Os corantes são amplamente utilizados nas indústrias têxteis, farmacêuticas, alimentícias, cosméticas, fotográficas, entre outras. Contudo, essas substâncias podem ser tóxicas, mutagênicas e resistentes a muitos processos de degradação utilizados em estações de tratamento. Estima-se que cerca de 15% dos corantes utilizados no mundo sejam perdidos durante o processo de tingimento e lançados no ambiente, atingindo principalmente os corpos d\'água. No entanto, apesar da grande quantidade de corantes comerciais disponíveis e da alta quantidade lançada no ecossistema aquático, os estudos sobre a toxicidade dessas substâncias são escassos e pouco se conhece sobre seus efeitos mutagênicos e principalmente ecotoxicológicos. Dentro deste contexto, o objetivo do trabalho foi avaliar a ecotoxicidade, bem como a capacidade dos corantes têxteis Reactive Blue 4 (RB 4) e Reactive Blue 15 (RB 15) de lesar o material genético, empregando ensaios de toxicidade aguda com Daphnia similis e Vibrio fischeri, toxicidade crônica com Ceriodaphnia dubia, genotoxicidade (Teste do Cometa) com fibroblastos de derme humana e mutagenicidade com Salmonella typhimurium. Adicionalmente, avaliou-se a concentração de cobre em Ceriodaphnia dubia expostas ao corante Reactive Blue 15, que possui esse metal na sua estrutura química. O corante RB 4 foi moderadamente tóxico e o corante RB 15 foi relativamente não tóxico para Daphnia similis. Ambos corantes reduziram a luminescência de Vibrio fischeri em elevadas concentrações, sendo o corante RB 4 mais tóxico para a bactéria quando comparado ao corante RB 15. O corante RB 4 induziu efeito hormesis nos ensaios com C. dubia, ou seja, houve um estímulo na reprodução nas menores concentrações, seguido por um decréscimo em concentrações mais elevadas, ao passo que, o corante RB 15 reduziu a fecundidade de C. dubia. Não houve acúmulo de cobre nos organismos expostos ao corante RB 15. Nenhum dos corantes foram genotóxicos para fibroblastos de derme humana e apenas o corante RB 4 induziu mutagenicidade, por substituição de pares de base. Os resultados obtidos mostram que os corantes podem causar efeitos adversos nos organismos mesmo em baixas concentrações e que o lançamento contínuo dessas substâncias nos corpos d\'água é preocupante. / Dyes are widely used in different types of industries, such as textile, pharmaceutical, food, cosmetics, photographic, among others. However, these substances can be toxic, mutagenic and resistant to many degradation processes used in wastewater treatment. It is estimated that about 15% of the dyes used in the world is lost during the dyeing process and released into the environment, affecting mainly water bodies. However, despite the large amount of commercial dyes available and high quantity released in the aquatic ecosystem, studies on the toxicity of these substances are scarce and little is known about their mutagenic and ecotoxicological effects. Considering that, the aim of this study was to evaluate the ecotoxicity, and the ability of the Reactive Blue 4 (RB 4) and Reactive Blue 15 (RB 15) textile dyes to damage the genetic material, using acute toxicity tests with Daphnia similis and Vibrio fischeri, Ceriodaphnia dubia chronic toxicity, genotoxicity (Comet assay) in human dermal fibroblasts and mutagenicity with Salmonella typhimurium. Additionally, we assessed the concentration of copper in Ceriodaphnia dubia exposed to the Reactive Blue 15 dye, which has this metal in its chemical structure. The RB 4 dye was moderately toxic and RB 15 dye was relatively non-toxic to Daphnia similis. Both dyes reduced the Vibrio fischeri luminescence in high concentrations, and the RB 4 was more toxic to bacteria when compared to dye RB 15. The RB 4 dye induced hormesis effect in the C. dubia tests. We observed that the reproduction was stimulated at lower concentrations followed by a decrease at higher concentrations. While the RB 15 dye reduced fecundity of Ceriodaphnia dubia. There was no accumulation of copper in organisms exposed to the RB 15 dye. None of the dyes were genotoxic to human dermal fibroblasts, and only the RB 4 dye induced mutagenicity, by base-pair substitution. The results show that the dyes can cause adverse effects on organisms even at low concentrations and that the continuous release of these substances in water bodies is worrying.

