PHOSPHATE SOLUBILIZING BACTERIA IN SOIL AND MINING TAILING FROM THE DISTRICT OF BENTO RODRIGUES – MG

A large diversity of microorganisms present in the soil are capable of solubilizing / mineralize insoluble soil phosphate to release soluble P and available to plants. After environmental disasters, such as the rupture of the dam of a mining company in Bento Rodrigues-MG, the modifications presented in the soil make it an environment of extreme conditions for microorganisms, presenting several adaptations of their own that must be studied and understood. Thus, the objective of this research was to quantify and isolate phosphate solubilizing bacteria (CaHPO4), contained in soil and mining tailing samples collected in Bento Rodrigues district, Mariana city, Minas Gerais, Brazil. For this, Cultivable Heterotrophic Bacteria (CHB) and Phosphate Solubilizing Bacteria (PSB) were quantified using standard plaque counting using Nutrient Agar (NA) and Glucose- Yeast extract Agar (GYA)- supplemented with phosphate, respectively. Gram stain tests were performed, catalase, oxidation and fermentation (O/F) for glucose, xylose and arabinose for phenotypic characterization of the isolated strains, in addition they were grouped in dendrogram through the technique MALDI-TOF MS of protein extraction. The CHB and PSB counts presented values of 2,6 × 104 CFU/g e 1,0 × 103 CFU/g, respectively for soil sample and 2,88 × 105 CFU/g e 1,2 × 103 CFU/g, respectively for the soil sample with reject. It was observed that all the isolates presented Gram-positive filamentous rod morphology and oxidative and fermentative (O/F) metabolism for xylose, positivity to catalase, while some showed sensitivity to lysozyme and other resistance. In addition, the grouping by protein profile resulted in a dendrogram with 4 distinct clades, thus demonstrating that the protein profile of the two samples (soil and mining tailing) are different, some organisms could not be identified; this failure was attributed to the organism not being included in the earlier databases rather than to the methodological error. However, the morphological, cultural and biochemical results confirm that these are actinobacteria belonging to the genera Streptomyces and Nocardia. Thus, considering the stress conditions found in the reject and the fact that it is an inert substrate that is still undergoing several biochemical processes, the contaminated soil of Bento Rodrigues may be a reservoir of distinct strains of Streptomyces and Nocardia phosphate solubilizers with vast biotechnological potential.