Utilization and Characterization of Microbes for Heavy Metal Remediation

Heavy metals in forest soils have substantial ecological implications, affecting the soil and the surrounding ecosystem. These naturally occurring elements, with high atomic weights, become toxic at elevated concentrations. Notable heavy metals in forest soils include lead, cadmium, mercury, and arsenic. The profound toxicity of heavy metal pollution poses a significant risk to modern agriculture, with the potential for accumulation in crops and soils, threatening food security. A crucial aspect of addressing this challenge involves promptly restoring disrupted agricultural land. This study contributes to agricultural soil restoration by employing a combination of microorganisms, which have proven effective in alleviating heavy metal pollution. When paired with Sunflower ( Helianthus annus), the combination ensures soil restoration and enhances food security. The study investigated microorganisms from contaminated soil, revealing Gram-negative bacilli and cocci arrangements. The colony characteristics, including hues and diameters, were assessed, with notable findings in samples 1, 2, and 5. The microbial ability to remove heavy metals (Pb, As, Hg, Ni, and Cd) was quantified, highlighting the diverse capacities among isolates. Selected isolates (1, 3, 6, 7, and 10) exhibited 25% higher biomass accumulation than the control, extracting at least 40 mg/L of each metal. Bacterial identification using a Vitek 2 Compact analyzer revealed Pantoea sp., Achromobacter denitrificans, Klebsiella oxytoca, Rhizobium radiobacter, and Pseudomonas fluorescens. Biocompatibility testing led to the formation of consortia for soil remediation, with Coalition D ( Achromobacter denitrificans, Klebsiella oxytoca, and Rhizobium radiobacter in a 1:1:2 ratio) confirming the effective removal of Ni and Pb. Various consortia showed differing performances in removing composite contaminants, with Coalition D being promising, indicating a potential for phytoremediation. Optimal cultivation conditions were identified, with Coalition D excelling at metal removal and biomass accumulation. The temperature, pH, and soil conditions were crucial for Coalition D efficiency, and combining them with phytoremediation techniques showed promise. Laboratory experiments with sunflower seedlings confirmed the efficacy of Coalition D in enhancing soil phytoremediation, improving plant survival, and removing mixed heavy metals.