Enhanced removal of heavy metals by wetland plant-microbiome symbiont: Prospect of potential strategies and mechanisms for environmental heavy metal regulation

Wetland plants and their related environmental interfaces are colonized by a wide range of microbial communities, and the symbiotic system of plants and microorganisms can interact and cooperate with each other, playing an important role in environmental remediation of metal pollution, which has garnered significant attention. The dominant communities of wetland plants still have high treatment performance and survival rate under pollution conditions. Many studies show that hyperaccumulating metallophytes have the capacity to accumulate heavy metal up to several times higher than the plants in sterile soil, due to the interaction of microbes within the rhizosphere. Thus, biotechnological efforts are being explored to modify plants for heavy metal phytoremediation and to improve the adaptation of wetland plants, endophytes, and rhizospheric microorganisms to adverse environment. New phytoremediation techniques and enhanced symbiosis technique for endophytic bacteria inoculation with high efficiency are being pursued and utilized in heavy metal phytoremediation in wetland systems. Therefore, in this review, we systematically summarized the interface characteristics of wetland systems and the interaction of symbionts, with emphasis on the enhanced removal potential and regulation mechanisms of heavy metals by plant-microbe symbiosis in wetland systems, along with the applications of plant-microbiomes for heavy metal remediation in wetlands. Moreover, we explored the remediation mechanisms of combined endogenic-ecophytic microorganisms for wetland systems. In recent research, the exogeneous bacteria drastically remodeled the rhizospheric microbiome and further improved the activity of rhizospheric functional enzymes, with the metal removal at the rhizospheric region reaching up to 95%. In order to increase the effectiveness of plant-microbiome engineering in addressing wetland environmental pollution, the significance of incorporating synergistic techniques and taking a variety of environmental factors was discussed.