Soil microbiological aspects upon the Fundão disaster

• Autor(a) principal: Vasconcelos, Ana Luisa Soares de
• Data de Publicação: 2021
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/11/11140/tde-11052022-161255/
• topic: Mucilaginibacter sp.; Mucilaginibacter sp.; Áreas úmidas; Atividade biológica; Biological activity; Coalescence; Coalescência; Desastre de Mariana; Mariana disaster; Rio Doce; Rio Doce; Wetlands

The microbiota is responsive to the changes even in resilient environments with high diversity, such as soil. It is possible to notice changes in structure, function, and activity due to stress events. In the case of environmental contamination, such as dam failure, the effects of this stress are even more evident and can occur at different scales. Selection pressure leads to a change in diversity and ecological relationships between species. This effect, over time, leads to functional changes in the environment. Contamination can alter selection rules at the cellular level, highlighting phenotypes derived from horizontal gene transfers and mutations. In this study, we seek to understand how contamination can change the soil microbiota concerning the structuring of communities and the occurrence of bacterial groups resistant to the conditions imposed by environmental contamination. In this sense, this study had specific objectives: (i) to determine the differentiation in the structuring and biological activity of the soil, seeking to describe differences along with soil profiles at points of occurrence of contamination. Field collections through different methods (i.e., enzymology, TRFLP); (ii) assess the competition and settlement that occurs in the soil with the occurrence of contamination by mimicking the process under controlled conditions; (iii) evaluate the event of bacteria resistant to the contamination conditions and describe genomic alterations in this organism. No patterns were found between the analyzed points since the contamination occurred uniformly on a distinct base previously present in the analyzed areas. Factors such as the height of the tailings layer, the vegetation, and properties of the initial soil, generated unique profiles of microbial responses at each of the points evaluated along with the profiles. Under controlled conditions, we demonstrated the importance of understanding the contamination process through its chemical and biological aspects. In this, it was possible to identify the effect of the tailings on the soil previously existing in the area, indicating that it completely changes the soil community throughout the contamination event. This evidence is reinforced by the similar effect of the tailings deprived of their biological fraction, which indicates that the imposed stress conditions are the major differential event of the observed selection. At the cellular level, bacteria present in contaminated soil have high resistance/tolerance to metalloids such as Zn, Cd, Mn. Through genetic sequencing of selected bacteria, Mucilaginibacter sp., it was possible to identify resistance mechanisms associated with horizontal transfer processes, such as efflux pumps in genomic island positions and mobilomes with genes with cross-resistance of antibiotics and metals. And in Mucilaginibacter a potential for bioremediation due to high genes associated with EPS and efflux pumps.