O controle das águas residuárias nas indústrias e nos terminais de armazenagem de produtos químicos líquidos a granel é uma difícil tarefa, por conta da alta rotatividade e grande variedade de produtos químicos orgânicos armazenados e movimentados em suas atividades. Oito terminais e duas indústrias químicas localizadas no Porto de Santos foram avaliados por 10 anos. Foram realizadas mais de 2.500 análises químicas e ecotoxicológicas em 200 amostras de efluentes brutos e tratados. Nosso principal objetivo foi verificar se o teste de toxicidade aguda usando Vibrio fischeri poderia ser utilizado na gestão de águas residuais nas diferentes instalações dos terminais químicos e mostrar o seu papel como instrumento de prevenção a poluição, reduzindo a descarga de substâncias tóxicas persistentes nos ambientes aquáticos. Os índices de biodegradabilidade obtidos pela relação de Demanda Bioquímica de Oxigênio (DBO5) / Demanda Química de Oxigênio (DQO) dos efluentes brutos indicaram que 44% das amostras apresentaram matéria orgânica recalcitrante. Das 86 amostras do efluente final analisadas, 45 (52%) apresentaram resultados tóxicos para o teste com V. fischeri. Não houve correlação de DQO e ecotoxicidade, mostrando que efluentes com DQO baixa podem conter substâncias tóxicas com baixa capacidade de degradação. Foi possível recomendar a aplicação das melhores práticas operacionais, incluindo a segregação dos efluentes brutos ou um pré-tratamento com base nos resultados de ecotoxicidade e índice de biodegradabilidade. O reúso de água também foi abordado, indicando fontes e oportunidades de reutilização. Testes de ozonização também foram conduzidos nas águas pluviais dos terminais químicos e nos efluentes tratados das indústrias com resultados promissores. A integração da análise química e ecotoxicológica se mostraram uma excelente ferramenta para gestão de águas residuais nos terminais químicos, permitindo a tomada de decisão rápida para o controle da poluição e a adoção de medidas de prevenção / Wastewater control at industries and storage terminals of liquid chemical products in bulk is very difficult task due to the high turnover and great variety of organic chemicals handled and stored in their activities. Eight terminals and two chemical plants located in Santos Port, SP, Brazil had been evaluated for 10 years. More than 2,500 chemical and ecotoxicological analysis were performed in 200 samples of raw and treated effluents. Our main objective was to verify if the acute toxicity test using Vibrio fischeri could be used in the wastewater management of those facilities and show its role as a tool for pollution prevention by reducing the discharge of persistent toxic substances in estuarine systems. The indexes of biodegradability obtained by the ratio of Biochemical Oxygen Demand (BOD5) / Chemical Oxygen Demand (COD) of raw effluents indicated that 44% of the samples presented recalcitrant organic matter. Out of 86 final effluent samples analyzed, 45 (52%) presented toxic result for V. fischeri test. No correlation was observed of COD and ecotoxicity, showing that with low COD effluent may contain toxic substances with low degradation capacity. It was possible to recommend the use of best operational practices including segregation of influents or a pre-treatment based on toxicity results and index biodegradability. Water reuse was also discussed indicating sources and opportunities for reuse in these facilities. Ozonisation tests were also conducted on the rain waters collected at the terminals facilities and on the treated effluents of the industries, showing promising results. The integration of chemical and ecotoxicity analysis turned out to be an excellent tool for wastewater management in chemical terminals, allowing rapid decision making for pollution control and prevention measures

The individual behaviour of prokaryotic organisms such as bacteria often gives rise to complexity that is commonly associated with multicellular behaviour. The transition from unicellular to multicellular behaviour occurs in response to chemical signals, called autoinducers, which bacteria generate and receive internally within a given population. These autoinducers control the gene expression necessary for the emergence of group-behaviour-phenotype. This phenomenon is called quorum sensing (QS). An example of the quorum sensing control of gene regulation has been the luminescence (lux) operon in Vibrio fischeri. The luxI and ainS quorum signalling systems work in conjunction to regulate luminescence in V. fischeri. LuxI and AinS are acyl-synthases