A comparative meta-analysis of Cu, Ni, Cd, Zn, and As uptake by plants after inoculation with Pseudomonas or Bacillus

Bacillus and Pseudomonas are among the most extensively studied rhizobacterial genera. This meta-analysis demonstrates that their interactions with plants distinctly modulate heavy metal bioaccumulation. Specifically, Pseudomonas significantly enhanced zinc (Zn) accumulation in plants by 30.48%, while Bacillus increased nickel (Ni) accumulation by 51.72%. This stimulatory effect was consistent across various plant species and most pronounced within the first month after inoculation. Conversely, both genera reliably reduced arsenic (As) buildup under all conditions included in this meta-analysis. The accumulation of cadmium (Cd) exhibited a strong dependence on environmental and biological factors, showing a negative correlation with soil pH and a positive correlation with planting period. Furthermore, the impact of both rhizobacteria on Cd was highly plant-specific, varying significantly across different plant families. Therefore, selecting appropriate rhizobacteria-plant pairs and optimizing the planting period are critical for managing heavy metal uptake. Our study offers a comprehensive, quantitative framework of how key variables-soil pH, planting period, and plant species-influence this process. These insights provide a valuable foundation for designing effective phytoextraction strategies in contaminated soils.