Humus-reducing bacteria in heavy metal bioremediation: Mechanisms, challenges, and prospects

Heavy metal contamination has become a critical global environmental issue due to the widespread industrial activities and urbanization, posing serious risks to human health and ecosystems. Conventional methods of heavy metal remediation, such as physical and chemical treatments, often suffer from high costs, inefficiency, and secondary environmental damage. In contrast, bioremediation using humus-reducing bacteria (HRB) offers an environmentally sustainable and economically viable alternative. HRBs utilize mechanisms like biosorption, biomineralization, and electron transfer to immobilize or detoxify heavy metals, including lead (Pb²⁺), cadmium (Cd²⁺), and mercury (Hg²⁺), in contaminated environments. This review examines the biochemical and ecological roles of HRBs in the bioremediation of heavy metals, with a focus on their metabolic pathways, microbial species involved, and factors influencing their efficiency. The challenges and limitations of HRB-based remediation, including environmental conditions, microbial community dynamics, and redox sensitivity, are also discussed. Future perspectives are provided on integrating HRBs with other bioremediation strategies, such as phytoremediation and advanced nanomaterials, to enhance the efficiency and scalability of metal detoxification processes.