that catalyse the production of the autoinducers C6-HSL and C8-HSL respectively. These autoinducers bind to LuxR, a transcriptional activator of the lux operon, which activates expression of the lux genes causing an increase in luminescence. It was shown that quorum signalling also affects motility and biofilm formation in bacteria. However, the evidence with respect to these phenotypes is conflicting and inconclusive, the reason being the state of quorum is ambiguously defined. It is not properly known whether the observed collective behaviour is purely a result of physical crowding of bacteria, or that both chemical signalling and crowding contribute to this phenomenon. This work attempts to address these issues by studying luminescence, motility, and biofilm, a diverse set of behaviours, yet closely linked to each other in V. fischeri-squid symbiosis. We studied the luminescence response of V. fischeri to both endogenous and externally added signals at per-cell and population level. Experiments with ES114, a wild-type strain of V. fischeri, and ainS mutant showed that (i) luminescence per cell does not mutually correlate with the cell-density, indicating that bacteria do not show greater response to the signal at higher densities; (ii) the activity of the lux signalling circuit shows a strong dependence on the growth stage, (iii) the cells do not show enhanced growth, i.e., they do not derive fitness benefits at higher densities in response to the signal. We anticipated that the culture with a higher cell-density should exhibit greater per-cell-luminescence. However, we found that the luminescence curve of the culture with lower density crosses that of the cultures with higher densities during the exponential phase. Kinetic modelling of the luxI mRNA expression showed that the expression profile qualitatively agrees with the luminescence trend observed in the cultures, supporting the observation that growth-phase plays a major role in regulating the luminescence gene expression. We also studied the effect of autoinducers on motility of V. fischeri. V. fischeri uses flagella to move into the inner crypts of the light organ of the squid. The bacterium secretes autoinducers, encounters secretions of the light organ, and slows down during the final stage of colonization process. Studies have shown that flagellar elaboration is repressed as a consequence of ainS signalling. However, those studies were soft-agar migration assays and carried out with the mutant strain of ainS. We measured real-time planktonic motility of ES114 and the signalling mutant strains of V. fischeri in response to autoinducers added exogenously at different concentrations. We found that the autoinducers do not affect the motility of the strains. We also showed that reduction in motility is purely a consequence of physical crowding of bacteria, and chemical signalling may not be involved in the process. It was shown that reduction in motility leads to biofilm formation. Motile bacteria must lose flagella in order to form biofilm, and signalling controls biofilm formation in many species. Our study on motility showed that reduction in motility occurs because of physical crowding in V. fischeri. Hence, we explored the possibility that physical crowding might lead to formation of biofilm rather than signalling in this species. We quantified exopolysaccharide production by crystal violet assay, which revealed that planktonic cells produce exopolysaccharides, in addition to biofilm cells. The study revealed that V. fischeri cells always produce exopolysaccharides irrespective of their physiological state. We examined the effect of signalling on biofilm in ES114 and the mutant strains using gene-expression analysis. We quantified the expression of various genes involved in biofilm formation and found that both ES114 and the mutants expressed rscS and sypP indicating that exopolysaccharide production is not under the control of autoinducers. Therefore, we hypothesized that biofilm formation in V. fischeri may be a result of physical agglomeration of cells. Our observations indicate that the state of quorum is inadequately defined and there is no direct measure of the underlying process. Multicellular behaviour in V. fischeri is regulated by a complex interplay of cell-density, signalling, and other factors such as the growth phase of the culture, indicating that the state of quorum employs different mechanisms to regulate various phenotypes. Our study reveals that QS is an intricate process, and the accepted mechanisms for QS are incomplete at best.

