Maize associated bacterial microbiome linked mitigation of heavy metal stress: A multidimensional detoxification approach

The indiscriminate discharge and consequent accumulation of heavy metals (HMs) from various anthropogenic sources into the environment is a major global concern for food security and human health. Since HMs are non-degradable, they persist in soils, and above threshold levels alter the soil-plant systems. Following accumulation in soils and uptake by maize plants, HMs either alone or in synergism modify the composition and physiological activity of root-associated bacterial microbiome, soil nutrient pool, metabolism of maize plants, and pose risks to living organisms via the food chain. To solve HMs issues, the root-associated microbiome (rhizobiome) with high metal tolerating ability has been identified and applied for enhancing maize yield in contaminated soils; though reports on the use of metal tolerant rhizobiome in maize cultivation are limited. Recognizing the importance of maize as a food/feed crop and the lack of information on metal-induced phytotoxicity and its abatement strategies, this review attempts to provide the latest information on the importance of the metal tolerant microbiome in stress alleviation and crop nutrition and yield optimization/stability of maize in changing metal-enriched agro-ecosystems. In addition to the ameliorative roles of microbiome and plants in counteracting the stress, the distinct advances made in the metal tolerant rhizobiome-maize interactions are discussed, including the strategies and mechanisms adopted by biosensor microbiomes to accelerate maize-metal tolerance and growth. This review further explains the translocation, internalization, and distribution of metals in different maize organs. The impact of several metal tolerant biological enhancers as one of the incredibly attractive and highly promising technology to clean up metals and their importance in maize nutrition and crop production are highlighted. The simultaneous metal detoxification and bio-enhancing activity of the metal tolerant microbiome provides a better option for optimizing maize production in contaminated open field conditions.