0.54-0.63) dw µg/mL for cylindrospermopsin and 2.0 (1.8-2.2) dw µg/mL for microcystin-LR. This species was also used to investigate the protective efficacy of the antioxidants vitamin E and Trolox against microcystin-LR. It was revealed that both of these antioxidants offered significant protection against the lethal effect of microcystin-LR. These findings support the use of A. franciscana as a suitable test organism for both the detection of cyanotoxins and as a model for exploring mechanisms of toxicity. It was found, however, that caution should be exercised regarding the importation and free availability of this species because of its invasive potential in Australia. Thus, the native Australian species of brine shrimp Parartemia spp. should be investigated for future bioassay development. An insect bioassay was developed using the globally distributed speckled cockroach Nauphoeta cinerea for the selective detection of Paralytic Shellfish Poison toxicity of an Anabaena circinalis aqueous extract and saxitoxin. This bioassay was found to be tolerant to cylindrospermopsin and microcystin-LR at doses 10 fold greater than the mouse LD50 values while being sensitive to saxitoxin. Likewise, it was found to be tolerant of toxin containing aqueous extracts of C. raciborskii, Microcystis aeruginosa and Nodularia spumigena while being sensitive to A. circinalis. Peak sensitivity of N. cinerea to saxitoxin was 60 min post injection with an ED50 of 31.2 (27.7-35.1) ng/g body weight. As the limits of detection for whole organism bioassays are often considerably higher than the health alert values for cyanotoxins, techniques for sample concentration were considered. The use of passive sampler technology was demonstrated for the sequestration and concentration of cylindrospermopsin and deoxy-cylindrospermopsin with the recommendation that future studies refine this technology and that its use is combined with laboratory bioassays. Both the A. franciscana nauplii and N. cinerea bioassays were deemed as suitable complementary methods for extending the laboratory capacity in commercial laboratories, normally contracted to undertake cyanobacterial monitoring, to include toxicity testing.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Public Health
Griffith Health
Full Text
16
Osborne, Nicholas John Thomas. "Investigation of the toxicology and public health aspects of the marine cyanobacterium, Lyngbya majuscula /". [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18107.pdf.
Testo completo
17
Senogles-Derham, Peta-Joanne. "The evaluation of methods for the removal of cyanobacterial toxins and formation of treatment by-products /". [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17139.pdf.
Testo completo
18
Jayatissa, Loku Pullukkuttige. "The role of cyanobacterial toxins as grazing inhibitors in the fresh water cladoceran Daphnia magna straus". Thesis, University of Stirling, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261824.
Testo completo
19
Knierim, Tika L. "The photodegradation of domoic acid and the effects of metal chelation /". Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/knierimt/tikaknierim.html.
Testo completo
20
Antoniou, Maria G. "Mechanistic studies on the degradation of cyanobacterial toxins and other nitrogen containing compounds with hydroxyl and sulfate radical based Advanced Oxidation Technologies". University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1267460267.
Testo completo
21
Andrade, Fabiana Martins de. "Determinação de cianotoxinas em amostras de florações de cianobactérias coletadas em pesque-pagues e pisciculturas situadas na região do Alto Mogi". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-12112009-153503/.
Testo completoAbstract (sommario):
O crescimento acelerado da aqüicultura no estado de São Paulo, ou seja, a implantação de pesque-pagues e pisciculturas pode estar causando uma série de problemas ambientais. A contribuição para o processo de eutrofização é uma das conseqüências desses empreendimentos, pois tanto os tanques utilizados na piscicultura como os afluentes em torno desses estabelecimentos, estão sendo eutrofizados pelo excesso de nutrientes. Uma das conseqüências da eutrofização é o aparecimento de florações de cianobactérias, e a principal preocupação está nas toxinas liberadas por estas cianobactérias, que se ingeridas pelos seres humanos e animais, podem causar efeitos de intoxicação, como fraqueza, cefaléia, vômito e dependendo da concentração ingerida pode levar à morte. Desta forma é necessário que haja um programa de controle da qualidade da água dos tanques e reservatórios e também dos peixes que ali são criados, pois florações de cianobactérias vêm sendo encontradas em diversos corpos d\'água. Este estudo teve como foco a determinação da cianotoxina microcistina-LR, empregando técnicas como a extração em fase sólida e a cromatografia líquida para a detecção e quantificação da microcistina-LR em amostras de florações de cianobactérias. Os testes feitos com a extração em fase sólida demonstraram que esse procedimento não se faz necessário para todas as amostras, pois houve casos em que não se obteve diferença nos picos interferentes mais próximos ao tempo de retenção do analito de estudo. Como as matrizes desse tipo de amostras são muito complexas e variam muito conforme o meio em que se encontram, recomenda-se que sejam avaliados caso à caso a necessidade de se promover a extração em fase sólida, pois o mesmo é um processo que demanda um tempo maior de análise e conseqüente aumento nos custos. Foi determinado e validado um método cromatográfico considerado capaz de fornecer dados reproduzíveis e confiáveis, por meio de testes de seletividade, limite de detecção e de quantificação, linearidade, precisão, exatidão e recuperação, conforme critérios de aceitação da Resolução n°899 de 2003, da ANVISA. O limite de detecção do método ficou estipulado em 0,1 µg mL-1, e o limite inferior de quantificação em 0,5 µg mL-1, determinados conforme a relação sinal-ruído proposta pelo Guia de Validação de Métodos Bioanalíticos da ANVISA. A quantificação da microcistina-LR foi feita utilizando o método de superposição de matriz, que minimiza e/ou compensa o efeito de matriz ou de possíveis interferentes presentes na amostra, e a curva analítica obtida y = 1,5888+21,849 x, com um coeficiente de correlação de 0,997 mostra uma boa linearidade. Foram analisadas amostras de florações de cianobactérias, coletadas em pesque-pagues e pisciculturas situadas na região do Alto Mogi (subdivisão da bacia do Mogi Guaçu), conforme o método de extração e análise estudado.The rapid growth of aquaculture in the state of São Paulo may be causing a number of environmental problems. The contribution to the eutrophication process is among the consequences of these undertakings, given that the tanks used in fish farming as well as the changes around these establishments are becoming eutrophic systems due to excessive nutrients. A frequent consequence of eutrophication in waters is the massive development of cyanobacteria.The occurrence of these blooms induces severe problems, as Microcystis aeruginosa, the most widespread distributed cyanobacteria, which can produce microcystin-LR. Toxic effects of MC have been described in liver, lungs, stomach, and intestine. Deaths in wildlife, livestock and human beings were also associated with microcystin exposition, which can occur directly by ingestion, inhalation, contact, intravenous inoculation of contaminated water (hemodialysis) or indirectly, by the consumption of animals, as fish and mollusks, the major ingestors of cyanobacteria and its toxins. Thus we need a program to control the quality of water tanks and reservoirs and also the fish breeded there, as cyanobacteria blooms have been found in various water bodies. This study focused on the determination of the cyanotoxins microcystin-LR, using techniques such as solid phase extraction and liquid chromatography for the detection and quantification of microcystin-LR in samples of cyanobacteria blooms. Tests performed with solid phase extraction showed that this procedure is not necessary for all the samples because there were cases where no difference was obtained in interfering peaks near the retention time of the analyte studied. As the parent of such samples are very complex and vary greatly, because the extracts contained too much coextrated material that interfered in the LC-UV detection, and depending on the way in which it is recommended to be assessed, case by case, the solid phase extraction needs to be promoted, because it is a process that demands a longer period of analysis and consequently an increase in costs. A liquid chromatography method was established and validated, which is deemed capable of providing reproducible and reliable data, by testing for selectivity, limit of detection and quantification, linearity, precision, accuracy and recovery, in accordance with the acceptance criteria of Resolution No. 899 of 2003 of ANVISA. The detection limit of the method was set at 0.1 µg mL-1, and the lower limit of quantification at 0.5 µg mL-1 determined according to the signal to noise ratio proposed by the Validation Guide of Bioanalytical Methods, ANVISA. Quantification of microcystin-LR was performed using the matrix-matched method, which minimizes and/or offsets the effect of possible matrix interference or present in the sample. The analytical curve obtained y = 1.5888 + 21.849 x, with a coefficient of correlation of 0.997 shows a good linearity. Real aquaculture samples were analyzed that were detected and quantified according to the method developed.
22
Jaja-Chimedza, Asha D. "Contribution of Lipophilic Secondary Metabolites to the Toxicity of Strains of Freshwater Cyanobacterial Harmful Algal Blooms, Identified Using the Zebrafish (Danio rerio) Embyo as a Model for Vertebrate Development". FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1535.
Testo completoAbstract (sommario):
Cyanobacteria (“blue-green algae”) are known to produce a diverse repertoire of biologically active secondary metabolites. When associated with so-called “harmful algal blooms”, particularly in freshwater systems, a number of these metabolites have been associated - as “toxins”, or commonly “cyanotoxins” - with human and animal health concerns. In addition to the known water-soluble toxins from these genera (i.e. microcystins, cylindrospermopsin, and saxitoxins), our studies have shown that there are metabolites within the lipophilic extracts of these strains that inhibit vertebrate development in zebrafish embryos. Following these studies, the zebrafish embryo model was implemented in the bioassay-guided purification of four isolates of cyanobacterial harmful algal blooms, namely Aphanizomenon, two isolates of Cylindrospermopsis, and Microcystis, in order to identify and chemically characterize the bioactive lipophilic metabolites in these isolates.
