Exploring cadmium bioaccumulation and bioremediation mechanisms and related genes in soil microorganisms: a review

Cadmium (Cd) is a highly toxic heavy metal that poses serious environmental and health risks. It reduces soil fertility and can cause renal failure, liver damage, bone fractures, hypercalciuria, and cancer in humans. Cd contamination in soil, originating from both natural and human activities, is especially concerning because it bioaccumulates in plants, entering the food chain and affecting crops like tomatoes, rice, cocoa, and lettuce. Understanding the mechanisms of Cd bioaccumulation and bioremediation in microorganisms isolated from Cd-contaminated soils is crucial for developing effective strategies to mitigate Cd contamination in soils. This review highlights recent studies on the mechanisms of Cd uptake and detoxification in microbes, emphasizing genes and enzymes that mediate Cd response. Microbial species such as Pseudomonas aeruginosa, Burkholderia sp., and Bacillus subtilis, along with various fungal species, show resistance mechanisms influenced by genes that enhance their Cd tolerance. Enzymes like peroxidases, ATPase, and sucrose play roles in Cd stress responses. Key genes such as czcA, czcD, zntA, cadA, and cadD encode proteins that improve their tolerance to Cd. These microbial mechanisms offer sustainable solutions to improve soil health, crop productivity, and environmental safety. Future research should focus on engineering microorganisms with improved Cd-binding mechanisms, optimizing their effectiveness across different soil types, pH levels, and exposure durations.