Prospec??o de bact?rias com potencial aplica??o na biorremedia??o de efluentes industriais contendo ars?nio.

O Ars?nio (As) est? naturalmente presente no ambiente terrestre associado a minerais sulfetados em rochas e sedimentos. Devido a oxida??es qu?micas e biol?gicas e principalmente a atividades ligadas ? minera??o e metalurgia, o As ? mobilizado de dep?sitos naturais tornando-se um importante contaminante ambiental. Em baix?ssimas concentra??es, esse metal?ide ? t?xico para diversos seres vivos. V?rios estudos t?m sido realizados a fim de remediar tais impactos imobilizando este elemento. Dentre as metodologias propostas podemos citar com destaque a utiliza??o de micro-organismos na remo??o de metais de efluentes e corpos d??gua contaminados. Bact?rias podem remover metais de uma solu??o por diferentes mecanismos, tais como aqueles que envolvem a acumula??o extracelular/precipita??o, a adsor??o i?nica na superf?cie celular ou complexa??o, e a acumula??o intracelular ou bioacumula??o. A remo??o de metais dos ambientes aqu?ticos tamb?m pode ocorrer pela a??o de metab?litos produzidos pelas bact?rias presentes como, por exemplo, pelo H2S produzido pelo grupo das Bact?rias Redutoras de Sulfato (BRS). Estes micro-organismos s?o peculiares por, atrav?s da redu??o qu?mica do sulfato, produzir sulfeto que, por sua vez, ? capaz de precipitar metais, na forma de seus sulfetos insol?veis. O presente trabalho teve como objetivo geral a prospec??o e identifica??o de bact?rias resistentes ao Ars?nio presentes em corpos d??gua, sedimentos e em reator de tratamento de esgoto, visando uma potencial aplica??o na biorremedia??o de efluentes industriais contendo este elemento. Foram coletados sedimentos de c?rrego contaminado com esgoto dom?stico em Ouro Preto, de lodo de reator UASB (Reator Anaer?bio de Manta de Lodo e Fluxo Ascendente) da ETE (Esta??o de Tratamento de Esgoto) Arrudas, em Belo Horizonte, ambas em MG; e do sedimento do Mangue de Carneiros, em Tamandar?, PE. Os diferentes cons?rcios microbianos obtidos foram caracterizados morfol?gica e metabolicamente inclusive na presen?a de compostos arsenicais a fim de identificar aqueles com maior potencial de aplica??o biotecnol?gica. A an?lise do perfil eletrofor?tico das bandas obtido por DGGE (denaturing gradient gel electrophoresis) mostrou uma maior diversidade de bact?rias tolerantes ao As em dois cons?rcios provenientes de ambientes contaminados com esgoto. Houve, entretanto, uma diminui??o da diversidade microbiana quando em presen?a do As. Os resultados mostram a adapta??o dos micro-organismos ? concentra??es de As superiores ao exigido pelo padr?o de limite m?ximo de lan?amento xvi de efluentes permitido pelo CONAMA 357 (0,5 mg.L1), indicando potencial de aplica??o dos cons?rcios na remo??o de As de efluentes e ?guas contaminadas. An?lises de redu??o de sulfato pelo cons?rcio I indicam percentuais de remo??o de sulfato da ordem de 93%, nas condi??es adotadas. A an?lise do precipitado formado pelo Cons?rcio I indica a presen?a do mineral whitloquita (Ca,Mg)3(PO4)2) sugerindo ? hip?tese de forma??o bacteriana que pode estar relacionado a mecanismos de substitui??o do f?sforo pelo ars?nio na c?lula ou servir como armazenamento para a regula??o de elementos essenciais pelas bact?rias. A identifica??o morfol?gica, bioqu?mica e molecular dos s do Cons?rcio I indica como presentes Escherichia coli, Clostridium sp e Bacillus sp., esp?cies estas que s?o usualmente citadas na literatura como estando relacionadas a processos de biorremedia??o de metais.Arsenic (As) is naturally present in the terrestrial environment associated with sulfide minerals in rocks and sediment. Because of chemical and biological oxidations and especially the activities related to mining and metallurgy, As is mobilized from natural deposits becoming an important environmental contaminant. This metalloid is toxic to many living things even if in very low concentrations. Several studies have been done trying to minimize such impacts by immobilizing this element. Among the methods proposed we would like to emphasize the use of microorganisms for metal removal from wastewater and contaminated waterbodies. Bacteria can remove metals from solution by different mechanisms such as those involving the extracellular accumulation/precipitation, adsorption or ion complexation on the cell surface and intracellular accumulation or bioaccumulation. The removal of metals from aquatic environments can also occur by the action of metabolites produced by bacteria, for example, H2S produced by Sulfate Reducing Bacteria (SRB) group. These microorganisms are peculiar due to the fact that they are able to chemically reduce sulfate producing sulfide, which by it turn is able to precipitate metals like their insoluble sulfides. This study is aimed to the searching and identification of arsenic resistant bacteria naturally present in water bodies, sediments, and sewage treatment reactor with potential application for water and wastewater treatment, targeting on bioremediation of industrial arsenic containing effluents. The different microbial consortiums were morphologically and metabolically characterized even in the presence of arsenic compounds in order to identify those with the greatest biotechnological application potential. The electrophoretic bands profile obtained after DGGE (denaturing gradient gel electrophoresis) analysis showed a great diversity in arsenic tolerant bacteria for two studied consortia (both obtained from sewage contaminated environments). As expected, there was a decrease in microbial diversity in the presence of As. Nevertheless, results shown that some of those microorganisms were adapted to the cultivation in the presence of As concentrations above those established by the Brazilian National Council of Environment as the maximum arsenic content for effluent discharging (0.5 mg.L-1), indicating potential application for As removal in effluent and contaminated water. Analysis of sulfate reduction by the consortium I indicate xviii sulfate removal rates of around 93% under the adopted conditions. The analysis of the precipitate formed after Consortium I cultivation by X-Ray diffraction indicates the presence of the mineral whitlockite (Ca,Mg)3(PO4)2) suggesting the possibility of biomineralization that may be related to the mechanisms of phosphorus substitution by arsenic within the cell or, as a second hypothesis this mineral could be use by bacteria cells like a storage stock for metabolic regulation of those essential elements. The morphological, biochemical and molecular identification of some of the microorganisms presents in the Consortium I indicate Escherichia coli, Clostridium sp. and Bacillus sp., as being the predominant species. These species are usually cited in literature as being related to metals bioremediation processes