Impact of Fundão Dam Tailings on Rhizospheric Soil Microbial Communities in Mariana, MG, Brazil

Bioremediation using plants and microorganisms effectively mitigates heavy metal soil contamination and improves soil conditions. Phytoremediation with leguminous plants and rhizobacteria enhances metal bioavailability and promotes plant growth. This study evaluates microbial community structure in soils with varying concentrations of tailings from the Fundão Dam disaster in Mariana, MG, Brazil. Microbial diversity was measured by fluorescent in situ hybridization in treatments with different tailings concentrations and in the presence of Leucaena leucocephala . Higher tailings proportions reduced bacterial densities, with pure ore tailings (T100%) showing the lowest bacteria percentage. However, after 14 months of leucaena cultivation, this treatment had the highest number of prokaryotes. The presence of leucaena plants modified the densities of Bacteroidetes and the Pseudomonas genus. Experimentation time influenced the densities of Actinobacteria, Acidobacteria, and Firmicutes. The interaction between legume presence and sampling time altered the density of Proteobacteria and Gallionella ferruginea . The results show that iron ore tailings impact the microbial community in the plant rhizosphere, offering insights for bioremediation strategies to restore soil quality in mining-affected areas.