Bacterial infections are an increasing problem for human health. In fact, an increasing number of infections are caused by bacteria that are resistant to most antibiotics and their combinations. A new solution to fight bacteria and infectious diseases, without promoting antimicrobial resistance, is required. A promise strategy is the disruption or attenuation of bacterial Quorum Sensing (QS), a refined system that bacteria use to communicate. In a QS event, bacteria produce and release specific small chemicals, signal molecules - autoinducers (AIs) - into the environment. AIs regulate gene expression as a function of cell population density. Phenotypes mediated by QS (QS- phenotypes) include virulence factors, toxin production, antibiotic resistance and biofilm formation. In this work, two polymeric materials (linear polymers and molecularly imprinted nanoparticles) were developed and their ability to attenuate QS was evaluated. Both types of polymers should be able to adsorb bacterial signal molecules, limiting their availability in the extracellular environment, with expected disruption of QS. Linear polymers were composed by methyl methacrylate as backbone and itaconic acid or methacrylic acid as functional monomer. IA and MAA monomers were identified by computer modelling to have strong interactions with the AIs produced by Gram-negative bacteria. Cont/d.

Wood is a natural raw material, and would hardly be considered a risk to the environment. However, the handling of wood materials on an industrial scale has been shown to have a negative impact on water bodies that run-off from industrial sites that process wood-based materials. Most investigations related to water pollution from wood-based industries have focused on large industrial sites such as pulp and paper mills. The goal of the present thesisis to understand better such environmental problems and treatment solutions that occur at most wood handling sites. Where there are large outdoor storage areas for logs and sawdust that are exposed to rainfall or irrigation, such as the wooden-floor and bio-energy sectors. Leachate generated by the contact of water with wood in storage areas contains a large amount of organic matter that is potentially hazardous to water bodies that receive run-off from the site. It has been found that different wood species yield different leachate compositions, with leachate from oak having the highest pollutants content, followed by leachate from pine. This investigation shows that oak has the potential to leach about 10 times the amount of polyphenols compared with other investigated species (i.e., pine, beech and maple). Furthermore, oak leachates have the lowest ratio of biological oxygen demand at 7 days tochemical oxygen demand (0.12), which suggests a potential problem with the biological degradation of this leachate. It has also been shown that leachate from wood are potentially toxic to aquatic organisms. Treatability studies with the aim of reducing the environmental impact of wood leachate were conducted on a pilot scale as part of the scope of this thesis. The results showed, among other options, the possibility of using constructed wetlands to treat leachate. It was found that plants and aeration can affect the performance of a wetland. However, the most important factor is the time water spends in the wetland. Filter material that could be used to absorb leachate was also studied. A filter consisting of a mixture of peat and ash (from incinerated organic matter), was used to absorb a specific chemical group (polyphenols) in the leachate. It was also shown that polyphenols are vulnerable to ozone, representing a third viable treatment process. / Trä är ett naturligt råmaterial som knappast anses vara en risk för miljön. Däremot har hanteringen av trämaterial i industriell skala visat sig ha negativ inverkan på vattendrag. De flesta utredningar avseende vattenföroreningar inom träbaserade industrier har fokuserat på stora industrier med stor vattenförbrukning så som massa- och pappersbruk. Lakvatten som alstras vid kontakten mellan vatten och trä innehåller höga halter av organiska ämnen som är potentiellt farliga