Microbe-assisted phytoremediation of toxic elements in soils: Present knowledge and future prospects

In the face of escalating anthropogenic impacts stemming from urbanization and industrialization, our study delves into the critical realm of potentially toxic elements (PTEs) contamination in soil, unraveling a complex web of interactions that imperil soil environments and their vital microbial and enzymatic activities. Unlike organic pollutants, PTEs resist microbial degradation and their presence disrupts soil microbial and enzymatic activities, affecting the nutrient cycle and plant growth. There is a need to find effective nature-based solutions for addressing soil contamination with PTEs; this quest has led to increased interest in bioremediation, utilizing bacteria, fungi, algae, and plants for sustainable environmental cleanup. While previous reviews have addressed general principles about the bioremediation of PTEs contaminated soils, there are no critical reviews which have been published about the current state of the microbe-assisted phytoremediation (MAP). Particularly, this review aims at meticulously examining the understudied roles of diverse microbes-archaea, bacteria, and fungi in the rhizosphere of hyperaccumulators under PTEs stress. In doing so, it also expands our understanding of the plant root microbiome's contribution to phytoremediation of PTEs in hyperaccumulator plants. We focus on how PTE pollution influences plant signaling pathways, root exudate profiles, and subsequent interactions with diverse microbial communities. Also, we discuss the behavior of archaea towards MAP, filling a significant gap in current understanding. Moreover, we comprehensively analyze how microbial communities interact with hyperaccumulators, and discuss the most recent research that expands beyond the known role of organic acid producers to explore how a wider range of diverse phytobiome collaborates with plants to detoxify PTEs, influencing biogeochemical cycles in intriguing ways. This review examines the biochemical and molecular mechanisms that promote plant growth, offering a comprehensive perspective on the present knowledge and future prospects in this field. By synthesizing existing knowledge, this review provides insights into effective strategies for remediating PTEs-polluted soils. The findings are relevant for researchers, environmental scientists, and policymakers, guiding future efforts to address the growing issue of PTEs contamination and its impact on soil ecosystems.