We have recently isolated a group of polymethoxy-1-alkenes (PMAs), as potential toxins, based on the bioactivity observed in the zebrafish embryos. Although PMAs have been previously isolated from diverse cyanobacteria, they have not previously been associated with relevant toxicity. These compounds seem to be widespread across the different genera of cyanobacteria, and, according to our studies, suggested to be derived from the polyketide biosynthetic pathway which is a common synthetic route for cyanobacterial and other algal toxins. Thus, it can be argued that these metabolites are perhaps important contributors to the toxicity of cyanobacterial blooms. In addition to the PMAs, a set of bioactive glycosidic carotenoids were also isolated because of their inhibition of zebrafish embryonic development. These pigmented organic molecules are found in many photosynthetic organisms, including cyanobacteria, and they have been largely associated with the prevention of photooxidative damage. This is the first indication of these compounds as toxic metabolites and the hypothesized mode of action is via their biotransformation to retinoids, some of which are known to be teratogenic. Additional fractions within all four isolates have been shown to contain other uncharacterized lipophilic toxic metabolites. This apparent repertoire of lipophilic compounds may contribute to the toxicity of these cyanobacterial harmful algal blooms, which were previously attributed primarily to the presence of the known water-soluble toxins.
23
Downing, T. G. "The role of nitrogen in the regulation of microcystin content in Microcystis aeruginosa". Thesis, Stellenbosch : Stellenbosch University, 2005. http://hdl.handle.net/10019.1/50523.
Testo completoAbstract (sommario):
Thesis (PhD)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: Several genera of cyanobacteria produce a range of toxins. The increased rate of eutrophication of surface fresh waters due to anthropogenic inputs has resulted in more frequent and severe cyanobacterial bloom events. Such bloom events make impoundments unsuitable for recreational use and increase the cost of production of potable water due to the necessity for removal of toxins released from cells during the purification process. Microcystis aeruginosa is the major freshwater bloom-forming toxic cyanobacterium. Concentrations of the hepatotoxin, microcystin, are highly variable in blooms. Published literature on environmental conditions leading to increased microcystin production was often contradictory and in many cases did not consider all relevant parameters. However, environmental nitrogen and phosphorus, temperature and light, and growth rate were implicated in regulation of toxin content. The purpose of this work was therefore to investigate environmental factors (specifically nitrogen and phosphorus) and cellular activities (specifically carbon fixation and nitrogen uptake rates and growth rate) involved in the modulation of microcystin production in M. aeruginosa in order to clarify the role of these parameters, and in an attempt to identify regulatory mechanisms for microcystin production. Environmental nitrogen, phosphorus and growth rate were shown to co-modulate microcystin production in M. aeruginosa. Adequate phosphorus is required for photosynthetic carbon fixation. Phosphorus uptake by M. aeruginosa is strongly correlated with carbon fixation rate. Although microcystin content increased with increasing nitrogen:phosphorus ratios in culture medium, under phosphorus limitation microcystin content was lower irrespective of nitrogen concentrations. This observation and the requirements for fixed carbon for nitrogen assimilation therefore prompted investigation of the effects of cellular carbon fixation and nitrogen uptake in the modulation of microcystin production. Microcystin production was found to be enhanced when nitrogen uptake rate relative to carbon fixation rate was higher than that required for balanced growth. The cellular nitrogen:carbon ratio above which microcystin concentrations increased substantially, corresponded to the Redfield ratio for balanced growth. Investigation of potential regulatory mechanisms involving the cyanobacterial nitrogen regulator, NtcA, yielded putative NtcA binding sites indicative of repression in the microcystin synthetase gene cluster. In culture, the polypeptide synthetase module gene, mcyA, and ntcA were inversely expressed as a function of carbon-fixation:nitrogen-uptake potential. However, no increase or decrease in microcystin production could be linked to either glutamine, glutamate or a-ketoglutarate, metabolites that are involved in regulation of ntcA. The role of NtcA in regulation of microcystin production could therefore not be confirmed. In conclusion, these data suggest that microcystin production is metabolically regulated by cellular C:N balance and specific growth rate. The primary importance of nitrogen and carbon was demonstrated by a simple model where only nitrogen uptake, carbon fixation and growth rate were used to predict microcystin levels. The model also explains results previously described in literature. Similarly, an artificial neural network model was used to show that the carbon fixation dependence on phosphorus allows accurate prediction of microcystin levels based on growth rate and environmental nitrogen and phosphorus.
AFRIKAANSE OPSOMMING: Verskeie genera van sianobakterieë produseer 'n verskeidenheid van toksiene. Die toename in die tempo van eutrofikasie van varswater oppervlaktes as gevolg van antropogeniese insette veroorsaak al hoe meer en al hoe erger sianobakteriële infestasies. Dit veroorsaak probleme vir ontspanninggebruik van hierdie waters en verhoog die koste van produksie van drinkbare water as gevolg van die noodsaak om die toksiene wat deur die selle gedurende die suiweringsproses vrygelaat word te verwyder. Microcystis aeruginosa is die belangrikste varswater bloeisel-vormende toksiese sianobakterium. Die konsentrasie van die hepatotoksien mikrosistien is hoogs varieerbaar in sulke bloeisels. Gepubliseerde literatuur oor die omgewingskondisies wat lei na verhoogde mikrosistienproduksie is dikwels weersprekend en neem in vele gevalle nie al die relevante parameters in ag nie. Desnieteenstaande word omgewingstikstof, fosfor, temperatuur en lig, asook groeisnelheid, geïmpliseer in die regulering van toksieninhoud. Die doel van hierdie navorsing was dus om omgewingsfaktore (spesifiek stikstof en fosfor) en sellulêre aktiwiteite (spesifiek koolstoffiskering en die snelheid van stikstofopname en van groei) betrokke by die modulering van mikrosistienproduksie in M. aeruginosa te ondersoek in 'n poging om die rol van hierdie parameters te verstaan en om regulatoriese meganismes vir mikrosistienproduksie te identifiseer. In hierdie studie is aangetoon dat omgewingstikstof en fosfor sowel as groeisnelheid mikrosistienproduksie in M. aeruginosa ko-moduleer. Genoegsame fosfor word benodig vir fotosintetiese koolstoffiksering. Fosforopname deur M. aeruginosa korreleer sterk met die snelheid van koolstoffiksering. Alhoewel mikrosistieninhoud toegeneem het met 'n toename in die stikstof:fosfor verhouding in die kultuurmedium, was die mikrosistieninhoud onder kondisies van fosforlimitering laer ongeag die stikstofkonsentrasie. Hierdie waarneming, tesame met die noodsaak van gefikseerde koolstof vir stikstofassimilering, het gelei na 'n studie van die effekte van sellulêre koolstoffiksering and stikstofopname op die modulering van mikrosistienproduksie. Dit is gevind dat mikrosistienproduksie verhoog was wanneer die snelheid van stikstofopname relatief tot die snelheid van koolstoffiksering hoër was as die waarde wat benodig word vir gebalanseerde groei. Die sellulêre stikstof:koolstof verhouding waarbo mikrosistienkonsentrasies beduidend verhoog is stem ooreen met die Redfield verhouding vir gebalanseerde groei. 'n Ondersoek na potensiële reguleringsmeganismes waarby die sianobakteriële stikstofreguleerder NtcA betrokke is het gelei na die ontdekking van moontlike NtcA bindingseteis; dit kan dui op die repressie van die mikrosistiensintetase geengroepering. Onder kultuurkondisies is gevind dat die geen vir die polipeptiedsintetase module, mcyA, en ntcA omgekeerd uitgedruk word as 'n funksie van koolstofopname:stikstofopname potensiale. Geen toename of afname in mikrosistienproduksie kon egter gekoppel word aan óf glutamien, óf glutamaat, óf a-ketoglutaraat nie, metaboliete wat betrokke is by die regulering van ntcA. Die rol van NtcA in die regulering van mikrosistienproduksie kon dus nie bevestig word nie. Die gevolgtrekking is dus gemaak dat mikrosistienproduksie metabolies gereguleer word deur die C:N balans en die spesifieke groeisnelheid. Die primêre belang van stikstof en koolstof is gedemonstreer deur 'n eenvoudige model waarin slegs stikstofopname, koolstoffiksering en groeisnelheid gebruik word om mikrosistienvlakke te voorspel. Die model verklaar ook resultate wat tevore in die literatuur beskryf is. Soortgelyk is 'n artifisiële neurale netwerkmodel gebruik om te toon dat die afhanklikheid van koolstoffiksering van fosfor akkurate voorspelling van mikrosistienvlakke gebaseer of groeisnelheid en omgewingstikstof en fosfor moontlik maak.
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Boff, Paulo Henrique. "Avaliação sazonal da comunidade fitoplantônica e da cianotoxina microcistina e a relação com parâmetros físico-químicos em três lagoas do município de Osório - RS". reponame:Repositório Institucional da UCS, 2017. https://repositorio.ucs.br/handle/11338/3276.
