Rhizospheric Soil Bacteria as Biostimulants for Phytostabilization and Reclamation of Mine Tailings

The mining activity around the world produces huge amounts of wastes usually deposited in the open-air as tailings’ dams with no rehabilitation strategies, which menaces the health of the neighboring villages’ populations and the environment. The use of heavy metal-tolerant plants as a cover around the mining areas contributes to attenuate such risks, by the reduction of wind-borne residue dispersal and the infiltration of metals to the table water. Additionally, most of these plants can limit the transport of metals to the aerial parts by their capture in the roots. However, although plants can thrive and tolerate metallic and climatic stresses, they are often assisted by organic amendments and/or activities of the plant growth-promoting rhizobacteria (PGPR). Assisted phytostabilization is a plant-based bioremediation technique that aims to reduce the availability and mobility of heavy metals in the soil. The PGPR has a significant positive impact on plant growth and metabolism and improvement of soil health. They may control plant diseases by inducing systemic defenses and competing with phytopathogens. They also improve the plant growth by providing nutrients such as nitrogen by fixation of N2 from atmosphere, phosphorus, potash, zinc, etc. through solubilization in soils, iron and other cations by producing siderophores, and they also supply secondary metabolites and phytohormones, such as indole acetic acid, gibberellins, or organic compounds. The use of heavy metal-tolerant plants and PGPR for phytostabilization is considered as one of the most environment-friendly and effective techniques to limit the transport and mobility of metals and their introduction to the food chain. This chapter reviews and discusses the role of PGPR on phytostabilization and reclamation of mine tailings.