Bacterial Assisted Phytoextraction of Heavy Metal from Polluted Soil

Heavy metal contamination in soils is a critical environmental concern due to the toxicity and persistence of metals. This study investigates the potential of bacterial-assisted phytoextraction for the removal of heavy metal from metal-contaminated soil collected from Iba, Lagos State. Laportea aestuans, a non-edible weed, was used as the test plant, while two bacterial isolates, Bacillus cereus strain TPLC and Proteus mirabilis strain BY, tolerant to multiple heavy metals, were introduced to enhance metal uptake. The experiment involved six treatments combining control and contaminated soils with or without bacterial inoculation. Soil samples were analyzed for physicochemical properties, showing pH differences between sample A (acidic) and sample B (alkaline), with significantly higher heavy metal concentrations in sample B. Plant growth parameters, such as stem height, leaf length, and number of leaves, were measured weekly for five weeks. After 35 days, cadmium accumulation in plants and residual concentrations in soil were determined to assess the efficiency of bacterial-assisted phytoextraction. The results showed that Laportea aestuans exhibited better growth in control soil (Sample A) compared to contaminated soil (Sample B), where high metal toxicity stunted plant development. Transfer factor (TF) and extraction rate (%) calculations revealed a moderate TF of 0.14 and an extraction rate of 996% for Sample A treated with Proteus mirabilis strain BY, while Sample B with Bacillus cereus strain TPLC recorded an exceptional extraction rate of 17,650%, despite a lack of TF values. These findings highlight the potential of Bacillus cereus strain TPLC and Proteus mirabilis strain BY to enhance the phytoextraction process, particularly in heavily contaminated soils