Testo completoAbstract (sommario):
A extensa rede de lagoas presente no litoral do Rio Grande do Sul constitui ecossistemas de grande diversidade ecológica. Esses corpos de água, também se caracterizam por apresentarem pequena profundidade, tornando-os sensíveis às mudanças naturais ou antrópicas. As interferências antrópicas podem acarretar em diversas modificações físicas e químicas, provocando a eutrofização dos corpos de água. Esse processo modifica as variáveis ambientais em diversos aspectos, influenciados principalmente pela concentração de nutrientes inorgânicos, penetração da luz, temperatura e pH da água, bem como a alteração da comunidade fitoplanctônica, especialmente as cianobactérias. Assim, o presente trabalho teve como objetivo avaliar a dinâmica da comunidade fitoplanctônica e da cianotoxina Microcistina e a relação com parâmetros físico-químicos em três lagoas localizadas no Município de Osório-RS. Os dados foram obtidos por meio de amostragens realizadas sazonalmente em quatro pontos amostrais distribuídos em três lagoas (Marcelino, Peixoto e Pinguela). As amostras foram analisadas quanto aos parâmetros físico-químicos, a densidade fitoplanctônica e a concentração de microcistina. Com base nos dados obtidos foram elaboradas PCA’s considerando os parâmetros fisico-químicos e a relação com o fitoplâncton, bem como avaliada a relação entre as variáveis utilizando-se a correlação de Spearman. Os resultados mostram um processo de eutrofização nas lagoas estudadas, onde 67,6% da variabilidade ambiental total nos pontos amostrais está relacionada diretamente à clorofila-a, DBO5, N-NH4, P-total, condutividade e inversamente à transparência de Secchi. Quanto à dinâmica da comunidade fitoplanctônica conforme os parâmetros físico-químicos, a análise demonstrou efeito antagônico das variáveis com carga positiva (N-NH4, DBO5, P-total, clorofila-a, condutividade, densidade de Cyanophyceae, Chlorophyceae e Bacillariophyceae) versus as de carga negativa (transparência de Secchi). A concentração de microcistina variou de 0,02μg/L a 0,51 μg/L, permanecendo abaixo do limite permitido pela legislação brasileira para água potável. Contudo, a baixa concentração não assegura que os corpos hídricos estudados estejam livres de cianotoxinas, uma vez que não foram analisadas outras toxinas, como cilindrospermopsina, saxitoxina e anatoxina-a, abordadas na legislação vigente e produzidas por espécies pertencentes ao mesmo grupo taxonômico. Com os resultados verifica-se um nítido gradiente de eutrofização entre as lagoas, que se inicia na Marcelino, que é o corpo receptor do efluente doméstico proveniente de Osório, e segue em direção ao norte. Esse gradiente influencia diretamente a comunidade fitoplanctônica e favorece condições e recursos para o crescimento de grupos relacionados a elevada eutrofização, como as classes Chlorophyceae, Cyanophyceae e Bacillariophyceae. Apesar da baixa concentração da cianotoxina microcistina, o elevado número de cianobactérias encontradas durante a amostragem sugere que outras cianotoxinas possam estar presentes em altas concentrações nas lagoas. A elevada densidade de indivíduos do gênero Dolichospermum evidencia a necessidade de um constante monitoramento das lagoas, uma vez que a presença deste grupo taxonômico acarreta a possibilidade da existência de diversas cianotoxinas causadoras de efeitos nocivos à população humana, além de impactar os organismos aquáticos e a vida selvagem de diversas formas.Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2017-11-08T10:52:54Z No. of bitstreams: 1 Dissertacao Paulo Henrique Boff.pdf: 10630714 bytes, checksum: fd78c4c0389ab8da31133f0f28a7836e (MD5)
Made available in DSpace on 2017-11-08T10:52:54Z (GMT). No. of bitstreams: 1 Dissertacao Paulo Henrique Boff.pdf: 10630714 bytes, checksum: fd78c4c0389ab8da31133f0f28a7836e (MD5) Previous issue date: 2017-11-01
Petróleo Brasileiro, PETROBRAS
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Masango, Mxolisi Goodwill. "A comparative analysis of the cytotoxicity of cyanotoxins using in vitro (cell culture) and in vivo (mouse) assays". Diss., Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-05122008-100402/.
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Balsano, Evelyn [Verfasser], Lima Stephan [Akademischer Betreuer] Pflugmacher, Lima Stephan [Gutachter] Pflugmacher, Enamul [Gutachter] Hoque e Vera [Gutachter] Meyer. "Uptake, physiological responses and technical application of the aquatic fungus Mucor hiemalis EH5 for the removal of cyanobacterial toxins / Evelyn Balsano ; Gutachter: Stephan Pflugmacher Lima, Enamul Hoque, Vera Meyer ; Betreuer: Stephan Pflugmacher Lima". Berlin : Technische Universität Berlin, 2017. http://d-nb.info/1156011086/34.
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Müller, Luciana. "Avaliação da toxicidade e degradação de M. aeruginosa e Microcistina-LR por AOPs e nanopartículas de prata". Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2601.
Testo completoAbstract (sommario):
Florações de cianobactérias são facilmente encontradas, devido ao crescente aporte de nutrientes nos corpos de águas naturais e artificiais, ocasionado pelos acelerados processos de eutrofização frutos da ocupação urbana e rural sem a observação de critérios mínimos. Microcystis aeruginosa é uma espécie de cianobactéria potencialmente produtora de cianotoxinas, comumente associada a casos de intoxicação em escala mundial. Novas tecnologias para o tratamento de água têm sido implementadas para cumprimento dos padrões de potabilidade exigidos pela legislação. O presente trabalho buscou analisar a produção científica mundial relacionada ao tratamento de água com presença de M.aeruginosa e MCLR, buscando identificar o estado da arte, além de embasar a discussão dos métodos propostos. O presente estudo está dividido em três artigos, no primeiro realizou-se uma análise bibliométrica das pesquisas mundiais relacionadas à cianobactérias, cianotoxinas e o tratamento de água, a partir da base de dados Scopus. No segundo artigo buscou-se avaliar a aplicabilidade dos AOPs UV-C e UV-C/H2O2 na degradação de Microcystis aeruginosa BB005 e MC-LR, e a análise dos efeitos da adição de nanopartículas de Ag, com base em um produto comercial composto por peróxido de hidrogênio (H2O2) e nanopartículas de prata (NAg). No terceiro artigo buscou-se avaliar a qualidade da água produzida a partir de ensaios de toxicidade aguda com Daphnia magna. Os resultados indicam que a fotólise e o processo UV-C/H2O2 apresentaram resultados satisfatórios, sendo uma alternativa eficiente. Porém, os resultados dos ensaios de ecotoxicidade inferem que estes tratamentos utilizados com a finalidade de degradar M. aeruginosa e MC-LR, possuem potencial de geração de subprodutos de degradação tóxicos: os ensaios com D. magna demonstraram toxicidade mesmo quando a água submetida a fotólise foi diluída quatro vezes. Com relação ao processo UV-C/H2O2 (sem e com adição de NAg), a amostra foi tóxica quando não diluída. Já quando empregada as NAg combinadas a radiação UV-C, esta apresentou toxicidade extremamente alta, afetando a mobilidade de todos os organismos teste em todas as diluições (até 16 x).Cyanobacterial blooms are easily found, due to the increasing nutrient supply in natural and artificial bodies of water, caused by the accelerated processes of eutrophication, fruits of urban and rural occupation without observing minimum criteria. Microcystis aeruginosa is a specie of cyanobacteria that are potentially cyanotoxin-producing, commonly associated with cases of worldwide intoxication. New technologies for water treatment have been implemented to meet the standards of potability required by legislation. The present study looked for analyze the world scientific production related to the treatment of water with presence of M. aeruginosa and MC-LR, seeking to identify the state of the art, besides supporting the discussion of the proposed methods. The present study is divided into three articles, the first one was a bibliometric analysis of the world-wide research related to cyanobacteria, cyanotoxins and water treatment, from the Scopus database. In the second article evaluated the aplicability of UV-C e UV-C/H2O2 AOPs on degradation of Microcystis aeruginosa BB005 and MC-LR, and the analysis of effects Ag nanoparticles addition, based on a commercial product composed of hydrogen peroxide (H2O2) and silver nanoparticles (NAg). In the trird article evaluated the water quality produced, from acute toxicity tests with Daphnia magna. The results indicate that photolysis and the UV-C/H2O2 process presents satisfactory results, being an efficient alternative. However, the results of the ecotoxicity assays infer that these treatments used for the purpose of degrading M. aeruginosa and MCLR, have potential to generate toxic degradation byproducts: the D. magna assays demonstrated toxicity even when the water submitted to photolysis was diluted four times. Regarding the UV-C/H2O2 process (without and with NAg addition), the sample was toxic when undiluted. When NAg was used in combination with UV-C radiation, it showed extremely high toxicity, affecting the mobility of all test organisms at all dilutions (until 16x).
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Chaivimol, Jittra. "The study of peptide toxins from freshwater cyanobacteria". Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389448.
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Pope, Phillip Byron. "Metagenomics of Cyanobacterial Blooms". Thesis, Griffith University, 2007. http://hdl.handle.net/10072/368095.
