This review provides a critical summary of the biological remediation of heavy metals by leveraging the potential of microbes in soils and water ecosystems, highlighting major research findings and practical obstacles. Heavy metals (HMs) pose a severe threat to environmental health due to their toxicity and persistence, necessitating effective remediation strategies. Biological remediation, especially through microorganisms and enzymatic actions, offers a promising alternative to conventional methods due to its eco-friendly and cost-effective nature. The review discusses various microbes, including bacteria, fungi, and algae known for their metal-binding capacities and transformation abilities. It delves into the mechanisms of bioremediation, such as biosorption, bioaccumulation, and biotransformation, facilitated by microbial enzymes like oxidoreductases and hydrolases that remove or bind the chemical structure of HMs. This paper also explores genetic engineering approaches to enhance microbial efficacy in HMs’ uptake and resistance. Furthermore, the review addresses the significant challenges in scaling bioremediation from a laboratory to the field, such as the complexity of environmental conditions, the presence of mixed contaminants, and the need for system optimization to improve efficiency and sustainability. It also evaluates the current legislative framework governing bioremediation practices, suggesting a need for clearer policies to support the integration of biological methods into mainstream remediation strategies. Conclusively, while microbial and enzymatic remediation presents considerable potential, extensive research is needed to overcome existing hurdles and develop robust, field-applicable systems. This paper calls for a multidisciplinary approach combining microbiology, engineering, and environmental sciences to advance this promising field.

It is well known that some plants have the capability of taking up sulfur as a nutrient from the atmosphere through foliar absorption and can survive well in polluted environments. In order to observe the effects of the relationship between atmospheric hydrogen sulfide (H₂S) deposition and soil sulfur nutrition, the current study used Brassica pekinensis as a model plant. The objective in conducting this study was to understand the regulatory mechanisms engaged in the uptake and assimilation of sulfate (SO₄²⁻) in plants by studying the modulation of transcription levels of sulfate transporter genes (STGs) (Sultr1;1 and Sultr1;2), changes in growth physiology, and the potential of roots to uptake the SO₄²⁻ when allowed to grow in the presence or absence of SO₄²⁻ in a hydroponic nutrient solution. Changes in growth, physico-chemical parameters, and gene expression levels of Group 1 STGs were observed when sulfur-treated and non-treated plants were exposed to phytotoxic H₂S levels in the air. Sulfur deficiency enhanced nitrate and free amino acid (FAA) concentrations in the shoot and root regions of the plant. However, there was a significant decrease in the biomass, shoot/root ratio (SRR), chlorophyll content, and thiol content, with p-values < 0.01. This, in turn, increased the sulfur-uptake capacity of plants from the atmosphere through foliar absorption. When the sulfur-uptake capacity of plants increased, there was an increase in the expression level of Group 1 sulfate transporter genes (Sultr1;1 and Sultr1;2), which regulate sulfur transportation through roots. The growth, physico-chemical characteristics, and level of gene expression of Group 1 STGs were unaffected by the availability of excess sulfur in the atmosphere of up to 0.3 μL l⁻¹.