Effect of Engineered Nanoparticles on Rhizospheric Microbes

The numerous applications of nanoparticles (NPs) are gaining momentum in various industrial sectors. The augmentation of NPs due to increased usage aids their entry into the terrestrial ecosystem through waste streams, treatment plants, and fertilizer applications. The excessive release of these engineered nanoparticles (ENPs) affects the plant growth-promoting rhizobacteria (PGPR), which are paramount for maintaining soil fertility. The PGPR inhabit the rhizosphere of the plant roots and derive their nutrition from the root exudates. The ENPs change the physiological and functional attributes of these useful microbes. In addition, ENPs alter the soil exoenzyme profile of these microbes. The exoenzymes are crucial in regulating the biogeochemical cycles and soil fertility. The interactions between ENPs and the PGPR may disturb the overall soil ecosystem, its fertility, thus impacting crop production. There is limited understanding on how concentration of NPs may influence the plant growth-promoting traits of microbes in synergistic as well as antagonistic ways. There are very few ecotoxicological studies on these NPs, and so far, there is no specific legislation or regulation for proper disposal of ENPs. The present book chapter elucidates the positive and negative role of ENPs over rhizospheric microbes.