Avaliação da toxicidade da água e da patogenicidade de bactérias entéricas isoladas do lago artificial Lagoa da Pampulha, Minas Gerais, utilizando o modelo invertebrado Caenorhabditis elegans

• Ano de defesa: 2022
• Autor(a) principal: Lainy Ana Siqueira de Oliveira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ICB - DEPARTAMENTO DE MICROBIOLOGIA; Programa de Pós-Graduação em Microbiologia; UFMG
• Palavras-chave em Português: Lagoa da Pampulha; Bactérias entéricas; Toxicidade; Caenorhabditis elegans; Microbiologia; Lagoa; Microbioma Gastrointestinal
• Link de acesso: http://hdl.handle.net/1843/77787

Lagoa da Pampulha is an important and polluted artificial lake in Belo Horizonte, where fishing is practiced and people come into contact with the waters. The present work aimed to evaluate the water toxic effects and the potential pathogenicity of bacteria isolated from the lake, using the Caenorhabditis elegans model. From the water collected from 4 points along the Lagoa da Pampulha and from a point in the Rio do Bicudo (healthy water body), its toxic effects on worm survival, fertility and development were evaluated. The survival of the worms kept for 24 hours in the samples was measured through the colorimetric assay using MTT. Fertility and development were evaluated by counting the progeny of exposed adults and the developmental time of these progeny kept in the samples. Samples were also seeded and bacteria isolated on MacConkey Agar and identification by MALDI-ToF was performed. Was evaluated the C. elegans (N2 and KU25) survival after infection by bacteria isolated from Lagoa da Pampulha (19 isolates), Rio do Bicudo (3 isolates), 2 bacteria from reference strains (Enterobacter aerogenes ATCC 13048 and Citrobacter freundii ATCC 8090) and Escherichia coli OP50 (negative control). Infected worms were counted (live and dead) every 48 hours for 16 days. In the evaluation of toxicity, it was found that there was no significant difference between the samples, however there was a reduction in fertility (about 50%) in worms exposed to Lagoa da Pampulha waters, when compared to worms exposed only to M9 (physiological buffer of the C. elegans). It was observed that Lagoa da Pampulha had a higher bacterial density than the control sample (390 CFU/ml), being heterogeneous along the points, higher at the beginning of the lake (22,500 CFU/ml) and lower near the spillway (1,530 CFU/ml), due to the dilution effect. It was also verified that there was no significant difference in the survival of C. elegans infected by bacteria isolated from Lagoa da Pampulha or Rio do Bicudo, in which the N2 strain had an average LT50 of 14 days and KU25 had an average LT50 of 10 days. The environmental isolates decreased the LT50 of C. elegans (N2) in relation to the OP50 (from 16 to 14 days), while the reference strains E. aerogenes ATCC 13048 and C. freundii ATCC 8090 led to the lowest LT50, respectively, 12 and 8 days. It is concluded that the Lagoa da Pampulha waters had low toxic effect to C. elegans when compared to the Rio do Bicudo waters and the bacteria isolated from the environmental samples did not impact the C. elegans KU25 survival and had low impact on N2 survival. The results may suggest that the approaches applied to restore the lake quality are showing positive results. However it must be considered that contact with it involves risks to human health, because it has a high density of bacteria that are opportunistic pathogens and have toxic effects to the model organism.