Rhizoremediation: A Plant–Microbe-Based Probiotic Science

Abstract

Global health is at the tipping point with the emitters of a myriad of anthropogenic environmental pollutant chemicals by industries. From these sites, an array of xenobiotic compounds, i.e., polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, heavy metals, etc. get released, entering into our food chain, thereby threatening our lives too. The establishment cost for the remediation of these recalcitrant compounds with the traditional techniques (landfilling, incineration) is quite high. So, an alternative, safe, economical, ecofriendly, biological-based method is required. Microbes assisted remediation, rhizoremediation, appears to be particularly effective for the degradation of specific xenobiotic compounds in the rhizosphere due to the higher microbial communities than the non rhizospheric or bulk soil. Root exudates (such as organic acids, carbohydrates, phenolic compounds, etc.) in the rhizospheric region act as inducers for the catabolic genes during rhizosphere colonization to degrade the various xenobiotic compounds. The key step involved in degradation mechanism is the activation or reduction of pollutant molecule by bacteria such as Pseudomonas, Alcaligenes, Sphingomonas, Rhodococcus, and Mycobacterium, creating reactive sites for the next reactions, converting substrates into acetyl-CoA, which is catabolized in Kreb’s cycle. Fungi generally co-metabolize organic pollutants, but they do grow on some aliphatic and aromatic compounds by extracellular oxidation or intracellular catabolism. Although the process involved in rhizoremediation occurs through natural process, it can be optimized with the suitable plant-microbial interaction using individual strain or consortium to increase the microbial population density. However, studies on potential microbial communities, their selection from the niche area, characterization with their degradation capacity, proliferation in the applied root system can be a novel and useful tool to improve the plant.