Testo completoAbstract (sommario):
Cyanobacteria are a diverse and widely distributed group of organisms common in soil and in both marine and freshwater. Under favorable conditions they can reproduce explosively, forming dense concentrations called blooms. Fresh water cyanobacterial blooms in particular are commonly associated with toxin production in drinking water supplies and are increasingly becoming a risk to human health. Beyond toxin production these extremely complex, constantly interacting and changing microbial communities have vast impacts on their surrounding ecosystem. The triggers that initiate bloom formation and/or toxin production remain poorly understood. This stems from the fact that there is still very little known of cyanobacterial bloom population structure and their function in the real environment. A greater understanding of the interactions of different microbial populations and their functions in the blooming process leading to toxin production could come from using metagenomics to investigate the genetic and metabolic diversity of the mixed populations rather than the difficult to culture cyanobacteria. Two distinct cyanobacterial bloom communities existing in contrasting Australian freshwater lakes were selected and high molecular weight DNA extracted. PCR-amplified 16S rRNA genes were subsequently cloned and a total of 75 clones from Lake Samsonvale and 50 clones from Lake Ainsworth were examined. Sequences identified belonged to species from 6 different phyla from the Bacterial domain, including Cyanobacteria, Actinobacteria, Firmicutes, Verrucomicrobium, Bacteroidetes, and á-, â- and ã-Proteobacteria. The majority of the bacterial sequences were most closely related to sequences recovered from other freshwater clones or isolates (80% homology), whilst few were closely related to sequences recovered from soil or marine habitats. In particular 9 % of the total sequences were most closely related to sequences recovered from freshwater lakes that are susceptible to cyanobacterial blooms. A total of 12 novel clusters consisting of 22 sequences were noted spanning all divisions represented in the analysis. Of this, 7 were found to lack any close relatives suggesting that sequences in these clusters may be characteristic for bloom events. Preliminary results also indicate that physio-chemical differences in lake character appear to influence bacterial community composition associated with cyanobacterial blooms. Bloom communities from Lake Samsonvale demonstrated high levels of toxinproducing Cyanobacteria and uncultured Actinobacteria. These findings were used to justify its selection for further metagenomic analysis to gain insights into the genomes of these and other organisms. DNA was fractionated and used to construct a bacterial artificial chromosome library (CBNPD1) of 2,850 clones which had an average insert size of 27 kb. A PCR-based single-gene polyketide synthase library was constructed in tandem and used as an additional assurance that high quality DNA was being extracted and cloned. Phylogenetic analysis of gene sequences recovered from this library demonstrated an abundance of novel bacterial polyketide synthase genes. Sequence-based screening of library CBNPD1 was performed to identify clones of interest and provide a physiological insight within cyanobacterial blooms. A random BAC-end sequence survey generated 67 sequences (40 kb in total) from 36 randomly selected clones. G+C composition ranged from 33.33 to 72.91%. Fifteen sequence tags (22%) were found most similar to sequences affiliated to genera with no available genome. Another 17 sequence tags (25%) were most similar to sequences affiliated to genera with available genomes, however similarities were less than 80%. Sequence tags were also found with affiliation to proteins involved in a wide array of cell metabolism processes including amino acid metabolism (e.g. methionine synthase), carbohydrate metabolism (cellulose), inorganic ion metabolism (nitrite/sulfite reductase), and lipid metabolism (fatty acid hydroxylase). A number of genes involved in cell structures (e.g. flagella), DNA processes, energy production (photosynthetic reaction center L subunit) and defense mechanisms (nucleases) were also affiliated to sequence tags. PCR screening of CBNPD1 was used to detect clones containing 16S rDNA to establish a link between physiological and phylogenetic information of uncharacterized microorganisms in cyanobacterial blooms. Screens from 480 clones identified 2 clones containing a 16S rRNA gene. Clone 545 and 578 contained 16S rDNA affiliated to 2 different phylogenetic genera within the Proteobacteria division, Pseudomonas and Roseateles respectively. From library screens 7 BAC inserts were selected and sequenced to completion comprising 144 kb of a cyanobacterial bloom metagenome and spanning 3
phyla including Proteobacteria, Actinobacteria and Bacteroidetes. 130 genes have been identified and assigned to COG (clusters of orthologous groups of proteins) functional categories. Also identified, were many housekeeping proteins spanning the majority of the COG functional groups as well as physiologically and ecologically important proteins some of which were looked at more in depth. These include a putative phenylacetyl catabolon, a putative
RTX toxin, several putative oxidoreductases and several putative bacterial transcriptional regulators that are inferred in controling a wide variety of activities in various biological processes, the most notable being quorum
sensing. This culture-independent experimental approach has provided a phylogenetic community snap shot of the cyanobacterial bloom community structure and their physiological functions within the bloom. Moreover it represents an important biodiversity resource which has already been shown to contain novel biomolecular biodiversity.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Biomedical Sciences
Faculty of Science
Full Text
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Humpage, Andrew Raymond. "Tumour promotion by the cyanobacterial toxin microcystin /". Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phh9258.pdf.
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Papaefthimiou, Dimitra. "Phylogeny, diversity and toxin production related to cyanobacterial symbioses". Doctoral thesis, Stockholm : Department of Botany, Stockholm university, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6861.
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Misson, Benjamin Olivier. "Potentiel toxique et structure génétique de populations de Microcystis en lien avec les différentes phases de son cycle de vie". Thesis, Clermont-Ferrand 2, 2011. http://www.theses.fr/2011CLF22168/document.
Testo completoAbstract (sommario):
L‟eutrophisation croissante des écosystèmes aquatiques favorise le développement des cyanobactéries, parmi lesquelles Microcystis est la plus représentée dans les régions tempérées. La capacité de Microcystis à produire une puissante hépatotoxine, la microcystine, est à l‟origine de diverses perturbations écologiques, et de nombreuses nuisances sanitaires. La compréhension des facteurs déterminant la toxicité des efflorescences de Microcystis constitue, de fait, un enjeu majeur des recherches actuelles. Dans ce contexte, l‟objectif premier de ce travail de thèse était d‟étudier la variabilité temporelle et l‟implication potentielle de la toxicité de Microcystis à l‟échelle de son cycle de développement annuel. Pour cela, il était nécessaire de considérer, en particulier, les parties les moins connues du cycle de développement : la phase de survie benthique, et les transitions entre les phases benthique et planctonique, via les processus de recrutement et de sédimentation. Nous avons alors étudié le potentiel toxique des populations de Microcystis grâce à des approches complémentaires menées à différentes échelles spatio-temporelles, en considérant à la fois les gènes impliqués dans la synthèse de microcystines, leur transcription et les concentrations en microcystines. Cette étude s‟est appuyée, en parallèle, sur la caractérisation de la structure génétique des populations de Microcystis dans les compartiments benthique et planctonique. La prise en compte systématique de la phase de vie benthique a tout d‟abord permis d‟améliorer nos connaissances sur cette phase du cycle de développement de Microcystis. Ainsi, Microcystis peut survivre plusieurs années en profondeur dans les sédiments, sans que les populations ne perdent leur potentiel toxique, ou que leur structure génétique soit altérée. En revanche, en surface des sédiments, le potentiel toxique et la structure génétique des populations sont variables, de manière similaire à ce qui peut être observé dans la colonne d‟eau. Enfin, ces travaux ont également mis en évidence l‟influence des phases de transition entre l‟eau et les sédiments dans la variabilité du potentiel toxique et de la structure génétique des populations de Microcystis. Les processus de recrutement benthique et de sédimentation occasionnent, en effet, une sélection génétique, qui, bien que paraissant indépendante du potentiel toxique des génotypes, peut grandement affecter le potentiel toxique des sous-populations benthiques et planctoniques de MicrocystisThe increasing eutrophication of aquatic ecosystems promotes the development of cyanobacteria, among which Microcystis is the most widespread in temperate regions. The ability of this cyanobacterium to produce a potent hepatotoxin, called the microcystin, represent a serious threat for both natural life and human health. Thus, understanding the factors determining the toxicity of Microcystis blooms is a major challenge of actual research. In this context, the main goal of this work was to study the temporal variability and the potential implication of Microcystis toxicity, at the scale of its annual life cycle. For that, it was necessary to consider more particularly, the least known parts of the cycle : the benthic survival phase, and the transition between the benthic and the planktonic phases, through the benthic recruitment and the sedimentation processes. Then, we studied the toxic potential of Microcystis populations through complementary approaches conducted at different spatio-temporal scales, by considering the genes controlling the synthesis of the microcystin, their transcription and the concentrations of microcystin. In parallel, the genetic structure of Microcystis populations was characterized in both benthic and planktonic compartments. By considering systematically the benthic life stage, we were first able to improve our knowledge on this phase of Microcystis development cycle. Thus, Microcystis is able to survive several years in deep sediments, without the population‟s toxic potential or genetic structure being degraded. On the other hand, at the sediment surface, the toxic potential and the genetic structure of the populations vary, in a similar range to what observed in the water column. Furthermore, this work also shed the light on the influence of benthic-pelagic transitions in the variability of the genetic structure and the toxic potential of the populations of Microcystis. Indeed, a genetic selection occurs during the benthic recruitment and the sedimentation processes. Although such a selection does not seem to rely on the toxic potential of the genotypes, it can greatly modify the toxic potential of both benthic and planktonic sub-populations of Microcystis
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Duan, Hongmei. "Monitoring and characterization of toxic cyanobacterial blooms". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66915.
