Bioremediation potential of Brevibacillus parabrevis AMB-CD-2 in spinach under lead toxicity

The present study was conducted to evaluate the impact of lead toxicity on the growth parameters of spinach and the performance of lead-resistant bacterial isolates under lead stress conditions. Out of four bacterial isolates selected for this study, only two isolates AMB-CD-2 and AMB-CD-4 were selected based on their lead tolerance ability. A polybag experiment was conducted with six treatments and four replications in spinach. The treatments included T-1 (RDF + control), T-2 (lead acetate), T-3 (AMB-CD-2 + lead), T-4 (AMB-CD-4 + lead), T-5 (AMB-CD-2), and T-6 (AMB-CD-4). Results showed that lead contamination significantly decreased plant growth parameters, particularly in the treatment T-2 (lead acetate) when compared with other treatments. Similarly, reduced uptake of nitrogen, phosphorus, and potassium (NPK) was recorded in T-2. Inoculation with lead-resistant bacteria, AMB-CD-2, significantly improved plant growth parameters (plant height, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, and root length). The uptake of NPK was higher in T-5 (AMB-CD-2) in the absence of lead by approximately 0.81%, 0.37%, and 0.42% than in the control, respectively. Through atomic absorption spectrophotometer analysis, the lead concentration in treatment T-2 (control) was about 3.20 mg/g while in treatment T-3 (AMB-CD-2 + lead) it was about 1.32 ppm. The 16S rRNA gene sequencing revealed that AMB-CD-2 resembles Brevibacillus parabrevis. The results demonstrate that the lead-resistant bacteria B. parabrevis AMB-CD-2 showed a significant lead reduction of approximately 58.75% compared to the control.