för vattendrag. Målet med denna avhandling är att få kunskap om ovanstående miljöproblem och möjlig behandlingar av dessa. Förorenat lakvatten skapas av industrier, där stora mängder timmer och sågspån är placerade utomhus och utsätts för regn och bevattning, såsom inom trägolv och bioenergisektorn. Man har funnit att lakning från olika träslag ger olika sammansättningar på lakvattnet, där lakvatten från ek har den högsta halten av föroreningar följt av furu. Denna undersökning visar att ek har potential att laka ut tio gånger så mycket polyfenoler jämfört med andra undersökta arter (tall, bok och lönn). Dessutom har lakvatten från ek den lägsta andelen av biologisk syreförbrukning efter 7dagar per kemisk syreförbrukning (0,12), vilket tyder på ett potentiellt problem med den biologiska nedbrytningen av detta lakvatten. Man har även påvisat att lakvattnet från trä är potentiellt giftigt för akvatiska organismer. Studier för att försöka minska miljöpåverkan av lakvatten från denna trädsort gjordes i pilotskala inom ramen för denna avhandling. Dessa studier visade bland annat på möjligheterna att använda sig av våtmarker som reningsmetod, där växter och luftning påverkar hur bra en våtmark fungerar. Men den viktigaste faktorn var den ökade uppehållstiden som vattnet får i våtmarken. Utöver studier av våtmarker har också ett filtermaterial studerats, filtret bestod av en blandning av torv och aska, som användes för att absorbera en specifik kemisk grupp i lakvattnet (polyfenoler). I en tredje typ av behandlingsprocess visade det sig också att polyfenoler effektivt kan brytas ned av ozon.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 162-167). Also available via World Wide Web.

All animals exist in lifelong relations with a complement of bacteria. Because of the ubiquity of these symbioses as well as the derived biomedical applications, the study of both beneficial and pathogenic host-microbe associations has long been established. The monospecific light organ association between the Hawaiian sepiolid squid Euprymnascolopes and the marine luminous bacterium Vibrio fischeri has been used as a experimental model for the study of the most common type of animal-bacterial interaction, i.e., the association of coevolved Gram-negative bacteria with the extracellular apical surfaces of polarized epithelia. A fundamental step for understanding the mechanisms of host-symbiont associations lies in defining the genetic components involved; specifically defining changes in host gene expression. The studies presented in this dissertation identify and characterize V. fischeri-induced changes in host gene expression at both the transcript and protein level.

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Ambiental, florianópolis, 2013. / Made available in DSpace on 2013-07-16T21:10:01Z (GMT). No. of bitstreams: 1 317387.pdf: 3330083 bytes, checksum: d2a2a4bf3cdeab831581ae3c92e84809 (MD5) / Devido à natureza diversa dos resíduos sólidos urbanos (RSU) e às diferenças das fases de decomposição, o lixiviado formado resulta em uma mistura química complexa com potencial tóxico. Esses compostos químicos podem causar problemas ambientais como contaminação de águas superficiais ou subterrâneas, interferindo no equilíbrio de ecossistemas aquáticos. Este trabalho tem como principal objetivo determinar a taxa de transferência dos elementos-traço (Cr, Cu, Pb, Ni e Cd) contidos nos RSU para o lixiviado, além de avaliar a toxicidade aguda para Daphnia magna e Vibrio fischeri, e identificar as principais variáveis físico-químicas que influenciam na toxicidade dos lixiviados de aterros sanitários, produzidos em reatores com simulações pilotos. Para a realização deste estudo, foram construídos três reatores que simulam a produção de lixiviados de aterro sanitário. Os reatores pilotos possuíam diferentes composições de massas de preenchimentos, codificados como: 1- preenchido exclusivamente com material orgânico, 2 - preenchido com RSU sintético (RSU-S), uma mistura de material orgânico e inorgânico e 3 - preenchido RSU provenientes da coleta municipal. Foram coletadas amostras de lixiviados a cada 7 dias durante um período de 17 