Phosphate-solubilizing bacteria for lead heavy metal phytoremediation by reducing bermudagrass stress and enhancing lead bioaccumulation

Phosphate-solubilizing bacteria (PSB) are responsible for improving soil nutrient availability and enhancing the bioavailability of heavy metals through bioactivation. However, the physiological responses of plants to PSBs and their phytoremediation efficiencies have not yet been investigated. This study explored whether PSB alleviates bermudagrass (Cynodon dactylon (L.) Pers.) oxidative stress from soil lead (Pb) pollution and alters Pb bioaccumulation via soil Pb form transformation and nutrient bioavailability improvement. The results showed that inoculation with PSB, such as Pantoea rwandensis or Acinetobacter calcoaceticus, alleviated Pb stress in bermudagrass by reducing the accumulation of malondialdehyde (MDA) in tissues and increasing the biomass and leaf chlorophyll content. After inoculation with P. rwandensis or A. calcoaceticus, the Pb extraction efficiency of bermudagrass was improved with an increase in the acid-soluble Pb fraction in soil, as evidenced by the increase in Pb bioaccumulation of biomass and bioaccumulation factor (BCF_above and BCF_under). The nitrate-nitrogen and available phosphorus in the soil were more available for uptake of bermudagrass. Moreover, the relative abundance of heavy metal-resistant microbial groups, such as Proteobacteria, Bacteroidetes, and Chloroflexi in rhizosphere soil, was enhanced, which is crucial for the phytoremediation efficiency of bermudagrass in Pb-contaminated soil. The application of PSB provides a new strategy for improving the phytoremediation efficiency of bermudagrass in Pb-contaminated soils.