Biodiversidade de bactérias fixadoras de nitrogênio em área de mineração de carvão

Abstract

Coal is a fossil fuel extracted from underground by mining processes with the greatest availability in the world. In the state of Rio Grande do Sul, Brazil, the main source is the Candiota Mine with reserves of a billion tonnes likely to be mined in the open. This activity results in built environments with a high degree of disorganization, acid pH, heavy metal toxicity and susceptible to erosion. Exposing this weathering and sulphide minerals facilitates the formation of acid mine drainage, changing and affecting the quality of water, soil and air. Aiming to restore and preserve the desirable environmental conditions it is necessary to recover those mining areas. An alternative is the introduction of nitrogen-fixing bacteria that benefit the growth of leguminous plants. In this perspective, this study aimed to investigate the biodiversity of nitrogen fixing bacteria in soils built after coal mining. Contruidos soil samples were collected and after, in solution, added on substrate with plants-baits siratro and vetch to perform the isolation of nitrogen-fixing bacteria (BNF) through nodes. After the isolates were subjected to the pH (3.0, 4.0, 5.0, 7.0 and 9.0) testing and heavy metals (Cd, Cu, Pb, Ni and Zn in 3 different dosages ). Later isolates efficient at pH test were subjected to molecular characterization and verification of Noda and nifH genes. The data obtained showed a large number of isolates tolerant to different pH values and different metals with different concentrations. Molecular characterization showed 4 phyla α-β-γ-Proteobacteria and Firmicutes, whichever phylum α-proteobacteria, mainly Bradyrhizobium sp. Due greater adaptation in acidic environments, the predominant characteristic of degraded areas after coal mining.