Heavy Metal Tolerance and Biosorption Potential of Fungi and Bacteria Isolated from Metal Contaminated Soil

Abstract

Heavy metal-contaminated soils pose significant environmental and health risks due to activities such asmining, negligent waste management, and garbage burning. Heavy metals, characterized by atomic numbersgreater than 20 and high density, are particularly hazardous. This study evaluates the tolerance and biosorp-tion capacities of bacteria and fungi isolated from metal-contaminated soils. Soil samples yielded bacterialisolates including Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, and Serratia marcescens,and fungal isolates such as Rhizopus sp., Aspergillus flavus, and Aspergillus niger. Among these, P. aeruginosaand B. subtilis exhibited the highest bacterial tolerance to metals, while A. flavus and A. niger were the mostmetal-tolerant fungi. Biosorption capacities for copper and chromium (by bacteria) and cadmium and nickel(by fungi) were assessed using atomic absorption spectrophotometry. Microorganisms were cultured in brothscontaining 5–20 ppm of metals for 15 days. At 5 ppm, P. aeruginosa demonstrated the highest biosorption ofchromium (48.9%) and copper (34.8%), while A. niger and A. flavus showed the highest biosorption of nickel(59.9%) and cadmium (53.6%), respectively. These findings highlight microbial biosorption as a promisingbioremediation strategy for heavy metal-contaminated environments.