Potential of pigeon pea [Cajanus cajan (L.) Millsp.] associated with endophytic bacterium Bacillus cereus PEB-9 to remediate cadmium-contaminated soil

Abstract

Phytoremediation associated with plant-beneficial bacteria has gained considerable attention for its efficiency in remediating cadmium (Cd)-contaminated soil. In this study, we isolated an endophytic bacterium, PEB-9, from pigeon pea, which was identified as Bacillus cereus and exhibited strong plant growth-promoting traits along with high Cd resistance in vitro. Pot experiments demonstrated that PEB-9 inoculation increased in pigeon pea biomass (11.45–19.29 %), Cd accumulation (43.89–69.90 %), and the Cd transfer factor (4.17–16.89 %) in Cd-stress soil (2–10 mg/kg), with soil remediation efficiency improving by 11.1–15.4 %. Under Cd stress, PEB-9-treated pigeon pea exhibited significant improvement in the activities of superoxide dismutase, peroxidase, and catalase, while a notable decrease in malondialdehyde content, indicating a reduction in Cd cytotoxicity. Additionally, the chlorophyll content in PEB-9-treated plants was significantly higher than that in the control group. Furthermore, PEB-9 inoculation enhanced bioavailable Cd, soil enzymes activity and nutrient content, including available nitrogen, phosphorus, and organic matter, while also boosting the relative abundance of stress-resistant bacterial groups, such as Proteobacteria and Actinobacteria. Correlation analysis indicated that soil nutrient changes induced by PEB-9 significantly influenced bacterial community structure, thereby regulating plant physiological responses, and improving Cd remediation efficacy of pigeon pea. These findings offer a valuable basis for the practical implementation of PEB-9 in remediating Cd-contaminated soils.