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Resumo(s)
A variação da estrutura da comunidade bacteriana de águas residuais de uma estação
municipal de tratamento (ETAR) foi avaliada em amostras colhidas antes e após o tratamento,
através do método de eletroforese em gel de gradiente desnaturante (DGGE). Os padrões de
DGGE da comunidade correspondentes a catorze amostragens realizadas em diferentes
estações do ano, foram analisados em função de variáveis bióticas e abióticas com recurso a
análise estatística multivariada.
Com base na análise das sequências nucleotídicas das bandas de DGGE, foi possível
concluir que as populações predominantes pertencem ao filo Proteobacteria, às classes Beta-,
Epsilon- e Gama-, e ao filo Bacteroidetes. A análise de componentes principais (PCA) com
base em padrões de DGGE mostrou que a composição e estrutura das comunidades
bacterianas variaram ao longo do tempo e de forma diferente para cada tipo de águas residuais
(água residual bruta ou efluente tratado).
A análise de correspondência canónica (CCA) dos padrões de DGGE em relação às
variáveis ambientais sugere que alguns fatores, como a temperatura e humidade relativa do ar
exercem uma influência significativa na composição do efluente tratado. A presença de alguns
compostos químicos, tais como as tetraciclinas, ou a abundância de coliformes cultiváveis
resistentes a ciprofloxacina ou a sulfametoxazol também mostraram estar relacionados com a
estrutura da comunidade.
Segundo este estudo, a comunidade bacteriana presente no efluente tratado é influenciada
por populações de bactérias cultiváveis resistentes a antibióticos, pela presença de agentes
antimicrobianos e pelas condições físico-químicas. É possível concluir que a comunidade
bacteriana pode sofrer rearranjos durante o tratamento, o que poderá contribuir para o
desenvolvimento de resistência a antibióticos e eventual disseminação no meio ambiente.
The variation of the bacterial community structure in a municipal activated sludge wastewater treatment plant (WWTP) was assessed before and after treatment, through the method of denaturing gradient gel electrophoresis (DGGE). The DGGE community patterns, corresponding to fourteen sampling campaigns over different seasons, were analysed as a function of different biotic and abiotic environmental variables through multivariate statistical analysis. Based on the analysis of the nucleotide sequences of the excised DGGE bands, it was possible to conclude that the predominant populations were Proteobacteria of the classes Beta-, Epsilon- and Gamma-, and Bacteroidetes. A principal component analysis (PCA) based on DGGE patterns showed that the composition and structure of bacterial communities varied over time and differently for each type of wastewater (raw or treated). The canonical correspondence analysis (CCA) of the DGGE patterns versus environmental variables suggested a significant influence of some factors, such as temperature and the relative humidity, in the treated effluent. The presence of some chemical compounds such as tetracyclines, and culturable coliforms resistant to ciprofloxacin or to sulfamethoxazole showed also to have a relationship with the structure of the community. According to this study, the bacterial community of the treated effluent is influenced by culturable antibiotic resistant populations, the presence of antimicrobial agents and the physicochemical conditions. It is possible to conclude that the bacterial community may suffer rearrangements throughout the wastewater treatment, eventually leading to the development of antibiotic resistance in the environment.
The variation of the bacterial community structure in a municipal activated sludge wastewater treatment plant (WWTP) was assessed before and after treatment, through the method of denaturing gradient gel electrophoresis (DGGE). The DGGE community patterns, corresponding to fourteen sampling campaigns over different seasons, were analysed as a function of different biotic and abiotic environmental variables through multivariate statistical analysis. Based on the analysis of the nucleotide sequences of the excised DGGE bands, it was possible to conclude that the predominant populations were Proteobacteria of the classes Beta-, Epsilon- and Gamma-, and Bacteroidetes. A principal component analysis (PCA) based on DGGE patterns showed that the composition and structure of bacterial communities varied over time and differently for each type of wastewater (raw or treated). The canonical correspondence analysis (CCA) of the DGGE patterns versus environmental variables suggested a significant influence of some factors, such as temperature and the relative humidity, in the treated effluent. The presence of some chemical compounds such as tetracyclines, and culturable coliforms resistant to ciprofloxacin or to sulfamethoxazole showed also to have a relationship with the structure of the community. According to this study, the bacterial community of the treated effluent is influenced by culturable antibiotic resistant populations, the presence of antimicrobial agents and the physicochemical conditions. It is possible to conclude that the bacterial community may suffer rearrangements throughout the wastewater treatment, eventually leading to the development of antibiotic resistance in the environment.
Descrição
Palavras-chave
Estação de Tratamento de Águas Residuais Urbanas PCR-DGGE Comunidades bacterianas Municipal Wastewater Treatment Plant Bacterial communities