Microbial inoculation enhances phytoremediation performance of Camelina sativa in soils contaminated with multiple heavy metals

Phytoremediation offers an environmentally sustainable strategy for mitigating heavy metal contamination in soils. However, its effectiveness may be constrained by limited plant growth and metal uptake under multi-metal contamination. The comparative effects of bacterial and fungal inoculants on the phytoremediation performance of Camelina sativa under simultaneous contamination with multiple heavy metals remain insufficiently understood. This study evaluated the phytoremediation performance of C. sativa under microbial inoculation with Bacillus subtilis and Trichoderma harzianum . Plants were cultivated for eight weeks in an artificially established multi-metal contaminated soil system created by the simultaneous addition of Cd, Pb, Zn, and Ni to the same soil at a target concentration of 100 mg kg⁻¹ for each metal. The following treatments were evaluated: an uninoculated control, Bacillus subtilis inoculation, and Trichoderma harzianum inoculation, to determine whether microbial inoculation improved plant growth and phytoremediation performance under simultaneous multi-metal contamination. Compared with the uninoculated control, Trichoderma harzianum decreased post-harvest DTPA-extractable Cd, Pb, Ni, and Zn concentrations by approximately 31%, 32%, 53%, and 32%, respectively, while increasing shoot metal uptake and maintaining plant growth. The fungal treatment generally produced greater improvements in Ni and Zn uptake and accumulation indices than Bacillus subtilis , whereas the bacterial treatment resulted in the highest Pb uptake. These findings indicate that microbial inoculation may enhance early-stage phytoremediation through metal-specific effects on soil–plant acquisition processes. In addition, microbial treatments promoted plant growth and enhanced soil biological activity. Overall, microbial inoculation, particularly with Trichoderma harzianum , improved the phytoremediation performance of C. sativa under the experimental conditions, highlighting the potential of microbial inoculation to enhance phytoremediation in multi-metal-contaminated soils.