meses. Os resultados das análises das variáveis físico-químicas indicam que as amostras dos lixiviados são misturas complexas, compostas por substâncias orgânicas e inorgânicas, contendo consideradas concentrações de micro e macro nutrientes. As concentrações destes compostos encontradas no lixiviado evidenciam o transporte dessas substâncias da matriz sólida para o meio aquoso. Os testes de toxicidade aguda, realizados com Daphnia magna e Vibrio fischeri, mostraram que os lixiviados produzidos no interior dos reatores são tóxicos, apresentando para Daphnia magna CE50 < 1% e para Vibrio fischeri CE50 < 12% em média indica que os microcrustáceos são mais sensíveis a estes compostos, sendo mais apropriados para o estudo. A variável pH foi a que demonstrou maior correlação com a CE50, sugerindo que o pH é a principal variável química indicadora de toxicidade, para as condições do experimento. Utilizou-se da modelagem matemática (modelos de regressão não linear com ajuda do programa estatístico Minitab 16, a função exponencial foi à que melhor se ajustou) baseados em modelos compartimentais para determinar e descrever a taxa de transferência dos elementos-traço dos RSU para o lixiviado. A análise dos elementos traços no lixiviado dos três reatores pilotos mostrou que o Ni foi o elemento que apresentou a maior taxa de transferência, o que é preocupante devido à alta toxicidade deste elemento. Enquanto o Cd foi o que apresentou a menor taxa de transferência, porém constante. E as menores taxas de transferência foram apresentadas por o Cr, Cu e o Pb.<br> / Abstract : Due to the varied nature of Municipal Solid Waste (MSW) and differences of phases of decomposition, the formed leachate results in a complex chemical mix with toxic potential. These chemical compounds can cause environmental problems such as contamination of surface or groundwater, affecting the balance of aquatic ecosystems. This work has the main objective to determine the transfer rate of trace elements (Cr, Cu, Pb, Ni and Cd) contained in MSW for the leachate in addition to evaluate acute toxicity for Daphnia magna and Vibrio fischeri, and identify the principle physicochemical variables that influence the toxicity of landfill leachate, produced in reactors with pilot simulations. For this study three reactors were built to simulate the production of landfill leachate. The pilot reactors had different composition mass fills, encoded as: 1 - exclusively filled with organic material, 2 - filled with synthetic MSW (MSW-S) a mixture of organic and inorganic material and 3 - filled with MSW from municipal collection. Leachate samples were collected every 7 days over a period of 17 months. The results of the analyses of the physicochemical variables indicate that the leachate samples are complex mixtures, consisting of organic and inorganic substances containing considered concentrations of macro and micro nutrients. The concentrations of these compounds found in the leachate showed the transport of these substances of the solid matrix to the aqueous media. The acute toxicity tests conducted with Daphnia magna and Vibrio fischeri, showed that the leachate produced inside the reactors are toxic to Daphnia magna CE50 < 1% e for Vibrio fischeri CE50 < 12% indicating that in average the microcrustaceans are more sensitive to these compounds, being more suitable for the study. The variable pH demonstrated the highest correlation with CE50, suggesting that pH is the principle variable chemical indicator of toxicity, for the conditions of the experiment. Utilizing mathematical modeling (regression models not linear with the help of the statistical program Minitab 16, the exponential function was the best fit) based on compartmental models to determine and describe the transfer rate of the elements traced for RSU to the leachate. The analysis of trace elements in the leachate of the three pilot reactors shows that the Ni was the element that presented the highest transfer rate, which is worrying because of the high toxicity of this element. While the Cd presented the lowest transfer rate, but constant, and the lowest transfer rates were presented by Cr, Cu and Pb.