Testo completoAbstract (sommario):
Molecular tools were used to monitor the dynamics of Microcystis populations and the potential microcystin producers in Missisquoi Bay (the Canadian part of Lake Champlain). This study showed the GF/C filters, which are typically used to prepare samples for microcystin analysis, were not ideal for the characterization of total bacterial communities, but were sufficient for the chemical analyses of cyanobacterial microcystins. The mcyD gene copy number determined by Q-PCR correlated well with the microcystin concentration determined by ELISA and HPLC in 2006; therefore mcyD Q-PCR could be used as a rapid and sensitive method and as an effective monitoring system for toxic cyanobacterial blooms in Lake Champlain. Escherichia coli was also monitored as an indicator of manure contamination of lake water. Manure application and rain events positively related to the high nitrogen concentration in the lake in 2006, suggested that good manure management is necessary for the reduction of agricultural nutrient loads into Missisquoi Bay, believed to be a major cause of cyanobacterial blooms.Un suivi de la dynamique des populations de Microcystis qui ont la capacité de produire des toxines a été effectué à la baie Missisquoi (partie canadienne du lac Champlain) à l'aide d'outils moléculaires. Deux types de membranes ont été utilisés : un filtre standard (GF/C) pour quantifier les microcystines, et un filtre pour capturer les bactéries. Cette étude a démontré que le filtre standard (GF/C) est approprié pour déterminer les concentrations de microcystines, mais qu'il n'est pas adéquat pour caractériser avec des techniques moléculaires, les populations de bactéries et de cyanobactéries. Une bonne corrélation a été obtenue en 2006, entre les concentrations de microcystines déterminées par les méthodes ELISA et HPLC et le nombre de copies du gène mcyD (impliqué dans la biosynthèse des microcystines). Les résultats ont donc démontré le potentiel de cette méthode de PCR en temps réel, ciblant le gène mcyD, pour la détection et le suivi des proliférations de cyanobactéries qui produisent des toxines. La présence du pathogène fécal Escherichia coli a été évaluée afin de déterminer la relation entre l'application de lisier et de fumier et l'augmentation dans l'eau du lac, des nutriments qui causent les proliférations. Une bonne corrélation a été obtenue entre l'application du lisier et du fumier et les précipitations ainsi qu'entre les concentrations élevées d'azote dans le lac, suggérant qu'une meilleure gestion des matières fertilisantes est nécessaire pour réduire les apports de nutriments dans la baie Missisquoi.
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Albuquerque, Junior Eden Cavalcanti de. "Produção e caracterização de carvão ativado para remoção de microcistinas". [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267150.
Testo completoAbstract (sommario):
Orientadores: Telma Teixeira Franco, Aparecido dos Reis CoutinhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-08T03:24:02Z (GMT). No. of bitstreams: 1 AlbuquerqueJunior_EdenCavalcantide_D.pdf: 5506754 bytes, checksum: 149084e24491605061535d97418d544f (MD5) Previous issue date: 2006
Resumo: As microcistinas, hepatotoxinas, são os principais agentes tóxicos produzidos pelas cianobactérias. Essas toxinas vêm despertando atenções em razão do aumento do número de registros de florações tóxicas de cianobactérias em reservatórios destinados ao abastecimento público; da descoberta de novas toxinas e dos riscos associados a elas e do aumento de intoxicação aguda e crônica, tanto em animais como em seres humanos. A eficiência na remoção destas toxinas de água por carvão ativado depende de algumas características físico-químicas deste adsorvente, além da matéria-prima utilizada na sua obtenção. Neste trabalho, materiais como casca de macadâmia, endocarpo do coco seco e mesocarpo do coco verde da baía, bagaço de cana-de-açúcar e resíduo de madeira de pinus foram selecionados para obtenção de carvões ativados com potencial aplicação na remoção de microcistina de água potável. Os carvões ativados obtidos da madeira de pinus e bagaço de cana-de-açúcar apresentaram melhores estruturas porosas com ASEBET e Vmesoporos de 1586 e 1222 m2/g e 0,39 e 1,05 cm3/g, respectivamente. A partir de uma investigação da cinética e equilíbrio de adsorção da [D-Leucinal]MCYST-LR por estes dois carvões ativados pulverizados foi possível estimar uma remoção desta toxina acima de 98% em 10 minutos de contato, além de ter sido observada adsorção em monocamada desta toxina, com qm e KL de 161 e 200 J.lg/mg e 1,23 e 2,33 L/mg, respectivamente, estimados a partir do modelo linearizado de Langmuir. A adsorção daquela toxina em processo contínuo foi estudada em leitos fixos dos carvões ativados do endocarpo do coco seco e bagaço de canade-açúcar juntamente com dois carvões ativados amostrados de estações de tratamento de água de dois centros de hemodiálise brasileiros. Após a exaustão de cada leito, o que aconteceu entre 132 e 320 min, foi observado adsorção daquela toxina entre 0,05 J.lg/mg e 5,43 J.lg/mg.
Abstract: Microcystins, hepatotoxins, are the main toxic agents produced by cyanobacteria. A sharp increase in the number of cyanobacteria toxic blooms in drinking water reservoirs, the discovery of news variants of microcystins and the risks associated with them, and the increase of acute and chronic poisoning in animaIs and humans, has drew public attention to cyanobacteria toxins. The removal efficient of these toxins from water by activated carbon depends on physical chemical characteristics of this adsorbent and on the starting material used to prepare the activated carbono ln this work, macadamia nut shell, coconut shell, unripe coconut mesocarp, sugar cane bagasse and pinus wood waste were used to prepare activated carbon with potential application for removing microcystins. The activated carbons from pinus wood and sugar cane bagasse had the porous structures with highest Surface area and volume of mesopore of 1586 and 1222 m2/g and 0.39 and 1.05 cm3/g, respectively. These activated carbons were used to remove [D-LeucineJ]MCYSTLR from water. After 10 minutes of contact time, more than 98%of toxin was removed 19y the activated carbons. The microcystin adsorption monolayer, qm, in the activated carbons recovered 200 and 161 flg/mg, with the Langmuir adsorption constant, KL, of 2.33 and 1.23L/mg. Adsorption of [D-LeucineJ]MCYST-LR in continuos process was studied for a fixed-bed activated carbon prepared from coconut shell and sugar cane bagasse and for t~o comercial activated carbons samples from treatment water plants of two Brazilian hemodialysis centers. Saturation of the beds occurred after 132 to 320 min, and the adsorption capacity for that toxin varied from 0.05 flg/mg to 5.43 flg/mg.
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química
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Mihali, Troco Kaan Biotechnology & Biomolecular Sciences Faculty of Science UNSW. "Biosynthesis of toxic alkaloids in cyanobacteria". Publisher:University of New South Wales. Biotechnology & Biomolecular Sciences, 2008. http://handle.unsw.edu.au/1959.4/41485.
Testo completoAbstract (sommario):
Freshwater cyanobacteria produce a wealth of biologically active metabolites, which can adversely affect human and animal health, and cause great economic damage to the fishing, tourism and water-management industries on a global scale. We describe the molecular genetics and biochemistry of biosynthesis for the cyanobacterial toxic alkaloids cylindrospennopsin, paralytic shellfish toxins (PST) and anatoxin-a. Characterisation of the 43 kb cylindrospennopsin biosynthesis gene cluster (cyr), in Cylindrospermopsis raciborskii AWT205 is described. Biosynthesis is initiated via an amidinotransfer onto glycine followed by five polyketide extensions. Rings are formed via Michael additions, while the uracil ring is formed by a novel mechanism. Tailoring reactions, including sulfation and hydroxylation complete the biosynthesis. We describe the characterisation of PST biosynthesis gene clusters in Anabaena circinalis, Aphanizomenon sp. and Lyngbya wollei. These gene clusters span between 28 and 36 kb and contain genes coding for the biosynthesis and export of PSTs. The Lyngbya wollei PST gene cluster represents a 'natural combinatorial biosynthesis' event, explaining its unique toxin profile. A biosynthetic pathway leading to the formation of saxitoxin and its analogues in these organisms is proposed, and a putative insertion/excision site of the PST gene cluster in Anabaena circinalis 310F was identified. Interestingly, PSTs are produced by distantly related organisms via this unique biosynthesis pathway. We Investigated the phylogenetics of PST biosynthesis genes from four different genera of cyanobacteria. The results suggested that PST biosynthesis in cyanobacteria is an ancient trait, whereby the sporadic distribution of PST production in extant isolates of Anabaena circinalis and Aphanizomenon sp. is a result of the repeated loss of the biosynthetic gene cluster. Horizontal gene ransfer also appears to have had a critical influence on PST biosynthesis in Lyngbya wollei. We additionally propose a hypothetical, mixed non-ribosomal peptide synthetase (NRPS)/polyketide synthase (PKS) biosynthesis scheme for anatoxin-a. Degenerate PCR primers were developed, for the specific amplification of mixed NRPSIPKS hybrid ketosynthase (KS) domains. Gene-walking distally to a novel hybrid KS domain in the anatoxin-a producer Planktothrix rubescens, revealed an orphan gene cluster, denoted pro, which spans 24 kb and codes for a mixed NRPS/PKS system, putatively producing an acetylated and sulphated dipeptide.
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DeMarco, Jonathan R. "Cyanobacterial Blooms in Chautauqua Lake, NY: Nutrient Sources and Toxin Analyses". Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1625052848648708.
