Exploring the synergistic effect of chromium (Cr) tolerant Pseudomonas aeruginosa and nano zero valent iron (nZVI) for suppressing Cr uptake in Aloe Vera

Abstract

Chromium (Cr) contamination of soil has substantially deteriorated soil health and has interfered with sustainable agricultural production worldwide and therefore, its remediation is inevitable. Inoculation of plant growth promoting rhizobacteria (PGPR) in association with nanotechnology has exerted broad based impacts in agriculture, and there is an urgent need to exploit their synergism in contaminated soils. Here, we investigated the effect of co-application of Cr-tolerant “Pseudomonas aeruginosa CKQ9” strain and nano zerovalent iron (nZVI) in improving the phytoremediation potential of aloe vera (Aloe barbadensis L.) under Cr contamination. Soil was contaminated by using potassium dichromate (K₂Cr₂O₇) salt and 15 mg kg⁻¹ contamination level in soil was maintained via spiking and exposure to Cr lasted throughout the duration of the experiment (120 days). We observed that the co-application alleviated the adverse impacts of Cr on aloe vera, and improved various plant attributes such as plant height, root area, number of leaves and gel contents by 51, 137, 67 and 49% respectively as compared to control treatment under Cr contamination. Similarly, significant boost in the activities of various antioxidants including catalase (124%), superoxide dismutase (87%), ascorbate peroxidase (36%), peroxidase (89%) and proline (34%) was pragmatic under contaminated soil conditions. In terms of soil Cr concentration and its plant uptake, co-application of P. aeruginosa and nZVI also reduced available Cr concentration in soil (50%), roots (77%) and leaves (84%), while simultaneously increasing the relative production index by 225% than un-inoculated control. Hence, integrating PGPR with nZVI can be an effective strategy for enhancing the phytoremediation potential of aloe vera.

NOVELTY STATEMENT

Combined effect of PGPR and nanotechnology in the bioremediation of toxic contaminants is well reported in literature. Most of these reports comprise the use of hyperaccumulator plants for phytoextraction of heavy metals. However, phytostabilization potential of hyperaccumulators is still un-explored. Current study investigated the role of PGPR and Fe-NPs in suppressing the uptake of Cr in aloe vera, a hyperaccumulator plant.

Keywords:

• Aloe vera
• chromium
• industrial effluents
• nano zerovalent iron
• PGPR
• phytoremediation

Acknowledgments

The authors extend their appreciation to the Researchers supporting project number (RSP2024R306), King Saud University, Riyadh, Saudi Arabia. The authors also highly acknowledge Soil Microbiology and Biochemistry Laboratory for providing all the necessary resources to carry out the safe conduct of the research project.

Authors’ contributions

Komal: Performed the experiment and gathered the data. Muhammad Shabaan: Analyzed the data, critically reviewed it and wrote the manuscript. Qasim Ali: Co-supervised the experiment, assisted in data recording and critically reviewed the data. Hafiz Naeem Asghar: Supervised the research project and critically reviewed the obtained results. Zahir Ahmad Zahir: Co-supervised the research project, and critically reviewed the obtained results. Kashmala Yousaf: Helped during data recording and laboratory analysis. Usman Zulfiqar: Critically reviewed the data and helped in writing and revising the manuscript. Noreen Aslam: Critically reviewed the data and helped in writing the manuscript. Mukkaram Ejaz: Critically reviewed the data. Mona S Alwahibi: Critically reviewed and edited the manuscript. M. Ajmal Ali: Critically reviewed and edited the manuscript.

Disclosure statement

Authors declare having no competing financial interests that may have appeared to interfere with the work reported hereby.

Additional information

Funding

Researchers did not receive grants of any sort from any specific funding agency (commercial, public or other nonprofit sectors).