Submitted by Marilene Donadel (marilene.donadel@unioeste.br) on 2018-10-31T18:19:56Z No. of bitstreams: 1 Larissa_Bortoli_2017.pdf: 2081912 bytes, checksum: 9d603950fbde6861b979910220779d8b (MD5) / Made available in DSpace on 2018-10-31T18:19:56Z (GMT). No. of bitstreams: 1 Larissa_Bortoli_2017.pdf: 2081912 bytes, checksum: 9d603950fbde6861b979910220779d8b (MD5) Previous issue date: 2017-03-13 / Recent studies have shown that silver nanoparticles (AgNPs) can bring potential health and environmental risks. Its growing production on large scale and wide incorporation into several products increases the risks of this nanomaterial of reaching different ecosystems, impacting the environment and human health. Facing this panorama, this work has as main objective, evaluating the efficiency of the treatment by electrocoagulation of different synthetic industrial effluents of AgNPs. Therefore, distinct AgNPs dispersions were developed in aqueous medium by chemical reduction, using silver nitrate (AgNO3) as a precursor, sodium borohydride (NaBH4) as a reducer, and stabilizers in concentrations of 1 and 3% (m/v), sodium carboxymethylcellulose (CMC), polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP), resulting in dispersions designated as AgNPs-CMC1 and AgNPs-CMC3, AgNPs-PVA1 and AgNPs-PVA3 and AgNPs-PVP1 and AgNPs-PVP3, respectively. Synthesized, the nanoparticles were characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM), pH, conductivity and turbidity. The UV-Vis absorption spectra of the AgNPs obtained by different synthesis reactions were similar, presenting bands in the 400 nm region, typical of spherical-shaped AgNPs. The predominantly spherical morphological appearance of the AgNPs of the different dispersions was confirmed by transmission electron microscopy. In the treatment by electrocoagulation with aluminum electrodes, the dispersions containing CMC as a stabilizing agent proved to be difficult to treat by electrocoagulation. The dispersions AgNPs-CMC1 and AgNPs-CMC3 obtained a reduction in total silver concentration of 71.72 and 52.15%, respectively, after 15 min of electrolysis. While the dispersions AgNPs-PVA1, AgNPs-PVP1 and AgNPs-PVP3 obtained a reduction in total silver concentration above 99.90% in 10 minutes of treatment, and AgNPs-PVP3 route dispersion reduction of total silver of 99.98% at 20 min of electrocoagulation. From these results, it was possible to observe that the elimination of AgNPs from effluents is possible and that the efficiency of the treatment by electrocoagulation is directly related to the physicochemical characteristics acquired by the dispersions of AgNPs when stabilized with different compounds. Finally, through the toxicity analysis with the test organism Vibrio fischeri, and according to the IAP Ordinance No. 019/2006, it was possible to verify that only the dispersions that used PVP as a protective agent became suitable for disposal after treatment by electrocoagulation. / Estudos recentes têm demonstrado que nanopartículas de prata (AgNPs) podem trazer riscos potenciais a saúde e ao meio ambiente. A crescente produção em escala industrial e ampla incorporação em diversos produtos aumentam os riscos desse nanomaterial alcançar os diferentes ecossistemas e, assim, causar impactos nesses ambientes e na saúde humana. Diante deste panorama, este trabalho teve como objetivo principal avaliar a eficiência do tratamento por eletrocoagulação de diferentes efluentes industriais sintéticos de AgNPs. Para isto, sintetizou-se distintas dispersões de AgNPs em meio aquoso por redução química, utilizando nitrato de prata (AgNO3) como precursor, borohidreto de sódio (NaBH4) como redutor, e os estabilizantes nas concentrações 1 e 3%, carboximetilcelulose sódica (CMC), álcool polivinílico (PVA) e polivinilpirrolidona (PVP), resultando nas dispersões denominadas AgNPs-CMC1 e AgNPs-CMC3, AgNPs-PVA1 e AgNPs-PVA3 e AgNPs-PVP1 e AgNPs-PVP3, respectivamente. Sintetizadas, as nanopartículas foram caracterizadas por espectroscopia UV-Vis, microscopia eletrônica de transmissão (MET), conversão reacional, pH, condutividade e turbidez. Os