Testo completo
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Cornish, Benjamin J. P. A. "The destruction of the cyanobacterial toxin microcystin-LR by semiconductor photocatalysis". Thesis, Robert Gordon University, 2000. http://hdl.handle.net/10059/3094.
Testo completoAbstract (sommario):
In fresh waters where cyanobacteria (blue-green algae) flourish, dense growths known as blooms occur. Such blooms present a threat to human and animal health as many of these cyanobacteria produce toxins. One such group of toxins are the microcystins which are hepatotoxic resulting in haemoraging and tumour promotion in the liver. There have been several reports of human poisonings resulting from the presence of cyanotoxins in potable waters, some of which have resulted in fatalities. The most frequently cited cyanotoxin in these poisonings has been microcystin-LR, which has prompted the World Health Organisation (WHO) to set a guideline for the recommended safe level of this toxin in drinking water of 1 mgl-1. Removal of microcystin-LR from potable waters has proven to be inefficient using conventional water treatment techniques such as coagualtion, filtration and chemical oxidation using chlorine. While activated carbon adsorption and membrane filtration have been shown to physically remove microcystin-LR from water the toxin is not destroyed. Recently the use of photocatalysis was shown to rapidly degrade microcystin-LR even at high concentrations. The process involves the illumination of a titanium dioxide catalyst with ultraviolet (UV) light to produce highly oxidising hydroxyl radicals in solution. While several researchers have demonstrated the process's effectiveness in degrading the toxin none have determined the fate of the compound, or if the toxicity related to microcystin-LR has been removed. This study was carried out to determine if photocatalytic oxidation of microcystin-LR was suitable as a treatment method for potable water supplies. Analysis of treated toxin samples by high performance liquid chromatography (HPLC) with photo-diode array detection (PDA) and mass spectroscopy established that the toxin was not completely degraded during photocatalysis. A simple toxicity assessment however indicated that by-products were non-toxic. Using the data from this work a proposed pathway for toxin destruction was produced giving the speculative identity of some of the by-products. The use of hydrogen peroxide to enhance UV mediated destruction of microcystin-LR has been previously reported. There have also been reports of the enhancement of photocatalytiC reaction in the presence of this oxidant. The work carried out in this study demonstrated that the destruction of microcystin-LR by photocatalysis was both more rapid and more efficient when hydrogen peroxide was present in the system. The use of a fixed film flow reactor was also investigated for microcystin-LR destruction. While degradation of the toxin occurred it was demonstrated that batch reactors were more efficient as a treatment method. The effectiveness of the photocatalytic process on microcystin-RR, -LW and -LF was also investigated. While destruction of a" the variants occurred during photocatalytic treatment each microcystin demonstrated different rates and efficiencies of photooxidation. It was concluded from this study that photocatalysis is a promising treatment method for the removal of microcystin-LR and other variants from potable waters. Further research however is required to assess if the tumour promoting effects of microcystin-LR are rendered inactive and to determine the behaviour of the toxins degradation in natural water supplies. The study also allowed for speculation as to how the degradation of the toxin occurred during the photocatalytic process.
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Delaney, James M. "The biological activity of microcystin-LR, isolated from the cyanobacterium Microcystis aeruginosa against insects". Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308015.
Testo completo
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Craggs, Joanna K. "Structure-function relationships of Clostridium difficile toxin A". Thesis, University of Nottingham, 1999. http://eprints.nottingham.ac.uk/12047/.
Testo completoAbstract (sommario):
Ten overlapping fragments covering the entire Clostridium difficile toxin A gene were cloned and expressed in Escherichia coli. Eight fragments (a', a2, b, c, d, e, f and g) represented the first 5.55kb of the gene whereas two fragments (hl and h2) each spanned the entire C-terminal repeat region of the molecule. All activities relating to binding to carbohydrates (i. e. cold haemagglutination of rabbit erythrocytes), binding to bovine thyroglobulin and non-specific binding to a murine monoclonal antibody were restricted solely to peptides H1 (amino acids [aa] 1834-2683) and H2 (aa 1832-2683). Peptide H2 alone also displayed the ability to bind to cells and to be internalised into endosome-like compartments within the cells. Taken together with the observation that peptide H2 caused a cytopathic effect on Vero cells which was atypical of the holotoxin, these results may indicate that the repeat region of toxin A stimulates intracellular signalling pathways prior to Rho glucosylation. Peptide A2 (aa 1-536) glucosylated recombinant RhoA (rRhoA) in vitro, whereas peptides A'(aa 1-205), B (aa 542-859), C (aa 114-859), D (aa 869-1330), E (aa 542- 1161), G (aa 869-1830) and H2 (aa 1832-2683) did not. The results obtained for peptides A', A2 and C indicate that the first 536 as encompass the catalytic domain for this activity, that more than the first 205 as alone are needed for expression of enzymic activity, and that for a peptide to be active it must not lack the first 113 aa. The first 113 as of the holotoxin are probably essential for the correct folding of the catalytic domain and expression of its activity. These studies were also the first to locate the toxin A ATP binding site to a peptide spanning as 542-859 (peptide B) of the holotoxin. Antibody reaction profiles of antiserum to holotoxin A against toxin A peptides and of antiserum to the peptides against holotoxin A indicate that this region is unexposed in the native state. Also of interest was the observation that the only peptides, which contained the nucleotidebinding site (B and E), lacked the ability to glucosylate rRhoA. Further peptide A2, which possessed glucosyltransferase activity, lacked the nucleotide-binding site. These studies therefore, suggest that a nucleotide-binding site is not required for in vitro glucosylation of rRhoA by toxin A, and fail to identify a role for the toxin A nucleotide binding site. An engineered truncated form of toxin A, consisting of the first 539 as of the holotoxin (encompassing glucosyltransferase activity) fused to the 852 as C-terminal peptide H2 (repeat end binding portion) caused a conventional cytopathic effect (CPE), but was 1,400 fold less cytotoxic to Vero cells than the holotoxin. Peptide A2 (aa 1-536) alone had no effect on Vero cells or in rabbit ileal loops suggesting that peptide H2 aided delivery of the glucosyltransferase molecule into cells leading to a CPE. The truncated toxin lacked the nucleotide binding site and the putative membrane-translocating domain (internal hydrophobic region). The reduced activity of the truncated toxin suggests that although not essential for cytotoxic activity, the nucleotide-binding site and the internal hydrophobic region are important for stability and/or efficient translocation of the holotoxin into the cytosol.
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Elias, Luciana Mecatti. "Análises moleculares, químicas e ecotoxicológicas de cianobactérias presentes em florações de lagoas do estado de São Paulo". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-02082011-154909/.
Testo completoAbstract (sommario):
Cianobactérias são microrganismos que desempenham um papel ecológico fundamental na natureza. O processo de eutrofização em ambientes aquáticos, tais como lagos e reservatórios, constitui um dos principais fatores relacionados à ocorrência de florações de cianobactérias nestes locais. Quatro lagoas presentes no Estado de São Paulo, nas cidades de Campinas, Limeira e Piracicaba foram estudadas visando descobrir a diversidade de cianobactérias presentes, seu potencial para a produção de cianotoxinas e os efeitos destas em organismos aquáticos bioindicadores, como Hydra attenuata. As amostras foram coletadas no mês de setembro de 2010 e divididas em 3 partes: a primeira foi utilizada para extração de DNA de cianobactérias para análises em DGGE, construção de bibliotecas genômicas e amplificação de genes produtores de toxinas; a segunda para a extração de cianotoxinas e análises em LCMS/ MS; e a terceira parte foi usada em ensaios ecotoxicológicos utilizando organismos aquáticos bioindicadores. A análise de DGGE mostrou que o padrão de bandas entre as diferentes amostras ambientais de água pareceu não apresentar grandes variações entre si e mostrou a predominância de poucas UTOs em todas as amostras, o que sugere que nessas localizações algumas espécies são predominantes sobre as outras. A construção de bibliotecas genômica gerou 233 clones, distribuídos da seguinte maneira: 57 clones da lagoa de Limeira, 60 clones da Lagoa do Taquaral, 59 clones da lagoa ESALQ1 e 57 clones da lagoa ESALQ2. Um total de 9 gêneros de cianobactérias foi observado nas amostras das lagoas, os quais são Anabaena, Brasilonema, Cylindrospermopsis, Limnococcus, Microcystis, Nostoc, Pseudanabaena, Synechococcus e Woronichinia. Neste estudo, as lagoas ESALQ2, Taquaral e Limeira apresentaram mais do que 80% da comunidade de cianobactérias avaliadas como sendo do gênero Microcystis. Este fato comprovou que no período analisado estavam ocorrendo florações de Microcystis em 3 das 4 lagoas analisadas. Pela amplificação de genes codificadores de cianotoxinas e cianopeptídeos foi possível detectar a presença de aeruginosina, cianopeptolina, microcistina e saxitoxina nas amostras ambientais. Estes dados foram comprovados através das análises em LC-MS/MS onde foi possível detectar a presença de aeruginosina, cianopeptolina e microcistina. Somente a presença de saxitoxina não foi confirmada por esta análise. Os ensaios toxicológicos com H. attenuata mostraram que todos os extratos foram tóxicos para este organismo teste, com exceção do extrato da lagoa ESALQ2, que causou apenas efeitos sub-letais nestes organismos.Cyanobacteria are microorganisms that play a crucial ecological role in nature. The process of eutrophication in aquatic environments such as lakes and reservoirs, is one of the main factors related to the occurrence of cyanobacterial blooms in these locations. Four ponds located in the state of São Paulo at Campinas, Limeira and Piracicaba cities were studied in order to explore the diversity of cyanobacteria, their potential for cyanotoxins production and their effects on aquatic organisms as biological indicators, such as Hydra attenuata. The samples were collected in September 2010 and divided into 3 parts: the first one was used for cyanobacterial genomic DNA extraction, DGGE analysis, genomic library construction and amplification of toxinproducing genes; the second was used for the cyanotoxins extraction and LC-MS/MS analysis; and the third part was used in ecotoxicological tests using aquatic bioindicators. DGGE analysis showed that the banding pattern between the different water environmental samples did not seem to vary widely among themselves and showed the dominance of a few UTOs in all samples, suggesting that some species in these locations are predominant over the others. The construction of genomic libraries generated 233 clones, distributed as follow: 57 clones from Limeira lake, 60 clones from Taquaral Lake, 59 clones from ESALQ1 lake and 57 clones from ESALQ2 lake. A total of nine genera of cyanobacteria were observed in samples of the ponds, which are Anabaena, Brasilonema, Cylindrospermopsis, Limnococcus, Microcystis, Nostoc, Pseudanabaena, Synechococcus and Woronichinia.In this study, the lake ESALQ2, Taquaral and Limeira had more than 80% of the community of cyanobacteria assessed as belonging to the genus Microcystis. This fact proved that in the analyzed period the occurring blooms were of Microcystis in three of the four lakes studied. By amplification of genes coding for cyanotoxins and cyanopeptides it was possible to detect the presence of aeruginosin, cyanopeptolin, saxitoxin and microcystin in environmental samples. These data were confirmed by LC-MS/MS analysis and it was possible to detect the production of aeruginosin, cyanopeptolin and microcystin. Only the presence of saxitoxin was not confirmed by this analysis. The toxicological tests with H. attenuata demonstrated that all extracts were toxic to this organism, except the extract of ESALQ2 lake, which caused only sub-lethal effects in these organisms.
