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Environmental Science and Pollution Research
Springer
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Abstract: |
Microorganisms are cost-efective and eco-friendly alternative methods for removing heavy metals (HM) from contaminated agricultural soils. Therefore, this study aims to identify and characterize HM-tolerant (HMT) plant growth-promoting
rhizobacteria (PGPR) isolated from industry-contaminated soils to determine their impact as bioremediators on HM-stressed
pepper plants. Four isolates [Pseudomonas azotoformans (Pa), Serratia rubidaea (Sr), Paenibacillus pabuli (Pp) and Bacillus
velezensis (Bv)] were identifed based on their remarkable levels of HM tolerance in vitro. Field studies were conducted to
evaluate the growth promotion and tolerance to HM toxicity of pepper plants grown in HM-polluted soils. Plants exposed
to HM stress showed improved growth, physio-biochemistry, and antioxidant defense system components when treated
with any of the individual isolates, in contrast to the control group that did not receive PGPR. The combined treatment of
the tested HMT PGPR was, however, relatively superior to other treatments. Compared to no or single PGPR treatment, the
consortia (Pa+Sr+Pp+Bv) increased the photosynthetic pigment contents, relative water content, and membrane stability
index but lowered the electrolyte leakage and contents of malondialdehyde and hydrogen peroxide by suppressing the (non)
enzymatic antioxidants in plant tissues. In pepper, Cd, Cu, Pb, and Ni contents decreased by 88.0-88.5, 63.8-66.5, 66.2-67.0,
and 90.2-90.9% in leaves, and 87.2-88.1, 69.4-70.0%, 80.0-81.3, and 92.3%% in fruits, respectively. Thus, these PGPR are
highly efective at immobilizing HM and reducing translocation in planta. These fndings indicate that the application of
HMT PGPR could be a promising “bioremediation” strategy to enhance growth and productivity of crops cultivated in soils
contaminated with HM for sustainable agricultural practices
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