Magnetic nanoparticle-assisted colonization of synthetic bacteria on plant roots for improved phytoremediation of heavy metals. (July 2023)

• Record Type: Journal Article
• Authors: Shi, Cong; Zhao, Zirun; Zhu, Nali; Yu, Qilin
• Is Part Of: Chemosphere. Volume 329(2023)
• Publication Date: 2023-07
• Subjects: Heavy metal removal -- Phytoremediation -- Synthetic bacterium -- Magnetic nanoparticle -- Rhizosphere microbiome; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2023.138631
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Phytoremediation is a facile strategy to remove environmental heavy metals by using metal-accumulating plants from the rhizosphere environment. However, its efficiency is frequently compromised by the weak activity of rhizosphere microbiomes. This study developed a magnetic nanoparticle-assisted root colonization technique of synthetic functional bacteria to regulate rhizosphere microbiome composition for enhanced phytoremediation of heavy metals. The iron oxide magnetic nanoparticles with the size of 15–20 nm were synthesized and grafted by chitosan, a natural bacterium-binding polymer. The synthetic Escherichia coli SynEc2, which highly exposed an artificial heavy metal-capturing protein, was then introduced with the magnetic nanoparticles to bind the Eichhornia crassipes plants. Confocal microscopy, scanning electron microscopy, and microbiome analysis revealed that the grafted magnetic nanoparticles strongly promoted colonization of the synthetic bacteria on the plant roots, leading to remarkable change of rhizosphere microbiome composition, with the increase in the abundance of Enterobacteriaceae, Moraxellaceae, and Sphingomonadaceae. Histological staining and biochemical analysis further showed that the combination of SynEc2 and the magnetic nanoparticles protected the plants from heavy metal-induced tissue damage, and increased plant weights from 29 g to 40 g. Consequently, the plants with the assistance of synthetic bacteria and the magnetic nanoparticles in combination exhibited much higher heavy metal-removing capacity than the plants treated by the synthetic bacteria or the magnetic nanoparticles alone, leading to the decrease in the heavy metal levels from 3 mg/L to 0.128 mg/L for cadmium, and to 0.032 mg/L for lead. This study provided a novel strategy to remodel rhizosphere microbiome of metal-accumulating plants by integrating synthetic microbes and nanomaterials for improving the efficiency of phytoremediation. Graphical abstract: Image 1 Highlights: A synthetic bacterium/magnetic nanoparticle-combined system was constructed. Chitosan-grafted MNP enhanced root colonization of synthetic bacteria. The synthetic bacterium/MNP system protected plants from tissue damage. The synthetic bacterium/MNP system improved heavy metal removal by plants.