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Miller, Robert. "EVALUATION OF TOXIC CYANOBACTERIA IN CENTRAL FLORIDA STORMWATER PONDS". Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3089.
Testo completoAbstract (sommario):
Algal blooms are a common occurrence in water bodies of all shapes and sizes throughout the United States and countries around the world. The State of Florida is no exception to this phenomenon. Cyanobacteria, or blue-green algae, have proven to be of special concern due to its proliferation and potential to produce toxins that are harmful to humans, livestock and wildlife. A casual drive along the roads and in the neighborhoods of central Florida will confirm algal conditions in many areas. The potential for exposure to harmful and possibly fatal toxins associated with these algal blooms are becoming more evident as urban development progresses. Detailed studies have been previously performed for large lakes and rivers in the State of Florida, but no studies have been performed regarding stormwater ponds. Since stormwater ponds in residential neighborhoods are a common source for irrigation, research in this area is warranted due to the potential health effects associated with Cyanobacteria. This research was conducted to determine if Cyanobacteria does exist in stormwater ponds and to what extent. Cyanobacteria were found to be in stormwater ponds of various sizes, locations and watersheds in the central Florida area. Even though the algae and its associated toxins were encountered in the stormwater ponds evaluated for this study, the levels detected were much lower than the values discovered in previous studies performed in the larger lakes and rivers around the State.M.S.Env.E.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engineering
42
Pearson, Michael John. "The management of a national environmental problem 'toxic cyanobacteria'". Thesis, University of Dundee, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311866.
Testo completo
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Brookes, Justin Dean. "The influence of nutrients and light on the metabolic activity and buyoancy of Microcystis aeruginosa and Anabaena circinalis /". Title page, contents and summary only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phb8711.pdf.
Testo completo
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Deberdt, Gina Luísa Boemer. "Estudo de cianobactérias em reservatório com elevado grau de trofia (Reservatório de Salto Grande - Americana - SP)". Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-18042016-112245/.
Testo completoAbstract (sommario):
O estudo das florações de cianobactérias potencialmente tóxicas é de fundamental importância, principalmente se tratando de um reservatório de grande valor econômico e social, devido a seus usos múltiplos e localização próxima a grandes centros urbanos como é o reservatório de Salto Grande (Americana - SP). Assim, este trabalho visou fornecer subsídios para formulação de prognóstico da ocorrência de cianobactérias e produção de toxinas em ambientes aquáticos com elevado grau de eutrofização. Para isto, a pesquisa foi desenvolvida em três escalas: em macrocosmo (represa), foi determinada a variação da ocorrência das espécies de cianobactérias e das demais classes fitoplanctônicas, e analisado o potencial tóxico das amostras coletadas nos meses chuvosos (janeiro, fevereiro e março/98) e de estiagem (junho, julho, agosto e setembro/98) em duas estações de coleta no reservatório de Salto Grande; em mesocosmo (tanques), verificou-se, durante o período de seca, as variações na ocorrência das classes fitoplanctônicas e das espécies de cianobatérias e produção de toxinas, em função da manipulação da razão N/P através da dosagem de nitrogênio e fósforo na água; em microcosmo (garrafões de vidro, em laboratório), foi testado o efeito da redução de fósforo e conseqüente aumento da razão N/P sobre o crescimento e produção de toxinas em culturas de cepas de Microcystis aeruginosa (Kützing) Kützing, isoladas a partir de amostras de florações desta espécie no reservatório de Salto Grande, durante os meses chuvosos e os secos. No ambiente foi detectada a presença de microcistinas na água de todos os dias de coleta, exceto em 25/02/99. Em geral, as concentrações estiveram abaixo do limite de aceitabilidade (1 μg.L-1), com exceção da estação 2 nos dias 27/01/99 (39,53 μg.L-1) e 22/03/99 (3,98 μg.L-1). Nos experimentos em mesocosmos notou-se um aumento da densidade fitoplanctônica) nas 3 condições distintas. Na condição controle (sem manipulação), ocorreu um sensível aumento da porcentagem de contribuição das cianobactérias e diminuição dos demais grupos ao longo dos 11 dias. Na condição de razão N/P baixa, houve um pequeno aumento na porcentagem de contribuição das cianobactérias e clorofíceas, uma diminuição das criptofíceas e os demais grupos não apresentaram grandes alterações. Sob razões N/P alta, as cianobactérias tiveram um aumento, as clorofíceas mantiveram-se constantes e as criptofíceas diminuíram em relação às porcentagens iniciais. As condições dos tanques mantidos com razão N/P baixa foram mais favoráveis às clorofíceas. As cianobactérias apresentaram um aumento de biomassa nas condições dos tanques mantidos com razão N/P alta. Em microcosmos, a fase exponencial teve início no oitavo dia de cultivo em todos os testes. Ao completar aproximadamente 18 dias de experimento, notou-se uma diminuição no rendimento das culturas em meio ASM-1 com redução de fósforo. Em todas as escalas estudadas constatou-se que a concentração de microcistina esteve relacionada a fatores favoráveis ao desenvolvimento das espécies tóxicas. Entretanto, os fatores determinantes para o crescimento de cianobactérias tóxicas, apresentaram diferentes papéis em casa escala estudada. No macrocosmo, a estabilidade da coluna d\'água foi fundamental para o estabelecimento de maiores densidades de espécies tóxicas. Nos mesocosmos, o enriquecimento foi responsável pelo aumento da densidade de espécies tóxicas. Nos microcosmos, a disponibilidade de fósforo esteve diretamente relacionada à taxa de crescimento de Microcystis aeruginosa e conseqüentemente, ao aumento da concentração de microcistina.The study of the bloom of potential toxic cyanobacteria is of paramount significance, mainly when a reservoir endowed with great social and economical values due to both its multiple uses and its nearness to big urban centres - such as the Salto Grande reservoir, located near the city of Americana in the inland of the State of São Paulo, Brazil - is concerned. Based on such actuality, this work was aimed at supplying resources to devise forecasting the occurrence of cyanobacteria as well as the production of toxins in aquatic environments in which high eutrophication levels are observed. Towards this target, the research was carried out in the three steps that follow. In macrocosmic level (reservoir), the variations of the occurrence of both the cyanobacteria species and the remaining phytoplankton classes were found out, and then the toxic potentiality of the samples collected during the rainy season (January, February and March 1998) and the dry season (June, July, August and September 1998) in two sampling stations at the Salto Grande reservoir was analysed. In mesocosrnic scale (tanks), the variations in the occurrences of the classes of phytoplankton and of the cyanobacteria species - as well as the variations in production of toxins as a function of the ratio N/P that was dealt with by means of dosing nitrogen and phosphorus in the water - were observed during the dry season. In microcosmic level (glass bottles \"in lab\"), the effect of reducing phosphorus (and consequently increasing the ratio N/P) on the growth and the production of toxins in cultures of Microcystis aeruginosa (Kützing) Kützing strains - isolated from bloom samples of this species at the Salto Grande reservoir, during the wet and the dry seasons - was tested. At the environment, the presence of rnicrocystin in the water of all the samples, with the exception of the 25th of February 1999, was detected. Apart from the station 2 during January 2th 1999 (39.53 µg.L-1) and March 2th 1999 (3.98 µg.L-1), the concentrations stayed below the limit of acceptability (1 µg.L-1). At the experiments in mesocosmic scale, in 3 different conditions, increasing in phytoplankton density was observed. At the control condition (without manipulation), both reasonable augmentation of the percentage of the cyanobacteria contribution and diminishment of the other groups during the 11 days were detected. Under the condition of low N/P ratio, a slight rise of the percentage of the cyanobacteria and chlorophycea contribution and a decrease of the cryptophycea were observed; the other groups did not present much change. Under the condition of high N/P ratio, it was seen that the cyanobacteria increased, the chlorophycea remained unaffected and the cryptophycea decreased in comparison to the initial percentages. The conditions ofthe tanks that had been maintained at low N/P ratio favoured more the chlorophycea. The cyanobacteria presented biomass augmentation under the conditions of the tanks that had been maintained with high N/P ratio. For every test at the microcosmic level, the exponential stage had begun at the 8th development day. After being experimented for nearly 18 days, yield decrease of the cultures at the environment ASM-1 with phosphorus reduction was observed. In every scale that had been studied, it was noted that the microcystin concentration is related to unfavourable factors as far as the development of the toxic species is concerned. However, the determining causes for the growth of toxic cyanobacteria played different roles in each scale studied. At the macrocosmic level, enrichment was the responsible for increasing the density of the toxic species. At the microcosmic level, phosphorus availability had been directly related to Microcystis aeruginosa growth rate and, therefore, to the increase of microcystin concentration.
