Assessment of PGP traits of Bacillus cereus NDRMN001 and its influence on Cajanus cajan (L.) Millsp. phytoremediation potential on metal-polluted soil under controlled conditions

Abstract

The current study looked at the plant growth-promoting (PGP) traits of the pre-isolated and metal-tolerantBacillus cereusNDRMN001 as well as their stimulatory effect on the physiology, biomolecule content, and phytoremediation potential ofCajanus cajan(L.) Millsp. on metal-polluted soil. The bauxite mine, which is surrounded by farmland (1 km away), has been severely polluted by metals such as Cd (31.24 ± 1.68), Zn (769.57 ± 3.46), Pb (326.85 ± 3.43), Mn (2519.6 ± 5.71), and Cr (302.34 ± 1.62 mg kg−1) that exceeded Indian standards. The metal-tolerantB. cereusNDRMN001 had excellent PGP activities such as synthesis of hydrogen cyanide (HCN), siderophore, indole acetic acid (IAA), N2fixation, and P solubilization. Furthermore, the optimal growth conditions (temperature of 30°C, pH 6.5, 6% glucose, 9% tryptophan, and 1.5% tricalcium phosphate) for effective synthesis and expression of PGP traits inB. cereusNDRMN001 were determined. Such metal-tolerantB. cereusNDRMN001 traits can significantly reduce metals in polluted soil, and their PGP traits significantly improve plant growth in polluted soil. Hence, this strain (B. cereusNDRMN001) significantly improved the growth and phytoremediation potential ofC. cajan(L.) Millsp on metal-polluted soil without [study I: 2 kg of sieved and autoclaved metal-polluted soil seeded with bacterium-freeC. cajan(L.) Millsp. seeds] and with [study II: 2 kg of sieved and autoclaved metal-polluted soil seeded withB. cereusNDRMN001-coatedC. cajan(L.) Millsp. seeds]B. cereusNDRMN001 amalgamation. Fertile soil was used as control. The physiological parameters, biomolecule contents, and the phytoremediation (Cr: 7.74, Cd: 12.15, Zn: 16.72, Pb: 11.47, and Mn: 14.52 mg g−1) potential ofC. cajan(L.) Millsp. were significantly effective in study II due to the metal-solubilizing and PGP traits ofB. cereusNDRMN001. These results conclude that the test bacteriaB. cereusNDRMN001 considerably improved the phytoremediation competence ofC. cajan(L.) Millsp. on metal-polluted soil in a greenhouse study.