Plant-Microbe-based phytoremediation and bioremediation of Cd-contaminated soil

Abstract

Cadmium (Cd) is a heavy metal known to be harmful to both the environment and human health. It is released into the environment through various human activities, such as industrial processes, sewage, plastic, Ni-Cd batteries, and phosphate fertilizers. This metal can accumulate in soil and air, posing a threat to crops, and food security, and causing economic losses. To address this issue, it is crucial to develop sustainable and cost-effective methods for removing Cd from contaminated soil. Phytoremediation and bioremediation are two environmentally friendly and cost-effective techniques that can be used to remediate Cd-contaminated soil. Sunflower is a plant known for its ability to absorb and reduce the toxicity of heavy metals like Cd from polluted soil. Additionally, Bacillus subtilis, a type of bacteria, can enhance plant growth and biomass production, aiding in Cd remediation. Cadmium pollution is a significant problem that requires immediate attention to safeguard agricultural land and human health. Traditional remediation methods, such as excavation and soil washing, are expensive and can cause soil erosion. Hence, there is a need to explore sustainable and cost-effective approaches for Cd remediation. To investigate the combined effect of Sunflower's hyperaccumulation property and Bacillus subtilis' resistance to Cd transport in plants, pot experiments were conducted. These experiments compared the impact of Cd stress on plant growth, yield quality, and quantity, with and without the presence of the bacteria. Morphological, physiological, and biochemical analyses of the plants were performed, along with comparisons of root and shoot structures. The results revealed that plant growth and development were more adversely affected by increasing concentrations of Cd. However, the presence of Bacillus subtilis significantly improved the plants' morphological and physiological traits. This effect was particularly notable at high Cd concentrations, indicating that the bacteria reduced Cd toxicity. The activity of antioxidant enzymes increased, indicating the presence of reactive oxygen species (ROS) under stress conditions. Nevertheless, the presence of bacteria further activated the plants' defense mechanisms, preventing damage to plant structures. This research has significant implications for the development of environmentally friendly and economically viable approaches to remediate Cd-contaminated soil. Moreover, this approach can be extended to address other heavy metal contaminants, contributing to environmental protection and human health. It can be applied to restore contaminated industrial sites, leading to cleaner environments, and reducing Cd exposure in food, thereby improving public health.