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Kardinaal, Willem Edwin Adrianus. "Who's bad? molecular identification reveals seasonal dynamics of toxic and non-toxic freshwater cyanobacteria /". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2007. http://dare.uva.nl/document/51515.
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Lister, Michelle M. "Understanding the genetic mechanisms of Clostridium difficile toxin regulation and clinical relapse". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/53216/.
Testo completoAbstract (sommario):
Clostridium difficile is the leading cause of health care associated diarrhoea and remains a burden for the NHS. Disease symptoms can range from mild diarrhoea through to fulminant pseudomembranous colitis, resulting in mortality for some patients. Recurrence is a major problem and estimates are that 20% of all patients with disease will either relapse (with the same strain) or have a re-infection (with a different strain). Arguably, the main virulence factors are toxins A (TcdA) and toxin B (TcdB) which cause disease symptoms. The genes encoding TcdA and TcdB are located within the pathogenicity locus (PaLoc) along with three accessory genes; tcdR, tcdE and tcdC. The regulatory network has been studied but we aimed to add to this knowledge by using two under investigated strains R20291 a so-called hypervirulent strain and VPI 10463 a strain known to produce higher levels of toxin. Two different methods of investigation were employed during this study to improve our understanding of both the regulation of TcdA / TcdB but also the genetic mechanisms behind clinical relapse. These methods were; using forward and reverse genetic analysis to assess phenotypic differences and using bioinformatics to identify genes and / or single nucleotide variants (SNP) that may play a role. Using a combination these methods we have identified potential regulators of toxin production in both strains. We have also identified unique genes and SNPs that might provide a fitness benefit to strains of C. difficile that were isolated from patients who had suffered relapse episodes.
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Zajac, Meron Petro. "Investigação da cilidrospermopsina e PSPs em amostras de águas superficiais no Estado de São Paulo (OU) Investigação da presença de cilindrospermopsina e saxitoxinas em amostras de águas superficiais no Estado de São Paulo". Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/9/9141/tde-27102009-120004/.
Testo completoAbstract (sommario):
O crescimento desordenado das cidades tem trazido à tona problemas de saneamento e degradação dos recursos naturais, entre eles a água. O despejo de efluentes domésticos e industriais têm ocasionado a eutrofização dos mananciais, culminando com a proliferação dos fitoplânctons. Esta proliferação tem chegado ao ponto, em certos momentos, de acarretar episódios de floração de algas. Entre os organismos fitoplanctônicos que se desenvolvem no ambiente, estão as cianobactérias, com vários gêneros capazes de produzir diversas cianotoxinas, tais como as microcistinas, anatoxinas, cilindrospermopsinas (CY), saxitoxinas (PSPs), entre outras. Com o aumento da freqüência dos episódios de floração de algas, a probabilidade da ocorrência destas toxinas também aumenta. Como conseqüência disto e devido às exigências legais, os corpos dágua devem ser monitorados para garantir a qualidade da água para consumo humano. Com vistas ao monitoramento da presença das cianotoxinas CY e PSPs, foram realizadas investigações em alguns corpos dágua do Estado de São Paulo. Das investigações realizadas, a neosaxitoxina foi identificada pela primeira vez no Reservatório Billings e os congêneres, saxitoxina, goniautoxina 2, goniautoxina 3, foram identificados de forma inédita em amostras de água deste reservatório. Com relação à CY, foi desenvolvido um método analítico, parcialmente validado. Entretanto, esta cianotoxina não foi localizada nas amostras de água ou cianobactérias das águas superficiais dos corpos dágua estudados. Este estudo mostra a importância do monitoramento da qualidade das águas dos mananciais quanto à presença de cianotoxinas, especialmente daqueles corpos dágua com a finalidade do consumo humano.Cities growth usually occur in an unorganized manner. This tendence can generate a variety of sanitary problems, including the degradation of natural resources, such as water bodies. As a consequence, domestic and industrial efluents cause eutrofication of water reservoir, increasing the natural level of phytoplancton, what may form algal bloom. Among the phytoplanktonic organisms that grow in this modified environment it is found the cyanobacteria. Some of them can produce different types of cyanotoxins such as microcystin, anatoxin, cylindrospermopsin (CY) and saxitoxin (PSPs). The probability of production of these cyanotoxins increase according to frequent occurrence of algal blooms episodes. Consequently, water bodies monitoring becomes important to assure water quality. The aim of this project was to develop a specific method to identify the presence of cyanotoxins CY and to investigate PSPs in water bodies in São Paulo State. The results confirmed the presence of neosaxitoxin (NEO), a toxin of PSPs family. It was the first time that Neo was indentified in Billings Reservoir along with other PSPs types: saxitoxin, gonyautoxin 2, gonyautoxin 3. Although the study also included CY monitoring, CY was not identified in the tested samples. The present study confirmed the importance of continuous searching and monitoring of water bodies to grant quality to water used for human consumption.
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Chintalapati, Pranav Sankar. "Degradation of cyanobacterial toxin microcystin-LR using UV/vacuum-UV advanced oxidation for drinking water treatment". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/63028.
Testo completoAbstract (sommario):
Cyanobacterial blooms have been increasing in magnitude and frequency around the world and studies have concluded that climate change, population growth, and industrial development will accelerate this phenomenon. The presence of cyanobacterial blooms in drinking water sources is a concern due to the production of cyanobacterial toxins, which are known to damage internal organs and disrupt nervous system functions. Shallow surface water sources for small water systems are at a greater risk of eutrophication and small, remote communities often lack the resources and infrastructure for adequate treatment. In conventional water systems, instances of cyanobacterial blooms are typically addressed by chemical addition. However, many remote communities are difficult to access and are unable to maintain a consistent supply of chemical oxidants.
This study investigated the capability of ultraviolet radiation at 254 nm and 185 nm wavelengths (UV/Vacuum-UV) to degrade microcystin-LR (MC-LR), one of the most commonly occurring and toxic cyanobacterial toxins. Results showed that substantial toxin removal could be achieved solely by direct photolysis with 254 nm. The addition of 185 nm increased MC-LR degradation through advanced oxidation by hydroxyl radicals (•OH). The presence of alkalinity and organic matter (DOC) reduced MC-LR degradation by scavenging •OH. DOC also absorbed 254 nm and 185 nm, requiring additional irradiation time to achieve a target UV dose. Chloride scavenged •OH, but in a reversible reaction, resulting in minimal impact on MC-LR degradation. The order of impact on MC-LR degradation by these common water constituents was DOC>Alkalinity>Chloride. In natural water with a complex matrix, MC-LR could be degraded from a typical concentration (15 µg/L) to below detection (<0.5 µg/L) with a UV254 fluence of 200 mJ/cm2. The presence of cyanobacterial cells impeded MC-LR degradation by adding turbidity to samples, absorbing 254 nm photons and scavenging •OH. However, substantial MC-LR degradation could still be achieved in the presence of cyanobacterial cells. UV/Vacuum-UV appears to be a promising chemical-free technology that is capable of MC-LR degradation in a variety of water conditions, and may be a suitable treatment option for small, remote communities.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate
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Bertani, Paul. "Advancing Healthcare: A 3D Nanoscale Cell Electroporation Platform and AlGaN/GaN Biosensors for Cyanobacterial Toxin Detection". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu159828807909402.
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SILVA, JOSE R. L. da. "Cianobactérias e cianotoxinas no reservatório da UHE Lajeado, Palmas - TO: fatores condicionantes ao surgimento de floração e avaliação da remoção por meio de uma instalação piloto de dupla filtração". reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23274.
Testo completoAbstract (sommario):
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-19T10:12:52Z
No. of bitstreams: 0Made available in DSpace on 2015-01-19T10:12:52Z (GMT). No. of bitstreams: 0
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP