Bacterial-assisted phytoremediation of heavy metals: Concepts, current knowledge, and future directions

Abstract

The presence of heavy metals in soil are an emerging problem owing to the increasing number of contaminated sites worldwide and the harmful effects of toxic metals on the environment and human health. Because heavy metals are persistent and cannot be degraded to non-toxic forms, it is crucial to mitigate metal contamination and clean up the thousands of contaminated sites around the world. Bacterial-assisted phytoremediation has been gaining attention because the process is eco-friendly, low-cost, and had promising advancements over the last few decades. Bacteria are a vital part of ecological systems and are essential for the restoration of those ecosystems. In fact, microbes are essential for plants to withstand toxicity in metal-polluted soil. Therefore, a better understanding of this complex relationship may lead to improved methods of phytoremediation. This review summarizes the research of plant growth-promoting bacteria (PGPB) in enhancing phytoremediation in heavy metal-polluted soils. Examples of phytoremediation, including phytoextraction, phytostabilization, and phytovolatilization are described, as well as the use of soil inoculation with PGPB to improve the efficiency of phytoremediation. Lastly, future directions for the commercialization of bacterial-assisted phytoremediation are discussed. Significant advancements are needed to transition phytoremediation from bench-scale to field usable applications in order to fully validate and utilize PGPB-assisted phytoremediation. Additionally, current developments in genetic engineering are anticipated to contribute to enhancing the effectiveness of bacterial-assisted phytoremediation.