The Effect of Plant Growth Promoting Rhizobacteria Bacillus thuringiensis LKT25 on Cadmium Accumulation and Physiological Responses in Solanum nigrum L.

Cadmium contamination in soil threatens ecological safety and human health. Phytoremediation has gained attention due to its cost-effectiveness and environmental sustainability. Studies show that plant growth-promoting rhizobacteria can enhance the ability of hyperaccumulator plants to remove heavy metals. This research aimed to isolate and identify plant-growth-promoting rhizobacteria under Cd stress and assess their impact on the growth and Cd accumulation of <i>Solanum nigrum</i> L. Six bacterial strains were isolated from the rhizosphere of <i>S. nigrum</i>, all showing high Cd tolerance. Among them, LKT25 exhibited multiple growth-promoting traits, including indole-3-acetic acid production, nitrogen fixation, 1-aminocyclopropane-1-carboxylate deaminase, and siderophore synthesis. Under varying Cd concentrations (5, 25, and 50 mg/kg), the <i>Bacillus thuringiensis</i> strain LKT25 significantly improved Cd removal by <i>S. nigrum</i>. At 5 mg/kg Cd, the removal efficiency reached 45.13%. LKT25 also enhanced plant growth, photosynthesis, and antioxidant activity, contributing to improved Cd remediation. This study provides new microbial resources and technical support for using rhizobacteria in remediating heavy metal-contaminated soils.