espectros de absorção UV-Vis das AgNPs obtidas pelas diferentes reações de síntese foram similares, apresentando bandas na região de 400 nm, característico de AgNPs com formato esférico. A aparência morfológica predominantemente esférica das AgNPs das diferentes dispersões foi confirmada pela microscopia eletrônica de transmissão. No tratamento por eletrocoagulação com eletrodos de alumínio as dispersões contendo CMC como agente estabilizante se demonstraram dificilmente tratáveis por eletrocoagulação. Após 15 min de eletrólise a dispersão AgNPs-CMC1 apresentou uma redução de 71,72% na concentração de prata total e a dispersão AgNPs-CMC3 52,15%. As dispersões AgNPs-PVA1, AgNPs-PVP1 e AgNPs-PVP3 obtiveram redução na concentração de prata total acima de 99,90% em 10 min de tratamento, e a dispersão AgNPs-PVP3 redução de prata total de 99,98% aos 20 min de eletrocoagulação. Destes resultados foi possível observar que a eliminação de AgNPs de efluentes é possível, e que a eficiência do tratamento por eletrocoagulação se relaciona diretamente com às características físico-químicas adquiridas pelas suspensões de AgNPs quando estabilizadas com diferentes compostos. Por fim, através das análises de toxicidade com o organismo- teste Vibrio fischeri, e de acordo com a Portaria IAP n° 019/2006 foi possível constatar que somente as dispersões que utilizaram PVP como agente protetor se tornaram aptas ao descarte após tratamento por eletrocoagulação.

Quorum sensing is a mechanism used by many proteobacteria to regulate expression of target genes in a population-dependent manner. The quorum sensing system of Vibrio fischeri activates the luminescence (lux) operon when the autoinducer signaling molecule (N-3-oxohexanoyl homoserine lactone) is recognized and bound by the activator protein LuxR. LuxR subsequently binds to the lux box centered at à 42.5 bp upstream of the transcription initiation site and activates transcription from the lux operon promoter, resulting in the emission of light at high cell densities. LuxR consists of 250 amino acids arranged into an N-terminal (regulatory) domain and a C-terminal (activation) domain, and is thought to function as an ambidextrous activator capable of making multiple contacts with the alpha and sigma subunits of RNA polymerase (RNAP). Published work describing the results of alanine scanning mutagenesis performed on the C-terminal domain of LuxR (residues 190-250) has identified residues (K198, W201 and I206) that appear to play a role in positive control of transcription initiation. Additional mutagenesis of residues 180-189 has been undertaken via a three-primer or four-primer PCR-based method in this study. Variants of LuxR were screened for their ability to activate luciferase production and to repress transcription from an artificial promoter, and production of full-length LuxR was measured, in an attempt to identify additional positive control variants. No additional positive control variants were found in this study. Work has also been undertaken to identify intergenic suppressors between positive control variants of LuxR and the RNAP alpha subunit, RpoA. Starting with a recombinant Escherichia coli strain encoding the lux operon and LuxR variant I206E, a random chemical mutagenesis was performed on a vector encoding RpoA. Following transformation of the mutated plasmids encoding RpoA, high throughput luminescence assays were used to identify isolates with phenotypes brighter than the control. Isolation of an intergenic suppressor will confirm the existence of protein-protein interactions between LuxR and RpoA within the transcription initiation complex. The ability of other LuxR family members to establish productive protein-protein interactions with RNAP necessary for transcription initiation was also examined. LuxR homologues EsaR of Pantoea stewarti ssp. stewartii, a repressor of known function, and ExpR of Erwinia carotovora subsp. carotovora were also analyzed for their ability to activate the lux operon, as well as to repress transcription from an artificial promoter containing the lux box. / Master of Science